Transistor Circuit for IoT AC control

Thread Starter

stefan84

Joined Oct 24, 2019
2
Hi,

at the moment I'm trying to build an IoT control circuit for an air condition based on an ESP32.
So far I have decoded the IR signal and using IR I can already control the AC.
The goal is to integrate it into AC to also be able to read out the LED status and receive and decode the signal if the IR remote control is used.

There is a small board containing the LEDs and the IR receiver which is attached via plug to the main board.
So I would like to put my circuit between those two boards so that I do not have to change or solder anything directly on the boards but have it plug and play and can remove or replace it easily.

I attached two photos of the small board containing the IR receiver, the schematic of the IR receiving part of this board (at least as I understood it and hopefully didn't get anything wrong there) and also the schematic of my first attempt of a circuit to attach the ESP32.
I think I'm already pretty close with my circuit but still it doesn't work.
I'm a very beginner and could need some help there and I'm grateful for any advise.
Also I think that I might have to add some pull-up and/or pull-down resistors but I'm not quite sure about that.

br,
Stefan
 

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danadak

Joined Mar 10, 2018
3,682
What is the relationship between the IR out stream and the control
signal ? Is it inverted or non inverted ? Does control signal have a
pullup down stream, eg. connected to Q2, Q3 collectors ?

Truth table for all inputs and control signal output ?


Regards, Dana.
 

Thread Starter

stefan84

Joined Oct 24, 2019
2
What is the relationship between the IR out stream and the control
signal ? Is it inverted or non inverted ? Does control signal have a
pullup down stream, eg. connected to Q2, Q3 collectors ?

Truth table for all inputs and control signal output ?


Regards, Dana.
The control signal should be the same as the IR out stream.
So it should work like there wouldn't be anything in between as I don't want to change anything on the boards before or after my circuit.
The original signal is usually high and pulled down to GND by the IR receiver.
The signal that comes out of the ESP32 is usually low and therefore it has to be inverted.
So far as I understand on the mainboard in the AC is a pullup resistor and is pulled to GND if an IR signal is coming in.
I'm tryint to use two Transistors to pull it to GND. One for the signal from the ESP that has to be inverted (pulled to GND if high) and one that comes from the IR receiver board.

br, Stefan
 

danadak

Joined Mar 10, 2018
3,682
The 10K in the bases, that controls Ib of the transistors.

To saturate a transistor rule of thumb is Ib = Ic/10. So do
the calculations to make sure you are sating the Q's. Or simply
force the 10K high in circuit and measure the VCE of the Q to make
sure it is saturated, ~ 200 mV is fine.

Not a timing issue in code ? The various inputs ?

Regards, Dana.
 
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