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Hey everyone, just a quick question about my modulator, I used -this schematic- to build it first, but didn't like how the dead-time control worked. It took several turns of my pot to get it to actually start operating, and then only got the other 3 turns to vary it.
So I have added a 33K resistor from V+ to one end of the pot and the other end of the pot goes to ground, the wiper then goes to pin 4. I removed the connection from pin 2 to 4 so only the 47nF cap and pot wiper are connected to it. I now get 9 turns of variable output (using an LED with a high value resistor to see decrease of dead-time)
Question is, is this an okay way to do it? I currently don't have any test equiptment so I am unable to see the output or even measure the output frequency and duty cycle...so I'm clueless as to whats going on. Also how much do you think the output dead-time swings? I understand that each output puts out a max of 45% duty cycle, and when the outputs are tied they go to a max of 90% correct? Or does it stay at a max of 45%?
Registered Member #3900
Joined: Thu May 19 2011, 08:28PM
Location:
Posts: 600
Slow the circuit down to levels where you can see and think at. Then hook an led to the output . This will give you an idea of the duty. You can measure the frequency by speeding it back up again, and putting a small speaker on th output. Most computers have a mic and sound software, so turn on the circuit, then start the mic listening. I recommend audacity- I used it to measure the break rate of a rsgtc in my physics class before by putting tape on the motor shaft then going into audacity and measuring the full cycle between the noise spikes.
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TL494 Audio Modulator
