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I am using a a solar panel connected to this solar power manager. On the output (5 V) I will connect a circuit with an Arduino, sensors, and an INA219 on a breakout board to measure the total load current, voltage, and power, always on the load.

Will I have any problems with these connections? I know that solar panels are a bit strange, with the rationale that you do not use the common wall power supply. I also use a solar power manager, so I am a bit concerned about having any problems when using the INA219 on the load.

All the elements of the circuit (including the INA219) will be connected to the 5 V output of the solar power manager. Any ideas?

Here is the schematic: enter image description here

ocrdu
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just_learning
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1 Answers1

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That is not really a (good) schematic.

If you wire that up correctly and avoid weak grounding, it should work.

You did not mention how much current the Arduino and other loads consume.

The Arduino and the INA219 must work on the same GND level of your 5 V net after the power manager. Thus if the converter is isolated input and output GND must be connected together.

Since the voltage on the INA219 input is constant, it is mainly a current measurement.

Take care the current sensor board is rated to only 3.2 A and at this current produces a voltage drop of 0.32 V. If there are loads that produce current peaks beyond 3.2 A you get into trouble! Total load is a concern!

Why not supply the Arduino with 5 V directly? That would give a far better efficiency. Is there a good reason to give 12 V to the Arduino?

ocrdu
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datenheim
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  • I use 12 Volt for Arduino because I have a shield attach to it, which needs more than 7 Volts. The alternative is to use 5 Volts without the shield and use this: https://learn.adafruit.com/adafruit-fona-mini-gsm-gprs-cellular-phone-module?view=all which needs a LiPo battery to work. At this point I am really confused...What do you suggest? – just_learning Feb 02 '23 at 21:41
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    What shield? Is everything intended to run forever or is an on/off switch planned? – datenheim Feb 02 '23 at 21:48
  • https://wiki.dfrobot.com/SIM7600CE-T_4G(LTE)_Shield_V1.0_SKU_TEL0124 It will work 24/7 all day and night... – just_learning Feb 02 '23 at 21:49
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    I'd prefer the FONA, it is far better documented and needs only 5 V. Give it it's own lipo is cheap. But also the DFrobot could (in principle) be powered from 5 V (USB) even if that is not really advertised. Strangely there is a net called V_bat on that module but I can not see any battery connector... – datenheim Feb 02 '23 at 22:05
  • Yes, but the Lipo of the FONA does not causes problems to the solar power manager that has also a battery inside....? I am really confused at this point, that's why I am thinking of not using FONA the first time... – just_learning Feb 02 '23 at 22:07
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    For the solar manager the fona is just a 5 V load, it does not "know" there is another battery. I wonder why the DFrobot does not need a battery. Most GSM modules need either a supercap or a battery to buffer current draw peaks. – datenheim Feb 02 '23 at 22:42
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    @just_learning The sheild you link to (SIM7600CE-T) doesn't actually require 12V. You can power it entirely of the 5V USB connector it provides. – Tom Carpenter Feb 02 '23 at 23:23
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    you can add another 0.1R across the sensor leads and double the values in software if you need more current handling. – dandavis Feb 02 '23 at 23:36
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    @dandavis Be careful with that - the PCB traces might not be up to that current. But one can take a fat external shunt resistor and just wire the sense-lines to it. This unloads the PCB from thermal load and allows crazy currents. Well, for huge currents I'd choose another INA with only 50 mV drop voltage spec. – datenheim Feb 03 '23 at 08:05
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    @datenheim not sure i see a difference between "sense-lines" and "sensor leads", but paralleling a resistor with the wires you attach to the PCB is going to reduce current on the PCB. I add screw terminals to the adafruit-style PCB and clamp the wire and resistor and a 10k pot (for trimming) into the terminal. – dandavis Feb 03 '23 at 10:13
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    Ok, I thought paralleling it with the onboard shunt directly on the board. – datenheim Feb 03 '23 at 16:08