Since I’m masochistic, cheap, and overly fond of soldering (molten metal! toxic fumes! lead poisoning!), I plan on building as much as possible of the bot’s electronics from scratch. As of June 9, progress has been mostly straightforward: RAMPS 1.4 has been built, the new endstop design prototype is working, and I’m still unsure about sourcing stepper drivers.
Assembling RAMPS was a breeze: 0805-SMT is very friendly, even when soldering everything with just an iron, and soldering headers takes no real skill. RAMPS’ total cost thus came out to be $42.83, even when purchasing SMDs in absolutely excessive quantities. If one ignores most vendors’ minimum purchase quantities and the attrition rate inherent in dealing with lots of 2.5 mm2 resistors, this cost is reduced to $37.80 - compare this to ultimachine’s $85 pre-assembled board or $50 kit.
The following BOM has been tested and is about equivalent (in price) to the official BOM. N.B. the project’s Mouser BOM includes the wrong 8x1 female headers, a fact I didn’t realize until I had soldered them in. Otherwise, the official documentation is spot on - although they do claim that unnecessary tools are required.
|RAMPS 1.4 board||1||Part #||Per||Ordered||Cost Per|
|PTC Fuse 1||Digikey||MF-R500-ND||1||0.81|
|PTC Fuse 2||Digikey||RGEF1100-ND||1||0.86|
|4 pin header||Digikey||3M9449-ND||5||0.26|
|6 f header||Digikey||S7039-ND||1||0.74|
|8x1 pin header||Mouser||855-M20-9990846||5||0.18|
|8x1 f header||Digikey||S7041-ND||4||0.97|
|2x18 f header||Mouser||649-78548-436HLF||1||0.58|
|6 pin header||Digikey||3M9451-ND||1||0.35|
|24 f header||Digikey||S7057-ND||2||1.77|
Pololu drivers seems to be the current favorite, but they’re out of stock everywhere and are somewhat expensive ($12 x 4). Certain shops currently stock them, but at quite a premium ($5??!?! For something you don’t even actually make? Lulz wut, LulzBot). The StepStick is an open alternative, and comes out to be much cheaper ($6.29). However, it does require soldering QFN and 0402 SMD, can’t deal with as much current, and uses a chip that seems to be suffering from global shortages. At this point, I’ve purchased all the components (sans A4988 and boards) but may just eat the loss/play with 0402 passives and purchase real Pololus when they’re actually in stock at Pololu.
|StepStick||4||Part #||Per||Ordered||Cost Per|
I’ve decided I like the idea of optical endstops but hate the current through-hole implementation, so I designed optos that use entirely SMT. I have a working prototype but want to tweak the design a bit before release.