Loading...
« previous topic   next topic »
Pages: [1]   Go Down
Author Topic: measure a resistor?  (Read 531 times)
0 Members and 1 Guest are viewing this topic.
cjdelphi
Offline Offline
God Member
*****
Karma: 10
Posts: 871
View Profile
« on: September 13, 2012, 09:17:09 pm »
 Bigger Bigger Smaller Smaller Reset Reset
Measuring how many ohms?

5v ~~~~ 1k ~~~~ A0

sure i get a voltage reading... but how many ohms? Cheers
Logged

James C4S
Austin, TX
Offline Offline
Faraday Member
**
Karma: 41
Posts: 5171
CMiYC
View Profile
WWW
« Reply #1 on: September 13, 2012, 09:26:24 pm »
 Bigger Bigger Smaller Smaller Reset Reset
Ohms Law
Logged
www.cmiyc.com - A guide to being an Enginerd

Goofballtech
South Louisiana
Offline Offline
Full Member
***
Karma: 0
Posts: 178
Arduino rocks
View Profile
« Reply #2 on: September 13, 2012, 09:46:41 pm »
 Bigger Bigger Smaller Smaller Reset Reset
http://arduino.cc/forum/index.php/topic,21614.0.html
Logged

marco_c
Sydney
Offline Offline
God Member
*****
Karma: 14
Posts: 717
Big things come in large packages
View Profile
WWW
« Reply #3 on: September 13, 2012, 10:56:27 pm »
 Bigger Bigger Smaller Smaller Reset Reset
You already have the ohms written down as 1k ohm
« Last Edit: September 13, 2012, 11:16:31 pm by marco_c » Logged
My Arduino libraries at http://code.google.com/p/arduino-code-repository

Goofballtech
South Louisiana
Offline Offline
Full Member
***
Karma: 0
Posts: 178
Arduino rocks
View Profile
« Reply #4 on: September 13, 2012, 11:09:02 pm »
 Bigger Bigger Smaller Smaller Reset Reset
Quote from: marco_c on September 13, 2012, 10:56:27 pm
You already have th ohms written down as 1k ohm

 smiley-eek-blue
Logged

cjdelphi
Offline Offline
God Member
*****
Karma: 10
Posts: 871
View Profile
« Reply #5 on: September 14, 2012, 12:35:33 am »
 Bigger Bigger Smaller Smaller Reset Reset
Cool... a 2nd resistor's required.... cheers
Logged

marco_c
Sydney
Offline Offline
God Member
*****
Karma: 14
Posts: 717
Big things come in large packages
View Profile
WWW
« Reply #6 on: September 14, 2012, 09:03:44 am »
 Bigger Bigger Smaller Smaller Reset Reset
How do you propose to use this second resistor to measure resistance?
Logged
My Arduino libraries at http://code.google.com/p/arduino-code-repository

danb35
Offline Offline
Jr. Member
**
Karma: 1
Posts: 83
View Profile
« Reply #7 on: September 14, 2012, 12:08:21 pm »
 Bigger Bigger Smaller Smaller Reset Reset
Quote from: marco_c on September 14, 2012, 09:03:44 am
How do you propose to use this second resistor to measure resistance?
Simple voltage divider.  5V -> R1 -> analog input on arduino -> R2 -> ground.  Given the voltage reading at the Arduino and the value of one of the resistors, the value of the other can be calculated.
Logged

CrossRoads
Global Moderator
Boston area, metrowest
Offline Offline
Brattain Member
*****
Karma: 247
Posts: 16526
Available for Design & Build services
View Profile
WWW
« Reply #8 on: September 14, 2012, 02:04:28 pm »
 Bigger Bigger Smaller Smaller Reset Reset
Voltage divider: Vin - R1 -Vout-R2- Gnd
Vout = Vin *R2/(R1+R2)
Do some rearranging:
Vout(R1+R2) = Vin*R2
VoutR1 + Vout R2 = VinR2
VoutR1 = VinR2 - VoutR2
VoutR1 = (Vin - Vout)R2
VoutR1/(Vin - Vout) = R2

Ex: Vout 3V, Vin5V, R1=10K
3*10000/(5-3) = 15000

check Vout = Vin *R2/(R1+R2)
Vout = 5*15000/(10000+15000) = 3V
Logged
Designing & building electrical circuits for over 25 years. Check out the ATMega1284P based Bobuino and other '328P & '1284P creations & offerings at  www.crossroadsfencing.com/BobuinoRev17

Pages: [1]   Go Up
Print
« previous topic   next topic »
 
Jump to: