How to use the XH-M452 temperature and humidity module
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- เผยแพร่เมื่อ 12 ม.ค. 2024
- This very common general purpose module has two sections - temperature and humidity.
Each section has its own volt-free relay contact. The heating section can control either heating or cooling (but not both) and the humidity section can control humidifying or dehumidifying.
If switching mains power or high loads I recommend using an off board relay with a 12V coil switched by the module's relay contact.
For safety reasons I always recommend having an extra safety thermostat in line with heating elements in case of relay or circuit failure. The safety thermostat can be a simple bimetallic one with a fixed limit temperature.
Each section has its own two buttons underneath its three digit display.
To set the heating/cooling mode and temperatures, start by holding the left button down until the display starts to flash. You can then adjust the relay-on temperature, with the left button incrementing and the button next to it decrementing the temperature. Holding a button down makes it count quickly after a slight pause. If you pause between presses too long the setting is stored and the display reverts back to normal mode.
Then set the heat/cool relay-off temperature by holding the second button from the left and adjusting as before.
If the on temperature is lower than the off temperature it will act as a heating control.
If the on temperature is higher than the off temperature it will act as a cooling control.
Then set the humidity settings in the same way using the two right hand buttons under the humidity display.
All settings are stored in non volatile memory.
Pressing the buttons briefly in normal mode will display the current temperature/humidity setting on that button.
To reset all the settings to factory defaults, press all four buttons down together until the display shows 888888.
Take care to mount the sensor module where it can't get wet or contaminated with oils or solvents. The humidity membrane may have its accuracy skewed if it is contaminated.
The search keywords to find these modules are "humidity M452". Typical cost for both the control module and sensor as a pair should be less than £10 shipped.
An interesting use for this module could be to wire the two contacts in series to directly control a small positive pressure ventilation fan. That way it could be programmed to turn the fan off if the air was too cold or humid.
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:- www.bigclive.com/coffee.htm
This also keeps the channel independent of TH-cam's algorithm quirks, allowing it to be a bit more dangerous and naughty.
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When the 5v side goes low the body diode of the MOSFET conducts pulling the 3v low, it later gets enhanced when the MOSFET turns on. When the 3v side goes low the MOSFET turns on, because the gate is biased on, pulling the 5v side low through the source. When I first saw these I thought it the most clever way to do the level shift.
Makes sense, cheers!
yep that's a very basic bidirectional shifter. pretty common when dealing with I2C chips.
Given the pinout on the sensor (1 data, 1 clock), I suspect this is using i2c (aka two wire or IIC) as a communication protocol to the processor. A bit of datasheet surfing shows that a common manufacturer of this module is Sensirion, and the slightly odd level shifter is actually taken directly from the reference design on the datasheet (interestingly they say 5v and 3v rather than 3v3). This specific humidity sensor is already deprecated with the manufacturer pointing to their SHT40 range instead. It looks like a fairly mainstream sensor; those raw chips can be purchased from the usual places like Mouser, Digi-Key, Farnell & RS in their hundreds - not cheap though - around $2-3/per in bulk means they are using a quality sensor (assuming they are real).
Only problem is that I'm convinced that all SHTx0 chips sold from china are unfortunately all counterfeit. The specs seem to be much worse than the specs in the datasheet, and the prices are suspiciously low compared to legitimate channels.
Those 20 ohm resistors also provide brute force power supply damping. "You can run [from trace inductance], but you can't hide," and without those resistors, you'd have high-Q poles within the switching frequency bands of many power supplies.
If you accidentally reverse the setpoints you'll run your device into runaway. i.e. if you put your heater in a/c mode it'll come on and stay on as the temp gets higher and higher. Same for A/C and humidity.
I am in my car pushing the gas pedal buy it doesn't want to stop, any advice?
@@user-yh7zc9ke4sSlam on the brake pedal and put the shifter in Neutral.
