What's the function of capacitors in dynamos?

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Discussion Overview

The discussion centers on the role of capacitors in dynamos, particularly in the context of toy motors. Participants explore the function of a specific capacitor (cap 104) and its implications for electrical noise suppression and historical terminology related to dynamos and motors.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant questions the function of cap 104 in a dynamo, noting its common use in motors for power factor correction.
  • Another participant suggests that the capacitor may serve to absorb or suppress electrical noise generated by sparking at the motor's brushes, highlighting its placement near the noise source.
  • A third participant agrees with the noise suppression idea and identifies the capacitor as 100nF, emphasizing its role in preventing RF noise radiation from the brushes.
  • There is a discussion about the terminology of "dynamo," with one participant noting that it is an outdated term in the US, which may refer to generators or alternators, and questioning if it is used differently in Australia.
  • A historical perspective is provided, indicating that "dynamo" referred to a DC machine capable of both generating and motoring, with a reference to its use in vintage vehicles.
  • One participant shares a personal experience of using a similar motor controlled by a 555 IC, noting the immediate need for a bypass capacitor.

Areas of Agreement / Disagreement

Participants express differing views on the terminology of "dynamo" and its implications, while there is some agreement on the capacitor's role in noise suppression. The overall discussion remains unresolved regarding the exact function and historical context of the term.

Contextual Notes

The discussion includes assumptions about the terminology and the specific application of capacitors in different contexts, which may not be universally applicable. There are also unresolved aspects regarding the precise function of the capacitor in relation to the motor's operation.

ChrisToffer
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what is the function of the cap 104, why is it there? what's the function of this cap in the dynamo.. i know caps are used in motors for P.F correction, but what about the dynamos in toys??
 

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probably to 'absorb'(or suppress) the electrical noise from sparking at the motor's brushes.
Observe it's been placed as close to the noise source as physically possible which is good practice.
 
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I agree.
That looks more like a DC motor than a dynamo. The worm gear confirms it.
The 104 capacitor is 10 0000 pF = 100nF and is there to prevent radiation of RF noise from the sparking at the brushes.
 
Dynamo in the US is an outdated term that used to mean generator and/or alternator not sure which. I was wondering if dynamo might just be Aussie for motor in the US?
 
in 1890's it referred to a DC machine which of course can both generate and motor.

As late as 1963 Austin-Healey 3000 labelled its dashboard ammeter with word "Dynamo"
but here the term is quaint.

I once used a small motor like the one pictured and controlled it with a 555 IC. Need for bypass capacitor at motor was immediately obvious.
 

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