Potentiometer for LCD

Question

hi, I'm searching a potentiometer for the contrast control of an LCD. One side of it should be connected to 5V and the other to GND. The middle pin will be connected to V0 which adjusts the resistance. However, I found that the power rating of most potentiometers in market is just 50mW with the minimal resistance of them is 50 Ohm. Assuming the potentiometer works at extreme condition which is 50 Ohm and the voltage on it is 5V. The power it consumes would be 5x5/50=0.5W >>50mW. It would be unacceptable. There is 0.5W potentiometer in the market but it's rare, so I guess I'm thinking this wrong. Does anyone have any clue for such condition? Thanks!

mcb1 · Accepted Answer

This is the normal configuration. The Pin simply receives a voltage and there is little or no current drawn. At the upper end it will receive 5 volts, 2.5v at the middle and 0v at the lower end. Mark

mcb1 · Answer

I was so stupid I don't think that is correct. You asked relevant questions, and more importantly gave enough information for us to work out how you were connecting it, and verify it wasn't an issue. Stupid would be not asking the question. Mark

beacon_dave · Answer

Try using a 10k pot instead ? https://www.arduino.cc/en/Tutorial/HelloWorld

jw0752 · Answer

Hi Bin,

If you were connecting a potentiometer as you described (where the voltage or ground was on the variable wiper) you would likely destroy the potentiometer even if it were rated at several watts. The wattage rating is for a situation where a voltage is across the entire resistance of the potentiometer. If the voltage is on the wiper the current would increase as the wiper is turned closer and closer to the ground. More importantly the heat produced would be in an increasingly smaller area of the potentiometer's resistance strip. I have in the past smoked a 25 Watt reostat by making this mistake. The diagram of mcb1 is correct and don't be fooled into thinking that the zero in V0 has anything to do with 0 volts. It is just a pin designation.

John

Potentiometer for LCD

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