Circuit setups for pulse motors

[Ren]

Thaelin I had an idea the other night about constructing at sturdy switching mechanism/commutator that would create minimum drag on a rotor. I got to thinking that if a brush was placed against a rotating disc (commutator) it would create some amount of drag, depending on size and pressure against the tab I guess. But what if the brush was a small bearing that was fixed and rolled against the disc, completing the circuit as required when the sections of copper (or conductive material) passed the bearing. It would look like a figure eight, the top loop being a small bearing and the bottom loop a larger timing wheel. Anyone care to comment?

[hoptoad]

Thaelin I had an idea the other night about constructing at sturdy switching mechanism/commutator that would create minimum drag on a rotor. I got to thinking that if a brush was placed against a rotating disc (commutator) it would create some amount of drag, depending on size and pressure against the tab I guess. But what if the brush was a small bearing that was fixed and rolled against the disc, completing the circuit as required when the sections of copper (or conductive material) passed the bearing. It would look like a figure eight, the top loop being a small bearing and the bottom loop a larger timing wheel. Anyone care to comment?

Hi Ren,  and happy new year to all you "pulsars".

When I first started experimenting with Adams motors in 1990, I was using mechanical switching with contacts from old Telephone relay circuits. They worked well enough for high impedance coils but when I switched to low impedance coils, they had a tendency of burning out very quickly and also damaging the "star" switch. I eventually used a small bearing set from an old VHS motor in place of the relay contact, and this worked very well in reducing wear and tear on both the "star" and the contact (bearing).

I mounted the bearing on the spring wire from a clothes peg.

Eventually the sparking would cause the ball bearings inside the bearing to embellish and "pit" which caused the bearing to stick occasionally, but it was still very effective for much longer periods than using the relay contacts which would wear out quite quickly.
It also spread the spark, and reduced physical friction on the "star switch" , thus allowing a much greater runtime with the star before
it needed refacing.

Cheers and happy motoring from the Toad who Hops. 

[adam flow nemo]

Happy new year people
Keep up the great work !!!!
Peace& love& Respect .

[Ren]

Awesome Hoptoad, I was sure I couldnt have been the first person to think of it. I thought a nice stainless bearing would roll quite smoothly and  make a good contact for conductive paths. I was considering looking for some shockies out of an RC car, they would provide suitable tension and adjustment and would probably already have good mounting options to a frame and small bearing. Have to see.

My other option is a couple of contacts I salvaged out of a power saw. They are spring mounted and look like carbon based?


Thanks again Knee Deep!

[hoptoad]

My other option is a couple of contacts I salvaged out of a power saw. They are spring mounted and look like carbon based?

@Ren
Yes they are carbon based. They are usually impregnated with very fine powdered copper.

The trick here (generally speaking) when using these types of contacts is to use brushes designed for low voltage DC motors. Most 240 Volt AC motors use carbon brushes that have a built in resistance which can often measure from a few ohms up to a 100 ohms, depending on the motor requirements. The other thing to be aware of, is that they are usually quite thick, and this will impact on the actual duty cycle by extending it a little bit, because the switch needs to travel the full width of the contact before it turns "off" again. This is overcome by adjusting your contact with the switch by moving the contact to a smaller (narrower) region of the switch.

Cheers from The Toad who Hops........KneeDeep