Liquid medicine automatic dispenser

Every day I mix up my medicine into a drink, because drinking oil straight is not fun. The process goes something like this: Fill a pint mason jar about halfway with milk, put half a scoop or so of protein powder in for flavor, dose out the medicine and put in in, then put in the shaker ball and lid. This was getting tedious, so I made this project to help streamline the process, and to save my fingers from being covered in oily powder every day.

The project has two parts, the oil dispenser and the protein powder dispenser. While PLA (one of the most common printing materials) isn't necessarily unsafe, the layered texture of 3D prints means that it is practically impossible to wash the food and bacteria from it. This means that if you choose to add the protein powder dispenser, you'll need to coat those pieces in a food safe epoxy to smooth them out. Remember that this plastic is designed to melt under high temperature, so don't put it in the dishwasher.

I already had some of the stuff on hand when I built this, but I'll add the link for the other items.

You'll need:

• Food safe silicone tubing (2mm inner diameter, 4mm outer diameter)
• 12V DC peristaltic pump
• Food safe epoxy
• Hot glue
• Velcro strap
• Electronics:
  • An Arduino Uno
  • L298N motor driver board
  • Arduino mini breadboard
  • button (that fits on breadboard)
  • 10k ohm resistor
  • 12v power supply

Notes:

• Rather than buying several different types of very specific screws that may or may not stay secured in the print, I just hot glued everything in place. It ended up being a tighter fit than I thought. Make sure to put glue on each individual electrical connection first, so that nothing comes loose when you're cramming everything in there. This is the setup that worked for me:
  • the Arduino Uno in the upper left corner. Make sure the data port is facing down, so that you can still plug it in to upload the code.
  • Driver board in the upper right corner, above the Velcro holes
  • Pump glued to the inside of the back panel, between the breadboard and the power plug.
• Fancy peristaltic pumps use the more precise stepper motor instead of a DC motor, but this would have driven up the price and made the wiring much more complicated. You'll need to figure out how many seconds it takes to dose however much oil you need. For me it was 61 seconds for 65ml of oil. I found this by measuring out 65 ml of oil, and weighing it with a scale that could measure to a precision of a tenth of a gram. Then I just used trial and error to find the whole second that got closest to that weight value. The tube is small and the pump isn't super fast, so if you're off by one second it shouldn't make a significant difference.
• There are some design improvements that could be made here that I probably won't fix, but you should be aware of:
  • (FIXED IN VERSION 2) The back panel doesn't fit very well at the bottom. I had to use tape to keep it on.
  • For the powder dispenser, the hopper rotates freely against the floor when it shouldn't. You'll need to align it based on the slot for the disk handle and glue it in place.
  • The distance between the inside surface of the back panel and the breadboard is larger than it needs to be, which adds to the space issue. This is because in previous versions there were a lot more pins on the breadboard. I'm attaching the design files, if you look in there make sure to check out the custom parameters to  change these kinds of things.
  • (FIXED IN VERSION 2) The semicircles at the base could be a little wider, especially the one for the oil bottle.
• If the motor runs in the wrong direction, go into the code and swap “in1Pin” and “in2Pin” declared at the very start.

UPDATE: The dispenser struggles to consistently dispense, because the powder doesn't like to go down the hopper. I added the optional protein powder bowl, which replaces the hopper, disk, and floor. It fits both the lid and the main body. I use a small scoop, which can usually be found in whatever protein powder you buy.

UPDATE 2: Version 2. Added Med_mixer2 body and clip file, these are used in place of the original body file. The design file is also included, but doesn't share a timeline with the original version. This new version directs the tube downward, which reduces splash, and includes a drip tray so it doesn't get oil all over the counter. The bottle clip is printed separately so that it can be printed from PETG, which can bend further before snapping. The new body is NOT compatible with the hopper attachment, because it would interfere with the block that points the tube downward, and the hopper didn't work that well anyway. The door also fits much better in this version, especially at the bottom. The top attachments are very fragile, and you might still need a velcro strap or tape to keep it together.