I would like to find schematics for dimming on the primary winding of an 50W transformer. It seems that halogen dimmer schematics would be suitable, but did not find any :-(
The transformer secondary is 1.5-3VAC, so it is hard to effectively dim on this side.
One trick is to use a transformer with several voltage taps on the primary and switch between them. This will not produce a continuous range, but might have enough steps for your use.
If you cannot find one with the 3 V output you need, you can put a 1:1 transformer with primary and secondary taps in tandem on the primary side.
Already tryed with a dimmer and a transformer:
bad results, the regulation is not linear and is going at steps instead than be smooth.
Some impruvements obtained applying in parallel the transformer a lamp or a resistor with the same power of the transformer.
A snubber ( at least in my case ) didn't help.
Yes, a variac is an excellent solution if your application can accommodate the size and weight. Feed the variac output into your step-down transformer. Nice clean waveform, unlike a triac lamp dimmer.
One trick is to use a transformer with several voltage
taps on the primary and switch between them. This will not produce a
continuous range, but might have enough steps for your use.
Now this is funny.I have seen a dimmer connected on the primary side of the transformer of an unregulated DC power supply so that the output voltage can be adjusted.It worked fine even with such a strange load.Suppose you didn't try the right circuit.
I was doing a motor control speed last week and I found interesting info in to Applications Note, some of them are:
**broken link removed** in this one there are a ckts for solving your problem, I didn’t test it. **broken link removed** in this one, you have a good theory and applications about triacs. I found it very useful.
Thanks for the useful info! I used the triggering method described in ST AN308, but as I found no schematic, I built my own controller.
It operates between 0-180 phase angles, and unlike a standard dimmer, sends a series of pulses after the set angle. The pulses are 100 usec long with a delay of 500 usec between them.