Quote:
Originally Posted by GMB
What temperature do you get inside a DAC90?
You might want to check the temperature range that the Bluetooth device can stand.
I would just stick a zener at the bottom of the heater chain and then smooth the resulting asymetric squarewave that results, making sure it was powerful enough to stand the switch-on surge.
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There is a problem with that approach, in that the "asymetric squarewave" actually reverses polarity at its lower point. In fact, it will try to discharge any smoothing capacitor placed across the zener.
Also the zener must be substantial enough to withstand the full heater current.
Your circuit would
still require a series rectifying diode before the smoothing cap. to overcome the "square wave " problem i.e. to stop the cap. partially discharging back into the circuit during part of the cycle.
The point you make about the ambient temperature is
very valid, and certainly should be a consideration in a DAC90a. Tony.