# 5v to GND through 3k resistor

Due to misunderstanding potentiometers, I've just built and soldered a circuit board with a permanent 3k (actually 3x 10K pots in parallel) resistor between 5v and gnd. Everything appears to be working OK, but I was wondering if it's OK to leave it like this permanently or could it do some damage?

Thanks, Mark

Due to misunderstanding potentiometers,

What misunderstanding? The normal way to use pots is to wire one end to +5V and the other end to ground. Then the wiper taps off the voltage you set by the knob's rotation.

That's what I did (following http://arduino.cc/en/Tutorial/AnalogReadSerial), but I hadn't realised (or I have the wrong pots or something), that there is a fixed 10k resistance from 5v to gnd through the pot, hence with 3x 10k pots, there is now a permanent 3.3k resistance from 5v to gnd.

Simply calculate the current - i=5V/3.33k=1.5mA. That cannot be dangerous for your power source.

@pito cool thanks! I thought it would be OK, but this is about to get rather permanently fixed in place, and this is my last chance to back anything out without major hassle!

there is now a permanent 3.3k resistance from 5v to gnd.

That is how pots are supposed to work.

PS - I've just checked with the the pot that came with my arduino kit, and it is the same. So presumably connecting these things up always link 5v to gnd through whatever their resistance value is. Obviously if it's low enough ohms that could cause problems, but as put above, at 3k it shouldn't be a problem.

The only big concern is whether the wiper (The part that moves) gets connected something that can handle being connected directly to VCC or GND. Some devices don't like their pins to be connected directly to VCC, as it could create a low impedance to ground, and short things out when the wiper is at full. I usually add a series resistor between VCC and the Pot to always prevent this. Additionally, you can use it to reduce the overall voltage range, giving yourself more precision with the Pot if you have a limited voltage input on an ADC.

The only problem (or an issue) you can create with your wiring is when you go with the wiper to 5V or GND side of the pot, while the wiper is connected to digital output set to low or high. So to be safe you may wire a 470ohm resistor from the wiper to the arduino - to limit the current to aprox 10mA worst case..