Self destruct mode :-)
Hi i think I have some problem with my m452 controller it's not turning off the relay after the temperature and humidity goes above the turn off limits i set for My egg incubator please help
Clive, if you're using android now, there is an option for "pro video" in the camera modes, where you can set your own white balance, but crucially the shutter speed and the iso, meaning you can eliminate the multiplexing effect of these leds
I did this with an rgb vu meter and produced some amazing visual effects
Open Camera.
@@MostlyInteresting nowhere near as good
What version of Android ? And when was it released ? Some of us don't change our phones as often as our socks.
@@michaelmoorrees3585 you can always update your phones software, go to settings then software update... Its been around for at least 3 years, and Clive has a later model phone than I
I have a 5 year old Nokia with "pro" mode in the default camera app. Nowhere near as good as OpenCamera for options. Still struggle to take decent videos of my LED projects though :-(
About the level shifter, I've seen (and used) BJTs in a similar layout. When the 5V side outputs a "0", the transistor works on "reverse active" region, where the emmiter acts as the collector, pulling down the resistor on the 3.3V side.
Always enjoying your videos, pretty instructive and sometimes a jolly good laugh! Keep the good work!
I wonder if that's why the 10kΩ gate resistor- so they can sub a BJT. I'm thinking the 20Ω may be related to short protection for when the user shorts the 3.3V to ground.
Thanks Big Clive. It sure does a lot for under eight bucks. Amazing.
Thanks again Clive. A handy device as a quick fix for central heating or a dodgy fridge thermostat.
Thanks for another great video clive
Have a nice day everyone 👍
Thanks, you too
That price point made my day, Inkbird is a manufacture of the humidification/temp I’ve been using for quite awhile for my growtents. And they are pricey . They use the same probe sensor as this one and made me want to look these up for cost savings on another setup I want. Inkbird has been reliable, but at this price I’ll allow a little failure here and there 😂 over time I began to remove the relays on the controllers and just soldering ssr’s to eliminate potential mechanical failures related to relay qualities. Other than price - the two in one small form factor has me liking the benefit of making my mess a little more tidier and cleaner looking. You made my day 👍 gonna go look these up 🍻
These are old DHT21 modules they're using the rest of for those kinda PCBs. DHT22 would be a more state of the art way to handle things. Switching out the relays is a VERY good step.
What kind of stuff are you growing? Anything with really particular needs in terms of temperature and humidity?
I always wanted to do similar PCBs with better components, but was lazy so far, as the Chinese ones are pretty cheap and doing what you need them to do... most of the time. But one of these days... lol
@@rebel4466 it was shear laziness and absolute convenience when I started ordering the Inkbird style controllers. I was knees deep in pressurized aeroponics ( lettuce tomatoes peppers ) total automation with ( don’t judge 😂) parallax basic stamp ii controllers. That pbasic is just so drilled into my head I’m able to write what I need when I needed it without having to think. So I stuck with them .
Ran opto couplers to control the Inkbird via the output pins and just soldering to the microswitch pads. To change night and day humidity and temp ranges depending on light cycles and such.
With the drain to waste of the pressurized aeroponics I was able to see down to the ml per hour differential between vpd enviormentals and light cycles so on and such.
But- what was cool about him posting this was I was complaining about the ever rising cost of the controllers as they rises because my setups are always changing and growing and multiplying 😂 I thought to myself why am I paying for convenience when ultimately the chambers are going to be upgraded again with a common control cabinet. I guess I got so lazy I just didn’t even think to look at bare bones systems till this video. Just kinda had my head every other direction . So this video was like the lightbulb that made me go “ darn it now I can save some money for other stuff “
The tolerances don’t need to be medical grade as in all my findings there is a broad range of acceptable enviormentals for my concerns. Just reliability needs to be addressed in event of temp runaway .
I’d like to eventually migrate all units into a programmable state to have a global input, but the older I get the more the brain spins but the wheels slow down 😂 enjoy your weekend
@BreatheScotland so true. One day I woke up and said it’s funny how when I was younger I had a million ideas and no resources, now; older. I have those resources but not the energy. 😂 somebody please slow down that clock, I think it’s running way faster than it used too. Be Well !
