Wednesday, 6 June 2018

range detector - Where to put stabilising capacitor?


Following on from this question. Can I place the capacitor anywhere in the circuit before the IR Distance Sensor? In my project I have 2 PCBs: A power circuit and a Processing Circuit. In the Diagram below you see the two PCBs Power Board and Processing as well as the Sharp distance sensor. Following the diagram, can I place the capacitor on the power board or will it be ineffective by the time it reaches the sensor? I don't want to damage my expensive sensors.


---------------         12V             ------------------
| |-------------------------| |
| Power board | 5V | Processing |
| |-------------------------| Board |
| | GND | |
|_____________|-------------------------|________________|
| | |

| | |
GND | Out | 5V |
| | |
------------------
| Sensor |
------------------

Answer



See my answer to your previous question here, specifically this image:
this image.


You want the caps to be as close as possible to the components which are drawing current. The voltage varies due to to trace/wire inductance, so it doesn't help to locate the cap before this inductance. The caps absolutely must be on the sensor. You should already have output caps on your power board and decoupling caps near every IC on your 'processing board'.



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