ESP8266 Community Forum

I'm trying to interface an esp with my Mitsubishi mini split AC units. There is a library built already here: https://github.com/SwiCago/HeatPump

He posted an example circuit but my limited understanding of ESP's serial and 5v has me scratching my head with his circuit. It looks like he is pulling the serial up to 5v. This isn't going to hurt my AC units (I don't think) as they are 5v but won't that either wreck or slowly kill the ESP? They will be talking continuously for months at a time not just during a quick flash or something.

I want to put the circuits together once. I appreciate any input you may have. Thanks!

The LM3940 is a voltage regulator which is being used to drop 5V to 3.3V for the ESP-01 module.
I haven't seen many that do it that way for the 5V to 3.3V conversion for the ESP8266.

You could just as easily use a bi-directional logic converter board.
https://www.sparkfun.com/products/12009


The ESP-01 are cheap, so it isn't a big deal if you burn one up.

I purchased these 5v transformers: http://www.ebay.com/itm/112352870355

That handles transforming the 5v supply of the heatpump unit to 3.3v to power the esp. The esp would then send 3.3v serial to the heatpump unit but receive 5v serial back? That's what I'm concerned about. Usually I see people doing voltage dividers on the serial lines (at least those with attention to detail). He seems to just be pulling the voltage up to 5v which to me seems like the exact opposite of what you should do.

ESP is cheap, no doubt. BUT, I'm going to be putting the circuit inside of the heatpump heads. Taking them apart isn't easy. I wouldn't want to do it every few months or something.

I use a USB-TTL adapter from my PC to ESP-01. I didn't do any level shifting and the two ESP-01 are still working.

The ESP-01's TX is fine. It is the ESP-01 RX that ideally needs the level shifting.

You're going to be putting this in a place that isn't easily acessible?
The ESP-01 can be flaky.
What are you going to do when it acts up?
How exactly were you planning on debugging this?
Were you thinking it is going to work 1st fime???? Good luck.