These sensors are based on the Allegro ACS712ELC chip.
These current sensors are offered with full scale values of 5A, 20A and 30A.
The basic functional operation of each of these devices is identical. The only difference is with the scale factor at the output as detailed below.
Other ACS712 Henry’s Bench Articles
ACS712 Arduino Tutorial Shows how to use the device with an Arduino
ACS712 AC Voltage Measurement shows how to measure a Sine Wave Voltage with an Arduino
18650 Battery Charger shows another implementation of the ACS712
ACS758 Tutorial Shows a similar device for monster currents.
How to Get One
If you don’t have one of these modules and think that you may want one, you can try these links. It will only set you back a few dollars.
|5A Module||20A Module||30A Module|
|Supply Voltage (VCC)||5Vdc Nominal||5Vdc Nominal||5Vdc Nominal|
|Measurement Range||-5 to +5 Amps||-20 to +20 Amps||-30 to +30 Amps|
|Voltage at 0A||VCC/2|
|Scale Factor||185 mV per Amp||100 mV per Amp||66 mV per Amp|
ACS712 Module Pin Outs and Connections
The picture below identifies the pin outs for the ACS172 Modules.
Pay attention to the polarity at the load end of the device. If you are connected as illustrated below, the output will raise. If you connect it opposite of this picture, the output will decrease from the 2.5 volt offset.
As mentioned before, these modules are primarily designed for use with micro-controllers like the Arduino. In those applications, the connections would be as picture below:
If the light bulb shown in the picture above were disconnected, the output of the ACS712 module would be 2.500 volts.
Once connected, the output would be scaled to the current drawn through the bulb. If this were a 5 Amp module and the light bulb pulled 1 Amp, the output of the module would be 2.685 volts.
Now imagine the battery polarity reversed. Using the same 5A module, the output would be 2.315 volts.
IMPORTANT NOTE – This device is a Hall Effect transducer. It should not be used near significant magnetic fields.
The datasheet below will give you greater insight into the specifications and operation of this manual.