Hi:
As far as I know the recommended value for a potentiometer to be used in an Arduino board ir 10K.
But I need to use 5 potentiometers read by the analog pins. Of course the pots will be wired in paralell, with a terminal to +5V and another to ground. So each pot "will have 2K" of total resistance (10K / 5).
Will I fry the UNO?
Thanks
The power suppy will see the 10k pots in parallel, yes. Each analog input will just see the voltage level at the wiper of its own pot, and draw 1uA of current max per the '328P spec.
CrossRoads:
The power suppy will see the 10k pots in parallel, yes. Each analog input will just see the voltage level at the wiper of its own pot, and draw 1uA of current max per the '328P spec.
OK, I understand that each wiper will be correctly read by the analg pin, now my concern is about having a 2K load instead of a 10K load.
Is the Arduino designed to cope with n 10K potentiometers, when their total load will be 10K/n? Or should I replace them with n x 10K each?
5V across 2K is a mere 2.5mA
And this seems to get even worse.
So far there is no Arduino board, I'm just wiring the potentiometers. Now I measure 2K between both ends in each pot. At one end, the wiper measures 0K, and 2K at the other end. But in the middle of its travel it reads around 3.2K! So the resistance increases and then decreases from one end to the other, and this has to do with the parallel wiring of the potentiometers.
Analog or digital inputs take essentially no current, they merely sense voltage (this is true of all CMOS,
and "no current" means "an incredibly small amount of current" - far less than 1uA, usually
measured in pA at room temperature, nA if the chip gets hot).
A 10k pot takes 500uA from the 5V supply, not enough to damage anything.
The things you have to avoid are connecting high current things to outputs, or over-voltage to
any pin ever.
The only solution for the problem of the out-of-scale reading that I mentioned later is to wire the wiper and the ground terminal together, so each wiper reads 0 to 2K (I'm using the tester as ohmmeter to see what is going on).
Now will that damage the board?
No it will not.
Yes it will damage the board. If you have grounded the wiper and you have 5V on one end then moving the pot all the way to that end will short out the supply with a zero resistance. It will get hot and release the magic smoke.
Yes, I've done it accidentally.
CrossRoads:
No it will not.
But then it will not work, as the pin will read always 0, regardles of the wiper position.
You're right.
MorganS:
Yes it will damage the board. If you have grounded the wiper and you have 5V on one end then moving the pot all the way to that end will short out the supply with a zero resistance. It will get hot and release the magic smoke.Yes, I've done it accidentally.
So the only way would be leaving one of the pot terminals unconnected. Then there would be a terminal connected to 5V, the wiper to the analog pin and the other terminal in the air. Will this cause instability problems?
That won't work either. It will read 1023 all the time.
Just follow the instructions in any online tutorial anywhere except "instructables". This is really simple stuff.
MorganS:
That won't work either. It will read 1023 all the time.Just follow the instructions in any online tutorial anywhere except "instructables". This is really simple stuff.
I've been trying for a while to no avail. Seems as if nobody had ever to use more than one pot in an Aruino...
Stop trying to test the circuit with resistance readings. It is obviously just confusing you. Build it up, and look at the voltages on the wipers. You will see that everything is correct, if you have connected the ends of all the pots to ground and +5V.
rva1945:
I've been trying for a while to no avail. Seems as if nobody had ever to use more than one pot in an Aruino...
It proves more, that you have never had to use more than one pot.
I have a device on my desk right now with 5 conventional pots and two linear pots plus empty holes for more. It has an Arduino Micro on the inside and a 3D printed case on the outside.
It works just fine.
aarg:
Stop trying to test the circuit with resistance readings. It is obviously just confusing you. Build it up, and look at the voltages on the wipers. You will see that everything is correct, if you have connected the ends of all the pots to ground and +5V.
Ok that is precisely what I am going to do in minutes. But I bet the strange behaviour will be reflected when reading the pin value. I promise to post the results. Thanks.
You're talking about this setup, yes? This will not damage anything and analogRead will return proper values.
I've just tested it with a couple of pots and even though the total resistance is half that of each pot, both are correctly read by the analog pins. I should now test it in my projec, with the 5 pots.
Thanks.
