Using an NPN Transistor as a Relay
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- เผยแพร่เมื่อ 16 พ.ย. 2013
- One more thing one can do with an NPN transistor is use it as a relay. Basically here I'll be using a 3.5V source to control a 12V source to power a strip of LED lights.
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I'm so glad I came across your video. I've watched so many others and read so many forums trying to work out how to turn on an LED strip from a low voltage source (arduino). Your vid and drawing made it very easy to understand and I just tested it and got it working within minutes! Thanks :)
Good video and "Bless you" to the lady sneezing.
this is great. i couldn't figure out how to do this exact setup for the life of me. but this video showed me 1 for 1 what i need to get my project under way. thank you!
DAMN all you haters out there! Yes, he misspoke; he should have said to attach the led's to the collector, and the emitter to ground, rather than the opposite, but his basic concept is sound & at least he's trying to share his knowledge with others so that we can all enjoy this exciting hobby! For all you who want to slam this video, I have one challenge: YOU show me something BETTER!
Simple and to the point. Appreciate the vid. I was trying to find a way to switch a circuit with an external power source without actually having to get a mechanical relay/contactor involved and this should do the trick!
excellent vid. just needed this to get my circuit working. worked a treat. thanks
Why the downvotes? Great video, fixed my issue.
The worst video production ever but the content was simply awesome, this solution helped me to activate a circuit with a only 2 volts trigger source, thank you so much for this video
Quite informative and helping me with a project i am currently working on. Thanks
Such a fantastically manly chin. This coupled with the glasses makes me suspect that this guy is indeed a super hero in his mild mannered civilian form. Keep looking to the skies, you will see that I am right eventually.
Thanks for your tutorial! Needed a little recap on transistors! Going to switch a 12v RGB LED with my computer harddisk activity led :). Going to sepperate it with an opto coupler! This circuit made perfect sense! Thanks!
Now I can get a job turning LEDs on and off
Yes. I took the liberty of borrowing your circuit to create an On Off switch without the need for a relay. It's cheaper to use a transistor as a solid state relay. Thanks a lot!
You helped me very much sir thank you. I didn't know that i should connect both grounds together...
After see this guy I decide to make my own channel. If he can do that poor video and I saw it, and he got a lot a good comments, then I know I will have success.
Glad I can inspire you :) never give up
That's not very nice.
In Npn transistor emiter is grounded and positive is given to collector
Nice demo! It would be interesting to see how this circuit degrades as the voltages rise.
thanks! great video!
question: n channel mosfet would do a better job?
If it's a spst relay it would work but would need some real modification if you need to substitute a spdt relay
Hi thanx for sharing - great video yet again
CAN I ASK A QUESTION... I need 12 5 and 3.5v for a large project that i am doing. Could I use a Computer 250w 240v power supply that gives me the voltages and amps (and more) that I require. thanx
1. its a transistor switch, not a relay
2. with NPN positive connects to collector, not emitter with load on high side and transistor on the low side (eg: a low side switch)
3. you're getting confused with a PNP transistor, were positive goes to emitter and load is on low side and transistor is on the high side (eg: a high side switch)
Sure about that? I was on the understanding that NPN was neg from source to the collector and pos from switch to base then neg back out the emitter to the neg side of the device. I'm sure that's how we were taught to do them else would that make it an NPP or PPN?
EDIT .. wait after some thought and more looking .. I'm guessing you mean right rail wrong direction? Load on the collector side and the earth/0v/neg of the batt/source on the emitter? In which case I can understand and work with as well (the old thing of P->N when it's actually N->P gets me. I look at the circuits particularly for diodes and stuff that up forgetting they still diagram it in reverse. However does the base still share the emitter or is it now the collector? Or does it matter?
I completely agree with you. This right here is fundamentally very wrong from his explanations
is it ok to connect same ground for 12v and 3.5 v in an emitter...
Thanks, was just what I was looking for. I basically want to connect a bunch of LED's inside my PC case, and have the HDD light header power them. As the header doesn't supply the voltage needed to run them all, I knew I needed a transistor to do it, but didn't know exactly how....
may i asked 1 thing, in your video, that supply #2 will controlling supply #1 right? i not really get it..
omg!! when i touch the base with my hand(only the base) the led strip lights up just a little bit...and why is my transistor dropping 3v? i used 2 aa batteries(3V) and get ground to ground, positive to the base trought 10k, ground of supply1 to collector and ground of the leds to the emitter. everything works but when i measure the led input voltage, it's around 9v instead of 12V....
Which NPN transistor did you use. The video did not specify ?
Thanks
What transistor did you use for this application? There should be a number stamped on it. Thanks
I tried it with a solar panel but only problem is that the led only goes on when it's daytime and turns off when it's dark.
Anyone knows if a NPN can really be used to turn off an LED when light is present?
thanks heaps... I had been trying to get this exact thing done.. but kept failing coz I didn't join the grounds. thanks for not making it overly complicated as well.
VERY GOOD VIDEO
I need to do something similar to that, but instead of a LED belt I have a 12v buzzer and instead of a 3.5v battery I have a 1.5v circuit (smal digital clock/alarm).
