Potentiometers in Analog Inputs

[EricVanWyk]

Originally Posted by AustinSchuh

While you may have done this to simplify things for non EEs, I find your choice of symbols for current very unique. Most, if not all, EEs use the symbol "I" for current. I thought you were talking about capacitance there for a moment.

I used C(urrent) instead of I(mperage?) to make it easier for non EEs. I find VCR and PVC easy to remember.

But yes, I use "I" in real life.

[Russ Beavis]

Gustavo,
To answer your question about whether the 5W potentiometer is okay -

Yes it's okay to use but I would recommend that you find something like a 220Ohm or higher potentiometer with 1/4W power rating. It's generally wasteful to use > 1W for a sensor and it will probably get warm. But it will work.

There is an upside to using a 22 Ohm 5W pot, though - it's probably a very durable part and unlikely to be damaged during competition. There's something to be said for ruggedness.

current needed = 5V over a 22 Ohm resistor = 5/22 Amps = 0.23 Amps (which is less than the 0.75 Amp rating for each pin of the Analog Breakout module)

power dissipated by the 22 Ohm resistor = 5V * 0.23 Amps = 1.14W (which is less than the 5W rating for the part)

The 2009 Analog Breakout module can supply enough power and the NI 9201 Analog Input module will provide 10 bits of resolution between 0 and 5V (ie the full range of the potentiometer).

Be very careful to connect the wiper of the pot to the analog input. If you connect 5V power to the wiper, you'll have a variable current draw from the power supply which will short circuit the supply at one end of the potentiometer's range.

Russ

[Dick Linn]

You can find variations of this chart (Google image search ohm's law).

[rsisk]

Thanks for the basic EE training...

Sorry about hijacking your thread Gustavo