Products > Test Equipment
finding short on motherboards with a shorty (with display)
Kean:
--- Quote from: wacd on March 14, 2024, 12:32:45 pm ---Thank you for providing information. I'll go and spend some time on this to learn it better so i can implement it , hopefully :)
--- End quote ---
If you don't have experience with opamps, then a much simpler but slightly less accurate solution would be using an LM317L as the current source (in place of R1).
You can get the 50mA using just the LM317L IC and a 25 ohm 1% or better resistor, and calibrate the final result in the firmware.
This will perform much better than that part you suggested earlier.
Note that 25 ohms is not a standard resistor value, so just use a 24.9 ohm, or parallel 3 x 75 or 4 x 100 ohm. Or some other combination like 10 + 15 ohm in series.
kripton2035:
if you feed 50mA constant, I'm afraid you can't measure resistors above 0.5Ω
it would be better to stay with 30mA.
wacd:
Oktay, Lm317L looks easy enough , i'll give it a go.
wacd:
Hello again. I've been playin with the calibration settings and i think i finally arrived at a point that the results satisfy me.
Lower values are absolutely on point. It reads slightly lower value above 1ohm.
Ordered a couple mcp3421's , waiting for their arrival. The one i've set up on breadboard will stay for further tinkering.
And i made this pcb ordered from oshpark, hope it works as i'd like it to.
CaptainBucko:
PCBs for JDobrey's Shorty Pen have arrived from JLPCB.
5 x PCBs for $4.00USD delivered. Crazy at how low cost they can make these.
I have sourced all my components from LCSC and waiting for them to arrive, and happy to share the BOM if people want it. It's a bit different from JDobrey's which was from 2022.
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