Measuring how many ohms?
5v ~~~~ 1k ~~~~ A0
sure i get a voltage reading... but how many ohms? Cheers
Ohms Law
You already have the ohms written down as 1k ohm
marco_c:
You already have th ohms written down as 1k ohm
Cool... a 2nd resistor's required.... cheers
How do you propose to use this second resistor to measure resistance?
marco_c:
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.
Voltage divider: Vin - R1 -Vout-R2- Gnd
Vout = Vin R2/(R1+R2)
Do some rearranging:
Vout(R1+R2) = VinR2
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 = 515000/(10000+15000) = 3V