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Power supply and USB query

Posted by biscuits 
Power supply and USB query
August 25, 2012 06:01AM
Hi, I'm hoping somebody can help me out answering a few questions. I bought a second-hand Cupcake, it was an unfinished kit, and a couple of those "unfinished" bits were the power supply and the USB to ttl cable.

So, I bought an 750 watt ATX power supply, but have just discovered there is only 2 cables on it with the correct connections. BUT, those 2 cables have 2 connectors on each. My question then - is it possible to run two stepper motors from one cable and the third one from the other?

The USB to ttl cable is also a mystery. There are six pins on the motherboard (it is labelled "RepRap Motherboard V1.2"), that are meant to connect to the USB. I got in touch with Vik Oliver, who kindly supplied me with a 'CP 2102 USB to UART bridge controller'. This has a 5 pin output. Does this mean there is a pin on the motherboard not used? If so, which one?

Any help or advice you can give me would be gratefully received.


Re: Power supply and USB query
August 25, 2012 12:06PM
Hi Peter

Does the main pcb look like this


If so see http://www.reprap.org/wiki/Motherboard_1.2#Serial_Header for the serial pin descriptions

What you really want is one of these [www.ebay.com]

I don't know the device Vik has given you and a quick google shows a lot more pins on things with the same name, can you take a picture?

re power

Are you talking about the stepper boards eg the one on the left below?


If yes then yes you should be fine plugging them in like that. I would just make sure x and y axis where on separate cables and put z on the second connector

BTW this is really old hardware (read as obsolete)

Edited 5 time(s). Last edit at 08/26/2012 05:47AM by Dust.
Re: Power supply and USB query
August 25, 2012 04:30PM
For the FTDI cable, you can go the all-in-one cable that Dust linked to, or use a breakout like this:


Which will mean you can plug your cupcake in with a standard mini-USB cable.

If your cupcake is an unfinished original kit you'll want to plan some upgrades over time.

- First thing (which may be unplanned) is that the old MK4 extruder had a tendency to develop a leak around the PTFE barrier (I ended up switching to a hot end from Makergear).

- The original build platform is unheated, which means that there is a tendency for ABS prints to warp and lift off at the corners. Buying or making a heated build platform really helps with that. The problem is nowhere near as bad when printing with PLA, but the cupcake extruder is not up to it.

- At some point you will want to move from the geared DC motor extruder to a stepper motor controlled extruder. This gives much better extrusion control, particularly with reducing stringing when the extruder moves from one part/piece to another. Some more info here: [wiki.makerbot.com] This is where you start to get into electronics upgrades, so you may want to think about whether to stay with the makerbot electronics at this point or jump off into reprap land with Sanguinolo/RAMPS.

- The default stepper drivers are 1/2 stepping, and it makes the machine significantly quieter moving to 8th or 16th stepping drivers (mostly people use pololu's). Assuming you stay with the current electronics, you can get one of these: [www.thingiverse.com]

My cupcake is happily running an accelerated marlin style firmware, with the PSMD and "ugly cable hack" [www.thingiverse.com] so it's still capable of producing damn fine prints and has come a fair way since I got it in Feb 2010. I also ran the gen3 electronics on my Sells Mendel until I had an accident that let the magic smoke out.

I'm sure you'll have a lot of fun with it, the cupcakes are cool hackable machines, and there are a ton more upgrades that you can get into if and when you feel like it.

Re: Power supply and USB query
August 26, 2012 04:30AM

Thanks for the very detailed replies, but I'm afraid i've just made a fool of myself, which is great for a first time post. The device that Vik sent me is correct. It does have a six pin output, but only a five lead cable arrived with it. Somehow or other that threw me. Sorry about that, but all is not lost - the info there was still useful and educational (for me at least).

Dust - thanks for the photos and links. They'll be really useful when I finally plug it all in. And good news on the stepper motors too. I'll be good to go soon. I sort of suspected it would be "old" technology, but it's all very new to me.

Lenbok - Thanks for volume of help and advice. I knew about the warping issue, which is why I got some 3mm PLA through Vik. However it might not get used if the extruder won't handle it. Any upgrades are being put on hold until I get my head around running this thing.

Thanks again for your help


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