I’m using an INA219 and I’m trying to take a reading of voltage and current. When I’m looking at the current reading, it looks perfectly fine, however, the load voltage remains the same and it is stuck at 1 V.

I’ve used four 0.5 W solar panels connected in parallel that have a rated voltage of 5.5 V. Shouldn't the load voltage be 5.5 V as this is the typical voltage, and not 1 V?

As a side question, am I required to add a load (resistors) on the output (V-) of the INA219 as I thought the solar panels would be classed as the load? I can also attach the code if needed.

enter image description here

  • 1
    \$\begingroup\$ See figure 13 in the datasheet. The Solar cell is the "Supply". Current has no meaning unless you complete the circuit with a load (the INA219 is not a load, it is a measuring device). And to measure current you need to add a shunt resistor. Using figure 13, connect the solar cell to "Supply" and GND. Connect your load to "Load" and GND. \$\endgroup\$
    – Mattman944
    Sep 1, 2022 at 0:49
  • \$\begingroup\$ what current readings ? You must never put a PV into a CMOS that is rated to put out 8.2V open circuit in full sun and 100 mA short circuit and 5.5V typical ~ 100mA or 0.5W into an Arduino port. unless you clamp the max voltage to Vdd with a power Schottky diode. I hope you were working off dim light. \$\endgroup\$ Sep 1, 2022 at 0:55
  • 1
    \$\begingroup\$ You need to connect Solar- to GND to read bus voltage. And if you are correctly reading current, you must have omitted the shunt resistor from your schematic. There should also be a filter capacitor and resistors on the input as shown in the data sheet. \$\endgroup\$
    – PStechPaul
    Sep 1, 2022 at 1:40
  • \$\begingroup\$ Use a DMM on each PV and measure open-circuit voltage Voc=8.2 Vmax or at least 7V and short circuit current Isc = 100 mA max. or at least 20 mA then if OK put in parallel , recheck sums, then choose your full-scale current, Isc , the shunt value,Rsh for select PGA gain and full scale range Vfs. Rsh=Vfs/Isc then add 10 ohm 0.1uF filter \$\endgroup\$ Sep 1, 2022 at 5:08

1 Answer 1


The solar panel appears to be floating so the INA219 cannot make a proper measurement.

As a side question, am I required to add a load (resistors) on the output (V-) of the INA219

V- is not an output. It is an input as is V+. These are used to measure the voltages. The internal micro then calculates the current and power. The wiring is as shown in the datasheet. V- is used to measure the load voltage. $$I=\frac{V_{+} - V_{-}}{R_\mathrm{shunt}}$$.

So the IN219 must be calibrated according to Rshunt. The power is calculated according to the Power formula. Since it is a high side measurement the resistors should be used.

Read the data sheet.


simulate this circuit – Schematic created using CircuitLab


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.