i wilL SEE _YOU_ *_ALL_* *_N̸͍͕̍͐́̎̒͑E̶̖͕͎̝̣̻̯͇̦̠̩̯͓̼͇̿͌͌̄͆X̵̛̰̘͉̳̻͓͌̇͗͋͝Ṱ̷͚͈̂̄̄͌̇̈͋̅̓̔̍̓͌̂͘ ̷̛̖̌̉̾̌͗͌̀͆̍̐̌̕T̵̤̫͓̯̔̒̾̒̈́̀̓̉̾̚̕I̶̢̧̗̹̜͓͉̯͙͐͂́̿̂͠M̶͈͎͈̱͔͈̬͎͋͒͛͒̑̉̈̚͠͠͠È̶̠̳̾̄͌̒̋̏̿̉̕̕_*
Not the first one I've seen, @@not-pyroman. If you're been around for a while, you'll recognize a user with IRFZ44 username. That guy used to be popular in some videos. Don't see it anymore though, wondering what happened.
What i know that when you want to transmit an analog signal via a digtal transmmiter the first step is sampling the analog signal , and there is a condition to consider which is the sampling frequency must be as twice as the maximum frequency of analog signal , therefore if you picked a sampling frequency then you must make sure that the maximum frequency in the analog signal is half the sampling frequency, otherwise every frequency which higher than half the sampling frequency will be picked as noise. Sorry for long comment.
When the frequency of the signal is higher than half of sampling frequency it not generate noise, its aliasing wich is worst. And nyquist criteria of double of max frequency of the signal is just valid theoricaly for infinite signals. If you want good audio quality it just need to be at least 10 times.
Absolutely agreed. But for crying out loud this noisy approach as good as it may work for a D power amp seems pretty useless in this application. Wouldn't it be orders of magnitude easier and better to use good old FM. .. (in an analogue way of course)
Question, the module was able to send audio range analog signals. Why not directly send analog through? modulating the analog to digital would require a much larger bandwidth.
Honestly, even though he's from Germany, his English sounds better then most of the people in Holland (like me😁). It's clear, I can understand it, and he talks slow!! Great Job Scott!!! Keep up the good work!
I've noticed something, most people that don't have English as their first language speak it better than quite a lot of native speakers that I know (including myself)
@@KingJellyfishII I come from China,My English listening is too bad,in order to know the content of video,I must see English subtitles,Unfortunately there are only German subtitle options,I wonder why app provides Germany options when I know that host is speaking English. I go on listening and find the pronunciation of host like German.😄
I have read a bit through the comments. One person already suggested to use these moduls in their "analouge" mode. The transmitter is simmilar to one of these TTL oscillators. You simply can bridge the data pin to "+" from your supply, and series modulate it with a PNP or NPN Transistor. This will give you AM with FM. The FM Part is just narrowband FM, but on a selective receiver you´d need to use slope detection, but these receivers usually are "Super regenerative receiver(s)" I´m mainly talking about the green circuit boards (the ones completely on the left side in your frequency test, that just could take 5KHz). On the receiver there´s a two stage super regenerative receiver. One transistor works as RF preamplifier, to get the RF noise away from the antenna, whilst the other one is the actual receiver. On your modules, at least the RF preamp transistor is mounted - the modules I have, the receiver misses the transistor (probably were lower price due to this fact got them as a gift) On the receiver board, the output from the super regenerative receiver goes to a lowpass filter hence it´s quench frequency (thats why you only can transmitt up to like 5KHz). The 8 pin SMD Chip - LM 358 - only forms the sine wave into a square wave. You can "tap off" the signal from the receiver before the LM358 chip, and so you can make complete analouge audio transmission. All you need is a modulator + microphone amplifier on the transmitter side... and a small audio amplifier on the receiver side with "tapped in" audio pickup before the LM358. Practically - To get the transmitter to transmitt AM - Bridge "Data" to "+ UB" and take a standard NPN Transistor. Use double supply voltage, and tap the transistor between "-" of your transmitt module and ground. Now use a 1M Potentiometer, and a Multimeter. Connect the 1M Potentiometer between base and collector, and have it adjusted to "1M" at the start. Now decrease it´s value, untill you reach about the half supply voltage on the module. Via a 100nF capacitor and let´s say a 3,3k resistor (random values) you can now put Audio on base of the transmitter. The audio would already be received from the receiver, but it would be extremly distorted because the LM358 converts the sine wave signal from the regenerative receiver to a square wave signal. Take an amplified speaker, hook one pin up to ground from the receiver module (while the transmitter is on, try with a low volume level on your phone with my suggested values) and use a let´s say 10k + 10...100nF (whatever is in the parts box) between "audio in" from your speaker and the connectors around the LM358 - one connection will be "audio out" from the receiver. If you find it, you will hear your music over the speaker. Later if you want to use that "concept" you might need to add a lowpass filter between your receiver module and an audio amplifier Chip, because some remains from the receiver´s quench frequency might be left, and block / inteffer with the audio chip (very quiet, could start motor boating if connected to the same battery). For the transmitter you don´t need to use the full voltage. If you lower the voltage the "AM percentage" will increase, whilst the FM percentage will decrease, but "good" AM will cost a lot of TX power (like going down from 10 to 0,5mW) Anyhow, since the receiver is a wideband super regenerative type, it won´t care about "that bit" narrowband FM, but if you´d receive this on a more "proper" receiver, that has AM option, you´d need to use slope detection for it. I´m talking about the green modules ... some other modules might use a more "fancy" "Superhet" receiver. Regarding the 1M potentiometer... maybe a 250k might also work... I don´t know how these transmitters react to overvoltage. TTL modules "can take some" but I´m sure it´s not good for them. I´d appreciate it if you´d give this a try, but since my comment is just one of many... I´m not really expecting much
Have been following your channel since long & have learned a lot. Always heard your voice but really pleased to see your face, great work man keep it up :)
I created a 15m walkie-talkie with my bare hands! I made a cup with my hands and held them to my mouth. For receiving, I held my cupped hands to my ears. I think that I could get more range too if I raised my voice.