For all your grow room needs. 👍
@BreatheScotland CO2?
Beautiful solder job.
love this Mr Clive
I used one of these generic controllers on my daughter’s refrigerator when the thermostat failed. Basically the fridge became a freezer after the failure, and this sorted it.
Good timing. I'm in the middle of prototyping a modification to a dehumidifier using a very similar unit.
i wanted to design a positive input ventilation unit to help with damp and humidity and save a few hundred quid. already got the 70W heater. this sounds like the perfect controller. cheers
Thank you, this is just the thing I need for a cheap controller for my car wash.
This is perfect for drying and controlling the humidity of 3d printing filament... 👍
Those little Songle relays are pretty OK. I've "destruction tested" one of those (recovered from a damaged control module), flowing a full 10A (dc supply) and 5Hz switching cycle. It got a bit hot, but lasted well past the 24 hours I expected, and internal inspection revealed minimal contact damage despite the "deliberate abuse".
So if I understand this correctly...The SHIT chip tells you if the shit is hot and steamy or old and cold. 😂
I like the strobing. Camera. Interesting device.
Important in my experience: Don't trust important things with modules like this. I've had the relays sticking in the on position before and also unreliable ones not always switching. Of course you can absolutely get ones that are working fine, just a reminder, that it doesn't have to be the case.
Maybe not the thing you want to use to control the temperature and moisture for terrarium pets or similar.
Yes those relays do tend to weld shut as they age, and also fail as open circuit as well.
Thats why you use your own relay or contactor for high loads.
@@simontay4851 they're not talking about high loads. they're talking about unreliable functioning under normal switching. these relays are just cheap and shouldn't be trusted.
I really want to know and watch all of you videos.
I have a plug in humidity controller (apparently commonly used in the home hydroponics industry) and using it with a dehumidifier caused the relay to stop working, presumably due to burnt contacts. I now have a new plug in humidity controller and a plug in contactor device (again apparently from the hydroponics sector). Scary device with two plugs and a socket but I tested it and fortunately live is isolated between the plugs! I would repair the old humidity controller but the case is so cramped and design a bit dodgy, I wouldn't be confident of a good repair that would't cause a fire or something. The dehumidifier humidistat packed up years ago.
This may be a starting point to build a real nice controller. Here in the States, the HVAC industry uses 24VAC, with 3-volt DC programable thermostats that have to be manually switched between heat and cool. Even the best of them are a nightmare of battery changes. I thought I had a good one, but the weak battery clips, on each end, cause loss of control. Everything is junk anymore. The idea of using 2 of these, to also automate a humidifier in the winter, and a dehumidifier in the summer, leaves a lot of ideas rolling around. The AC usually dehumidifies, but on the third floor, we occasionally have issues. Adding a duct damper controller for time of day, sun beating against the house, or pushing more air to the 3rd floor in the summer would be great.
Nowadays only the cheap thermostats need batteries for main operation. Better electronic ones can use the C (neutral) along with R (24v live) wires for all power needs. My first thought for using one of these controllers in an HVAC environment is for changing the AC blower speed. On a fixed-capacity system running the blower slower provides better dehumidification but you risk freezing the evaporator coil. If the supply temperature is low or the humidity is low you should go to high fan speed.
Higher-end thermostats (keyword: IAQ) also have built-in humidistats and dehumidistats as well as the obvious temperature functions. They can get pricey though. For basic automations I would suggest using basic mechanical thermostats which are more flexible for off-label uses.
I've got a bunch of digital thermometer/hygrometer combo displays dotted around my flat. Once put them all next to each other, amazing how far off each other they were.
Yeh, the humidity in particular can be way off.
