Mounting the Raspberry Pi and Servo Motor to a Dry Food Dispenser

Mounting the Raspberry Pi and Servo Motor to a Dry Food Dispenser

You made it to the end! (or you happened to stumble upon this part of the guide). Looking back, part’s one, two and three weren’t so bad now that you’ve got the hang of things. Here in part four we’re going to mount the Raspberry Pi and servo motor onto the food dispenser.

The goals of this part are:

  • Connect the servo motor to the knob of the dispenser.
  • Cut the threaded rod down to size.
  • Mount the servo to the dispenser.
  • Bind the PVC fitting to the dispenser so the food has a path to follow.
  • Mount the Raspberry Pi to the dispenser.

I chose to connect everything to the dispenser and nothing to the stand. This offers a bit of flexibility: with everything relying on the dispenser the stand can be interchanged. Before we get started, power down the Raspberry Pi: sudo shutdown -h

Connecting the Parts

We’ll start by connecting the servo motor to the knob of the dispenser. I originally did this by using tape which actually worked fine for a while. However, over time the tape began to lose its grip on the knob, preventing it from turning as effectively. The tape has been replaced with zip ties which have been working flawlessly:

  • Take the knob of the food dispenser out of the dispenser.
  • To give the zip ties a flat surface to latch onto, I used a hacksaw to square off the rounded edges of the knob.
  • Wrap and connect a zip tie around the knob and servo, tightening it in place. Repeat this process until the servo is securely fastened. Use the image below as a guide to how I went about doing this.
  • Insert your creation back into the food dispenser.

Servo Attached to Knob

This is great! It looks complete, but what you’ll notice if you tried spinning the motor is that it won’t have anything to grasp onto, so it will spin with the knob. We need to fasten the motor to the dispenser. If you look at the top and bottom of the motor you’ll notice two sets of screw holes. The set that’s furthest away from the center of the dispenser knob is the one we’ll be dealing with. Using the image above as reference, that’s the set of screw holes on the top of the motor.

The screw holes are slightly smaller than the threaded rod, so we’ll need to do a tiny bit of surgery to get the rods to fit:

  • Using your box cutter, carefully cut away a very little piece of the plastic at the smallest point of the screw hole.
  • Try pushing the threaded rod into the screw hole. Did it fit? Then move on down! Otherwise repeat the previous steps until it fits snug.

Now we’ll cut the rod to the appropriate length, drill a couple holes into the dispenser and fish the threaded rods through. With the motor/ knob inserted into the dispenser (like the image above):

  • Measure the distance from the screw hole to the dispenser, then add about an inch or two.
  • Using your hacksaw, cut two pieces of threaded rod to the measured length.
  • Place the two pieces of threaded rod into the screw holes of the motor and push them flush against the wall of the dispenser.
  • Make a tiny mark on the dispenser where the threaded rods touch it. This will identify where we need holes for the rods to fit through.
  • Make an attempt to spin the wheel of the dispenser manually by rotating the knob. If any part of the knob hits the rod you’ll need to trim the knob’s plastic down a bit with your hacksaw.
  • Remove the motor/ knob, and the white rubber wheel from inside the dispenser.
  • Stop: obligatory (but very important) warning to put on your safety goggles, please.
  • Drill two holes slightly larger than the threaded rods into the dispenser where you made your markings.
  • Insert the threaded rods through the holes and fasten them down with a couple of hex nuts.

Did you wind up with this?

Threaded Rod in Dispenser

At this point mounting the motor is pretty straightforward. Before we bring it back into the picture let’s get the PVC fitting attached to the hole of the dispenser. We need two holes opposite one another at the mouth of the dispenser, and two more holes at the top of the PVC fitting.

  • Place the mouth of the PVC fitting flush against the mouth of the dispenser.
  • Use a pen to mark slightly below the lip of the PVC fitting closest to the dispenser. Make another mark directly above that on the dispenser itself. Make the same markings on opposite sides of the PVC fitting and dispenser.
  • Using a drill bit large enough for a zip tie to squeeze through, drill holes where you made the marks.
  • Using zip ties, bind the PVC fitting to the mouth of the dispenser.

The result should look something like this:

PVC Fitting Connected to Dispenser

Now that the threaded rods are in place, add back the motor/ knob. Position the threaded rod through the screw holes of the motor and tighten with a hex nut. You probably won’t have enough space to add two hex nuts. That’s alright, I didn’t either:

Motor Attached to Dispenser

Fantastic, we’re mostly there. We just need to mount the Raspberry Pi to the dispenser and we’re done! I mounted my Raspberry Pi as center to the dispenser as I could, but it doesn’t really matter:

  • Place the Raspberry Pi against the body of the dispenser where you’d like to mount it.
  • Make two markings on the dispenser, one on either side of the Raspberry Pi.
  • Drill two holes into the dispenser where you marked it.
  • Using a zip tie, mount the Raspberry Pi to the dispenser through those two holes.
Pi Mounted to Dispenser
Pi Mounted to Dispenser

Congratulations, you did it! An automated food dispenser is now at your command. 

Conclusion

The Raspberry Pi is an incredible little machine with endless possibilities. I sincerely hope this series of posts was as helpful to you as it was me. It was a long journey, but now you’re prepared to tackle any new DIY Raspberry Pi projects that may come your way.

I encourage you to leave comments letting me know what you think. If anything was unclear I’d appreciate hearing about it.

  • In part one we laid out the plan.
  • Part two we set ourselves up with the power of reading emails.
  • In part three we talked all about controlling servo motors.
  • And here in part four we put it all together to make an impressive new toy.

Hi, I’m Sam.
I’m a programmer and a DIYer. When I’m not finding things to build I enjoy cooking, hiking, camping and traveling the world with my best friend. Say Hello!

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