Problem Statement:
My application requires a 2A or 3A +/- monitor. The ACS712-05B is very limited on it range for what I need:
- 05B = 0.185V / 1A
- 20A = 0.100V / 1A
- 30A = 0.066V / 1A
The quiescent is 2.5V, so the 05B @ 5A will be:
- 2.5V+(0.185V *5) = 3.425V Max
- 2.5V-(0.185V *5) = 1.575V Min
3.15 volts are not used, that is a lot of waist for my project.
Solution:
I will amplify the output:
- For 2A MAX = 0.185V/1A to 1.250V/1A (gain of 6.8x)
- @ 1A = 3.750V (instead of 2.685V)
- @ 2A = 5.00V (instead of 2.870V)
- For 3A MAX = 0.185V/1A to 0.833V/1A (gain of 4.5x)
- @ 1A = 3.333V (instead of 2.685V)
- @ 2A = 4.166V (instead of 2.870V)
- @3A = 4.999V (instead of 3.055V)
A map will be used in the Arduino code to display the actual Amp value:
- 2A = map(0,1023,-2.00,2.00)
- 3A = map(0,1023,-3.00,3.00)
I searched the internet for a common solution, the below is close and I will update the values to expand the range.
As drawn, the gain is 3.3X. Add a 10K (10 turn) resistor between the 100K to be able to zero out the value (This can also be accomplished in code).
Here are the values I need:
- 2A
- R3 =6.8K
- 3A
- R3=4.5K
R1 and R2 can be as low as 1K and still consume only 2.50mA (12.5 mW). (Need to change the 10 turn resistor to 100 ohms).
I will use a LM741 instead of the LM321.
Conclusion:
Need to build and prove this solution has much better resolution.
Reference:
http://www.theorycircuit.com/hall-effect-current-sensor-circuit/
https://www.youtube.com/watch?v=RZmGt3-HVlw
https://www.youtube.com/watch?v=DVp9k3xu9IQ
https://www.engineersgarage.com/arduino/acs712-current-sensor-with-arduino/