Wednesday, 30 July 2008

Final stepper board complete!

Last night, I completed the final stepper motor driver board. I re-tested all three and all three leds light up nicely.
The final board went very smoothly. I'm finally getting a bit more confidence with soldering, and third time around I knew where most of the components went. I started after the police dogs program last night, and finished just before big brother, so it took me almost exactly one hour.

Timings for each board (starting from scratch, with little soldering experience, pretty cautious):
Practice - 1.5 hrs
Arduino shield, DC motor driver, PWM - approx 1.5 - 2 hrs each
6 opto-endstops - 2.5 hours total
stepper 1 - 1.5 hrs
stepper 2 - 1.25 hrs
stepper 3 - 1hr
(timings include setting up and tidy up for each session)

All in all, the electronics went better than I expected. Because of the separate boards, they fit well into doing a board during an evening. If you sat down and worked continuously, things would probably go faster - but I didn't have a weekend free.

I've been able to test the PWM and DC driver boards, but the steppers have yet to be connected to a real stepper.

Now, I'm just waiting for the bitsfrombytes kit to arrive...

Monday, 28 July 2008

Two stepper boards done!

Over the weekend, I finished off and tested the first stepper board. Loading up the arduino test, the LEDs flicker and everything appears to work! I haven't got a stepper yet (they're still on order) to test properly, but so far, so good.
On a roll, I soldered the second stepper board and connected it up. Flickering lights again! I think I'm finally getting the hang of soldering.

Only one more stepper board to go, and the electronics are done.

Wednesday, 23 July 2008

First stepper motor driver board - nearly done

Started soldering the three remaining stepper motor driver boards today. I'm glad I left them till last, they are more complex than the other boards, and have quite a mixture of components and headers. Print out a resistor colour chart, or label your resistors as there are several different values in different places.
I'm still impressed with the RRRF boards, they're very well printed and the instructions are good. On most of the pictures you can see the resistor values to help cross-check after you've inserted the components.

The first board is 95% done. All I have left is the wiring and connectors, then testing :-)

Sunday, 20 July 2008

Six opto-endstop boards finished

I sat down last night to 'finish off' the six opto-endstop boards that I'd added the components to last week. It's surprising how long a simple task takes, like cutting a couple of feet of 3-core wire, stripping the ends, and attaching the plugs and soldering to the board, especially when you have to do it six times.

All the endstop boards are now complete, so I can run the stepper motors from end to end without banging into the mechanical stops at either end.

I've only got the three stepper controller boards to go!

Thursday, 17 July 2008

Laptop power plug fixed.

For a while now, my laptop power plug has been getting really annoying. It will only charge the laptop if it is left in a certain position - with the plug fully inserted and the wire bent to the side - and often runs the battery down, as my laptop is typically on most of the time. The screen keeps dipping in and out of power saving mode (going dim and then bright) as the power is connected and disconnected.

This got too annoying last night, so I fiddled with the power plug and the entire plug barrel came out of the plastic shield. It seems that the tiny solder joints holding the plug into the shield had broken (leading to the intermittent power connection).

Time for a fix.

I cut away the shield to expose the connectors at the back. This was a replacement 'generic' PSU, so it had a generic two-pin connector to several sizes of power plug. I could then re-solder the power connectors, like so:

Then I grabbed some of the 'Polymorph' (CAPA) plastic from my RepRap project. Softening a bit in some hot water, it could be moulded into a custom 'made to fit' plug shield for the laptop:

It looks a bit different, but it does provide a stable power connection and will allow my aging tablet PC to limp along for a while yet. It also seems to be more securely plugged in.

Tuesday, 15 July 2008

Mechanical kit ordered!

I sat down and soldered all six opto-endstop boards, in the style of an assembly line. They're pretty small and only have a few components. All I need to do to finish them is add the wire connectors.

