Connecting relay switch to GPIO

Question

I am a complete noob in this field but am trying to embark on this project to modify an old automatic pet feeder to have better control by using Raspberry Pi. Below is a picture of what is under the hood, I believe it's a motor connected to a relay. The wires go to C and NO. The grey wires on the bottom go to an on/off switch and the red and black on the left go to the power inlet. The bundle goes up to what I assume is its micro controller.

I'm trying to control the motor with the Raspberry Pi with the least amount of modification. I'm wondering whether I can route the connections going to the relay to Raspberry's GPIO, or is it not as simple as that, or is it not possible to tell just by looking at this setup.

Answer 1

That looks like a micro-switch rather than a relay.

I'd guess that the micro-controller is starting the motor at set times (or has some other way of initiating the event) and the motor runs until the micro-switch closes (which is done by the knobbly bits turning and pushing the arm of the micro-switch in).

C is common and NO is normally open (meaning the switch is normally open but when the arm is pushed in it closes.

You will want to check the voltage on the NO wire both when the switch is activated and when it's not to ensure it is within the range of the GPIO pins (0v-3.3v).

I'd start by driving the motor from one of the Rapberry Pi GPIO pins (via a motor driver circuit or a transistor, as the GPIO will not supply enough power). Next I'd use the micro-switch to signal to a GPIO pin (possibly via a voltage divider circuit to get the voltage in the correct range) that we have reached the desired point and stop the motor.

Good luck!!