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Registered Member #9039
Joined: Wed Dec 26 2012, 03:31PM
Location: Epping, Victoria, Australia
Posts: 117
The only difference is that I am powering the whole things from a 12V battery.
1) I can measure a voltage with my multimeter on the TC4422 side of C3 and the voltage goes up and down as I change the duty cycle of my 555 as expected
2) I cannot measure any voltage on the other side of C3, but surely I should be able to able to. I don't understand this.
3) If I connect a white LED plus resistor to each of the3 windings of my gate driver then it lights up bright as expected, so clearly power is getting to it despite my multimeter not being able to register a voltage on this side of the TC4422.
4) If I connect up the gate drive windings as in the circuit diagram then it is having no effect on the FETS and an automotive light bulb (and the LED) connected in place of the flyback primary fail to light up.
So power is getting through to the FET gates but they are not turning on.
Is this likely to be a toroid problem - I got it from the circuit board of a microwave oven. I.E. The square wave is not being reproduced properly.
Registered Member #42796
Joined: Mon Jan 13 2014, 06:34PM
Location:
Posts: 195
it the ferrite of the toroid is exposed try to use the multimeter to measure the resistance between 2 random points. If it register a few Kohms the toroid is ok to be used as a GDT but you tested with a LED each winding so it seems to be ok
so you should check the phasing of the GDT output coils because if connected wrong both mosfets will turn on at the same time creating a short and one or both fail check each mosfet to see if it is still working...
Registered Member #9039
Joined: Wed Dec 26 2012, 03:31PM
Location: Epping, Victoria, Australia
Posts: 117
If the FETs were shorting then surely them and my connecting alligator clips would be heating up or melting.
But alas everything remains cold to the touch.
Perhaps a heavily distorted square wave is enough to turn a LED on but not enough to overcome the capacitance in my power FETs. Nor will my automotive light bulb light up in the slightest if I connect it to the windings of the toroid in place of the LED.
I saw one of cool dude klem's videos where he used the ferrite core from TV flyback transformers for a GDT, and his flyback driver worked great with it.
He was saying that he also had a lot of trouble producing a working GDT.
I have several flyback cores so I will try one of them.
Registered Member #9039
Joined: Wed Dec 26 2012, 03:31PM
Location: Epping, Victoria, Australia
Posts: 117
OK well I just tried making my GDT with a TV flyback transformer core, I connected my automotive light bulb up to one the the secondaries and started the 555 + TC4422 part of the circuit.
And my automotive light bulb partially lights up.
So apparently my toroid from the discarded microwave is crap despite it being able to light up an LED as a GDT.
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Problem with Steve Ward's flyback transformer driver
