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selbersuess
Joined: Mar 21, 2017 Posts: 10 Location: Trier
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Posted: Thu Apr 13, 2017 4:26 am Post subject:
short protection for cv-out |
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hello friends,
i have a question (maybe a stupid, i'm not very experienced with electronics, more in programming.) about what happend when cv-out shorten to ground.
for example:
i built a midi2cv by an arduino with 8 cv, 4 gate and 4 trigger outs.
to fit in a small unit, i used stereo jacks.
the signal line goes:
midi-in -> arduino -> mcp4922 -> lm324 -> 1k resistor -> cv-out-jack
my question is, what happend if i plug in mono-cable. is it a problem?
if yes, is there a simple way for a short protection?
thank you
daniel |
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Grumble
Joined: Nov 23, 2015 Posts: 1294 Location: Netherlands
Audio files: 30
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Posted: Thu Apr 13, 2017 10:14 am Post subject:
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The 1k resistor is sufficient to prevent the 324 from breakdown due to short circuit. |
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PHOBoS
Joined: Jan 14, 2010 Posts: 5599 Location: Moon Base
Audio files: 705
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gdavis
Joined: Feb 27, 2013 Posts: 359 Location: San Diego
Audio files: 1
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Posted: Thu Apr 13, 2017 11:47 am Post subject:
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LM324 is protected from short to ground on one output at a time. A short to a higher voltage than the output or on more than one output at a time could damage the part.
A brief short as the patch cable is being inserted is one thing, but I would avoid a continuous short. I don't recommend plugging a mono plug into a stereo output jack. _________________ My synth build blog: http://gndsynth.blogspot.com/ |
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PHOBoS
Joined: Jan 14, 2010 Posts: 5599 Location: Moon Base
Audio files: 705
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gdavis
Joined: Feb 27, 2013 Posts: 359 Location: San Diego
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Posted: Thu Apr 13, 2017 12:43 pm Post subject:
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Ya, in theory you should be able to short one of the outputs to ground indefinitely without any problems, I just think it's a bad practice to be relying on that by design. Especially since in use you would have to pay attention to which jacks are on the same opamp and mentally make sure not to connect more than one of them incorrectly. Someday something bad will happen.
The output resistor may be an option but as you alluded to earlier, for pitch CV it may have an audible effect on the pitch. _________________ My synth build blog: http://gndsynth.blogspot.com/ |
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Grumble
Joined: Nov 23, 2015 Posts: 1294 Location: Netherlands
Audio files: 30
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Posted: Thu Apr 13, 2017 1:28 pm Post subject:
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gdavis wrote: | for pitch CV it may have an audible effect on the pitch. |
It all depends on the impedances of the connected input(s).
If all the inputs connected to this CV are buffered, it is not a problem, but if the connected input is a potentiometer of say 100k, the mismatch will be 1% of the full scale, and it gets worse if more than one input is connected to this CV.
So that indeed is something to take into account. |
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selbersuess
Joined: Mar 21, 2017 Posts: 10 Location: Trier
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Posted: Thu Apr 13, 2017 1:54 pm Post subject:
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until now i used stereo plugs and was observant to that, i will do furthermore.
the motivation was to have more space in my modular.
now i realize that it was not a perfect idea.
thank you
daniel |
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Grumble
Joined: Nov 23, 2015 Posts: 1294 Location: Netherlands
Audio files: 30
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Posted: Fri Apr 14, 2017 11:50 pm Post subject:
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I just can't understand how a mono jack would be different from a stereo jack in terms of shorting the output? |
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PHOBoS
Joined: Jan 14, 2010 Posts: 5599 Location: Moon Base
Audio files: 705
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Grumble
Joined: Nov 23, 2015 Posts: 1294 Location: Netherlands
Audio files: 30
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Posted: Sat Apr 15, 2017 3:18 pm Post subject:
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selbersuess wrote: | until now i used stereo plugs and was observant to that, i will do furthermore.
the motivation was to have more space in my modular.
now i realize that it was not a perfect idea.
thank you
daniel |
If the only reason to refrain from using mono connectors is worries about shorting outputs, I would use mono connectors still the same.
Because for mono and for stereo connectors both the tip of the connector will touch the gnd connection when inserting the plug into the connector. |
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gdavis
Joined: Feb 27, 2013 Posts: 359 Location: San Diego
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Posted: Sat Apr 15, 2017 4:14 pm Post subject:
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Grumble wrote: | selbersuess wrote: | until now i used stereo plugs and was observant to that, i will do furthermore.
the motivation was to have more space in my modular.
now i realize that it was not a perfect idea.
thank you
daniel |
If the only reason to refrain from using mono connectors is worries about shorting outputs, I would use mono connectors still the same.
Because for mono and for stereo connectors both the tip of the connector will touch the gnd connection when inserting the plug into the connector. |
Yes, inserting can create a momentary short, which is why modular outputs typically have some sort of short protection. But a stereo jack creates a continuous short, and as we've discussed here already, a momentary short on a single jack when plugging in is a different scenario than continuous shorts on potentially multiple jacks. _________________ My synth build blog: http://gndsynth.blogspot.com/ |
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Grumble
Joined: Nov 23, 2015 Posts: 1294 Location: Netherlands
Audio files: 30
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Posted: Sun Apr 16, 2017 12:34 am Post subject:
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Ow.... I misread the whole thread
I failed to notice that the stereo jacks were used as...wel...stereo jacks |
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