Lawnmower Switch - capacitor

The capacitor is there to reduce sparking at the switch so prolonging it's life. It's best as near the switch as possible. You could move it but it's benefits would be reduced.

Possibly not 0.1pF - there's more capacitance in the wires to the motor :)

It's probably there to suppress back-EMF spikes when the switch is allowed to open. I don't see any issues with moving it to the motor.

It is almost certainly in parallel with the switch contacts so how can you move it to the motor without routing an extra wire between the switch and motor housing?

Tim Watts wrote in news: snipped-for-privacy@squidward.local.dionic.net:

That wasn't totally clear, but it could be the case.

Bob Minchin wrote in news:lgu5u7$ogc$ snipped-for-privacy@dont-email.me:

It was across the live and neutral of the load side of the DP switch.

Secondary question. The wires are gripped by spring claws and I quess they need poking in. Should I lightly tin the wires to make them more rigid to overcome the spring resistance of the grip?

I would have though a diode would be the more normal solution should that be required. I would expect its there as an RF noise suppressor.

Definitely not 0.1pF. 0.1uF (100nF) would be about right though. The OP needs to be sure to use an approved Class X AC rated component.

On an AC motor?!

I would expect its there as an RF noise suppressor.

Agreed. If mounted near the motor it will be more susceptible to heat, moisture and vibration so it would need to be suitable for that environment and mounted with a clip, not left dangling on its leadouts.

Being that far away from the switch contacts would defeat its purpose as an RFI suppression capacitor. It has to be wired directly across the switch contacts with a minimum of lead length for maximum benefit.

Err, it'll be there as a suppressor for interference from the motor (brushes), not from the switch contacts. I think you'll find it's across the line, to reduce differential-mode conducted interference being fed back into the mains. As such, and considering we're talking about quite low frequencies here (up to 30 MHz at most), its positioning won't be that critical.

It'll almost certainly be a standard snubber, 0.1uF + 100ohms. 0.1pF would be completely ineffective.

Don't tin wires before putting them into connectors, solder is too soft.

NT

The component leads by themselves would be more than 0.1pF, even if the component was just a passive lump of resin.

It will be 0.1 microfarads, most likely.

Yes fair point ;-)

Or leave it off altogether, since its presumably only intended to suppress switching RFI rather than motor running RFI.

Since it's wired across the load side of the original switch (100nF not 0.1pf) wiring it directly to the motor terminals would be the optimum placement (assuming a universal ac/dc motor with brush gear) provided you can gain access to the motor terminals and safely wire it in place.

You're right. I lost sight of the fact that the OP mentioned it being wired across the load side of the double pole switch and got blind sided by mentions of switch noise/arcing suppression in the subsequent responses.

I've actually advised him to wire it directly across the motor terminals if he can gain access and there's room for it to be safely mounted there.

It'll reduce switch arcing, avoiding premature failure.

NT

Probably.

Tim Watts wrote in news: snipped-for-privacy@squidward.local.dionic.net:

Job done - I fitted it to the switch terminals - I had to modify the housing slightly to accomodate it (the terminals were in a different position to the original switch)

Conventionally, one uses a lowercase 'u' for that.