Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Resistance Reading on variable resistor

Status
Not open for further replies.

Jasonb61

Newbie level 1
Joined
Oct 28, 2009
Messages
1
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Location
Commerce, Ga
Activity points
1,288
This should be pretty simple but I put together a circuit that calls for an adjustable resistor (pot) and I was wondering if there was some way to output the current value of the POT to the user without affecting the actual value. What all would I need and how should I set it up? Thanks
 

pranam77

Advanced Member level 5
Joined
Apr 22, 2008
Messages
2,786
Helped
552
Reputation
1,102
Reaction score
371
Trophy points
1,363
Location
INDIA
Activity points
16,417
Jasonb61 said:
output the current value of the POT to the user without affecting the actual value.
Sorry...I didnt understand the term. Could you please explain in detail a bit? Cheers
 

ChrisC

Member level 2
Joined
Sep 30, 2009
Messages
51
Helped
14
Reputation
28
Reaction score
2
Trophy points
1,288
Location
London, UK
Activity points
1,760
You could find a dual-track pot compatible with the one you're currently using, wire up one track as normal to your circuit requiring the variable resistance, and wire up the second track to a sensing circuit.

If that's not an option, would using a digital pot be viable? If you keep track of the control signals sent to the pot, you'd know on which tap the wiper was positioned, and thus be able to calculate a resistance value. It wouldn't be a direct measurement, but depending on what sort of accuracy you require it may be good enough.

Alternatively, depending on your application you may be able to stick a current sense resistor in series with the pot, measure the current through the pot, and do a quick R=V/I calculation...

On a similar vein, you may be able to sense the voltage at the wiper terminal and determine the wiper position/resistance value from that.

Alternatively alternatively, you could either try to find, or bodge one together yourself, a pot which includes some form of positioning feedback - e.g. a slotted disk/photosensor setup attached to the pot spindle - so you could detect any motion of the wiper and infer the pot position/value from that.

If all else fails and you don't need the result presented electronically, then perhaps a mechanical approach will suffice - stick a pointer on the pot spindle, stick a scale marking around the pot, and let the user read off the value manually...


Basically, there are many options (including all the ones that didn't spring to mind whilst writing the above) for determining the position/value of a pot, choosing which one to use is then down to how the pot is being used in your application, and in what form you want to present the result to the user.
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top