I have bought an electrical appliance which has buttons sticking out of it. I want to interface with these buttons from a microcontroller, but the buttons are baked on a flex PCB in the underlying circuitry. I can not get to their pins, partly because I'll void warranty, and therefore I decided that a mechanical solution would be best. I would've much preferred an optoisolator wired to the signal lines, but it showed that it can't be done.
I measured the force needed to press the button and calculated that it would be around 4 Newton. (Placed object on scale, zeroed and measured weight while pressing button)
Because the electrical appliance is quite small (approx. 60x60x60mm) and my power supply is limited to 5V 2A I started looking at linear solenoids within this range and found that they are unable to deliver the required force. I then thought of using a stepper motor with gearbox, but this feels a bit overkill.
What are some recommendations to interface with either the physical button or its underlying circuitry, keeping in mind the constraints?
Best Answer
Assuming the button travel is not too much, you should be able to find a hobby servo that can generate that much force at the end of a short arm within your power requirements. This has the added advantage of being very cheap and easy.
https://www.pololu.com/blog/16/electrical-characteristics-of-servos-and-introduction-to-the-servo-control-interface
If a hobby servo will not work for this because of geometry constraints, then a photo of the buttons configuration might get better answers.