Be aware that a variac DOES NOT ISOLATE the input from the output and as such can become a shock hazard.
Since you only need 24v at 5 amps that is only 96 watts! Why such a large unit?
You still should use a transformer to isolate and drop the voltage to 24, and at less than 100 watts ....try a room light dimmer!
Mini variable Inverter?
Re: Mini variable Inverter?
Len
“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)
“To invent, you need a good imagination and a big pile of junk.” (T. Edison)
"I must be on the way to success since I already have the junk". (Me)
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Re: Mini variable Inverter?
Try adding resistor R3 as shown, that should protect the diodes and darlington base circuit. Maybe a 1K for starters
Steve G
Steve G
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Re: Mini variable Inverter?
"...blowing...1N914 diodes..." - is the load inductive? With so many in series the sudden transistor cut-off (~4V) on the falling side of each half cycle of AC could be causing a high voltage spike. Why so many 1N914s? Or, is the circuit somehow exceeding the max current of the diodes?
"...transistors get super hot..." - they are going to generate heat because they are being used as linear amplifiers not as switches. Are the heat sinks large enough for the power dropping on the transistors? Transistors correctly mounted on heat sinks?
Cheers,
"...transistors get super hot..." - they are going to generate heat because they are being used as linear amplifiers not as switches. Are the heat sinks large enough for the power dropping on the transistors? Transistors correctly mounted on heat sinks?
Cheers,
Dale Y
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Re: Mini variable Inverter?
Yes it is an inductive load, also I have the power resistors on 8 inch heat sinks.
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Re: Mini variable Inverter?
as for variac not being isolated, add in the isolation transformer
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