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I want to power my 10 sensors (2 MyoWare and 8 FSR sensors) from the 5V pin of the Raspberry PI4.

The 5V pin provides as voltage 5V and as current 1.5A.

The one sensor needs 5V and a current 9mA.

Can I only power them from the pin 5V of the Raspberry Pi and could the value current 1.5A damage the sensors?

JRE
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sarra marmouche
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    Certainly, if you pushed 1.5 amps into one of your sensors it might melt. On the other hand, if you put 5 volts across the sensor, it would take 9 mA so, how could you get 1.5 amps into your sensor I wonder? If I walked into my local store with 1500 dollars in my pocket and wanted to purchase a box of matches, would I hand over all the 1500 and walk away with just the box of matches? – Andy aka Nov 11 '20 at 15:37
  • Generally you should minimize what you power *through* and MCU board, but low current sensors may be okay. To understand the difference between current *capability* vs current utilized, please see the canonical power supply question at [Choosing power supply, how to get the voltage and current ratings?](https://electronics.stackexchange.com/questions/34745/choosing-power-supply-how-to-get-the-voltage-and-current-ratings). The pi's 5v rail comes more or less from its input, but its 3v3 rail is locally regulated, making that especially touchy and prone to causing crashes when load changes. – Chris Stratton Nov 11 '20 at 15:38
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    As long as the voltage is correct, the load will only draw the current it needs (9mA typ, 14mA max.) The source *can* deliver 1.5A max. but won't force it into the load. – Unimportant Nov 11 '20 at 15:41
  • Andy, that was some analogy XD. @sarra 1.5 A is the "current rating" of that pin. It can give out up to 1.5A safely. Not that it always gives out 1.5A. It depends on load resistance. Hint: Ohm's law :) – Mitu Raj Nov 11 '20 at 15:58

2 Answers2

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It is safer to externally power the sensors.

If they draw more power than expected that could damage the power control of the Pi.

However, the 1.5 amperes are the maximum you can draw from the pin. Since powering your 10 sensors would draw less than 100mA in total, it should not be problem.

You can't damage the sensors.

JRE
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Timur
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  • I wouldn't go as far as to say that you can't damage the sensors. It's more like: You can't damage the sensors when properly connected and configured. – JonathanG Nov 11 '20 at 15:44
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An electronic load has a specific current vs. voltage function that is it's alone. If you put 5V on it, it will consume as much current as it consumes. As long as the current capability of the 5V supply is greater than the total current taken from it, it will supply 5V*.

Add up the current required for your sensors that need 5V. If it's less than the 1.5A that's available from that pin, then you're fine.

* With exceptions: older wall-warts put out somewhat more voltage at no load (no current taken) and less under heavy load. There are also specialty supplies that are designed for delivering a constant current -- but those are super special, and not something you'll encounter even on a yearly, much less daily, basis.

TimWescott
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