Author Topic: Opto - Transistor Pulsing Circuit  (Read 15097 times)

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Re: Opto - Transistor Pulsing Circuit
« Reply #16 on: August 23, 2010, 02:48:33 am »
Also, Take out those diodes and add only a capacitor in parallel with the primary too about 100nf is well ,,,

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Re: Opto - Transistor Pulsing Circuit
« Reply #17 on: August 23, 2010, 02:58:31 am »
sebosfato, can you draw the circuit you are describing, i can't quite picture it

this driver it to pulse the primary of a toroid set up transformer, for a VIC

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Re: Opto - Transistor Pulsing Circuit
« Reply #18 on: August 23, 2010, 03:50:22 am »
The circuits shown are good you just need to add a capacitor between the drain and source, about 200nf works fine for irfp250 transistor (this allow the transistor to completely stop conducting the current during the of pulse and thus make it work cooler... use a mosfet driver is the best...


There are many ways you can do it... Can you tel us what you need this driver for?



In my projects page you find a good schematic of a pll circuit you can use it...


Best regards

Nah , neither those circuits are good , nor is your answer . Sorry sebos /:

He needs the driver for driving a mosfet , the relevance of your question ?

Donald , when using a mosfet on the high side ( positive side ) , you need 10 volt Vgs , that means you need 22 volts pulses if you wanna  saturate a N mosfet @ 12 volts at drain . So that circuit you claim to be in Stan's does not work ... Neither have I seen in in Stan's coloring book .

Thats why we use P channel on the high-side , these can work with totem pole and dont need much higher voltage source , but they are inverted compare to N type , On @ gate = no current  draw from mosfet .

But P channels are more expensive , have less current , has more capacitance , just inferior compared to N channel .

I think this is enough for you to research and have success , it really isnt rocket science to use a mosfet .
« Last Edit: August 23, 2010, 04:38:19 am by Dankie »

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Re: Opto - Transistor Pulsing Circuit
« Reply #19 on: August 23, 2010, 03:56:34 am »
dankie can you draw a circuit of something that will work good? please

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Re: Opto - Transistor Pulsing Circuit
« Reply #20 on: August 23, 2010, 04:25:16 am »
I am truely surrounded by pathetic individuals .

And you guys wanna be engineers and inventors ? Hmmph !


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Re: Opto - Transistor Pulsing Circuit
« Reply #21 on: August 23, 2010, 10:36:06 am »
Ok thanks, I see it now

This is what you described,


Yes, but the base of the middle transistor should be at the collector of the opto transistor and the emitter of the opto-transistor at ground.
the second could work, but you'll have a large voltage at the transistor (Uce + voltage over resistor).


Or just use Dankies's version. I don't know if it works but with the way he presented it it should better work.




Ironically he was laughing at people using bipolar transistors and presents one himself. Good job.

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Re: Opto - Transistor Pulsing Circuit
« Reply #22 on: August 23, 2010, 13:40:21 pm »
turns out the 40 amp and 12 amp mosfet I had don't work, but if i get the circuit switching properly then that should fix the heating problem and the voltage problem, the 7 amp mosfet i have is a K1400A, i think the tech sheet is on the first page.

I've got my circuit torn apart, and a better heat sink for the mosfet, now I just need to confirm a worth while circuit. I don't have any mosfet drivers that I know of, but maybe i can scavenge some of those too.

I think i'll start with the first circuit even though it has an inverting signal, then modify the code from the micro controller to deal with it, if that doesn't suit me i'll track down an npn transistor to add to the circuit.

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Re: Opto - Transistor Pulsing Circuit
« Reply #23 on: August 23, 2010, 13:44:02 pm »
You can use a driver chip for a FET, but its not needed.
FET's are switched on by voltage and not by current.
So, anything that switches on like 5 volts on a FET will work.
Dankie is right when he says that by using a driver chip is a perfect way of doing it, but again, its not needed.
 
Steve