Replacement components

I'm trying to build a set of RepRap electronics with an eye towards building a RepStrap (something like a WolfStrap) and printing proper Mendel parts. And I'm constantly running into problems with sourcing specific components, whichever electronics I try. There's an added complication that mail order is out of the question for various reasons, I need to use the components I can actually purchase locally. (If I were willing to mail order, I'd order a prebuilt board and be done with it.) That's a wide variety of them, but certain areas appear to be lacking.

Generation 6 looks tempting, but it relies on DRV8811 driver chips no component retailer within driving range has ever heard of, so it's out. The entire gamut of Pololu-based electronics are likewise impossible because all Pololu-based designs currently detailed enough for me to actually build them are built around an Arduino Mega. While there is no problem getting various Arduino clones, all of them are shortened variants of the board which aren't shield-compatible with these particular designs. That beside the Pololu board costing an arm and a leg and driving the cost of the entire assembly through the roof.

That brings me back to Generation 3 electronics, and everything seems to be available... Except NIF5003 MOSFETs, which, upon extensive googling, no design seems to have ever used except RepRap itself.

What can I replace them with? Forum postings caution against the use of unprotected MOSFETs, and while IRL3803SPBF appears to be pin-compatible and similar spec, it has no protection. It would very much help me if someone listed as many part numbers as they can think of that will be suitable replacements which won't necessitate redesigning the board. (I can't say I know very well what I'm doing in the first place, it just seems to work most of the time.)

Assuming I build the entire set of Gen3, there's still a question of endstops. HL21LOB is not available and nobody knows what one is. Neither is ZD1901. Will, say, a HOA1874-012 do?

Wow. You wouldn't bother to manufacture a 4 layer design (Gen6) yourself, but feel unable to match a RepRap board with one of the available Arduinos? That's interesting.

For one, you can build these Arduinos yourself, too. For two, there is no need to plug the RepRap board directly onto an Arduino, it's just fine to have some wire between them. For three, changing a board design to match your particular variant of Arduino isn't that difficult, as all design files are open source. For four, the same is valid for the RepRap boards. So I'd select more by chip availability.

Regarding chip comparisons, it would be most helpful to provide links to data sheets here. For example, the H21LOB is here: [www.alldatasheet.com]

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

Yes, I know it's silly. Amusingly, it's easier to order a 4 layer board made (at least for me) than get specific parts the local retailers don't stock, and I'd rather avoid board design altogether, since I know I'm not good at it... though, designing a board is a lesser obstacle than actually getting a component that's missing.

Since it looks like I won't be able to avoid it anyway, there's probably no reason not to design a board from scratch based on a row of A3982, to be connected over a ribbon cable to an Arduino clone. Then cross fingers and hope it works.

Still leaves the question of what to replace the H21LOB with. HOA2001 looks like it should work out, in the end, but it's also ten times more expensive.

The HOA2001 will work, but just about any opto-interrupt switch will work.
You could even build your own opto interrupt switch if you wanted to.

Or forget the opto-interrupt switch and use a momentary on push switch.

I ripped apart a couple of printers and I found a number of opto switches in them.

I am sure they can be made to work.

[cgi.ebay.nl]

I have some H21LOB available. Also some opto PCB's and DIY kits.