DIY : How to make a ping pong shooter robot – Thongchai Kolyutsakul – Medium

I will walk you through how I made a ping pong shooter robot. I’ll list all the tools, steps and what I learned.

There are so many pingpong shooter robot videos on YouTube. Surprisingly, none of them has any detailed description/blog on how to make it. I can’t even find it on the whole damn internet! I’ll have to make one and fill this gap in the universe.

Among many examples, I find this version by a Japanese dude named “rxr txt” to be the simplest and least-trouble-to-make model. I will use it as a guideline.

My early prototype notes. You can see that I still remember the “V=IR” formula.

Now it’s time to get the tools! 🔨

Equipments

First you need equipments, lots of them. This is a good time to get yourself a personal toolbox. I divided to 3 sets: basics, feeder, and shooter.

The Basics

  • a tool box — it may look weird to suggest a box here, but trust me, get one. It helps organize things. If possible, get a clear plastic one so you can find things inside a tangled mess a bit easier.
My beloved toolbox ❤️
  • electrical wires — either electrical wires, or breadboard + jumper wires + header pins for connecting the circuit
  • a power supply — I use my 5V 1A phone power bank and a USB cable with a type-a head. That broken usb cable lonely sitting years in your drawer will do. You can also use your laptop USB port (careful not to short the circuit)do. Or just get a bunch of AA batteries.
  • a glue stick — for attaching stuff. You don’t even need a glue gun if you have a stove. (Just don’t burn your house down.) Actually, you can also use it to easily connect wires together. It’s much easier than soldering, and less poisonous gas.
  • some screws & nuts — to hold stuff together. I can’t recommend the size as your motors/equipments may vary.
The 3mm x 20mm screw and nuts for my slow motor
  • a small screw driver set
  • a switch (optional) — for easy turning on/off the whole circuit. You can also just pull the wires in/out.
  • electrical tape (optional)

The Feeder

  • some foam pieces — to make the base for the feeder. Can also use something else.
  • a round plastic bucket — better use a clear one so you can see when it is empty or if something stuck. Don’t use too high bucket. If the bucket holds too much ball, its weight can stop the feeder from running properly.
  • a slow motor — aka. a “geared” motor. This is just a normal motor but with some extra gears to make the output turns a bit slower. I use a 6V DC 20rpm geared motor
    http://www.lazada.sg/small-dc-6v-electric-geared-motor-worm-brush-gear-motor-slow-speed20rpm-new-4672022.html
An enlarged image of the geared motor. Somehow I can’t make images small on Medium…
  • some hard cardboard for the feeder disk
  • screws & nuts to hold the motor — depends on what motor you use
  • a soldering iron
  • some newspaper — for wiping melted plastic off the solder iron
  • and lots of ping pong balls! 🏓🏓🏓

The Shooter

  • 2 pieces of PVC pipes, each about 10–15cm long. The ping pong ball diameter is 40mm (1.57in). So the inside diameter (ID) of the pipe has to be more than that. From the chart below, it would be a1–1/2″ size. I’m not sure why 1–1/2″ size has inside diameter of 1.61″ instead of ~1.5″ though…)
PVC pipe sizing chart from https://pvcfittingstore.com/pages/pvc-pipe-sizes-and-dimensions
  • a PVC coupling — to join the 2 pipes. The reason I use 2 pipes is because with this you can rotate the shooter around, changing the spin of the ball.
Schedule 40 PVC Slip Coupling
  • a wheel with rubber tire of RC (remote controlled) car
    https://www.lazada.sg/2pcs-48-19mm-rubber-rc-car-tire-diy-trucks-toy-wheels-model-robotic-intl-59371909.html
  • a 14k rpm motor. It’s bigger than what you find in those small RC cars.
    http://www.lazada.sg/14000rpm-dc-6v-high-speed-motor-390-gear-motor-forautomobileremote-car-buggy-intl-39156322.html
A BIG motor and a wheel
  • a low voltage motor speed controller
    https://www.lazada.sg/products/dc-new-18v-3v-5v-6v-12v-2a-low-voltage-motor-speed-controller-intl-i125666596-s140318043.html
An enlarged image of low voltage motor speed controller. Not that I like to enlarge it…
  • Steel hanger strap, and some nuts & bolts that fit it. One1-foot long strap should be enough to hold the fast motor with the pipe. But buy a few more, just in case.
Steel hanger strap. Took me 5min to find its name. I first googled “construction steel belt” lol.
  • a small gear puller (optional)— if your motor comes with a gear, you may need to pull it out to easier put in the wheel
Walkera W010 Gear Pinion Puller Remover Tools Set