To get rid of the 5kHz frequency, perhaps a band pass filter can be used... You can cascade the LPF with the 41kHz cutoff freq with a high pass filter > 10kHz or so
I was thinking that a band-stop filter could probably do the job. At the very least, you could use a series LC circuit to short out the 5KHz signal, though you could probably do better with a Butterworth or Chebyshev filter.
Hey your arduino walkie talkie worked . I tried andreas spiess solution, placed a potentiometer instead of resistor. After few tries, it worked like a charm, covered distance of probably 100 meters
While studying electronics and communications engineering, they teach us that we only use a bandwidth of 4 Khz when it comes to voice/speech transmission so technically the first tx rx pair is actually decent enough for use in a walkie talkie! That 4 Khz even includes the guard band which results in a useable spectrum from 300 to 3400 Hz.
From what I know, you should use the high frequncy TX signal as a carrier. Insert audio into it. In the RX section, you must separate the carrier signal from the audio, then amplify the audio. Just like FM TX or AM TX. On FM TX, you affect the carrier frequency range. In AM TX you affect the carrier amplitude. I learned a lot from this channel
Here's something else to consider: The reason you may want to bring an Arduino back into the mix is to use it to create a form of buffer. The idea is that if you buffer the signal, even for say 100 transmissions, you can use that to avoid choppiness. Of course, the transmission would need to be slightly higher than the buffer size so it can catch up, which in turn in a poor man method, results in some dropout of single packets, but that would be my basic, noncomplicated approach.
You can transmit and recive analog signal (using the first pair TX/TX boards) if you bypass the comparator on the receiver, the 8 pin chip normally is a lm328 amplifier configurate in one half amplifier and the other half like comparator, this last one is what you need to bypass to get an audio signal
if you want a decent range on those, you can get it by building yourself a dipole antenna to replace the monopole. I've even built a crude yagi antenna for use with modules like this, just with one guide element and one reflector element. there's some calculators around that can make it easier for people not so comfortable with antenna design to build their own antennas. fortunately, these are relatively low frequencies, so you can be a bit sloppy with your antenna construction and still get decent results.
Not trying to be critical here, just suggestions. Enjoyable video and well shot/narrated. I appreciate the effort. I've been using RF modules exactly like this for at least 22 years now. I've always used them to send serial data (9600 BAUD max is typical due to bandwidth limits) and most people have used them this way and that's why there's so many microcontroller and Arduino applications presented everywhere. Using them to send PWM modulated "audio" is an out-of-the-box idea. However, RC model radios have been sending PWM modulated analog values exactly this way for over 45 years. It works great for RC because the sampling rate of the analog channels is maybe 20 to 60 Hz, not several kHz. The RC radio can convey many analog channels on one RF carrier by sending several pulses as a string, like a short burst of pulses, followed by a pause to be used as a sync. At the receiver, a simple counter is used to separate the pulses and then each pulse is "stretched" to the standard "1ms to 2ms" range and then finally sent to a specific servo. I think the reason the receiver output sounds so bad is that it's not really demodulating the PWM signal but is instead attempting to filter out the frequency of it. Remember that the audio info is encoded just in the dutycycle, not the amplitude or frequency and a simple bandpass filter cannot separate those. Think about it this way, if you filter the PWM frequency out completely, nothing would be left and you'd get no audio. Conversely, filtering it less will retain some of the PWM signal and certainly you will hear it. The trick then is to properly demodulate it. Maybe pass the PWM signal through a diode, then resistor, and into a charge tank consisting of a cap with parallel resistor referenced to ground. This converts dutycycle to analog. It is basically a peak detector, like a cheap AM demodulator. Adding the resistors provides a means to control the cap charge and discharge rates, thus recovering the audio. Then pass the output of that through a lowpass filter to clean out the last of the PWM ripple and then finally into a power amp. The rule of thumb is that the PWM freq should be at least 10x the max audio freq that you want to pass, but the bandwidth limits of the system might force it down to the theoretical minimum of 2x (re Nyquist)) but then it'll definitely have noticeable PWM hum no matter what you do if using a single stage lowpass filter. Even a well tuned multi-pole filter would have a hard time separating it completely out. Brick-wall filters are generally not so simple. Also, a source for audio distortion, the 555 timer waveform is non-linear, not an ideal sawtooth. There's an old chip MC34060AP that can directly convert 0V to 3V analog into a stable linear PWM signal. Sorry it's obsolete but there's likely a modern replacement within DC/DC converter category. Alternatively, using a cheap opamp and a few discrete components, build a simple triangle generator (tech term is an oscillator based on an integrator). Yet another possibility might be to send the 555 square wave output through a pair of LM334Z constant-current source ICs into a cap. I said "a pair" because I don't think they're bi-directional so I was thinking a pair of them connected in reverse-parallel might work. I'd have to try it just for fun. The general rule is that if you charge/discharge a cap using a constant current, the voltage will be linear and the triangle would be perfect. Also, using a polymer or mica cap for the timing cap makes it temperature stable so it's value doesn't drift all over the place. Ceramics are cheap but loosely spec'd and sensitive to noise and temperature. One last thing, there are many cheap solutions for connecting to standard 0.1" pitch header pins. No need to wreck them by bending them and soldering wires directly to them. Cheers to all and happy hobbying.
