resistors

[xXAxHillbillyXx]

ok i have a question.. There are photoresistors, thermistors, and potentiometers.. so with those you can change resistance with light temp and with a knob.. is there one that will change resistance with anything else like sound or something?... it does not just have to be sound, just anything else that varies resistance. it is for an arduino project and i am just looking for all the different ways to have a variable resistance...pressure would be a great one, not atmospheric pressure but like the harder you press on it the higher or lower the resistance gets

 

[colin55]

The foam used for chips to prevent static, will change resistance when squeezed.
A diode will change resistance (the voltage across it will change) when heated.
A motor can be used with a propeller to detect wind
A hall effect will detect magnetism.
A coil will detect magnetism.
Things that produce a voltage can be wired so that they effectively change in value just like a device that changes resistance.
A device such as a pot needs a voltage across it for it to work, and you measure the change in voltage and call it a change in resistance. But you cannot measure a device that changes RESISTANCE. You are actually measuring the change in current flow or the voltage across it and converting the answer to a resistance value. You cannot measure resistance. You can only measure current-flow or the voltage across a device and by Ohm's Law, work out the resistance.
That's why all the things I mentioned above, fall into the same category. "A device that changes RESISTANCE."

 

[xXAxHillbillyXx]

oh ok.. thanks

 

[mozly]

wow cool i did not know that

 

[xXAxHillbillyXx]

yeah i tried that foam and it worked it was very cool

 

[koolguy]

Sir,
I have seen many ckt having SMD resistor plz tell how to find there value Without Multimeter.......?

 

[colin55]

All resistors have 3 or 4 numbers on them.
This is their resistance. But some have a code

 

[koolguy]

Thank's sir..........!

 

[Gary B]

You missed one; a carbon microphone from an old telephone will change resistance with sound pressure.