ADC problem, help needed

[TKS]

Hi,

this is a micrcontroller / basic electronic question.

I have a potenionmeter wich moves from 19,8K

to 17,4K's...

i need to generate with that the higest swing in adc value, how do i do that?

now i have just putted in series with a resistance and the voltage between then goes to the adin pin, but the swing is to small..


Tks

 

[Nigel Goodwin]

Use an opamp to amplify and bias it, probably a simple way would be to use the pot as one leg of a wheatstone bridge, with a differential opamp to amplify it's output.

 

[TKS]

Mhh ok,

first gonna try it by using the complete pot 3 pins..

the middle will be connedted to the adin pin one will be 5volts the other will be ground..

should give me a swing of 100..

sow think it will be enough.. to move a 90degrees thing..0.9degrees per step..

Tks

 

[Mike - K8LH]

May I ask if you're using the Pot simply as a control? If so, have you considered using a rotary encoder instead? They're a bit more expensive than a Pot but I've found them to be extremely flexible as controls. I often use one with detents and built-in push-button switch on the shaft.

Regards, Mike

 

[TKS]

yes i have, but the problem with that is that if the gearbox is changing gear..
and while you do that you would change the encoder then maybe it would be seen by the computer in this way its always noticed and adjusted as is..

Tks

 

[Nigel Goodwin]

In that case you might try just reading the value of it's resistance like you would a joystick? - check my PIC joystick tutorial for an example. Nice and simple, just the pot and a single capacitor required!.