/diy/ - Do It Yourself

>>2679178
I'm just using mini XLR plugs because they're available, small, and have a good assortments of both line and chassis connectors. I'd use mini DINs if they had both male and female chassis connectors, but they don't. At least not where I shop.

It's a "controller" for a laser and drill for my 3D printer setup. The digital logic is mainly to ensure that power never gets sent to something that isn't ready for it. Mainly, it won't send a PWM voltage from the printer to the laser if the laser doesn't itself have its external +12V PSU plugged in. But it also ensures that while sensing the +12V supply, it won't backfeed into the 3D printer if it's turned off, through the use of Q1 as an isolated source follower. And there's a schmitt trigger oscillator (U1D) that produces a low-duty-cycle PWM when the button is pressed, for manual focusing of the laser with a low-power pilot beam. U1A,B,C makes a sum-of-products logic array using only NAND gates with the logical equation:
>PWMout = (OSC AND 12Vgood) OR (PWMin AND 12Vgood)
The PWM signal also goes to the MOSFET gate driver circuit (Q2, D3, Q3, R7) and the main FET Q4 and its freewheel diode D4. This FET is meant to drive loads that don't have a PWM input, specifically my mini drill. It would arguably be better if the pilot button also turned the drill on slowly for testing, but that would have required another NAND gate and I couldn't manage to make one gate in the combinatorial logic stage also act as an oscillator. It was probably possible but I couldn't manage it.

There's also an RGB LED to tell me what signals are live, which shines through the holes in the casing, pic related.

>>2679180
>It’s so heavy i can’t really lift it
Is it one of those rear projection TVs?

Laser control box mostly assembled. Printed unreasonably nicely, though I think it would be better not in black. Only issues are:
>too much wire to shove in the tiny box
>still haven't found screws that nicely bite into the plastic for the connector to be seated where those wires are sticking out
But hey it bolts nicely atop my frame and should keep the wires out of the way. I'm going to do the wiring on the printer itself now, and remove my abortion of a microcontroller board I shoved in there last time. Now I'm doing everything with a digital logic chip and some transistors.