Few recommendations for improvements: try to use decoupling cap between pin 2 of the comp and pin 6 of the 555. Also you may use voltage divider and adjustable POT resistor to vary the level of the output from audio circuit - shift up and down. This may produce better PWM that improve on audio fidelity. Also you may use very weak pull down resistor on the Data in of the XMTR, if it is floating from the XMTR board module. If the XMTR board allows powering from higher voltage then you may try it for longer range, tinkering with the antenna and its impedance also may boost the communication range. Apparently the XMTR-RCVR pair modules are not designed to deal with those kinds of so called PWM wave forms, thus a conditioning circuits maybe needed as I described above. In Radio circuits, it is vital to insure impedance matching on input / output ports for both XMTR and RCVR circuits, not only on RF circuit (here you can not do anything about it, unless you tinker on the module board) but also the audio circuit.
Hello to the union of people who are watching this late at night. 11:37 pm to be specific. *YES*, I'm that fascinated and amazed at his videos that I want to watch them as soon as possible
The problem would be to line up the frequencies. If you don’t get it exactly right, you’d be adding instead. A low pass filter or band-stop filter would be better.
Finally! 'been waiting for this video for so long. I am always to lazy, to order the stuff i develop, so i firstly watch other people doing it :_D Great videos by the way!
i remember the 1st video, you wanted it for riding your motorbikes with your friends.. i know you will come back to this one until you crack it because of why you want them.. cant wait to see you crack it.. : )
Pl. make videos on how to charge Lead Acid Rechargeable Battery (4.1 ~ 4.7v DC)! I am awaiting for Portable Bluetooth Speaker to be made by renowned and our favourite GreatScott on their next iteration!
I hv sm fr module ( 1:00 not that one ) , but i wanna use it to make cheap rf tool for me I wanna make RF frequency analyser with serial port and 2nd portable display interface . But i don't know arduino programming I wish you make video on it.
Either go full analog or full digital. Try out RpiTx, it works amazingly well. You just need to figure out a way to attach a microphone to the raspberry pi zero and you can transmit on 0-900Mhz.
I've just builded my own automatic greenhouse based on the Arduino with Solarpower, Sensors, Waterpump and vetilation a few years ago. The only missing Thing in my Setup is the LoRa-Wan that i now had to have 😉. Great Scott 👍😁
@GreatScott! - instead of using a trim-pot variable resistor for your audio input, make a low pass R-C filter from the output of the 555 to ground, which will give you a DC level, at 50% of the triangle wave amplitude, use this voltage and connect to the lower end of a trim pot, connect the wiper to the op-amp input and connect the 'top' of the trim pot (which is now your volume control) to the audio source via a DC blocking capacitor. This arrangement will 'auto-level' so you always have 50% above and below. Also, on your output amp (TC4423 I think?) add a DC blocking cap to the speaker, those gate drive IC's don't like static DC current and you'll overheat the top of the totem-pole.
3:26 A small correction. It is a PWM signal, not a digital signal. Although there are only two voltage values, it is not a digital signal. The reason is that the duty cycle varies with the audio signal amplitude. An actual digital signal is created by measuring the voltage values at regular intervals and storing them as binary numbers in a process known as sampling.
Hello sir, I made this receiver and transmitter circuit using 433 Mhz module but I can't take any signal from speaker and also any sound my voice. Can you help me? I have to make Wireless Audio Transmission.
The 433MHz band is used by key fobs, remote controlled socket relays, and wireless tire pressure guages. Prolonged use of this walkie-talkie might jam those other devices. You should warn people that if they build this, only use it for four very short infrequent communications.
I leaned that maybe it's cheaper to pull apart a cheap commercial walkie talkie and check it's configuration than it is to try and start from scratch, lol. Great effort though, keeping with the "only know if you give it a go" tradition.
Try inserting a low pass filter in your audio path to limit the bandwidth of your audio signal to say slightly below the maximum allowable input frequency of your RF module,
5:12 One thing to know is that if you just want to create a Walkie-Talkie (to exchange words) then you can restrict the frequency between 300 an 3400 Hz as it's the common frequency used for VOIP calls. For example, the highest frequency a (trained) human can sing is around 1400Hz. So with 7kHz, it looks very fine (unless you want to transmit high-quality audio).
The range of human hearing is often said to be 20-20K Hz, but in reality, for most people over 25, the top end of that spectrum is cut off significantly. It's usually around 14 Khz for most middle-aged people. Not that you'd want to use it...a traditional analog phone line's bandwidth channel upper limit is around 3 Khz, and that's about as high quality as most people expect to hear from a walkie talkie too, so really any of those modules, in theory, could work for this experiment.
Would love to see an episode dedicated to tube amplifiers. Trying to make one myself (I've found some old soviet 6n3p-ev tubes) and can't get my head around calculating the cathode and anode resistors.
Hi! I am a beginner with electronics and I have a question: why is the low-pass filter behind the amplifier and not before the amplifier? Would it not be much easier to filter the small signal with smaller components and the amp would have to work less hard? What am I not understanding here? Love your videos Scott!
Try it out and see what happens. If you use a band pass filter before the signal is amplified there will still be noise present in the output signal. If you amplify the signal before filtering, you end up with the noise and desired signal seperated in frequency making it easier to find a band that can filter out the noise.
@@Blobcraft13 Interesting. Thank you! I will try it out next time when i am tinkering! Why do the frequencies get separated? You mean the signal to noise ratio or is there an actual shift in frequency? Does the amp act as a lowpass as well? So they are not communative? .... I'm sorry .... my math skills are so laaacking -.-
@@SciFiFactory technically it shouldn't matter if you filter it before or after, but for me, amplifying it first give me a bitter idea of the frequency band that I would need to reduce noise. If you look at the output before amplifying, you'll see a big mess of actual signal and noise. If you amplify the signal, the signal itself and the noise will take up more room on the oscilloscope, allowing you to get a better idea of what parts are noise and what parts are signal. It's kind of hard to explain, if you have an oscilloscope I would try it out smd you should see what I mean.