Wich transistor and resistor should I use to make it work?
Anything over 0.7v should trigger most NPN transistors; the trick will be making the buzzer work -- does the buzzer just buzz when you apply DC power, or does it need a waveform (like a normal audio signal)? -- If the former, you can just hook it right up. If the latter, you'll need to build a simple wave generator (I think a triangle wave generator should be pretty easy to do with a DUAL OP AMP IC, just google for "triangle wave generator op amp"), and then have it power the wave generator instead.
I can understand this subject, but I don't know how to choose a especific transistor for a project between many models, can someone help me ?
how can you give positive side to the (e) NPN transistor ?
After watching your other video, I totally 100% understand what you're doing. A little messy, but it's pretty good. (+1 : 177)
Grande amigo. no entiendo ingles , pero entendí todo el proceso y muy fácil . Saludos desde Chile
Dear Michael, I am trying to make a Pulse train that can act as a PWM for my RC helicopter at 38 kHz. Would this circuit be viable?
thanks allot dude
very helpfull ,...god bless
If I were to use a PNP transistor, how would the circuit be different.
Questions? Like the video:) Then you should connect the leds in the emitters side.
As a switch of course
I didn't listen to the video so maybe you explained it. If you take the output for your led's off the top 12v and ground it is just on all of the time the 12v is on. How is this switching it on or off?
Nice video
hook a solar cell in place of the button cell to detect infrared from a remote control. Also replace the led with a small speaker to hear the infrared transmission from a remote control
A NPN with emitter to +12? .... uhhh yea sure. The leds should be in the collector and the emittor have to be connected to gnd. Also not mentioned in the movie, be aware of the maximum collector-emittor voltage of the npn you gonna use and the maximum amps the npn can handle. As example, the BC847 can handle 100mA. Let's say you have 2 stripes of 5Watt 12V leds, you have 10Watt's total, resulting in a current of aprox 833mA. That BC847 will blow up faster than you can see the lights going on >< :D
Another one: He is using a 3.5V battery. In theory, every voltage higher than the Vbe (base-emitter), should result in the transistor going from saturation to open. That base-emitter voltage is (varying per type), around 0.6-0.7V, because it is a kind of diode. In the datasheet you can find this Vbe voltage. So, a 1.5V battery would have resulted in the same result.
Is it work by using 3.5 v instead of 12v and 1.5 in place of 3.5v,to operate a 1.5v dcmotor
is it okay to use a 5v input instead of 3.5v , id like to use as a relay for my arduino project
nice man thanks for the video
is your mom ok? Bless her
nice..... BTW what is the minimum and maximum source to trigger the transistor? and any NPN transistor can be use to that?
Mark Dave Granada you need to look up the datasheet for the transistor you are using. Some transistors can be triggered just by touching them
aldeed i know that for a fact, I've used them for touch sensors in my arduino projects
Great explaining and useful, however, don't use your hands to trigger the trigger because a button for the light circuit would be simpler in how you showed that.
hey , m using tip31 npn transistor, and had given 12 v from adapter, and in place of 3.5 using 5v from arduino , 1.6 kohm resistor appxdont knw why its not working , ...................
Make sure all the connections are correct. Try flipping the transistor (he wrote it backwards on paper), and also try flipping the LED (since if you hook it up backwards, it won't work).
nice!
You should ve prepared yourself before you get started
How can I solve this circuit
when a low voltage Source control a higher voltage Load OR low current Source control a High current Load ,,you can call it Relay Function. if you study any relay you will find out control side represent either low voltage or low current to control Higher current or higher voltage LOAD
I apologise for the loud snoring, folks.
That's just using it as a switch to turn something on.
A relay can turn things off or on when power is applied.
It's funny because you just repeated the title of this video quite precisely and i still get the feeling that you never did read the title, did you?...If you have no need to learn how to work with transistors as relays for low-current applications then what on earth are you watching this for?
Made ya laugh didn't I? :-)
You can turn things off with a transistor too!
Greate Tanks
It works :D
hi, i'm a 13yo french boy, your videos are very cool, before i watched this video i didn't understand anything of those transistors :)
Connecting collector to ground means it is a pnp
Jean Pierre Daviau thanks that explains why my circuit isn't working 😄
He connected the cathode of the led to the collector, not ground. So npn
So many people thanked you for this video. Why? It will not work if you attach the collector of an NPN to ground. Did you confuse NPN with PNP? I'd suggest you remove this video from TH-cam.
This application is perfect when used with an arduino nano as a 2-way radio repeater controller where the transistor switches the PTT line to High of the TX radio when the arduino detects a COS signal from the RX radio.
One flaw that could become potentially dangerous: You should put a diode in line with the batteries negative return line to keep the -12v from feeding back to the battery (a precaution in case it decides it needs to try and charge the button cell which is not rechargeable).
quien eres jak black delgado
this should be called "using a transistor as a transistor" LOL
good one pablo, you remind me of that funny comedian, Carrot Top.
No not really, I searched by this name exactly to try and think up a circuit diagram for a midway box between two radios and whilst his professionalism was destroyed by another post here, I learned what I wanted from the video. I'm used to trans being used as amps not relays and I'm green AF still on circuitry :(.
You can call me Parrot Cop.
This does not work for the simple reason that the transistor is connected backwards. Not in the one that you actually built, obviously, but in your instructions. If you connect your 12v to the emitter and the GND to the collector of your transistor, nothing is going to happen, because those go the opposite way. The base controls the flow of current from collector to emitter, wich emits the sum of the current applied to the base and drawn by the collector, minus some loss of course.
An easy mistake to make, and also an easy fix since everything else seems flawless =). Im not doing this whole elementary level explanation cause i think that you need it in any way shape or form, it's just for the viewers ;)
erm .. I'm a noob at this so admittedly easily confused .. but I think you miss-viewed. To me it seems he attached 12v on led to the 12v on rail, not the emitter.
He attached negative to emitter on led's and collector to gnd source.
etsme An NPN has a diode between base and emitter, with the cathode at the emitters side. He added 2 led's in series, positives to their anodes and the cathode at the emitters.. so.. a current should want to flow from the +12V to npn.. but hey, there's the cathode of the diode, so infinitive impedance, so no current at all (yes, a very tiny current, called leakage current), but general speaking, he did connect it in the wrong way. The diode should be in the collectors , having a resistor in series (to be sure the Ic won't be that high causing burn your leds) and the emitter to the ground (eventually, depending on Ibase a emittor resistor too).
this is called using transistor as a switch...
This is very important but your diagram is not complete and there is no link between it and the bulbs .when in showing your hands have obstructed the bulbs.
Better you use an opto-coupler.
Search "Electrical and electronics engineering Q&A" on android playstore and install it maybe useful for you.if you like it rate it 5 star.
Well folks at-lease you learn something you already know. hmmm
This is a useless video clip cause :
1) A relay is a device usually used to allow through the contacts ,switch high currents or voltages to a load ,using a low voltage/current to magnetism a coil !
2) why do i need 2 voltage supply ? after all u can use the same 12 volt supply to bais thru resistor the base of the transistor !
3) relay contacts must allow ac and dc currents ,that does not happen in this case !
Ever heard of an arduino? It cant handle a lot of current
The whole point of using a relay is to use a low current source to activate a higher current source, hence two supplies. You don't understand it because you don't have a need for it, but maybe someday you will, and you'll wish you had this video to help.
I FORGOT all tensiones by watching this video
Loughing a lot
This is a very amateur presentation with very poor circuit diagram. As mentioned in other comments, the information provided about connecting the transistor is WRONG.
You're mom is a poor presentation
+Michael Judge *your
Michael I was just going to say how I appreciated the vid and was thinking of subbing ... then saw the your (and it's your not you're but that's nitpicking) mum low foul swing and you lost me :(.
A better response perhaps would be "and HOW do I improve it". That way if they do have a better way we both learn something new.
There will always be haters and as frustrating as they are (not saying that Archi is a hater here) to swing back at them especially like that removes ALL your credibility and professionalism.
I'm sorry but all credibility and professionalism needs to be removed. As well as the wrong connection of the transistor, there is other extremely amateur content; for example the statement that any resistor can be used.
huhuhu, cool! Lets go break something! I hate numbers because there's, like, too many of them and stuff. FIRE! FIRE! FIRE! FIRE!
dude shoes fuckin sneezing in the background
NPNhaveonly3pins, Relay have >=4
Why does it sound like someone is dying in the background?
Luke Schmidt h by hh hi by
Low sound
Um, you don't connect the emitter of a NPN transistor to positive voltage. That's not how NPN transistors work. It's the same thing as if you were to try and connect the cathode of a diode to positive voltage. I don't know if you realize this but the emitter-base junction is a PN junction. Just like a typical diode. Current doesn't flow from the emitter to the collector (in conventional current flow), it flows from the collector to emitter.
Additionally, if you are serious about electronics it would be a good idea to:
(1) Invest in a breadboard for prototyping - they are super cheap and good for demonstrations such as the one you are attempting to do in this video.
(2) Use common circuit schematic drawing techniques. Google "circuit schematic" and you'll see that out of the millions of schematics, 99% all follow the same common formatting.
you guys are so childish, everyone is trying to tell him what he needs to do, where is your video douche bag?
silentscribes I don't need to post a video of how transistors work. It has been a fact of electricity for a while. Just pointing out errors in his instructional video.
Too bad and erronous
SVMS RemembeR dumbest comment ever
back vas ha ye
You Cannot use an NPN Transistor as a Relay...Do You mean You are Driving The Relay with the use of the NPN Transistor???? A Transistor can be used as a Switch or Amplifier But NOT A RELAY!!!!
not good
Downvote for inaccurate information
nauč sa kresliť
that was all wrong. it wouldnt have worked.
the connection is wrong, just saying.
Wrong information, Please remove this video
well it worked for me. I notice you don't have any relevant channels. Bog off
Your voice lower
boor
Wrong wiring, remove this video.
never ever show your full size of face.. it's sucks