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T[_1_] T[_1_] is offline
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Default Adjusting appliance temps w/ no rheostat

In article >, says...
> maxine in ri > wrote:
>
> >OK all you home-handypersons, mechanical geniuses and electrical
> >wiring experts, have i got a question for you!
> >
> >I got a new yogurt maker at a yard sale (lady had a failed
> >kitchen store business, it was brand new in the box sealed
> >etc.) First batch came out grainy (probably my fault)
> >so I made the second batch under closer observation.
> >
> >Finished product was just over 130 degrees, which is
> >the high end for yogurt cultures.
> >
> >Is there some way i can build a temperature control into
> >the electric wire to reduce the temperature, or do I need
> >to count this up to the usual yard sale failure?
> >
> >maxine in ri, soldering iron at the ready

>
> Sure. Although the classy way would be to use a rheostat or variable
> autotransformer, but can guesstimate the value (in ohms) of
> a fixed resistor to wire in series with the unit as follows:
>
> R = ((130 - T)/(T - 70)) * (14400 / W)
>
> where W is the actual wattage of the unit (which is probably a value
> somewhat lower than its rated wattage), 130 is the observed
> temperature now, 70 is the ambient temperature, T is the desired
> temperature, and 14400 is the square of the line voltage.
>
> So for example, let's say the unit is rated at 100 watts. Probably,
> it consumes 90 watts, and you want the temperature to be 120
> instead. In this case you need a 32 ohm series resistor. It better
> be rated at 15 watts or more (in this example).
>
> (Of course don't do this unless you're confident you can do
> a safe job of wiring it up and insulating it and protecting
> it from any mechanical trauma. Having a second person check your
> work is always a good idea. Etc.)
>
> Steve
>


If I may, R = ((130-T)/(T-70)) *(V^2 / W) since 120V isn't normal in
some places.

For example for me I'd have to do R = ((130-T)/(T-70)) * (125^2 / W)

I've measured it, and it's definitely 125V service where I live.