This seems like it should be trivial, but my limited knowledge is unable to figure it out (and my on-line search has been futile).
I have a simple remote, where I want to replace the physical buttons with Arduino-control (Nano ESP32, with its 3.5V logic). I can trigger the remote by simply applying 12V to the red contact.
I initially tried a simply NPN transistor as a high-side switch--which obvious didn't work (for reasons I now understand). However, I'm stumped trying to come up with a simple solution (other than using an optical-relay, which seems overkill).
That is an emitter follower so when the ArduinoPin is high, the RemotePad will be about 0.7V less than whatever voltage is on the ArduinoPin.
If you want to base your solution on transistors, I think what you are looking for is a "high side switch", e.g. like this
The solution in post #2 seems simpler with less components. You could also use a reed relay.
I think what's adding to my slow uptake, is all the "transistor 101" articles I've read, indicate that "transistors are basically an electric switch"--great, that's exactly what I need. And "optocoupler 101" articles seem to indicate they're used when voltages need to be isolated (such at between low-voltage and mains)--which that doesn't fit my situation.
I've looked through the H11F1M datasheet, and the "typical" applications don't seem to translate to the simple action I'm looking for (and that's ignoring their cost).
Anyway....is this the correct schematic that I need (below)? Not having any experience nor was I able to find a schematic similar to my use, it's not clear what additional components would be needed.
When the LED in the OPTO FET is ON (i.e. conducting). there is about 200 ohms between leads 6 and 4.
When the LED is OFF, this resistance > 300meg ohms.
You can do a test by putting a 220 ohm resistor between the switch's Red and Blue leads, if the 220 ohm works, the OPTO FET should work.
It will work, but you need a current limit resistor in series with the LED input.
The opto-coupler specification will tell you how much current is needed by the LED and its volt drop, then you apply OHMS Law with the 3v3 logic to calculate the resistance.
I'm able to trigger the button by applying 5-12V to the red contact, as it's connected to one of the data input pins on the HS2260A-R4.
Is there any reason why a simple logic-level shifter wouldn't work here (the output directly connected to the red contact)? Or addition components I would need?
Its easy enough to breadboard the circuit to test if it works.
Make sure to check if the manual switch still works with the addition of the Arduino circuit.
I was able to breadboard the left option (NPN/PNP) with a few components I had on hand, but wasn't able to get it to work (most likely an error on my side). I don't have any opto-couplers on hand, so wasn't able to try that option.
However I did also have some level shifters on-hand, and was able to get it functioning by shifting the Nano 3.5V up to 5V--triggering the red pad (and the remote). Is there any reason why this is a bad path to follow?
For a quick breadboard, I connected the output of level-shifter (SN74AHCT1G125DBVR) directly to the red pad on the remote, and it seemed to work (not using the schematic from #14). I presume it'd be a good idea to add a 1K resistor between the IC output and the remote pad--anything else?
Are you referring to an issue of the button was manually pushed, at the same time being triggered by the Arduino? Or is there something else Iām not seeing?
