Month: September 2019

Optical Commutation

I finished putting together an optical commutation circuit on a breadboard tonight. It uses an IR emitter/detector pair to trigger timer chips that ultimately turn on power transistors to drive solenoids. The solenoids are logically opposite, so they alternate as the IR beam is made and broken.

The timer chips aren’t strictly necessary, but they prevent the solenoids from staying on too long and burning up. You can see this in the video below when I am blocking and unblocking the IR path using a playing card–I sometimes leave the card in or out for a few moments, during which time whichever solenoid is powered returns to a resting state after about one second.

I’ll use this circuit to drive the two solenoids in my solenoid engine, which will have a rotating half-moon to block and unblock the IR beam.

Ball Game

I finished the first iteration of a Plinko-like ball game I started working on a while ago for my son. It uses printed parts, some plywood, a sheet of Lexan, and a Nerf Rival ball to create a simple combination of pinball and the famous Plinko game from The Price is Right.

The objective isn’t well defined, but the boys enjoy playing with it. A friend suggested replacing some of the peg openings with cups that correspond to score amounts to provide an objective for the player to work toward. I may do that in the next iteration.

Sorry about the video quality–I can’t find my better camera at the moment.

Solenoid Engine Prototyping

I’ve started thinking about how I might build a solenoid engine. I bought a couple solenoids on Amazon, Uxcell brand, and they seem to have quite a bit of zip to them, so I’ve been looking into how to mount them to a block in a way that would allow them to rotate around an axis, eliminating the need for the connecting rod to rotate with the piston head, which in this case is just the armature of the solenoid.

Pictured below is the first three attempts at printing a little box to hold a solenoid. The little wings on the side have 1/8″ holes in them that will fit over a rod, allowing the solenoid assemblies (I plan on having two of those) to lie directly over the crankshaft and rotate back and forth with the cranks.

You can see the design process as it unfolded, first with no venting on the sides, then with vertical venting and finally diagonal venting to allow the solenoids’ windings to cool off better during operation. I don’t know how much of a problem heat will be, though, since I’ll be running somehow around half the rated service voltage of the solenoids, at 50% duty cycle to boot.

I did melt the diagonal vents a little with a heat gun while trying to de-string the object. Oops.