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| short circuit detection with adjustable threshold |
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| OM222O:
I need to build a circuit that can detect if the resistance between the two probes is less than a certain threshold (max value would be 100ohms since it's used for short circuit detection). I've seen a few examples of short circuit detection circuits using BJTs that activate a LED and buzzer but that's not what I want. they also have next to no explanation on how the circuit actually works, so I don't know how to modify them. their output is also quite analog, but since I want to interface the output to an MCU, that's not a huge deal (MCU pins have schmitt trigger inputs). any ideas on how to do this? |
| SiliconWizard:
I guess the solution would largely depend on the surrounding circuit. Unless this would be a completely stand-alone detector without anything else connected to the load between the probes? |
| max_torque:
Are there any common mode voltages on the conductors you want to "short circuit detect" on, how fast a response do you need, what are the true thresholds for detection and is there any other noise or anything going on with those conductors? |
| OM222O:
it's not that complicated. noise / bandwith etc are non issues, I just want to use it as a sanity check to check shorts between nets on a PCB. there is no common mode voltage and again, the threshold is something between 10 and 100 ohms. I just want a digital signal which says if there is a short or not. Something like an in circuit tester used in production environments. I'm just not sure how active components like ICs behave when the PCB is populated. a simple voltage test also fails if there are any resistors, since very little current flows into the IO pins, the voltage drop across the resistors is almost 0. |
| Gyro:
To ensure that semiconductors are not detected as short circuits, you will want to limit the maximum voltage across the probes to less than about 0.3V. An unbalanced Wheatstone bridge circuit is a good approach, eg. https://www.nutsvolts.com/magazine/article/build-a-continuity-tester |
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