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Author Topic: Open Source 3 Channel Frequency Generator  (Read 36978 times)

Offline europeanhillbilly

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  • Posts: 25
Re: Open Source 3 Channel Frequency Generator
« Reply #30 on: January 01, 2009, 03:43:21 PM »
Just measured the output of the Arduino PWM.
Frequency and duty cycle are dead on, measured with a Fluke 124 40Mhz oscope.
Great stuff :)

Now how would I attach a mosfet to switch 60V or more? Possibly with an optocoppler or something to keep the 60V from getting to the Arduino?

Thanks alot Yucca, great work

Offline Yucca

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Re: Open Source 3 Channel Frequency Generator
« Reply #31 on: January 04, 2009, 03:41:25 AM »

Sorry for the delay in replying. Glad you got it going OK. yes freq and DTC are spot on thanks to using the hardware PWM circuit within the arduino chip. And because the arduino board uses a crystal clock it is almost jitter free and very temperature stable.

For switching at 1MHz use any old N channel FET like IRF730 which goes up to 400v. Use that to chop your neg line.

You could use an optocoupler to protect your MCU yes that´s a good idea. You could tie the FET gate to ground using a resistor and then wire the optocoupler output to the gate. Higher resistance value will give faster turn on and slower turn off and vice versa.

For the stuff I´m doing I like to have as fast rise and fall times as possible so I use a UCC27322 FET driver it also provides a level of protection for the MCU and has a built in charge pump so it even works fast off the MCU 5v supply. Some fast FET drivers need plus and minus 12v supply to achieve the fast switch.

Note, there are a couple of blind spots in the PWM output where certain frequency selections cause no output, this is a bug in the algorithm that sets up the hardware timers and I will try and remedy it soon.