I’m not quite sure if electronics fit in with the community, but maybe some of you could point me into right direction with ESPHome and IR transmitter to control my minisplit heatpump at the garage.

The thing is cheapest one I could find (I should’ve paid more, but that’s another story). It’s rebranded cheap chinese crap and while vendor advertised that you could control it over wifi I didn’t find any information beyond ‘use SmartApp to remote control’ (or whatever that software was called) but it’s nowhere to be found and I don’t want to let that thing into internet anyways.

So, IR to the rescue. I had ‘infrared remote control module’ (like this around and with arduino uno I could capture IR codes from the remote without issues.

But, transmitting those back out seems to be a bit more challenging. I believe I got the configuration in place and I even attempted to control our other heat pump with IR Remote Climate component which should have support out of the box.

I tried to power the IR led straight from nodemcu pin (most likely a bad idea) and via IRFZ44N mosfet (massive overkill, but it’s what I had around) from 3.3V rail. The circuit itself seems to work and if I replace IR led with a regular one it’s very clear that LED lights up when it should.

However, judging by the amount of IR light I can see trough cellphone camera, it feels like that either the IR LED is faulty (very much a possibility, what you can expect from a 1€ kit) or that I’m driving it wrong somehow.

Any ideas on what’s wrong?

  • JustEnoughDucksEnglish
    8·
    1 year ago

    Hey, your problem is likely your MOSFET.

    The IRFZ44N has a 2-4V gate threshold. Sometimes overkill will actually make things not work.

    This means that somewhere in that voltage range it will start to even turn on. You seem to have at least gotten one with around a 3V Vth.

    You are likely driving it in the cutoff region to the very low ohmic/triode. That means that you are controlling how much current is going through proportional to the voltage, but extremely low

    If you look at figure 1 on the datasheet, you can see that the 4.5V is pretty much the recommended voltage on the gate (assuming low side switch). A good way to think of it is a ball valve, you are just turning the handle a tiny bit right now when it should be open all the way.

    I would try a FET with a lower Vth. Also put a current limiting resistor in series with the IR lED if it isn’t there already since they only have a 1.2V Vfwd many times. Don’t want to blow it up.