Being new to the electronics side of robot control, I’m having trouble interpreting the specs for the ACS714 Current Sensor Carrier.
On the product page it says “The output is an analog voltage (185 mV/A) centered at 2.5 V.” How does the 185mV/A apply?
Say the current going through the sensor is 670mA. What value should I see on an analogue pin on the ATMega328 on an Arduino? Something between 0 and 1023 I assume.
I’m hoping to monitor the current the a robot’s motors are using.
The sentence you quote means that with no current, the output voltage is 2.5V. For every extra amp of current in the positive direction, the voltage will go up 185 mV; for negative current, the output voltage will go down 185 mV per amp. For 0.67A, your output voltage would go up by about 124 mV, so your output voltage would be about 2.624V, which with a 10-bit reading and a 5V reference should be about 537 out of your ADC. Another way of looking at it is that every increment out of your ADC will correspond to about 27 mA. The zero-current reading should be about 512, but you should calibrate that for your system by looking at what you actually get at zero current.
Thanks very much for your very quick reply. Remembering now that the analog pin values represent values fro 0.0V to 5.0V, and your very thorough explanation, I think I get it.
One thing I forgot to ask, If the motor I plan to monitor runs on 5V and draws less tha 1A, I assume the ACS714 -5 to +5A is the one I should use?
The +/-5 A current sensor is probably your best choice out of the current sensors Pololu offers. Generally, if you aren’t expecting more than 1A you might want a more sensitive current sensor. It is likely that the +/-5A one will do just fine for you though.