@@SciFiFactory the amp wouldn't act as a low pass filter, but an active low pass filter contains an op amp, so I see why you would think that. If you were to build a circuit to amplify and then filter a signal, you would need 3 op amps (assuming you're using 2 active filters). You would need one op amp with an input and feed back resistor, the ratio between the two creates a gain. The signal is then amplified by that gain factor. After the signal is amplified, you would have the low pass and high pass filter in place to cut off the upper and lower range of the signal. So you would need to know the highest and lowest frequency of your signal to construct the low pass and high pass filter. I amplify first in order to easily see the highest and lowest frequency of the signal. I've read online the it's best practice to amplify first in a lot of situations, but I'm not 100% sure myself.
Good enough. It sounds much better than the first revision). I think it should improve the sound quality: Add anti aliasing filter (1 or 2 order lowpass filter) and choose sample rate respectively. Audio signal spectrum has a frequencies from 0Hz to 20kHz (appr.). So when you try to convert audio signal from analog form to PWM form with a sample rate lower than 40 kHz the aliasing appears and creates additional noises. Thank you for your videos.
Btw, you can try a 3 kHz low pass filter and a 6 kHz (or more) sample rate to achieve a telephone quality. It's enough for communication like walkie-talkie.
Great video. Seeing the failings and shortcomings prompts discussion and encourages people to get involved. I don't know how to fix the circuit, my first step would be to straighten the antennas, but other than that I wouldn't know.
It’s not that difficult, it’s just that the design is terrible for transmitting audio. The modules use on-off keying which is not really suited to produce a quasi-analog-pwm signal for audio. Low pass filter is probably as beefy as it should be for aliasing.
thes transmitter modules actually can transmit audio, the data pin on the receiver has a comparator. therefore for digital signals, on the 7th pin on the chip if i remember right, theres the analog signal not passed through a comparator. just attach a wire to the pin.
I really like the raw, back to basics of this project. Here are my thoughts. Effectively you have a digital pipe with errors and you want to transmit voice in the best way possible. This topic has been covered to death of course for mobile phones since the 80's and the answer is ... voice codecs. What would make a really interesting project, is not to add one of the old voice codec chips, but to find a SW version and run it on an Arduino.
I have the receiver that got the best frequency results in the video. It is really surprising how good it is. I can use it through three walls over 10 meters and still get 95% of the data.
What do you think about sending the audio with packets? You start recording signal when i reaches threshould level. When audio level goes back to low - you compress signal in some way. Then send it as digital information. Yes there will be slight delay, but quality should be much better.
The "and I will see you next time" has been slowly getting more and more enthusiastic over the years... Lol
Eventyally he is going to explode
@@markusfpv1349 let's hope that's a long time away
Rusty Mustard It is... a common way to say goodbye
@@rustymustard7798 Occams razor my dude
i wilL SEE _YOU_ *_ALL_* *_N̸͍͕̍͐́̎̒͑E̶̖͕͎̝̣̻̯͇̦̠̩̯͓̼͇̿͌͌̄͆X̵̛̰̘͉̳̻͓͌̇͗͋͝Ṱ̷͚͈̂̄̄͌̇̈͋̅̓̔̍̓͌̂͘ ̷̛̖̌̉̾̌͗͌̀͆̍̐̌̕T̵̤̫͓̯̔̒̾̒̈́̀̓̉̾̚̕I̶̢̧̗̹̜͓͉̯͙͐͂́̿̂͠M̶͈͎͈̱͔͈̬͎͋͒͛͒̑̉̈̚͠͠͠È̶̠̳̾̄͌̒̋̏̿̉̕̕_*
Greatscott!: _"as you can hear, it still sounds acceptable"_ 8:17
The speaker: *demonic sounds*
@FQD2N never knew a MOSFET could post a comment
Not the first one I've seen, @@not-pyroman. If you're been around for a while, you'll recognize a user with IRFZ44 username. That guy used to be popular in some videos. Don't see it anymore though, wondering what happened.
@@Asu01 too much current, he blew up
@@Asu01 i think I've seen that one once or twice
Edit: ice to I've. Fucking autocorrect
Bluey!
What i know that when you want to transmit an analog signal via a digtal transmmiter the first step is sampling the analog signal , and there is a condition to consider which is the sampling frequency must be as twice as the maximum frequency of analog signal , therefore if you picked a sampling frequency then you must make sure that the maximum frequency in the analog signal is half the sampling frequency, otherwise every frequency which higher than half the sampling frequency will be picked as noise.
Sorry for long comment.
I absolutely agree.
Nyquist frequency!
When the frequency of the signal is higher than half of sampling frequency it not generate noise, its aliasing wich is worst. And nyquist criteria of double of max frequency of the signal is just valid theoricaly for infinite signals. If you want good audio quality it just need to be at least 10 times.
Yes i agree, it named the Shannon-Hartley theorem for whom wants to elaborate.
Absolutely agreed. But for crying out loud this noisy approach as good as it may work for a D power amp seems pretty useless in this application. Wouldn't it be orders of magnitude easier and better to use good old FM. .. (in an analogue way of course)
Question, the module was able to send audio range analog signals. Why not directly send analog through? modulating the analog to digital would require a much larger bandwidth.
Because it can't. 3:04
It would be nice if he tries to do this again but all analog, using a FM radio receiver and transmitter.
hi electroboom
Hey electroboom, big fan!
If transmitter works with high and low threshold levels trying to send any analog signal this will be distorted to squarewave.
8:34 I take it that you're not hearing the painful high pitched sound during the mike test... Oww, my ears
I'm still in hope of seeing you making one RF transmitter from scratch.
Honestly, even though he's from Germany, his English sounds better then most of the people in Holland (like me😁). It's clear, I can understand it, and he talks slow!! Great Job Scott!!! Keep up the good work!
