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In Reply to: Re: reducing heater voltage - one resister or two? posted by Erhard on March 25, 2007 at 06:54:08:
In your Case 2, what wattage are the 100 ohm resistors? 1/2 watt?
Follow Ups:
The formula is N = U * U / R. in the case of 6.3V filament voltage this will give 6.3 * 6.3 / 100 = 0.3969. I always take 1 Watt. In case of 12.6 V it's twice the value, about 0.8W.The reduction of voltage in his example 0.1R and an estimated current of 2.5A will be 0.25 V. So you must align this value for your specific situation. The load then will be 0.25 * 0.25 / 0.1 = 0.625 W. I take some more, because the nominal load of a resistor is defined for a certain temperature (e.g. 50 - 60 °C).
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Long Live Dr.Gizmo
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Long Live Dr.Gizmo
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