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Topic: What killed this MOSFET driver? (Read 3527 times) previous topic - next topic

allanhurst

To tidy things up...

Allan

tauro0221

Hi,
My apologies, maybe I missed one of the replays.

saximus

Just for fun, the 555 approach.

R2 and R38 are a 10k potentiometer shown near one end....

And r37 should be 100.

Allan
Interestingly enough, that was our first prototype before we were given permission to use Arduino :)

allanhurst

Why wasn't it satisfactory?

Allan...

saximus

Mainly, the brightness wasn't really linear. Down low it had a reasonable amount of control but then it would almost instantly go really bright around halfway on the pot.

It was almost certainly something we were doing wrong but that on top of the fact that we have a few other little things to simulate that need a bit more "brains", we figured why not just Arduino for all of it.

mottofreee

125W? I suppose many filament lamps in series / parallel.

1) Conductors of them creates a magnetic field that stores energy (in this case a little) and the law Lenz says:
I, the induced current
I have always opposed
Cause what I produced.
This gave rise to the high-voltage pulses.
The solution could be a diode in antiparallel to the consumer.
Internal diode transistor meets the protection requirements in theory but in practice it is not.
 
2) The marks do not correspond with the transistor datasheet.

In similar cases the best results we have obtained with dedicated optocoupler (eg TL350).

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