Roadblock overcome

The Monster has been resting for several months due to the (really rather trivial) problem mentioned in the previous post. I didn't want to start over with the new electronics, and had a frustrating time getting the things for the 2.3 board. Eventually, I got some old drivers (v 1.1!) from a fellow Googler (thanks, Tim!). Next Monday, I try running it!

A brief update on my RepStrap (now affectionally nick-named 'The Monster')

After getting all three axes to work, I decided making an extruder from ground-up would be an exercise in frustration and likely get me to never finish. So I purchased a Wade's Extruder - and realized I still needed a stepper motor driver for it.

While I have some stepper motor driver boards, they are of version 2.3, which are surface-mount and not something I've ever tried before.  I've been scared off a little by that, and by figuring out which exact components to get - the lists from the original description are gone (this is why you don't just link to some random other place, but copy it in). So it's slow going at the moment, but then, it's a nice summer right now.

I should also make some proper tags for the opto-endstops with better fastening. The cardboard ones I made got all broken by me fiddling around with other stuff. Not good enough.

It moves - in 3D

 I now have movement in all three directions at the same time, after some futzing with the Z axis.  Here is proof:

The noise in the background is the lasercutter.  You can faintly hear the motor noise if you know what to listen for.

TODO:
Find, test, fix and mount opto endstops.
Talk to Dieter about right screw for extruder.
Or go to RepRapSource.de/RepRap-Fab.org and buy a full extruder for ~€75 (without motor).
Mount extruder and go! :)

A new life in a new land

When last we heard from our intrepid robot, all three stages were almost built. Only the right way to keep the Z-stage from falling was missing, but a move had interrupted further building. Since then, another move has occurred, but things are now calmed down enough that I have been able to join FabLab München, the local maker group.

They have taken me and my robot in and kindly lent me the bits and pieces I hadn't brought over yet. The drivers have been re-tested and now all work.  The threaded rods have been oiled (this helped the X-stage quite a bit), and a solution for the dropping Z-stage has been found: Place a ball bearing on a block underneath, so it is supported without getting extra resistance. This has been implemented (with several layers of cardboard:), and the last few kinks of the Z-stage are being worked out, mainly bolts that are too long.

I have decided to not go the purist way and rather have the extruder head printed on one of the other machines (if they work by then). Especially since there's hardly any designs for non-printed extruder heads out there. Maybe, once all the other problems are worked out, and I know a little more, I will go back and make it pure. Maybe.

In the meanwhile, it has so happened that I have inherited a broken MakerBot. Some of the electronics smoked, and we're not sure which. Since the owner has moved on to other robots, he's happy to let me try to fix it and get it running. Sweet!

Update: Nothing has happened

Since my last post over a year ago (gasp!), nothing much has happened on my RepStrap. I got stuck at trying to mount the Z-axis threaded rod in such a way that it wouldn't just fall down, and then suddenly I got hired by Google and moved to München. Since I haven't had the opportunity to get all my stuff down, no further development has happened.

However, München does (now) have a maker group, FabLab München, of which I am planning to become a member once the last moving woes are over.

Motor testing (with several digressions)

I'm starting to collect motors and getting more ideas for what to do with them. Most of them I have no idea what the characteristics are, so I'll have to experiment with them. This page and this page gives some useful information on how to test unknown motors. Testing methods include turning the motors at known RPMs and measuring current/voltage and running the motors at known voltage and current while measuring RPMs. To measure RPMs, I would have to build a tachometer. There's an Arduino-based test at Instructables. Preferably one that gives a nice output, e.g. with 7-segment LCDs. I just happen to have a bunch of those lying around, so why not test them all?

This is how my projects typically progress, or rather digress.

On with the testing. A cute way of testing can be found on Instructables, using only components that I already have (yay electronics conspiracy!)...
Or so I thought. Turns out my big mess of resistors did not in fact contain the required one. Now, at least my resistors are sorted so I don't spend an hour every time I start a project finding out that I don't have the resistor (except I haven't labelled them all yet for lack of good label).

Actually, I didn't have the resistors. Instead, I just took a larger resistor onto my breadboard, gave 5 V through it, and tried all combinations until a light went on. From then on, it was easy enough to map out the segments. All but one worked nicely.

Problem now is that it would require 7 pins per display to run it, or a driver (e.g. 4511) to decode and latch them. I don't have enough pins to drive more than one, and I have no 4511. So I can't use that for a display. Instead, I'll just read output on the Arduino, adding a potientometer if needs be.

Fiddling around a bit, I now have a little board with a 220 ohm resistor going to a high-power LED that points at the light detector. There's a 1K ohm resistor on the other side of the reading wire. The analog reading with full light is 800ish, with light blocked it is 550ish. Enough difference that I can use it! That's enough for tonight, it's time to go to bed.

Motor testing (with several digressions)

I'm starting to collect motors and getting more ideas for what to do with them. Most of them I have no idea what the characteristics are, so I'll have to experiment with them. This page and this page gives some useful information on how to test unknown motors. Testing methods include turning the motors at known RPMs and measuring current/voltage and running the motors at known voltage and current while measuring RPMs. To measure RPMs, I would have to build a tachometer. There's an Arduino-based test at Instructables. Preferably one that gives a nice output, e.g. with 7-segment LCDs. I just happen to have a bunch of those lying around, so why not test them all?

This is how my projects typically progress, or rather digress.

On with the testing. A cute way of testing can be found on Instructables, using only components that I already have (yay electronics conspiracy!)...
Or so I thought. Turns out my big mess of resistors did not in fact contain the required one. Now, at least my resistors are sorted so I don't spend an hour every time I start a project finding out that I don't have the resistor (except I haven't labelled them all yet for lack of good label).

Actually, I didn't have the resistors. Instead, I just took a larger resistor onto my breadboard, gave 5 V through it, and tried all combinations until a light went on. From then on, it was easy enough to map out the segments. All but one worked nicely.

Problem now is that it would require 7 pins per display to run it, or a driver (e.g. 4511) to decode and latch them. I don't have enough pins to drive more than one, and I have no 4511. So I can't use that for a display. Instead, I'll just read output on the Arduino, adding a potientometer if needs be.