I've noticed something, most people that don't have English as their first language speak it better than quite a lot of native speakers that I know (including myself)
I am intermediate english student, i dont understand native english speakers, because they talk to fast, but i clearly understand great scott
I'm not English nor German but i still can understand him while he speaks English or German. He can speak both fluently and clear
@@KingJellyfishII I come from China,My English listening is too bad,in order to know the content of video,I must see English subtitles,Unfortunately there are only German subtitle options,I wonder why app provides Germany options when I know that host is speaking English. I go on listening and find the pronunciation of host like German.😄
@@bofeng2700 The host is German, so he likely provided German subtitles for his local viewers.
That moment when Great Scott posts and you get to it 30 seconds later...
Awesome!
"You can hear that the music transmission was also successful" 7:45 I only hear beeping.
Nobody will ever accuse him of being an audiophile. I can get at least 800 feet of very high fidelity audio by modulating my bench signal generator.
Most electronics engineers consider waveforms as music ^^
Not great, not terrible
that's what they said in Chernobyl when the radiation was 3.6 röntgen ( bud was 15000)
It was "Not great, not terrible" if I recall correctly.
@@kvlpnd
you're right
But then again, Chernobyl is a "tourist attraction". I have doubts this 433 walkie talkie will be a tourist attraction.
I have read a bit through the comments. One person already suggested to use these moduls in their "analouge" mode. The transmitter is simmilar to one of these TTL oscillators. You simply can bridge the data pin to "+" from your supply, and series modulate it with a PNP or NPN Transistor. This will give you AM with FM. The FM Part is just narrowband FM, but on a selective receiver you´d need to use slope detection, but these receivers usually are "Super regenerative receiver(s)"
I´m mainly talking about the green circuit boards (the ones completely on the left side in your frequency test, that just could take 5KHz).
On the receiver there´s a two stage super regenerative receiver. One transistor works as RF preamplifier, to get the RF noise away from the antenna, whilst the other one is the actual receiver. On your modules, at least the RF preamp transistor is mounted - the modules I have, the receiver misses the transistor (probably were lower price due to this fact got them as a gift)
On the receiver board, the output from the super regenerative receiver goes to a lowpass filter hence it´s quench frequency (thats why you only can transmitt up to like 5KHz). The 8 pin SMD Chip - LM 358 - only forms the sine wave into a square wave.
You can "tap off" the signal from the receiver before the LM358 chip, and so you can make complete analouge audio transmission. All you need is a modulator + microphone amplifier on the transmitter side... and a small audio amplifier on the receiver side with "tapped in" audio pickup before the LM358.
Practically
- To get the transmitter to transmitt AM -
Bridge "Data" to "+ UB" and take a standard NPN Transistor. Use double supply voltage, and tap the transistor between
"-" of your transmitt module and ground. Now use a 1M Potentiometer, and a Multimeter. Connect the 1M Potentiometer between base and collector, and have it adjusted to "1M" at the start. Now decrease it´s value,
untill you reach about the half supply voltage on the module.
Via a 100nF capacitor and let´s say a 3,3k resistor (random values) you can now put Audio on base of the transmitter.
The audio would already be received from the receiver, but it would be extremly distorted because the LM358 converts the sine wave signal from the regenerative receiver to a square wave signal.
Take an amplified speaker, hook one pin up to ground from the receiver module (while the transmitter is on, try with a low volume level on your phone with my suggested values) and use a let´s say 10k + 10...100nF (whatever is in the parts box) between "audio in" from your speaker and the connectors around the LM358 - one connection will be "audio out" from the receiver. If you find it, you will hear your music over the speaker.
Later if you want to use that "concept" you might need to add a lowpass filter between your receiver module and an audio amplifier Chip, because some remains from the receiver´s quench frequency might be left, and block / inteffer with the audio chip (very quiet, could start motor boating if connected to the same battery).
For the transmitter you don´t need to use the full voltage. If you lower the voltage the "AM percentage" will increase, whilst the FM percentage will decrease, but "good" AM will cost a lot of TX power (like going down from 10 to 0,5mW)
Anyhow, since the receiver is a wideband super regenerative type, it won´t care about "that bit" narrowband FM, but
if you´d receive this on a more "proper" receiver, that has AM option, you´d need to use slope detection for it.
I´m talking about the green modules ... some other modules might use a more "fancy" "Superhet" receiver.
Regarding the 1M potentiometer... maybe a 250k might also work... I don´t know how these transmitters react
to overvoltage. TTL modules "can take some" but I´m sure it´s not good for them.
I´d appreciate it if you´d give this a try, but since my comment is just one of many... I´m not really expecting much
I'm very impressed JLCpcb is still operating now. I bought 4 boards yesterday.
7:16
You killed my ears :'(
8:35 killed mine :D
Have been following your channel since long & have learned a lot.
Always heard your voice but really pleased to see your face, great work man keep it up :)
Thanks, Scott. It's inspired me to making wireless subwoofer. I don't need very high bandwidth rf module because my sub only need maximum 500hz.
I created a 15m walkie-talkie with my bare hands! I made a cup with my hands and held them to my mouth. For receiving, I held my cupped hands to my ears. I think that I could get more range too if I raised my voice.
I want your circuit sir
Hey...finally "let's get started" has his face out of hidden. Great Scott!!! Your projects are awesome!!
Is it just me or "hh" inhaling/gasping sound increased at the start of each voice audio clip?
Once you hear it, you cant un-hear it. It happens in every video :(
@@emyalfaro The problem is that if he removed it then everyone would notice that you can never hear his breath.
To get rid of the 5kHz frequency, perhaps a band pass filter can be used... You can cascade the LPF with the 41kHz cutoff freq with a high pass filter > 10kHz or so
I was thinking that a band-stop filter could probably do the job. At the very least, you could use a series LC circuit to short out the 5KHz signal, though you could probably do better with a Butterworth or Chebyshev filter.
I like the new new presenting style with more talking to camera! Good video!
Well thank you
@@greatscottlab but please find a way to increece the audio quality
Hey your arduino walkie talkie worked . I tried andreas spiess solution, placed a potentiometer instead of resistor. After few tries, it worked like a charm, covered distance of probably 100 meters
GreatScott, Andreas "The Guy With The Swiss Accent" Spiess and Marco Reps are high in the top 10 of my favorite youtubers :)
While studying electronics and communications engineering, they teach us that we only use a bandwidth of 4 Khz when it comes to voice/speech transmission so technically the first tx rx pair is actually decent enough for use in a walkie talkie! That 4 Khz even includes the guard band which results in a useable spectrum from 300 to 3400 Hz.
From what I know, you should use the high frequncy TX signal as a carrier. Insert audio into it.
In the RX section, you must separate the carrier signal from the audio, then amplify the audio.
Just like FM TX or AM TX. On FM TX, you affect the carrier frequency range. In AM TX you affect the carrier amplitude.
I learned a lot from this channel
Man, I do not recall seing your face before. Is like a new age for Scott channel. Good to you, brother. Keep the excel videos.
Best electronics & mad science channel ever!!!!! Keep coming amazing stuff Great Scott 👏👏👏
Here's something else to consider:
The reason you may want to bring an Arduino back into the mix is to use it to create a form of buffer. The idea is that if you buffer the signal, even for say 100 transmissions, you can use that to avoid choppiness. Of course, the transmission would need to be slightly higher than the buffer size so it can catch up, which in turn in a poor man method, results in some dropout of single packets, but that would be my basic, noncomplicated approach.
You can transmit and recive analog signal (using the first pair TX/TX boards) if you bypass the comparator on the receiver, the 8 pin chip normally is a lm328 amplifier configurate in one half amplifier and the other half like comparator, this last one is what you need to bypass to get an audio signal
I was remembering my master's time by watching your video. Anyway, Gr8 video and I am going to recommend your channel to our students. 🙏🙏
I love this video. I didn’t know you could generate a PWM signal via a triangular wave
if you want a decent range on those, you can get it by building yourself a dipole antenna to replace the monopole. I've even built a crude yagi antenna for use with modules like this, just with one guide element and one reflector element. there's some calculators around that can make it easier for people not so comfortable with antenna design to build their own antennas.
fortunately, these are relatively low frequencies, so you can be a bit sloppy with your antenna construction and still get decent results.
Not trying to be critical here, just suggestions. Enjoyable video and well shot/narrated. I appreciate the effort. I've been using RF modules exactly like this for at least 22 years now. I've always used them to send serial data (9600 BAUD max is typical due to bandwidth limits) and most people have used them this way and that's why there's so many microcontroller and Arduino applications presented everywhere. Using them to send PWM modulated "audio" is an out-of-the-box idea. However, RC model radios have been sending PWM modulated analog values exactly this way for over 45 years. It works great for RC because the sampling rate of the analog channels is maybe 20 to 60 Hz, not several kHz. The RC radio can convey many analog channels on one RF carrier by sending several pulses as a string, like a short burst of pulses, followed by a pause to be used as a sync. At the receiver, a simple counter is used to separate the pulses and then each pulse is "stretched" to the standard "1ms to 2ms" range and then finally sent to a specific servo.
I think the reason the receiver output sounds so bad is that it's not really demodulating the PWM signal but is instead attempting to filter out the frequency of it. Remember that the audio info is encoded just in the dutycycle, not the amplitude or frequency and a simple bandpass filter cannot separate those. Think about it this way, if you filter the PWM frequency out completely, nothing would be left and you'd get no audio. Conversely, filtering it less will retain some of the PWM signal and certainly you will hear it. The trick then is to properly demodulate it. Maybe pass the PWM signal through a diode, then resistor, and into a charge tank consisting of a cap with parallel resistor referenced to ground. This converts dutycycle to analog. It is basically a peak detector, like a cheap AM demodulator. Adding the resistors provides a means to control the cap charge and discharge rates, thus recovering the audio. Then pass the output of that through a lowpass filter to clean out the last of the PWM ripple and then finally into a power amp. The rule of thumb is that the PWM freq should be at least 10x the max audio freq that you want to pass, but the bandwidth limits of the system might force it down to the theoretical minimum of 2x (re Nyquist)) but then it'll definitely have noticeable PWM hum no matter what you do if using a single stage lowpass filter. Even a well tuned multi-pole filter would have a hard time separating it completely out. Brick-wall filters are generally not so simple.
Also, a source for audio distortion, the 555 timer waveform is non-linear, not an ideal sawtooth. There's an old chip MC34060AP that can directly convert 0V to 3V analog into a stable linear PWM signal. Sorry it's obsolete but there's likely a modern replacement within DC/DC converter category. Alternatively, using a cheap opamp and a few discrete components, build a simple triangle generator (tech term is an oscillator based on an integrator). Yet another possibility might be to send the 555 square wave output through a pair of LM334Z constant-current source ICs into a cap. I said "a pair" because I don't think they're bi-directional so I was thinking a pair of them connected in reverse-parallel might work. I'd have to try it just for fun. The general rule is that if you charge/discharge a cap using a constant current, the voltage will be linear and the triangle would be perfect. Also, using a polymer or mica cap for the timing cap makes it temperature stable so it's value doesn't drift all over the place. Ceramics are cheap but loosely spec'd and sensitive to noise and temperature. One last thing, there are many cheap solutions for connecting to standard 0.1" pitch header pins. No need to wreck them by bending them and soldering wires directly to them.
