lemmyman

If you just want a straight cut I’d think your slicer would be able to do that. Prusaslicer can, at least.

Pugjesus does an awesome job but it’s way above and beyond what’s necessary. Grumpus otoh just drops memes and leaves us hanging and that’s definitely not enough. I would settle for even just a fricken wikipedia link, but as it is I’m sadly on my way to just blocking grumpus because it’s so infuriating.

Fets will be better for voltage drop. But for high side switching in this design you definitely want p fets - they are basically a drop in replacement.

I don’t know if you need an lm317 replacement. Aside from the voltage drop issue, the only issue I’m aware of might be startup timing since you’re PWMing them. I could not find anything about this in a datasheet. Once you get the transistors figured out I would use an oscilloscope to probe your output and see if it is the waveform you want.

I do know there are multi-channel LED drivers that would work, and are definitely made for PWMing. So you have options if the lm317s are too slow.

My bad, thanks for the correction!

This is 100% the issue. OP should move to low side switching with NPN BJTs or N-fets for the simplest fix. The arduino IO is 3.3v so they won’t be able to fully turn off a pnp (without extra circuitry).

Also, I’ll just note: lm317 dropout voltage at 60 mA will be about 1.5 V. The adj pin will be another 1.25V. So there is only going to be about 2.25V available to drive the load. Minus whatever drops there are through the pdn and transistors. I don’t know what a typical Vf for a laser diode is, but I wouldn’t be surprised if OP isn’t getting the drive current they want.

A couple suggestions then:

• I have a LabJack that I use for things like this. I’d put a sense resistor on the high side, tie that into one of the differential inputs, set up the (admittedly awful) software, and boom I’d have battery voltage and current over time. But that’s several hundred dollars.
• Instead of that, you can homebrew a pretty similar thing.
  • Either use your Pi or a separate Arduino to read voltages. Store it in a file or send it to a host PC over serial every [1-3600] seconds
  • You could get a module like this one to capture everything digitally
  • Or you could do it the analog way
    • Probe battery voltage with an appropriate resistor divider
    • Probe current with an INA169 or similar
• If you are using a BMS, that could give you net power flows in/out of the battery. But you won’t know from that alone whether your solar setup is functioning well or your power draw is low (for example)
• For battery state of charge, you could worry about coulomb counting and fancy algorithms. I’d just use voltage. But know battery capacity is not linear with voltage (refer to charge/discharge curves).
• For full understanding of inflow/outflow, you’d want a current monitor at both the solar cell side and the load side of the battery.

Are you talking about just characterizing one unit one time? How long is “extended?” Do you want time series data or just an average?

For a very simple setup, I’ve used current measurement on a DMM in average mode for ~30 minute durations before.