Wiring

The diagram below shows the wiring for dogbot, which includes a few transformers to get the correct voltage needed to supply the various devices involved.   The source of power, of course, starts at the wall with 120VAC.  The first transformer converts this into 12VDC which powers the two auger motors used for meal and treat dropping.  I then transform the 12VDC into 5VDC to power the Raspberry Pi and NeoPixel LED string.  There is also a 120VAC to 24VDC transformer to get the correct voltage for the sprinkler system solenoid used to control water flow to the water bowl.

Below shows a standard Raspberry Pi 3 wiring harness that comes out of the Pi PCB and attaches to a short breadboard so I can connect signal wires for the DC motors, NeoPixel Pixel LED string, and solenoid relay.  See the write up on Adafruit about Raspberry Pi Wiring and using a 74AHCT125 level shifter.

The following photo shows the 120VAC to 12VDC continuous power supply on the upper-left and 120VAC to 24VDC transformer on the right mounted on the inside wall of the cabinet.  In the lower-left is one of the auger motors and to the right, the solenoid relay in a static proof bag held shut by a zip tie.

This is a close up of the solenoid relay outside of the bag.  This type of relay works for a wide range of voltage and amperages, which so it easily supports switching the 24VDC going to the solenoid.

This is a view of the back of the cabinet with the 120VAC power line coming out of the back with a cord stopper, and a 12VDC line going to the solenoid under the water bowl.

The solenoid used is one typically found in a home sprinkler system.