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when using two SN74123N Multivibrators, I always get "two voltage sources were found to be in parallel" when I connect the grounds

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Here is the whole circuit, where the 74123 is used in context. I'm using an array of comparators to send digital signals to the 74123's. These 74123's will then give a sustained pulse to indicate when the threshold has been reached.

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Message 11 of 18
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I just tried the other components you suggested, at least the ones available in Multisim, the 74121 and 74130, and they gave the same error as before.

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Message 12 of 18
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hello, thanks for response.

 interestigly enough, when I opened your file and started simulation - it worked just fine.take a look at the picture -

 

I am confused now -

 

nevertheless I have a few questions about curcuit itself  - but it is a diffrent topic andd we could discussed it if you want to.


with hope it helps

 

thanks

Michael

Message 13 of 18
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Oh right, I see. It works when only one of the 74123's is grounded, as is the case in the attachment. When you attach all the rest to ground, though, it won't work.

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Message 14 of 18
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Solution
Accepted by topic author Orvis_NSL

hello, thanks for response.

 

Look- I've done following  - I created circuit with 3 cases ( 6 pcs ) of 74123 - and tried to simulate it - it worked  fine - the file in attach.

 

 try it.

 

 

if it works for you - add more components to build your project.

 



with hope it helps

 

thanks

 

Michael

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Message 15 of 18
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Solution
Accepted by topic author Orvis_NSL

Aha! I found that by leaving the CT pin (6 and 14) open on the 74123, instead of connecting it to GND, I was able to get it to work. I need that pin to be at GND, but even when I leave it open it has a value of 0, so I don't need to connect it to GND. This is not what I will do in the actual PCB, but it seems to be an effective workaround for the multisim environment. Thank you, Michael, for your help and time, you've been very helpful!

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Message 16 of 18
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hello, thanks for response.

 
sure, we have to help each other.

 

 

BTW - check your schematic - you have 6V battery connected to +5V global connection.

 

and another something

- it looks to me the value's of resistors in top left corner are wrong - assuming you build kind of A2D.

- using that approach with 74123 should work but, you are going to get bunch of asynchronous  pulses plus need of 6 caps and 6 resistors and 3 IC's for that.

I believe there are  much more elegant ways to do that - just IMHO.

with hope it helps

 

thanks

 

Michael

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Message 17 of 18
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Thanks, Michael.

It is a charged particle detector. The circuit will receive a pulse signal from a preamplifier, the comparators turn on if it is above their threshold, and the 74123's emit a longer pulse that can be counted.

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Message 18 of 18
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