[Fabien-Chouteau] submitted his interesting solenoid engine. In an internal combustion, steam, or pneumatic piston engine, the motive force is produced by expanding gas. In [Fabien]’s little engine it is produced by the arm of a hard drive. Solenoid engines are usually just for show, and come in all shapes and sizes. If you want to move something using electricity an axial motor is probably a better bet. But if you want a challenge and a learning experience, this is hard to beat.
[Fabien] had some problems to solve before his motor made its first revolution. Just like a piston engine the timing needed to be exact. The arm firing at the wrong time could cause all sorts of trouble, the equivalent of backfire in a combustion engine. A STM32f4 discovery board was coupled with a Hall-effect sensor and a MOSFET. When the board read that the arm has moved back to the most efficient position for firing it sent a pulse through the coil. Just like a regular engine, getting the timing right makes all the difference. Once [Fabien] got it tuned up his motor could spin around at a steady 3000 rpm.
Why is the hall-effect sensor necessary, when he could have just used one of the phase outputs from the original platter motor?
I feel like the phase output would be really hard to read when the speed is low, just a gut feeling. It should still work though… I mean… the actual 3 phase driver has to read the same low signal when starting up anyways, so it can be done.
A hall effect sensor usually has a stable output, hysteresis, and clean edges, instead of a spike of unknown amplitude.
Yeah, like he said – hard to read at low speed.
Also – HDD platter motor is designed for speed and precisions. Precision motors like steppers can have hundreds of phases per revolution. A HDD platter motor probably has 3 to 9 phases.
Edit: “Also – HDD platter motor is designed for speed and *NOT* precision …”
From memory the platter motor has no pulse output. It’s a three phase motor in a Y configuration.
http://ww1.microchip.com/downloads/en/AppNotes/00894a.pdf
Section labeled Back EMF Control Method. I think this would work even though you are not actively driving the motor.
Even back emf controllers don’t use any feedback at very low speed. They have a preset sequence of pulses to initially bring the motor up to a speed where the backemf has sufficient amplitude
Some HDD platter motors have Star (y) configuration which is four connections for three phases and some have Delta (Δ) configuration which is three connections for three phases.
From memory, the motors are wired with three phase Y connection and they are inputs & not outputs.
If you are clever an input is indistinguishable from an output.
True, especially with coils and magnets. But in this case I doubt he would get anything measurable. Best case and with the right load he might get a small sine wave. But as slow as he’s running compared to the original 54K or 72K RPM he’s likely to get nothing.
5.4k…
Stupid hackaday can’t even make a video work on a phone. Thanks for nothing.
Works here brother. Get a new phone?
Works for me. Anyway, it’s direct-from-YouTube content.
What browser, what phone?
Stupid Apple and Android, can’t make something simple with these f*****g phones. Full of bloatwares and incompatibilities between every models/OS/browser/whatsoever (apple or google services? Dunno, pisses me off)
“I’ll go make my own cell phone, with blackjack and hookers!” – Shakipu
“In fact forget the cell phone!”