But once you figure levels that work you're golden
All it takes is working with multiple temperature measuring devices to realize there exists no such thing as "THE" temperature, anywhere, no matter what you use to measure. You'll be measuring the temperature of the air rising past the sensor (or stuck inside your allegedly "vented" case) and/or the temperature of the wall you bolted it to and/or the temperature of the PCB it's soldered onto and/or the temperature of the traces and ground plane on the PCB as heated by any other components nearby and and and... it never ends, and no two devices of different construction will give you the same number, even if you put them next to each other.
I use those Sensirion SHT2x sensors with the envionmental controller I've designed. They're very reliable and work at condensing humidity, which is very neat.
my issue with all the cheaper sensors is physical degradation/erosion of the board itself. I tend to run mine in high humidity environments, 80%+ and they all eventually rust and then stop functioning. They're cheap enough that you can just slap another one in there but it's really wasteful.
@@CRneu I use the round, sealed probes at 95+ %RH. They've been working for over a year, so I'm hoping they continue working. I can see exposed boards not lasting long in such an environment. How long do the exposed boards last for you?
@BreatheScotland Hello! That's a good idea. I think I recall that video. There are some good nano coatings now, too.
Great video! Nice change from the normal junk. 😆
I prefer using the MOSFETs (N), rather then voltage dividers, I use them a lot with my microcontroller projects when communicating to different GPIO voltage pins.
The Gate is wired to the low voltage side, when Gate/Source voltage (VGS) is below the threshold, and the MOSFET is not conducting it allows the bus line at the MOSFET’s drain to be pulled up by the higher-voltage pull-up resistor. The bus lines on each side of the MOSFET are held HIGH but at different voltage levels.
Interesting little board. When you went from the main board to the sensor I was kind of expecting a DHT sensor, haven't heard of SHT before. Main difference seems to be that the DHT chips use a one-wire protocol and not I2C (and can work with 3.3 and 5V). But they have the same restrictions with too frequent polling. I've experimented with a DHT22 on my Raspi a bit, and according to documentations you should only poll it every 3-5 seconds.
Given that in the real world, temperatures and humidities don't usually change all that quickly, I'd have thought that polling every 3-5 _minutes_ would be adequate.
The SHT20 is a nice chip. They work quite well. I have one in my 3D Printing Dry Box and it gets polled twice an hour.
I remember seeing a whitepaper or something from Philips/NXP/Nexperia (I don't remember which one exactly), explaining thie bidirectional level shifters using MOSFET and few 10k resistors as seen here. The MOSFET that particular article referred to was BSS138.
Edit : it was an Application Note (AN97055) titled "Bi-directional level shifter for
I2C-bus and other systems" by Philips
The SHT20 is an i2c device. I use them on pre-build modules with Raspberry Pi. The SHT2 and MCU use open-collector (or open-drain) outputs, so they only pull the bus low. The resistors provide the high level.
I'm wondering why they didn't use a 3.3V microcontroller in the first place? Driving the relays can still be done with transistors and the display is buffered.
I'm assuming it's because 3v3 is too close to the Vf of the blue LEDs. Having them on separate regulators also helps keep the LED switching noise from messing with the ADC in the temp/humidity sensor.
Many modern mcu's even don't need external levelshifting since they can do so themselves.
I agree but the MCUs they have easy access to in Asia are 10 for a penny...literally, Paduc springs to mind also here in UK the venerable 328p-AU is nearly 3 quid.
@@andymouse yep, they take whatever is the cheapest solution and in this case, this was apparently the one, despite it might not seem so at first glance.
@@Gin-toki Plus they tend to use the ones where they have the toolchain already installed, and many of these mystery micros are loosely based on the venerable 8051, though they may or may not have all the peripherals, and often include on die an oscillator that gives roughly an 8-20MHz clock. Saving 3 expensive components when you do not need great accuracy, is a big saving. Other one is roughly based on the 6502, because that is out of copyright, so is available as an IP core for many gate arrays, that you drop in and get a known core.
