The MAX471 is complete, bidirectional, high-side current-sense amplifiers for portable PCs, telephones, and other systems where battery/DC
power-line monitoring is critical. High-side power-line
monitoring is especially useful in battery-powered systems since it does not interfere with the ground paths
of the battery chargers or monitors often found in
The MAX471 has an internal 35mΩ current-sense resistor and measures battery currents up to ±3A. For applications requiring higher current or increased flexibility,the device has a current output that
can be converted to a ground-referred voltage with a
single resistor, allowing a wide range of battery voltages and currents.
An open-collector SIGN output indicates current-flow
direction, so the user can monitor whether a battery is
being charged or discharged. the device operate
from 3V to 36V, draw less than 100µA over-temperature, and include a 18µA max shutdown mode. and its scale factor as it outputs 1 volt per amp measured.
The principle of voltage test based on principle of resistive voltage divider design, can make the red terminal connector input voltage to 5 times smaller
for analog input voltages up to 5 v, the voltage detection module input voltage not greater than 5Vx5=25V (if using 3.3V systems, input voltage not greater than 3.3Vx5=16.5V).for AVR chips have 10-bit AD, so this module simulates a resolution of 0.00489V (5V/1023), so the minimum voltage of input voltage detection module is 0.00489Vx5=0.02445V
The MAX471 chip on the board used to test the consume current of the load
Test Voltage range: DC3 - 25V (for work on 5V) or DC3 - 16.5V (for work on 3.3V)
Test Current range: DC0 - 3A
PCB Size: 22*21*7mm/0.86*0.82*0.27"
MAX471 Pin Outs
GND: All of the grounds are connected to the same electrical point
VOUT: Connects the high side of your load
VIN: Connects to the Positive Pole of your voltage source ( This can be anywhere from 3 to 25 Vdc )
AT: Provides 0 to 5V signal that is scaled to 1 V per amp.
VT: Provides a 0 to 5V signal that is scaled to 1 volt per for every 5 volts input
Arduino MAX471 Watt-meter Tutorial
Connect Your Arduino to the MAX471, a Load and a Power Source
I’m using an 18650 battery, while the nominal voltage is 3.6 volts it can be as high as 4.0 volts when fully charged. I use that value to determine the load resistance for my test.
I find that if I put a 32 ohm resistor across the battery, I will draw about 0.124 amps and dissipated 0.5 watts through the resistor.
Since I had 1/2 Watt 68 0hm resistors, I put two in parallel to yield a nominal 34 ohms with the ability to safely dissipate 1 Watt of heat. So, I am above the 3V supply requirement, below the 3A current ceiling and have chosen a safe enough load for test purposes.
Copy, Paste and Upload the Power Meter Tutorial Sketch
Simple stuff. We read voltage, current and multiply them to get power. Remember, with voltage we’re going to multiply whatever value we read by five to yield the value measured by the MAX471.
// Henry's Bench
// MAX471 Power Meter Tutorial
#define VT_PIN A0
#define AT_PIN A1
int vt_read = analogRead(VT_PIN);
int at_read = analogRead(AT_PIN);
float voltage = vt_read * (5.0 / 1024.0) * 5.0;
float current = at_read * (5.0 / 1024.0);
float watts = voltage * current;
Verify Your Sketch Output
Open your serial monitor. If everything worked out, you receive will have an output that looks something like the picture below: