Comments on: How To Use A Photoresistor With Raspberry PI Pico

By: julian

julian — Fri, 05 Jan 2024 17:55:57 +0000

hi,
usually, LDR have a high resistance in dark and low when full light.
May not it be better to connect the LDR to the GND instead of the VCC,
and in the program, just print 100-round(light/65535*100) to cope with the expected behavior?
The 10k resistor would always protect the GPIO.
btw, this is how i see it mounted everywhere.
thanks for your articles, it helps a lot.

By: peppe8o

peppe8o — Mon, 01 May 2023 04:03:18 +0000

In reply to Alex. No, they are all the same. You can choose the one more convenient for your cabling

By: Alex

Alex — Mon, 01 May 2023 01:43:43 +0000

Is there any reason to choose GND pin 38, and not any of the others ? 28 or 23 (or the other side ? 3,8,13,18)

By: Ammy

Ammy — Wed, 29 Sep 2021 11:02:17 +0000

In reply to peppe8o. So if there is higher current then the gpio accept range. the current would try to escape from the easiest path which is through the resistor to the ground. am i right?

By: peppe8o

peppe8o — Tue, 28 Sep 2021 12:48:50 +0000

In reply to ammy. Usually, high resistors can be used to avoid a direct spike of current coming to your GPIO port. In this case, photoresistor is itself a resistor, but when it has low resistance it can let pass quite all the current (it isn't a voltage risk, but a current risk)

By: ammy

ammy — Tue, 28 Sep 2021 12:20:22 +0000

Why We Are Using 10K Ohm Resistor.
As We Are Passing 3.3v to the adc pin.
Which Is Also Looking For The Voltage Between 0 to 3.3v