Hey Clive,
I have used those exact 12v relays in other projects. I want to warn you and others that you were spot on with the high power devices being unsafe. I used one rated at 10A to switch a 120VAC load I later measured (after the relay failed in quite a dramatic way) at 4.7A. It didn't last more than a few months of less than 20 switches a week. I've got another one that's only switching about an amp on a small blower motor, and it's beginning to give off quite a burned smell, tho still working.
They are used in PLC's the rating is for pure resistive load, On an inductive load say a hydraulic solenoid they weld shut, I have seen it dozens of times.
I buy them by the dozen, as I use them in heat sealers. There is a version with thicker pins, rated at 16A, but otherwise identical, that does last longer. However with using them with inductive loads I simply put a 276VAC MOV across the contacts to tame the spikes, which does help a lot with contact life, but yes they really are only good for a resistive load of 2A, or 5A at 12V. Using this controller I would use a 24VAC transformer, and common 24VAC contactors to drive the power side, and then put in a small power board with a 12V regulator IC, bridge rectifier and capacitor to power it. Better yet a transformer with a 12VAC tap as well, and the bridge and regulator, so it does not expose the 7812 to 30VDC on the input, as most modern ones no longer actually are rated to survive 30V input any more. Probably a 12V zener diode and a small power transistor in TO220 package will work, as the controller current is very low, so the transistor will not need a heatsink.
@braddofner6407
I'm currently using one of the same relays but with a 5v coil to control a 230V 2500W space heater with a thermostat and it's working fine for now.
The relay becomes a bit warm but I haven't come across any issue yet.
The current measurements I have done reveal that it's always drawing 10A or a little bit more but never 11.
And it's a purely resistive load, not an inductive one since it's a oil-filled heater with no blower fan or anything else like that.
@@psirvent8 Exactly as long as it is resistive it will last a lot longer, however I always interface with a Contactor or SSR.
@@psirvent8 Remember that relay has a rated lifetime, and at full load is only warranted to do 30000 cycles of operation. It really does not take long with a load like a heater to get to that cycle count. With a 1A load you get 150 000 cycles. And that is for the genuine item, the clones perform worse in real life, because they cut costs by using smaller contact buttons, as silver cadmium is expensive.
Controlling temperature is easy, controlling humidity is MUCH harder. I got your sensor on a remote switch that has dedicated inputs. I tried to make my shower fan run until the humidity level is satisfactory down. Easier said than done. There are commercial products that work well in my opinion but I do get endless calls from users thinking they are not.
Happy birthday Clive
This is how the bi-directional logic works. When the sensor is the source the mosfet turns on when the sensor output is low and pulls the microcontroller input low. When the microcontroller is the source and goes low it pulls the input to the sensor low through the body diode in the mosfet. This the low input state for the sensor will be one diode drop above ground, not all the way low. You are correct that the resistor in series with the gate is not needed.
Interesting little thing 2x👍
It uses a Sensirion sensor, but an older version - still a good sensor. I use SHT31, now I am in the process of ordering new SHT41, but directly from the manufacturer
Thanks :)
Always interesting to see a fast ceramic C connected via a long printed inductor to the very end of the power line. At least there are no spikes at the C itself. 😅
Now that's value for money.
Those 10k resistors around the level shifter also act as pull ups for the SDA and SCL lines.
10:33 is the best part of this video.
holy multiplexed led's batman, could have used your courteous blink/flash warning on this one
Great. Converting an old underworktop freezer to an egg incubator in the next few weeks.
Some of the boards marked XH-M452 use an STmicro STM8S003F3, (2.95 to 5.5V) which is very common on thesecheap Chinese boards. Others, also marked XH-M452 use the Nuvoton N76E00AT20 (2.4 to 5.5V). It's odd that they didn't run the MCU and sensor (max 3.6V) at the same voltage to save the extra parts. Perhaps they decided there wasn't enough headroom to run the blue LEDs and not damage the SHT20.