Put it together

Now that we have all the equipments. Let’s rock!

Thumbs up, yo!

Let’s start from the feeder.

  1. Attach the slow motor to the bottom of the bucket. Use soldering iron to punch a hole in the center of the bucket. Then, punch 2 more small holes next to it for the screws to hold the motor in place, depending on your motor. Note: Prepare some paper to wipe out the plastics that will stick to the soldering iron.
  2. Punch a big hole on the side of the bucket near the bottom. This is to put the shooter pipe. It will have to be a bit of an oval shape. The shooter pipe actually doesn’t need to go into the bucket as much as I first thought. Let it in just about half the pingpong ball’s width is enough to catch the ball.
  3. Prepare the feeder’s disk. This one I just use a hard cardboard, cut into circle shape just enough to fit in the bucket. Cut a small circle on the edge of that circle for trapping the pingpong ball.
  4. Attach the disk with the slow motor. I use another smaller plastic disk to attach to the motor first as a base, and then attach the cardboard to it. This should provide a stronger base for the cardboard.
  5. Create the base. The motor will stick out of the bottom and make it hard to stand on its own. We have to create a base for it. I use some pieces of foam cut and just hot glue it to the bottom.
  6. Do some testing. Run the motor and see if it can trap the pingpong ball.
Punching hole in the bucket.
Punching a bigger hole in the bucket.
Early feeder prototype and pipe positioning

Now we move to the shooter!

  1. Make the feeder pipe. Take one of the 2 pipes. Cut a rectangular slot on one side of the pipe. This is to allow the feeder disk to rotate through and catch the incoming ball.
  2. Tape the feeder pipe to the feeder. Use taping first to allow some adjustment. We will hot glue everything later after we do the final test run.
  3. Test the feeder pipe. Put in some balls and run the slow motor. The ball should get in the disk and get caught by the pipe properly.
  4. Make the shooter pipe. Take the 2nd pipe. Cut a rectangular slot on one side of the pipe. This time it is for the fast motor.
  5. Attach the fast motor to the pipe. Here we use the steel hanger strap. Curl the strap around the pipe leave out some remaining part to provide a base for the motor. The steel hanger strap is a very good candidate for this because it is flexible for adjustment and hard enough to withstand the motor’s weight and vibration.
  6. Connect the shooter motor circuit. Connect the motor to the voltage controller. And connect the controller to your power supply. Test the motor.
  7. Test the shooter pipe. Run the motor, feed the ball into the pipe with your hand, and see the ball shoot out! This is where it gets more fun. 🚀
  8. Connect the 2 pipes together with the coupling pipe. Some coupling pipe may have an inside middle ring that is smaller than the rest, which can block the ball. You will have to file that out. I actually use my fast motor to file it. It feels really good. 😎
  9. Cut some foam for to hold the shooter pipe. Just to make it more sturdy. Use another big piece of cardboard to attach the base of the feeder, acting like a big base for the whole thing. One thing I notice is that the vibration from the fast motor can move your shooter robot around to unwanted positions 😂. You can add some rubber to the base to avoid this.
  10. Test the whole thing! Check out my video to see it in action. ✨

Summary

That’s it! If you ask does it help improve my skills? Definitely! But I feel that having to collect 30 balls on the ground at the end of every round is kind of depressing. Maybe my next project will be the “pingpong ball collector robot” 🤣.

Enjoy some more photos below. Let me know if you have any comments.

Testing the feeder motor
Finding and cutting the pipes at the hardware store.
The fast motor and power supply header pins

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