Combine analog outputs from difference sources, physically

[joehsiao]

Hi,

I made a LabView program which looks for rising edges as triggers from an external instrument. Everything is working fine.

Now for the purpose of testing, I want to use pulses generated by a USB 6501, so I don't have to turn on the actual instrument. My solution is use a T-shaped adapter (see image) to wire signals from both sources to the same port, not at the same time though.

When one source is active, I assume the other source is receiving the voltage through its analog output at the same time. My concern is is it going to cause circuit damage?

[RTSLVU]

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@joehsiao wrote:

Hi,

 My concern is is it going to cause circuit damage?

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Well that really depends on the source, some can sink current and are fine with a higher voltage applied to their outputs than they are set to, and some can not and could be damaged by this.

Why not just hook up one at a time since you only have one input?

[crossrulz · Accepted solution]

You have some BAD assumptions.  Almost NEVER should two sources be wired directly together.  In this case, it sounds like you need an OR gate to combine the two signals.  Of course, I am assuming TTL (5V) logic.

[joehsiao]

Is there any OR gate that I can purchase online? I did some google search but couldn't find one.

[RTSLVU]

My first thought was a "Diode OR" too, but it may not work in your situation so I did not suggest it.

Try it out and tell us if it worked.