There are nicer LCD versions at slightly higher cost called XY-TR01 (TRO1?) which also use the Nuvoton. However they appear to use a different SHT20 based sensor which bizarrely includes a voltage regulator and two ICs. The voltage reg is fine - doesn't matter if it's on the mainboard or sensor but the ICs cost money and shouldn't be necessary at all. Bizzare because the competition and pricing is cut-throat to the point where they will remove a sub 1 cent capacitor if they can get away with it. One of the ICs, a 20 pin TSSOP, looks to be another MCU. Maybe the sensor was repurposed from another product that required the MCU and they have large stocks.
Sensiron state that to keep self heating below .1C you should limit reading rate to 2 readings/s in 12 bit mode (0.04C resolution), slower in 14 bit mode (.01C resolution). Accuracy spec is +/- 0.4C maximum .3C typ between 5 and 60C. It would be very surprising if they were genuine Sensiron parts given their cost. win-source.net, fwiw, claims 57% probability of "Fake Threat In the Open Market". It may be possible to detect fakes by reading the 'device specific serial number' which might be different, or not implemented in counterfeits.
Need to set one up to cool and de humidify my sausage and salami curing cabinet .First I need it to keep the humidity and then dry the area after the sausage casings get immaculate with bacteria
Clive, have you ever considered connecting to a programming header on a board like this and trying to dump the firmware? Running it through a decompiler could potentially reveal interesting things about its inner workings, similar to how the schematic can contain interesting design decisions. That's of course assuming the manufacturer hasn't disabled the ability to download the firmware.
Almost all electronics manufacturers enable a secure bit to lock serial interface or memory access and many chips are simply not reversed engineered or just OTP.
And this is assuming we know what's the MCU and find its protocol, which is already tricky with PRC chips. A lot of them use HVprog which makes the operation risky.
For such a basic application, it's simpler to sniff the I2C bus and write your own program from scratch. Or for educational purpose, this is simpler to analyze existing source codes already available. Though Clive doesn't make software content, just hardware ones.
The tricky bit is working out what chip it is. The software also often has a protection option that will prevent it being read back out.
There is some software available for download. I wrote some PIC assembly code for various test devices.
Very nice. Any way to change to F°?
I used one them little "W1209" boards to add a thermostat to a tiny micro fridge that uses the thermal tec cooling plate , I figure it would be far more power efficient if it turned self off when target temperature reached.
I wonder if the microcontroller on the main board is a nuvoton part i have seen a few nuvoton mcus on similar modules (temperature and timer).
Thank you for the explination but can you show us how to hook it up?
Cute level shifting. "Common Gate" 3V to 5V. Fwd Bias the diode, 5V to 3V.
That SHT20 reminds me of how supermarkets justify the prices of toilet roll with their price "per 100 shts", they do mean sheets, but we all know what our minds say... :P
❤!
it was interesting to actually see bi direction level shifters used. i bought 50 of them ages ago, just to practise soldering headers with. in fact it was only last week i learned they need a 5v supply, on HV, a 3.3v supply on LV, along with ground, and the LV to HV, or HV to LV signal. so it was interesting to see them discussed.
I thought they would use a DHT-22 module over the SH20 module, because it works with 3.3V up to 6V, and uses the 1-wire protocol. it's as accurate as SH20 (3.3V only) and cheap.
They are all slow as hell. I think not faster than 8 Second intervals.
Amazing and instructive video as always!
I received this module, and there are some difference, on the back 3.3V regulator and capacitors are absents, but module seems to be working. Probably because it uses AHT30 Temperature and Humidity Sensor ,which works fine to 5,5V, so 3,3V is not needed. Not big deal there.
Unfortunatly R8 resistor for the Green Led is absent, I can hear the relay tick. Can you please let me know the value of the R8 resistor.
Thx
The resistor for the green LED is 2K as shown in the schematic.
@@bigclivedotcom Thx you very much, indeed I saw then in schematic, and addedd a 2.2K resistor. Everything is working as should.
