# Basic analog sensor usage :(

(Hey, sorry bout this, no electronics class during summer around here)

I've seen the 10k pot demos... lame.

I have a 10 ohm thermistor, and it works with a 10 ohm resistor (Pull down/up?) (10k ohm causes all the voltage to go to pin right?)

But it overheats like hell at theoretical 500mA

What am I doing wrong? (That doesn't cause me to need a 5000 jigawatt resistor : )

again, sorry for something so basic, but either way, thanks for your time!

If you want less heat you'll need to use less current. To do that you'll need to increase the resistance or decrease the voltage.

Perhaps you could draw or describe your circuit in more detail.

So then I guess my question is... How do I use low resistance analog sensors?

I know I should know this...

Circuit is just thermistor between 5v and point 1,
point 1 to analog 1 and to gnd through resistor

You can use a higher value for your current limit resistor to limit the self heating of the thermistor. Then you can use an amplifier to get the output of your thermistor circuit boosted up to a level that your a/d converter is designed for.

A typical glass bead thermistor has a dissipation constant of about 1.5mW per degree C in still air so that's about 40mW at room temperature which means for a 10 ohm thermistor you'll want to keep the current below about 60mA.

P = I^2 * R

So for your thermistor, you'll get a signal that centers around say 0.6V which won't give you very good resolution if you are going into an Arduino analog input that expects 0-5V. I don't know what k is for your thermistor, but if you know that, you can calculate what gain you need for your amplifier. You'll want a gain that doesn't amplify the thermistor voltage over 5V at the thermistor's maximum resistance.

Thank you

maybe I'll try to find something more compatible next time

Yeah, get a 10k thermistor, for example, although if you are interested in learning something about electronics, you could make what you have work.

I always like trying to make what I have work... I think it is because im cheap!!!! ;D