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Single chip solution pwm
This is a TL494 pwm I've built for the P-Channel mosfets. It will work with the N-channel mosfets also but you need to reverse pins 15 and 16 inputs.
Attachment 1214
This pwm does everything that the ZFF does and more. Although I only show here current limiting, duty cycle adjust, and PRF ( frequency ) adjust, there's also Dead time and a control that allows for two outputs with 48% max duty cycle at 180 degrees out of phase.
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bigger
This post is 6 months old, I know, but do you have a larger version of your sketch? Can't make this one out...
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This should be larger
Attachment 1217
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?
Sorry still cant see the values of the resistors and such. Looks great from what i can make out tho. Any chance you can make one slightly bigger again?
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It's really big on my machine. I've had this problem before on this site.
If you want to build one of these, I get my components from digi-key.
part
digi-key part number
amount
tl494
296-1799-5-nd
1 $.52
100k trimmer pot
490-2876-nd
1 $ .86
10k trimmer pot
490-2875-nd
2 $1.64
5.1k resistors
p5.10kcact-nd
5 $.32
1k resistors
1.00kxbx-nd
5 $.32
220 ohm resistor
p220cact-nd
5 $.32
.1uf cap
2
.01uf cap
1
tl494 pin-out
pin 1 connect center conductor 10k trimmer and then one side of pot to grnd and the other side to Vref ( pin 14 )
pin 2 connect to 5.1k resistor to pin 3 and connect another 5.1k resistor from pin 2 to grnd
pin 3 connect 5.1k resistor from pin 3 to pin 2
pin 4 connect to grnd
pin 5 connect to .1uf cap ( Ct cap used in Osc. ) and connect other side of cap to grnd
pin 6 connect a 1k resistor: connect 1k resistor to 100k trimmer pot connect center conductor of pot to one end conductor then end conductor to grnd
pin 7 connect to grnd
pin 8 Vc output connect to pin 11
pin 9 Ve output connect to grnd
pin 10 Ve output connect to grnd
pin 11 connect to 220 ohm resistor and other end of resistor to pin 12: connect to .1uf cap and other end of cap to grnd: connect to 1k resistor
and other of resistor to grnd
pin 12 connect to +12vdc filtered power ( pwr run circuit used by ECU is already filtered, this would be switched power )
pin 13 connect to grnd
pin 14 Vref output to high side of both 10 k trimmer pots
pin 15 to center conductor of 10 k trimmer pot: one side of pot to grnd and the other to Vref
pin 16 to Rshunt ( 8" of 12 guage solid conductor wire in grnd path of electrolyzer )
I us the breadboard from radio shack ( 2 boards in one package )
I also use there project box and terminal board
When setting up your pwm adjust pin 15 to about .5vdc and pin 1 to about 2.3vdc. You can adjust pin 6 to ground for 101k ohms for the lowest freq.
Make sure that pin 15 is a higher voltage than pin 16.
pin 1 sets your duty cycle and looking at pin 3 you can see a dc output from pins 1 and 2. Pins 15 and 16 make up the current limiting comparator. You will adjust pin 15 once the system is hot.
If you would like to try one of these but don't want to build it yourself, PM me about building you one. I can also make it work for N-channel mosfets, but it is for P-channel mosfets.
Russ
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Hi,
I'm new here, and would like to ask whether anyone was able to build this pwm with N-channel mosfets and ask his/her opinion/feedback about that pwm. I have built it with N-channel, and reversed the 15 and 16 pins, I could set .5vdc on pin 16 and 2.3vdc on pin 1 and could also set the frequency, but still I cannot regulate the current as i wish. Neither the freq. nor the duty cycle nor the current can be set or regulated. The HHO generator always works on maximum current,(as it is getting hot, it takes up more and more current) and the current can't be regulated.
If anyone can help me, please answer soon.
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