Thx
Good for indoor horticulture.
The good old 1117!
You should get some Magnesium Chloride and Sodium Chloride and set up a mositure test for 33% and 75%. I was surprised at how bad my humidity sensors were.
Have you considered changing your shutter speed so that you don’t get the rolling digits on displays? Should be able to set it to “180 degrees” or approx 1/48 or 1/50th of a second.
Very similar to Sparkfun’s bidirectional level shifter module.
Must admit I thought most modern processors were 3.3v these days. Would have saved the multiple power regulators.
Even 3.3v is old hat now. Newer micro-processors run on 1.8v and I was amazed to see a new Ryzen 9 processor running at around one volt (it can manage its own power +/- 20%) even though it's capable of supporting 35 watts of TDP!
Quite a few are fairly wide range. The PIC18 family I usually use are 1.8 - 5.5v. I'm guessing 3.3v would have been too close to the Vf of the blue LEDs, and having them powered by separate regulators keeps the PWM/multiplexing from messing with the ADC in the sensor.
Driving the LED displays might have been a problem on 3.3v.
This knob has been wondering how to hook up an attic fan to cool in summer, and also kicks in with high humidity. This may be the ticket. BigClive, what is the maximum size attic fan that you think this module can handle?
The contacts should be suitable for a fairly decently sized fan.
Just noticed 10A rating on the relay. Fan I have in mind is probably no more than 2A @ 115V.
This Temp/Humidity controller will be perfect for controlling my attic's nasty temps and humidity levels. And, at the same time help keep house cooler, less humid, prolong roof(shingles), etc. Thank you again! @@bigclivedotcom
if you apply masking tape over the display it improves visuals.
i would like you to test it at -10c, i have the xy-tr01 model of this with the big blue screen and when it goes below -9.9c it displays at c instead of a 1, so -13.2c is recorded as c3.2, does this have same issue? also you forgot to mention the sensor cable can be extended up to like 100 meters
Thankyou very interesting. Whats the MCU? Guess its an old one working on 5v .
Unknown MCU.
You should add a key to your videos to make it clear when they're honest reviews and when they're snarky or april fools-like. Love both, but I find myself focusing more on that issue than the meat of details in the video.
I wander if this would work with a low voltage heater, fan and humidifier for something like an animal enclosure. Where it would control a 12v heating lamp or pad. And a piezoelectric humidifier
"likewise when it stops flashing...." lol. i am still waiting for that! 2minutes 46 in. sorry everyone, saturday is a beer day, so i am a little over-excited.
👍
In other mosfet level shifters I've seen, the gate is wired directly to the lower voltage source without the resistor. I wonder why they bothered with it here?
I wonder, why not just use a 3.3v microcontroller? I assume the 5v unit must be much cheaper than any 3.3v alternative to go to the bother of having an additional voltage regulator and logic level converter on the board. Or maybe the relay drivers would be too expensive, but that seems unlikely.
Temperature and humidity don't change very fast. You really don't need to poll it any faster twice a minute. Once every two minutes will satisfy most applications.
Is it an outdoor controller? Because I want one right now...
I have a question since I'm a lay person. I recently became aware of the existence of zero resistance resistors. Obviously, they have a use, but I can not conceive how except single side board design to route electricity.
They can be used to bypass a resistor that is optional or to enable or disable sections of a PCB. I used to use them in my single sided designs.
I tried building one of these about 20 years ago, around an Atmel dev board (arduino precursor), for an embedded systems college class. It mostly worked, but working with the SHT was surprisingly difficult, probably because soldering to the tiny pins on the SHT20 demo board was nigh-impossible. In the end I could demo turning on the circuit via relay, but not actually monitor the temperature/humidity...
The market's come a long ways since then, given that the SHT demo board itself was easily twice what the full system with relays goes for now. Add to that the cost of an Atmel dev board at the time...
could build the 3/5 volt mosfet layout to see how it reacts ...
