H8-Multi-I/O board!

[norberto.collado koyado.com]

Any ideas on how to test the 20ma loop circuit designed to support Teletype printer/puncher?

Thanks,

Norberto

[Joseph Travis]

You could use a analog VOM and watch the needle bounce back and forth or place a resistor in series of the loop and connect an O'scope across the resistor to see the waveform.

Joe 

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[Joseph Travis]

BTW - You can use a battery or power supply with a resistor in series with the opto-coupler to form the loop.  Select the resistor value based upon the voltage to give you 20mA in a closed loop.

Joe 

[norberto.collado koyado.com]

Thanks Joe! Let me try the VOM first.

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From: se...@googlegroups.com <se...@googlegroups.com> on behalf of Joseph Travis <jtravi...@gmail.com>
Sent: Friday, May 1, 2026 5:57:19 AM
To: se...@googlegroups.com <se...@googlegroups.com>
Subject: Re: [sebhc] H8-Multi-I/O board!

 

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