I've built over half of the electronics kits and it's confirmed my interest in building and evolving a RepRap. So, I decided to take the plunge and order the full mechanical kit from bitsfrombytes. They sell laser-cut versions of the rep-rapable parts if you have access to the steel feedstock and want to start from scratch, but the best solution for me is to get the full kit. It contains all the motors, rods, connectors and laser-cut parts to build a reprap.

I'll post a review of the kit once it arrives....

Sunday, 13 July 2008

PWM controller done

Sat down this afternoon and built the PWM Controller board. Everything went smoothly apart from a slight soldering hiccup.
I arranged a fan so that it was gently blowing across the work area to remove the smoke and fumes, but my next couple of solder joints took a long time and did not look right. After re-reading a couple of soldering tutorials, I turned the fan off - the extra airflow cools the iron down, making the joints difficult to form. I re-melted the dodgy joints and added a bit more solder, and everything was fine again.
Plugging the completed board in, all the LEDs fired up and things looked good. I connected a small (3v?) old motor that I used for testing the DC Motor driver board.
Now, while the DC Motor board can supply 0.75 Amps, the PWM board can theoretically supply 5 Amps. My little motor ramped up (as expected) and then started to smoke. I thought it best to turn it off at this point.
A couple of minutes later, I had replaced it with an old PC fan which handled the load a lot better. Testing all three channels worked, so I'm declaring the PWM board a success. Now on to the next!

Friday, 11 July 2008

Number 2 board done!

After work, I sat down and put together the first 'real' board - with real components and everything. The DC motor driver board takes a direction and PWM signal from the arduino, and drives a dc motor - in fact, it can drive two motors independently.
Again, the RRRF instructions are very clear and even suitable for me. I'm finding soldering easier now, I'm getting more confident and speeding up a bit. It took me about an hour and a half from start to finish, including testing.
Plugging it in was a bit unnerving, but the power LEDs came on, and there was no smoke or flames, so thumbs up. After loading up the arduino with the test program, the little DC motor started slow, then ramped up faster and faster, ending up with high-pitched whine that drove the cat off the windowsill nearby. It then slows down slowly and reverses. Result!
Swapping the motor to controller B produces the same result.

I think this is the first electronics project I've actually soldered and got working correctly - ever!

Thursday, 10 July 2008

First board done!

After a bit of soldering practice, I put the arduino breakout board together!

The instructions were clear and easy to follow. Everything went OK, finally plugged in the arduino and the power light came on!

Having no confidence in my soldering skills, I unplugged it and went through every connection with a multimeter (since most are simple arduino pin to screw terminal), and they all seem OK.
I'm pretty impressed with the kits. The PCBs are professional, well marked, and the instructions are unambiguous with plenty of pictures. I'm a bit more confident that I can build the remaining boards now.

Wednesday, 9 July 2008

Building a RepRap - day one

I've been keeping an eye on the
RepRap project for a while, and I've finally decided to build one.
The RRRF is a non-profit organisation set up to help supply parts for RepRap research and development supplies some useful electronics pcbs and kits. After a little delay getting things back in stock, I ordered a bunch of useful RepRap odds and ends, and a full electronics kit.

Pretty soon, a box full of goodies arrived. I bought:
  • A full electronics kit - several PCBs with full sets of components ready to solder. My weakest area is electronics, so I need the help!
  • An arduino interface board
  • A few feet of Nichrome wire and a spare thermocouple - I'm hoping to build a seperate extruder to experiment with, and it will also act as spares.
  • A big 5lb coil of ABS. I've seen some good results that HydraRaptor's achieved with ABS, and I'm interested in experimenting with it.
Over the last few weeks, I've also picked up from Maplins:
  • a soldering iron and soldering kit
  • some Polymorph (CAPA)
  • stripboard
  • wire
I've also dug out a bunch of tools from the garage - some small pliers, cutters, 'helping hands', clips, tweezers, anything that might be useful. There's also a good pc power supply and a bunch of pc fans and cpu coolers from previous experiments that will come in useful.

My plan is to make the electronics first, and then get a kit from bitsfrombytes for the mechanical stuff.

I need to practice soldering a bit before I have the confidence to let loose on the kits!