Current Sensor Amplifier & Over Current Switch
This current sensor amplifier and over current switch project is based on
ACS714-30A current sensor and
LM358 OPAMP, ½ of LM358 op-amp used as an amplifier for low voltage and 2nd 1/2 LM358 op-amp used as a comparator which provides over current TTL output, trimmer potentiometer provided to set the over current limit. ACS714 sensor measures the current up to
+/-30Amps, the final output of the amplifier is
235mV/1A, and normally over current output is High-TTL. It goes low once the current overshoot than a set point. The circuit requires 5V DC and 40mA, and the onboard LED indicates the power. Resistor divider R1, R3 provides bus voltage output for a microcontroller interface to measure the bus voltage, choose the appropriate value for R3, R1 as per your application and bus voltage, it should be less than 5V DC.
ACS714 Current Sensor
The Allegro™ ACS714 provides economical and precise solutions for AC or DC current sensing in automotive systems. The device package allows for easy implementation by the customer. Typical applications include motor control, load detection and management, switch-mode power supplies, and overcurrent fault protection. The device consists of a precise, low-offset, linear Hall circuit with a copper conduction path located near the surface of the die. Applied current flowing through this copper conduction path generates a magnetic field which the Hall IC converts into a proportional voltage. Device accuracy is optimized through the close proximity of the magnetic signal to the Hall transducer. A precise, proportional voltage is provided by the low-offset, chopper-stabilized BiCMOS Hall IC, which is programmed for accuracy after packaging. The output of the device has a positive slope (>VIOUT(Q)) when an increasing current flows through the primary copper conduction path (from pins 1 and 2, to pins 3 and 4), which is the path used for current sampling. The internal resistance of this conductive path is 1.2 mΩ typical, providing low power loss. The thickness of the copper conductor allows survival of the device at up to 5× overcurrent conditions.
Note: OPAMP U2B is used as a comparator and Trimmer Pot PR1 swing from
0 to 5V so the threshold can be adjusted between 0 to 5V. Sensor output is 235mV/1 Amp, so, for example, is 2.35V for 10Amp
Features
- Supply 5V DC
- ACS714-30 low noise direct output 66mV/Amp
- LM358 Amplifier Output 235mV/Amp
- Over Current Output (Normally High-TTL Goes low at overcurrent set point)
- Trimmer Preset to set the Overcurrent limit
- Bus voltage output
- Power LED
- Screw Terminal for Current
- Header Connector for outputs and supply
Header Connector Connections
- Pin 1 : VCC 5V DC Supply
- Pin 2 : Supply GND
- Pin 3 : VOP- ACS715-30 Sensor Direct Output 66mV/Amp
- Pin 4 : OP1- Amplifier Output 235mV/amp
- Pin 5 : OP2 Over Current Output ( Normally High-TTL, Goes Low at Over Limit)
- Pin 6 : BSV- Bus Voltage Output
Schematic