Cheers to all and happy hobbying.
i loved the old intro format too, but i love the new one too! you look good on camera
Few recommendations for improvements: try to use decoupling cap between pin 2 of the comp and pin 6 of the 555. Also you may use voltage divider and adjustable POT resistor to vary the level of the output from audio circuit - shift up and down. This may produce better PWM that improve on audio fidelity. Also you may use very weak pull down resistor on the Data in of the XMTR, if it is floating from the XMTR board module. If the XMTR board allows powering from higher voltage then you may try it for longer range, tinkering with the antenna and its impedance also may boost the communication range. Apparently the XMTR-RCVR pair modules are not designed to deal with those kinds of so called PWM wave forms, thus a conditioning circuits maybe needed as I described above. In Radio circuits, it is vital to insure impedance matching on input / output ports for both XMTR and RCVR circuits, not only on RF circuit (here you can not do anything about it, unless you tinker on the module board) but also the audio circuit.
Hello to the union of people who are watching this late at night. 11:37 pm to be specific.
*YES*, I'm that fascinated and amazed at his videos that I want to watch them as soon as possible
your videos are always outstanding Great Scott
you are really amazing i love how you explain each detail
i'm student and this video helped me alot with my project 🤩🤩
*my big takeaway from this project is that **_take me home_** is on your playlist :-P*
I like how much enthusiasm you put on your videos, keep up the good work! :)
I don’t suprise anymore. I was sure about walkie talkie and you have done with it! Thanks for the video.
One of my favorite channels .... wow, great work, allways surprise me
Hearing you breathing after everything you say is blowing up my mind 😂😂.
I love your videos
Can't you use an OpAmp in a substract form to remover the unwanted fix frequency on the output? or the delay is too high?
The problem would be to line up the frequencies. If you don’t get it exactly right, you’d be adding instead. A low pass filter or band-stop filter would be better.
Finally! 'been waiting for this video for so long. I am always to lazy, to order the stuff i develop, so i firstly watch other people doing it :_D
Great videos by the way!
Thanks :-)
Great channel mate! Keep the great work up... Also hope you are safe during this nightmarish pandemic.
They survived two world wars, do you think this "made in china" low quality flu will make any harm to them?
@@joshtr4645 LOL
i remember the 1st video, you wanted it for riding your motorbikes with your friends.. i know you will come back to this one until you crack it because of why you want them.. cant wait to see you crack it.. : )
Pl. make videos on how to charge Lead Acid Rechargeable Battery (4.1 ~ 4.7v DC)!
I am awaiting for Portable Bluetooth Speaker to be made by renowned and our favourite GreatScott on their next iteration!
Great video Scott! Great to see your troubleshooting process even if results not amazing
I hv sm fr module ( 1:00 not that one ) , but i wanna use it to make cheap rf tool for me
I wanna make RF frequency analyser with serial port and 2nd portable display interface .
But i don't know arduino programming
I wish you make video on it.
Either go full analog or full digital. Try out RpiTx, it works amazingly well. You just need to figure out a way to attach a microphone to the raspberry pi zero and you can transmit on 0-900Mhz.
I've just builded my own automatic greenhouse based on the Arduino with Solarpower, Sensors, Waterpump and vetilation a few years ago.
The only missing Thing in my Setup is the LoRa-Wan that i now had to have 😉.
Great Scott 👍😁
1:16 it looks like he is dead on the inside XD
Has the walki talki finally got to you or do you feel sad for the wasted PCB's
;)
hey Scott! Been following you for a while and I have to say that seeing you in the videos definitely make them more interesting! Keep it up!
Greatscott is always great, I'm blinded by your schematic, will be great to receive it by mail.
I like the way you doing the show ☺️
@GreatScott! - instead of using a trim-pot variable resistor for your audio input, make a low pass R-C filter from the output of the 555 to ground, which will give you a DC level, at 50% of the triangle wave amplitude, use this voltage and connect to the lower end of a trim pot, connect the wiper to the op-amp input and connect the 'top' of the trim pot (which is now your volume control) to the audio source via a DC blocking capacitor. This arrangement will 'auto-level' so you always have 50% above and below.
Also, on your output amp (TC4423 I think?) add a DC blocking cap to the speaker, those gate drive IC's don't like static DC current and you'll overheat the top of the totem-pole.
Apparently as your intro starts my mind subconsciously starts the JLC PCB promotion 🤣🤣🤣
3:26 A small correction. It is a PWM signal, not a digital signal. Although there are only two voltage values, it is not a digital signal. The reason is that the duty cycle varies with the audio signal amplitude. An actual digital signal is created by measuring the voltage values at regular intervals and storing them as binary numbers in a process known as sampling.
Got to say that's pretty impressive for such cheap device! Thanks for sharing the idea! Stay safe!
Now that's a great episode we wanted....
Great job, there's always room for improvement and i love that you're always trying to better your designs. keep up the good work.
Well the FS1000A can transmitt upto 200 metres while using 12 volt supply.
Big fan from India🇮🇳
Hello sir, I made this receiver and transmitter circuit using 433 Mhz module but I can't take any signal from speaker and also any sound my voice. Can you help me? I have to make Wireless Audio Transmission.
The 433MHz band is used by key fobs, remote controlled socket relays, and wireless tire pressure guages. Prolonged use of this walkie-talkie might jam those other devices. You should warn people that if they build this, only use it for four very short infrequent communications.
This time I got the notification
Perfect :-)
@@greatscottlab He may be one of the algorithm's samples, I have all notifications on and I didn't get it :/
Great video anyways!
I leaned that maybe it's cheaper to pull apart a cheap commercial walkie talkie and check it's configuration than it is to try and start from scratch, lol. Great effort though, keeping with the "only know if you give it a go" tradition.
Your videos are very enjoyable. Thank you.
We are experimenting and learning, so, the video was fine.
Try inserting a low pass filter in your audio path to limit the bandwidth of your audio signal to say slightly below the maximum allowable input frequency of your RF module,
5:12
One thing to know is that if you just want to create a Walkie-Talkie (to exchange words) then you can restrict the frequency between 300 an 3400 Hz as it's the common frequency used for VOIP calls.
