Tiny Pulse Motor

thingiverse

This is my fourth pulse motor and a culmination of refinements from previous versions. The last pulse motor I published was kind of slow and power hungry. This one is considerably better. I've ran it at 12000 RPM using an Arduino controller. I also spent some time tweaking a Bedini-style circuit which topped out at over 6700 RPM. The circuit is interesting too so I thought I'd share that along with the updated motor design. I was very happy that I could reduce the current draw to 7mA at 12.6V while maintaining 2500+ RPM. Very sweet. In all tests I only configured it for a single pole, but the stator has slots for a second pole if desired. Feel free to build one and comment. Feedback and observations are appreciated. Observe safety precautions when operating at high speeds. Print Settings Rafts: No Supports: No Resolution: 0.25 Layer 0.4 Nozzle Infill: 10% Triangle Notes: 3 Perimeters, 3 Solid Layers. Build Notes Attach magnets to the rotor using a good quality superglue. I recommend Gorilla brand superglue with the brush applicator as this has proven reliable. Apply glue inside where the magnets sit. Insert magnets so that the same pole faces outward (i.e. all north or all south). For the Bedini-style circuit orientation doesn't matter too much but if you plan to use it with a unipolar hall sensor as the switching mechanism then plan accordingly. After placing magnets apply superglue evenly over the face of the rotor and magnets to create a protective seal that will hold the magnets in place when spinning. Let sit for several hours before using to ensure glue is entirely dry. Place 3 drive inductors in 3 opposing faces and the trigger inductor in the fourth opposing slot. The three drive coils should be wired in series so that when power is applied they repel the magnets. The rotor will require a vigorous spin to get started as it needs enough speed to create the required voltage in the trigger coil. Troubleshooting Orientation of the inductors is significant. This is true for both the drive coils and the trigger coil. If your trigger coil is too low-resistance you may find it doesn't generate enough voltage to easily start by hand. If the potentiometer is turned to 1k it probably won't start by hand either. Feel free to ask questions in the comments section. Mix it Up There are tons of possible variations involving different trigger coil values, changing the number of coils per pole (for example 3 per pole, 6 per pole, 8 per pole, etc). The video above was a 50mH inductor as trigger and I've tried it with a 25mH inductor (not recommended), and 200mH inductor which worked well with a larger pot for more range. I'm going to order some 100mH inductors if I can find them. If you have to choose, the 200mH inductor is probably the best starting point. If you change the number of drive coils you may want to move up or down, for example if you are using 5 or 7 drive coils you may be better off with 10mH inductors for them as the series resistance will be lower and easier to generate a magnetic field strong enough to repel the magnets. Also you may consider changing the circuit to run at a higher voltage. Or if you lower the resistance of the drive coils it may run at a lower voltage (I haven't actually tried this). You can even place a small neodymium magnet at the base of the coils to bias them causing them to run faster and draw more power or to run slower and draw less. Anyway, hopefully you get the idea. Parts List 4x Neodymium magnets - N35 12mmx3mm (mine were 12x2.8mm) 3x 0912 25mH Power Inductors - 9mmx12mm (mine were 25 Ohms each) 1x 0912 50mH, 100mH, or 200mH Power Inductor - 9mmx12mm (For trigger coil) 1x 608 Skateboard Bearing (mine was ABEC 9) 1x 1K Ohm Potentiometer (or 2K or 5K) 1x PC817 Photocoupler 1x BUL216 Transistor - Or use whatever you got (I just like these since they seem practically impossible to destroy) 2x White LEDs 8mm (or whatever you want to use, feel free to add or subtract leds as you feel are necessary or replace the snubbing part of the circuit with whatever you think will work better.) 1x 220 Ohm Resistor Common supplies such as wires, glue, tape, breadboards, etc. Where to Buy The electronic components can be purchased from Amazon, Arrow, Digikey, Aliexpress, and/or eBay. It just depends on how much you want to pay and how long you are willing to wait. Can cost as little as 20.00 to buy the parts with tons of left overs for other projects. Or even less if you have most of this stuff lying around. Part Substitution This is experimental and unproven, but I thought I'd share my opinion on substituting the inductors with different sizes/values since it may be hard to find these exact inductors. Aside from reworking the stator to accommodate the new size, what is probably most important when determining which inductors to use is to try and match the DC resistance value of the inductors. For example, the trigger coil should probably have between 50 and 400 ohms of resistance (not sure on the upper limit here) and the drive coils should work well with 27-90 ohms total resistance (9-30 ohms each for 3). Higher voltages should in theory help drive higher resistance coils or at least that would be my guess. Tinkercad Links You can customize this and make changes easily using TinkerCad and the links below. Rotor: https://tinkercad.com/things/jYTHk48xppS Stator: https://tinkercad.com/things/bXfB11x2pdw