I have a FPV camera in a stationary position 300m from my house, (at my front gate) which is part of a larger Arduino installation (including sensors etc) I communicate with from home with via a LoRa radio.
Thing is, the RunCam Night Eagle I'm using has nice digital features like zoom, brightness, exposure, you-name-it, all of which are controlled by this ducky little 5-button menu control board on a 4" cable.
How to adapt this to Arduino?
My first thought was do out the little press buttons with relays ... but I'd rather not use 5 hulking great clunky relays for such a light purpose. Ridiculous.
I'm thinking of soldering a FET over each button and triggering the control leg by a digital pin.
If I'm not way off beat a FET can act like a relay?
My concern is whether there is a resistance value in a FET, when activated? I haven't been able to find that out ... it would alter the reading of the buttons by the camera ... since the OSD circuit is simply 5 different value resistors, one on each button, if the resistance value of a FET is different from a simple button/switch it probably won't interpret it right, to my thinking.
Please do correct me I'm half-educated on the electronics side of things particularly FETs and three-legged bits in general.
Secondly, if it will work, then ... what "value/size" of FET would I be looking for for the task of 'pretending to be a little press button when triggered by +5V logic'?
You cannot determine this without knowing how the buttons are implemented....
First check if all 5 buttons have one side connected to eachother.
Then, check if those 5 buttons are also connected to ground on the camera.
If both of those questions are yes, then yes, you can do it - source of fet connects to ground, drain to other side of button, gate connected to ground by a small resistor, and each gate also connected to an I/O pin of the arduino. Ground of camera connected to ground of arduino. 5V fets are fine.
The FET should work, If it is + as common between the buttons use a P-Fet, if it is ground that is common use a N-Fet. You can probably use opto couplers assuming the current is not high.
OK, sounds good, thanks guys I'll have a closer inspection of the circuit polarity.
I'm also looking at this: https://shop.runcam.com/runcam-control-adapter/
But I'll probably be going with the FETs if I can because I probably have them already if I scrounge them out of boards.
ebarnes88:
But I'll probably be going with the FETs if I can because I probably have them already if I scrounge them out of boards.
I always advise to just buy new components - that way you know the specs, can get more if you need them, and know they aren't damaged. I used to scrounge parts, but eventually realized that the time involved in scrounging and added debugging was almost never worth the savings from just buying new, known, parts.