For example, the highest frequency a (trained) human can sing is around 1400Hz. So with 7kHz, it looks very fine (unless you want to transmit high-quality audio).
Really good work and fun watching.
The range of human hearing is often said to be 20-20K Hz, but in reality, for most people over 25, the top end of that spectrum is cut off significantly. It's usually around 14 Khz for most middle-aged people. Not that you'd want to use it...a traditional analog phone line's bandwidth channel upper limit is around 3 Khz, and that's about as high quality as most people expect to hear from a walkie talkie too, so really any of those modules, in theory, could work for this experiment.
Sir I don't understand what you explain but it looks great thanks
Amazing, this has more complex build than a Baofeng radio
It turned out it's not only me who gets green micro USB expansion modules and solder it directly using the pin headers to my circuit !
i will be very thankful to you for helping me on my humble request
Would love to see an episode dedicated to tube amplifiers. Trying to make one myself (I've found some old soviet 6n3p-ev tubes) and can't get my head around calculating the cathode and anode resistors.
Love your videos dude. Keep it up!
Great video, lot's of useful information for us "beginners." Keep up the good work!!
Hi! I am a beginner with electronics and I have a question: why is the low-pass filter behind the amplifier and not before the amplifier? Would it not be much easier to filter the small signal with smaller components and the amp would have to work less hard?
What am I not understanding here?
Love your videos Scott!
Try it out and see what happens. If you use a band pass filter before the signal is amplified there will still be noise present in the output signal. If you amplify the signal before filtering, you end up with the noise and desired signal seperated in frequency making it easier to find a band that can filter out the noise.
@@Blobcraft13 Interesting. Thank you! I will try it out next time when i am tinkering!
Why do the frequencies get separated?
You mean the signal to noise ratio or is there an actual shift in frequency?
Does the amp act as a lowpass as well?
So they are not communative? .... I'm sorry .... my math skills are so laaacking -.-
@@SciFiFactory technically it shouldn't matter if you filter it before or after, but for me, amplifying it first give me a bitter idea of the frequency band that I would need to reduce noise. If you look at the output before amplifying, you'll see a big mess of actual signal and noise. If you amplify the signal, the signal itself and the noise will take up more room on the oscilloscope, allowing you to get a better idea of what parts are noise and what parts are signal. It's kind of hard to explain, if you have an oscilloscope I would try it out smd you should see what I mean.
@@SciFiFactory the amp wouldn't act as a low pass filter, but an active low pass filter contains an op amp, so I see why you would think that. If you were to build a circuit to amplify and then filter a signal, you would need 3 op amps (assuming you're using 2 active filters). You would need one op amp with an input and feed back resistor, the ratio between the two creates a gain. The signal is then amplified by that gain factor. After the signal is amplified, you would have the low pass and high pass filter in place to cut off the upper and lower range of the signal. So you would need to know the highest and lowest frequency of your signal to construct the low pass and high pass filter. I amplify first in order to easily see the highest and lowest frequency of the signal. I've read online the it's best practice to amplify first in a lot of situations, but I'm not 100% sure myself.
You are FANTASTIC....
Best regards from Portugal
This was very thought provoking
Scott put a warning message before the high pitch noise !
He can't hear it. His hearing range doesn't go that far. Different people can hear different ranges. Mines screwed and I can't hear above 16khz ;~;
Was waiting for this video...love from india👍🏻
Good enough. It sounds much better than the first revision).
I think it should improve the sound quality:
Add anti aliasing filter (1 or 2 order lowpass filter) and choose sample rate respectively. Audio signal spectrum has a frequencies from 0Hz to 20kHz (appr.). So when you try to convert audio signal from analog form to PWM form with a sample rate lower than 40 kHz the aliasing appears and creates additional noises.
Thank you for your videos.
Btw, you can try a 3 kHz low pass filter and a 6 kHz (or more) sample rate to achieve a telephone quality. It's enough for communication like walkie-talkie.
Great video. Seeing the failings and shortcomings prompts discussion and encourages people to get involved. I don't know how to fix the circuit, my first step would be to straighten the antennas, but other than that I wouldn't know.
I'm surprised how difficult it is to transmit some low quality voice audio over a short distance, when walkie-talkies feel like ancient technology
Infra-red transmission works better over short distances.
It’s not that difficult, it’s just that the design is terrible for transmitting audio. The modules use on-off keying which is not really suited to produce a quasi-analog-pwm signal for audio. Low pass filter is probably as beefy as it should be for aliasing.
I was like why does this dude sound so familiar...then i realized it was GreatScott lol
Great project! Thanks for a very informational video :)
A good basis to start from. Thanks for this.
This is so great oh my god. I was literally just thinking of what to do with these. I bought quite a few of them thinking wireless would be usefull.
thes transmitter modules actually can transmit audio, the data pin on the receiver has a comparator. therefore for digital signals, on the 7th pin on the chip if i remember right, theres the analog signal not passed through a comparator. just attach a wire to the pin.
I really like the raw, back to basics of this project. Here are my thoughts. Effectively you have a digital pipe with errors and you want to transmit voice in the best way possible. This topic has been covered to death of course for mobile phones since the 80's and the answer is ... voice codecs. What would make a really interesting project, is not to add one of the old voice codec chips, but to find a SW version and run it on an Arduino.
I have the receiver that got the best frequency results in the video. It is really surprising how good it is. I can use it through three walls over 10 meters and still get 95% of the data.
What do you think about sending the audio with packets? You start recording signal when i reaches threshould level. When audio level goes back to low - you compress signal in some way. Then send it as digital information. Yes there will be slight delay, but quality should be much better.
Well, it needs 2 pairs of Transmitter & receiver module?
Now encrypt the signal
Honestly his voice is studio quality
It seems that everyone has all of their components sorted so neatly. Do you have a link to those bins that you use?
just search for tool drawers on amazon
Great work as always ,, Great Scott..!!