It's a wee bit chilly on the bench today.
Absolutely fine for me.
Almost on topic question - does anyone know of a temperature sensor(s) adapted to clip on to a copper pipe to measure flow & return delta T on heating systems?
The HVAC industry has some interesting bluetooth temperature senders.
SHT-20 made me snicker like a child.
Hello, can you share what recorder app you use for video?
Open camera.
I wonder what the difference would be between an SHT20 and the old AHT20. The latter is dead cheap, but works well.
Not sure if they'd be compatible.
Those relays (common on many cheap Chinese controllers) are terrible even with light loads, I replace them with Omron relays and I also have a drop in high side SmartFET board that I designed with the same pinout as the relay although obviously that's only good for SPST normally open applications.
Weird device. I work in HVAC and our thermostats in the US all work off 24vAC circuits and the equipment contains contactor relays for controlling 120/240vAC.
I'm trying to determine how this would be useful on my side.
I want to find one of these that will let me connect all four ac,heater, humidifier, dehumidifier and stay in the range set.
why is the display doing _that_ ? i am only 1 min in and i cant wait to find out! (i bet it involves PWM, but i really know feck all) talking of PWM reminds me of multi-plexing, i have had a great time with that, of late. i bought a bunch of SMD practise things from ebay, they all use 555 with 4017. after making a few i enjoyed it so much i bought some DIP 4017s to join the 555s i already owned. first i made a comedy motion picture bomb timer. i used 555 to make 1hz pulses and used 4017 with 10 leds, then with another on the carry out(interestingly the carry out pulse lasts for as long as 5 pulses) with another 10 leds, so it counted to 100 then set off the bomb (lit white LED). this was jolly interesting. but then i wondered, what if i used 2 4017s, with their outputs linked, using diodes, so it needs a pos output on the 2 to light up a led. it worked, and it seems i invented multiplexing. so that was nice.
Well that made me feel better, have a virus thing. 🥺
I wonder why they did not power the complete device by 3.3 Volt only. Saves a level shifter.
Hi please help me out my m452 is not turning off after the temperature and humidity goes above the turn off limits i set what could be the problem
Double check the turn on vs turn off limits. If the relay LED goes off, but the relay stays on then you may be running loads that are too high for the relays to handle, causing the contacts to weld.
I was heating some food and heard the clicking of the controller from my video and thought my food was exploding
I love these little Chinese devices that are shipped without a manual or a Chinglish conversion.
Are you aware of a circuit like this but it doesn't use fixed values, but the difference between the two values? Basically if A is greater than B turn on etc.
I've not come across something like that.
I guess you would actually want to have hysteresis like this chip when switching relays, or you could get fast on and off again switching when the temperature is just around the set point. Would wear out the relay and whatever appliance you're switching pretty fast
Very strange that they didn't use a DHT-22 module at 5V and not be messing with +3.3V! noobs!
Since every die has ESD protection diodes at every pin, which are rated to 5mA, one can use a single 4K7 resistor between the two devices.
I have done this dirty deed with great success in the past.
When the signal passes 3.6V, the diode will clamp the rest and be done with it.
I came across this by accident, when the PIC I was messing with (which was not being powered by the power supply) was still working!
It was drawing power from one of the pins connected to another device through this internal protection diode
❤❤❤❤❤❤❤❤❤❤❤❤❤❤❤ another wonderful video …. a plus plus plus plus ….. let’s all go to Sugar rock Candy Mountain
The problem with these Chinese relays seems tobe that there is no spark suppression. I have not had any close-welded since I started using RC quench circuit. 100 ohms and 100 nF.
when it stops flashing lol its never stoping cant see the display :(
What time dimension am I living in, I can see comments from 5 mins ago and 9 days ago but this says video posted 1hr ago 😂😂
@BreatheScotland yeh I assumed that was the case from ages ago but I thought I'd just put that in and see what replies I might get, so I'm in the peasants class then 😂