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I've been building a tank robot for a while now and in these days I'm struggling with some issues related to insufficient current in my configuration. For instance, some sensors stop working after a while. Could you help me sort it out? At moment I'm powering my rpi4 with a DYM UPS UPS Shield which should provide me of 5V and 2.2 A, I've also tried with a Chinese power adapter which should provide up to 3A ( I explicitly want to mention I bought it from aliexpress since I don't believe I'm getting 3A out of it) with the same results. I've bought a usb multimeter to check how much A my rpi absorbs and it should arrive somewhen by the end of this week, meanwhile I was hoping you could have given me some insight.

I don't think it's relevant but the program I wrote, to control the robot, is built on top of cross-compiled Qt 5.15, openCV 4 and raspiCam lib.

My only concern about the schema is that rpi GND which goes to GND 18650 batteries that power the motors (the 2 DC motors and the servo)

At moment I'm using a normal 1080p cam, I was using noIR camera before with 2 IR Leds but the outcome was odd, after few seconds every sensors stopped working and eventually rpi glitched forcing me to reboot it. I would like to find a solution to use the noIR camera with night vision btw..

I'm attaching some photos of my little 'Hope' and its configuration.

Tank 1
Tank 2
Wiring

There's a little mistake in the diagram, one of then pin of the H-Bridge is connected wrongly to a gnd pin of the rpi, don't take care of that, it doesn't reflect the real configuration which is fine

I think i've found what's wrong with this setup and is that the 8V ground coming from the 2 18650 batteries in series arrive directly to the i2c multiplexer power line and i believe this is the main cause of my issues. I don't know what i should do to fix it though..

Edit 1: Summarizing, the 3.3v power pin of rpi powers the i2c multiplexer with all the connected sensors, 3 VL53L1-X, a MPU6050, a HMC5883L and a PCA9685. The servo motor and the H-Bridge are powered trough another battery pack consisting of 2 18650 in series whose ground is connected to rpi. Thus rpi has 3 GND tied up together mainly the fan, the i2c multiplexer and the ground from battery pack in series ( plus the ground from the battery shield trough the usb c connector).

Edit 2: Referring to this post it seems i might haver encountered the same kind of issue..

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  • I see no mention of the current draw of the various components. I see no reason not to draw the obvious conclusion that the power supply is insufficient,
    – joan
    Jan 23, 2021 at 21:25
  • How could it be unsufficient? I mean, rpi is getting properly powered by the UPS but only draws 0.6-0.7A out of the potential 2.2A. Why does it do like this?
    – Manfredi6
    Jan 23, 2021 at 22:52
  • Learn to use the formatting tools here, please. It's called "Markdown", and you can view the guide here - it's very simple.
    – Seamus
    Jan 24, 2021 at 0:35
  • Your wiring diagram is not clear. I don't even see a power source for the RPi - where is it? In general, know this: All grounds must be "tied together" - opto-isolaters and transformers are two notable exceptions. Clear up the spaghetti in your diagram, and we'll try to help.
    – Seamus
    Jan 24, 2021 at 0:41
  • Sorry if i have not formatted the code properly, btw as i’ve written in the first post, i’m powering the rpi with that battery shield i’ve linked trough the usb c port. Regarding the spaghetti diagram, i’m pretty aware it’s a mess but it’s not that easy to “fix” .. the main logic is that 3.3v power pin of rpi powers the i2c multiplexer with all the connected sensors, 3 VL53L1-X, a MPU6050, a HMC5883L and a PCA9685. The servo motor and the H-Bridge are powered trough another battery pack consisting of 2 18650 in series whose ground is connected to rpi. Thus rpi has 3 GND tied up together
    – Manfredi6
    Jan 24, 2021 at 1:12

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