Hello all, this is my first post. I usually can figure what needs to be done by gratuitous searching. I was unable to find what I needed and I am ready to bang my head against a wall until I pass out.
Background:
I recently discovered node-red, mqtt and espeasy. Finally, I thought I could bring my goal of converting my AC to a Wifi enabled AC to life. I had put this off for several years mostly because my lack of coding ability. I have Node red set to send a 500ms pulse on pin 15 of a sparkfun thing dev board which is just a fancy esp8266. I also have node red listen to to the status of pin 4 which is connected to the power LED on the AC motherboard. The AC is a Freidrich window unit. I thought I was going to pull the board out, solder to the buttons and leds and be done with it. Well they had to cram a bunch of leds and buttons through a small ribbon cable. It appears to be multiplexed, but I am not sure how to interface to this reliably. The funny thing is I actually had this working on a breadboard and when I put it all onto a protoboard to make it permanent it doesn't work.
The problem:
Since it is multiplexed there is no real reference to ground that is shared between the esp and the motherboard. One pin has 80mv when referenced to the esp ground and the other pin for the switch has ~2.5 volts. All 7 buttons appear to be routed through 4 small signal transistors that are driven by the micro. Using my multimeter it looks like the matrix is scanned at 126 Hz. I dont have a scope so I cant verify exactly what it is doing. Originally when testing I was able to get the unit to turn on but not off then after some playing around it appeared to be my crappy breadboard with an intermittent connection somewhere. I got it working what seemed to be reliably and then when I transferred the design over to the protoboard it stopped working.
The design:
Pin 15 on the esp goes through a 660 ohm resistor to the base of a 2n6904 NPN transistor.
the collector of the transistor goes to a 10k resistor to ESP ground and to the pin of the AC daughterboard that had the floating mV.
The emitter of the transistor goes to the other side of the switch that has the 2 or so volts.
I checked that the transistor is functioning and when I turn pin 15 of the esp on the resistance drops to several ohms. I checked all the connections on the board multiple times. I checked all the component values multiple times. Everything looks good. I dont know if this has any effect on the rest of the circuit but i put a 100uf capacitor between pin 4 and ground that detects the LED status to get it to stop flopping back and forth between high and low in the software.
My questions are: Is this wired correctly? Is there a better way to do this?
Please let me know if you need any more information.
I really appreciate the help. Thank you -Ian
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