Pages: [1]   Go Down
Author Topic: How to choose the resistance of a pot for use with analog input  (Read 1025 times)
0 Members and 1 Guest are viewing this topic.
Offline Offline
Newbie
*
Karma: 0
Posts: 4
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Hello,
I'm in the process of gathering parts for a Arduino based RGBW LED area/mood light.I plan on using five panel mount pots,four to control each of the colors via  PWM from the Arduino to the LED driver module's PWM pin and one for overall brightness control through PWM of the LED driver's supply through a MOSFET.
Anyway,I'm having trouble choosing the pots resistance.I'm new to Arduino and have no formal electronics training so please excuse any ignorance.
As I understand it using a pot with Adruino's analog input acts as a voltage divider,with the pots 'ends' connected across the supply and the wiper connected to the analog pin.So what effect does a pots resistance have on the function of the analog pin?I assume that a 5k pot and a 10k pot would act in the same way.Am I correct/incorrect? Am I missing something? Thanks in advance for any responses.
Logged

Manchester (England England)
Online Online
Brattain Member
*****
Karma: 634
Posts: 34528
Solder is electric glue
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Quote
So what effect does a pots resistance have on the function of the analog pin?
As the analogue input pin is a very high impedance it has little effect. However, the analogue input is switched and the other side of the switch is a small capacitor. If you switch rapidly between analogue inputs the capacitor needs time to charge up to the new level. So unless the pot is below say 25K there is some affect of the previous pot on the reading of the current one.

Moral - use a 10K pot.
Logged

Offline Offline
Newbie
*
Karma: 0
Posts: 4
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Seeing what you quoted I now realize that I could have greatly simplified my post. smiley-red I've been know to be "long winded" it's a curse (For those around me.)   smiley-grin Thanks for your help.
Logged

Manchester (England England)
Online Online
Brattain Member
*****
Karma: 634
Posts: 34528
Solder is electric glue
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Don't worry often it take and outside view to cut to the chase.
 

Sent in a pub in Manchester with far too many beers inside me.   smiley
« Last Edit: December 14, 2011, 12:10:02 pm by Grumpy_Mike » Logged

Global Moderator
UK
Offline Offline
Brattain Member
*****
Karma: 309
Posts: 26488
I don't think you connected the grounds, Dave.
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

Is there such a thing as "too many beers"?
Logged

"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

Manchester (England England)
Online Online
Brattain Member
*****
Karma: 634
Posts: 34528
Solder is electric glue
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

Well yesterday there was.

Triped up just outside my house and ended up in casualty. Grased knee, cut chin, strained calf muscle. Mind you it was a 7 hour lunch time with a frend I had not see for two years. He was the one who intreduced me to the Arduino in the first place.
Logged

Pages: [1]   Go Up
Jump to: