Re: about those rheostats...

On 14 Jan 2007 01:07:32 -0800, mrdarrett@xxxxxxxxx wrote:

Let's say an incandescent light bulb is controlled by a rheostat. Does
a rheostat truly save power when set to low power? Or, is the same
amount of current going through the rheostat regardless of the power
setting?


I suspect that you are really thinking about a "dimmer", which
is not a rheostat. The control potentiometer handles only
low power, and is used to control the point on the AC line
cycle where a thyristor (Triac) turns on. The thyristor turns
off whenever the AC goes through zero, and the process
repeats on the opposite phase.

Yes, this really does save power, since no current flows
to the bulb until the thyristor goes on. So, if you set the
control so that it doesn't go on until halfway through each
phase of the cycle, then you use only half the normal power.

Best regards,



Bob Masta
dqatechATdaqartaDOTcom

D A Q A R T A
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Signal Generator
Science with your sound card!
.

Relevant Pages

  • Re: about those rheostats...
    ... a rheostat truly save power when set to low power? ... amount of current going through the rheostat regardless of the power ... A solid state lamp dimmer will convert much less of the reduced ... appears as if that 100 watt lamp is putting out 50 watts and you might ...
    (sci.electronics.basics)
  • Re: about those rheostats...
    ... a rheostat truly save power when set to low power? ... amount of current going through the rheostat regardless of the power ... A solid state lamp dimmer will convert much less of the reduced ... appears as if that 100 watt lamp is putting out 50 watts and you might ...
    (sci.electronics.basics)
  • Re: about those rheostats...
    ... a rheostat truly save power when set to low power? ... amount of current going through the rheostat regardless of the power ... The bulbs power dissipation will depend on the voltage across it and the ... Whatever part of the applied voltage is not across the bulb will be across ...
    (sci.electronics.basics)
  • Re: about those rheostats...
    ... a rheostat truly save power when set to low power? ... amount of current going through the rheostat regardless of the power ... The bulbs power dissipation will depend on the voltage across it and the ... Whatever part of the applied voltage is not across the bulb will be across ...
    (sci.electronics.basics)
  • Re: about those rheostats...
    ... a rheostat truly save power when set to low power? ... amount of current going through the rheostat regardless of the power ... The bulbs power dissipation will depend on the voltage across it and the ...
    (sci.electronics.basics)