Reprap Electronics

Thoughts on, and bill-of-materials for, RepRap electronics.

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.

Complete Components


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
Board Ultimachine 1 10.00
100nf Digikey 490-1726-1-ND 1 10 0.06
10μf Mouser 140-VE100M1ATR0405 3 0.12
100μf Mouser 140-VE101M1CTR0605 6 0.15
4.7kΩ Digikey 541-4.70KCCT-ND 5 10 0.09
100kΩ Digikey P100KACT-ND 8 50 0.02
1kΩ Digikey P1.0KACT-ND 1 50 0.02
1.8kΩ Digikey P1.8KACT-ND 3 50 0.02
10kΩ Digikey P10KACT-ND 5 50 0.02
10Ω Digikey P10.0CCT-ND 3 50 0.02
Mosfet Mouser 511-STP55NF06L 3 1.48
1N4004 Mouser 625-1N4004-E3/54 2 0.06
PTC Fuse 1 Digikey MF-R500-ND 1 0.81
PTC Fuse 2 Digikey RGEF1100-ND 1 0.86
Screw terminal Mouser 571-2828376 1 1.21
Green LED Mouser 720-LGR971-KN-1 1 10 0.1
Red LEDs Mouser 720-LHR974-LP-1 3 10 0.1
Switch Digikey 450-1648-ND 1 0.28
Power Jack Digikey WM7847-ND 1 1.26
2x3 header Digikey 3M9459-ND 8 0.35
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
Jumpers Mouser 151-8011-E 15 0.12

Incomplete Components

Stepper Drivers

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
Allegro A4988 Digikey 620-1343-1-ND 1 4 3.42
0.1μf Digikey 490-1327-1-ND 4 20 0.02
0.22μf Digikey 490-3273-1-ND 2 10 0.05
4.7μf Digikey 399-3699-1-ND 1 0.35
0.2Ω Digikey RHM.20MCT-ND 2 0.37
10kΩ Digikey P10KJCT-ND 1 100 0.01
20kΩ Digikey P20KJCT-ND 1 100 0.01
100kΩ Digikey P100KJCT-ND 2 100 0.01
10k trimpot Digikey 3302W-103ECT-ND 1 0.56
Circuit Board DIY N/A 1 1.00

End Stops

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.