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Old 6th Oct 2011, 2:26 pm   #1
Al (astral highway)
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Default TTL level output - how to feed signal into noisy cct?

This is related to my current post about components...

I'm making a simple PWM with a low-frequency (220Hz) TTL level output. It'll provide a signal to a buffer and modulator on a board that is noisy - as has a high-powered pulse xformer running at around 30KHz. Okay to use ribbon cable to connect my output to the input of the board? Twisted pair? What's the best 'transmission line' for such a signal. I'm sure it's not critical at such a low frequency but interested to know what's ideal.
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Old 6th Oct 2011, 2:57 pm   #2
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Default Re: TTL level output - how to feed signal into noisy cct?

Will these be 5 volt pulses at 220Hz? I wouldn't have thought there would be that much interference(particularly as you are going through a buffer)-that's the point of digital. Can you sheild the 30KHz in some way? And make sure they are both well de-coupled.
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Old 6th Oct 2011, 3:15 pm   #3
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Default Re: TTL level output - how to feed signal into noisy cct?

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Will these be 5 volt pulses at 220Hz?
Tim, yep, thanks for that.

Oh well, good to hear that it's not critical. I think some salvaged ribbon cable is my choice.
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Old 6th Oct 2011, 3:49 pm   #4
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Default Re: TTL level output - how to feed signal into noisy cct?

If you are concerned about noise getting off the board into your external PWM why don't you opto isolate.

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Old 6th Oct 2011, 5:24 pm   #5
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Default Re: TTL level output - how to feed signal into noisy cct?

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If you are concerned about noise getting off the board into your external PWM why don't you opto isolate.
Mike, great idea! Thanks
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Old 7th Oct 2011, 8:53 pm   #6
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Default Re: TTL level output - how to feed signal into noisy cct?

It is, I wish I had thought of it! Should be fine at 220Hz.
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