Y-Axis

The Y axis is the same basic design as the X axis.

Initially I built the Y axis rails too short. My father has told me to measure twice and cut once, Applying that would have saved me considerable time and materials. The upside is I have more travel on the Y axis than I expected, about 14".

I have just clamped the two frames together for now, I want the table on so I can level it before drilling the holes to attach the Y-axis.

I completed the z axis too, same basic design. I'm getting ready to move, so the last time my brother visited I gave him the semi-completed frame in hope that he may have more time to work on it than me. It just needs a table, motors and lead screws to be working. Whether he has time to work on it or not remains to be seen, but I know I won't have any time for at least a few months. I still want a 3d printer, I kept all my electronics, when I have time I'll build another one.

Foot Powered Edger

Well, I'm moving in less than a month! One of the things I have here is a underground fence for my dog. I love it, no unsightly fences, and she's good about staying in it. I dug the wire in by hand with a shovel 4 or 5 years ago. It took me way too long. So I was looking and the easy way is to get a lawn edger. So I've been looking at them, but I can't really justify buying a dedicated one just to bury my fence, so I was looking at weed whacker attachments, but people seem to have trouble using them normally (blown motors and broken shafts), so I doubt they would stand up to the abuse I intend to administer. I could probably rent a heavy duty one, and I will if it comes down to it. but I was looking and found this:
Amazon Link

People seem to like it except the blade bends easily if you hit a rock or large root with it. I think I can make a blade that will stand up to some serious abuse. Here's what I came up with:

I used some 3/16" x 3" stock I had lying around. I did 2x 3"x3" foot pads because I had 6" left over from the 12" blade. the pole is a 5' piece of 1/2" steel conduit. It seems to work pretty good in soft soil (yard), hard packed soil not so well (edge of driveway). It won't go through rocks, but I didn't expect it to. I doesn't bend. that's for sure. I don't know if it will work or not, if it does I think it will be quicker than the shovel, but harder and less fun than the edger. But that would cost a lot more than this. For a one time deal I think I'll manage.

Logitech Wave Missing Keystrokes & Teardown

My Logitech wireless keyboard started missing keystrokes. It's really irritating. I tried a few different things before I figured it out.

•  It was recommended to not have it's receiver plugged into a hub, so I plugged it directly into a usb port, that didn't fix it.
• I tried the "smash it in frustration" approach, which only succeeded in breaking one of the feet.
• It was so bad I decided to tear it apart and either finish it off or fix it. I didn't find anything to fix.
• I eventually discovered that it works great backwards, or if I hold my hands at a funny angle. it seems the PCB and antenna are under the wrist pad, and something is causing me to interfere with it.
• I dropped the receiver behind my desk almost at foot level and the keyboard seems to work great now. The mouse is another story...
• I'm contemplating running a new antenna around the perimeter, so part of it is not under my hands

Teardown
 It's all held together with philips screws, Thank you Logitech for not using some stupid tamper-resistant screws. Be careful, pulling the membrane off created quite a static charge, I hope I didn't do any ESD damage.

 The switch thingie is a 3 piece plastic thing with circuits and contacts on the top and bottom with a separator in the center with holes for each key

I wiped each piece down with rubbing alcohol.

 

Reassembly
 Put the zoom button and mute button on the lower part, all the other keys are snapped into the upper part.

Building a CNC Machine - Linear Bearings & X-Axis

I've been back and forth between buying the parts to build a RepRap off eBay or designing something myself. I've also been concerned that the Prusa frame wouldn't be strong enough to handle pcb routing. So I decided to build a somewhat heavier duty cnc machine to do pcb routing, but make it able to run an extruder. I may just use it with the extruder or use it as a RepStrap to print the parts for a Prusa at a later date. I intend to use the Sanguinololu board I built to control it.

Linear Bearings

The linear bearing were a hangup for me, all the best ideas were either expensive (v-groove bearings, 1/2"+ linear bearings), or looked flimsy for my application (8mm linear bearings).

I've seen this design on the internet before, and couldn't come up with a better solution that didn't cost a small fortune.

I bought 100 608zz bearings, some angle iron and a big bag of 5/16" nuts, 5/16" x 1" bolts and 1/4" washers. I made a jig to ensure the holes were in the right place, clamped it to the drill press and here's what I came up with.

I will weld 1 1/2" angle to the backs to make mounting brackets. 

Specs: 

• 1" angle iron cut to 4"
• Holes drilled at 1/2" and 1 1/8" in from each end (roughly)
• Clamped to a jig to ensure holes are perfectly aligned in relation to the center
• Each bearing has a 1/4" washer on each end of the 608zz bearing, a 5/16"x1" bolt and 2 nuts (one on each side of the angle iron)

X Axis
With the bearing design done I started the X-axis
I wanted a bigger work area that the RepRap's 8"x8"x5.5" My X-axis has 11 3/4" max travel. I was going for 12", but the frame interferes. I'll probably limit it to 11-11 1/2". the Y-axis should be about the same, haven't decided on the Z axis yet, I have 8" in mind, but probably between 6-10"

Specs:

• Slides are 16" long, allowing 12" travel (without the cross pieces). the slides are structural frame parts. they have 1 1/2 angle iron welded to the back of each end to attach them to the cross pieces
• Cross pieces are 18" wide, allowing slides to be bolted at 15 3/4" wide. It will work out to 16" when I do the Y axis mounts (1/8 added per side)

X-Axis

It seems very sturdy, I stood on it, and it was still easy to move. I'm out of 1" angle iron again, so that's it for now. I still need to attach a table, mount a stepper motor, and it hook up a lead screw of some sort.

Closeup View

 Weight Test

Fixed a dead 1284p

The Problem:
Through the 1284p saga I ended up with a 1284p that I couldn't burn the bootloader to. It was working (sprinter running, random serial errors and restarts though) then the next day it quit. Later, when I tried to burn the correct fuse bit and bootloader I received a Device Signature = 0x000000.

Unless something had corrupted it, it had the Ext Crystal Osc. setting. I figured the fuse problem out after this chip died. I came to the conclusion that either something was messed up with the fuses or the micro was completely dead. I wanted to build a Fusebit Doctor, but didn't have the time to start another project at this point, so I bought a 644p and shelved the 1284p.

The Solution, or "I Had a Lucky Break!":
I kept thinking about the dead micro, it was really bugging me. Finally I decided to try it with a crystal oscillator instead of the resonator to see if that was it. I found a 16mhz crystal in my spare parts box and replaced the resonator on my breadboard with it, couldn't find 22pf caps, and the caps I found didn't work with it.

I still managed to burned a bootloader on it with just a 16mhz crystal, no caps. Now it seems fine again with the resonator and the new fuse settings, go figure.

Parallax 7345 RV Power Converter (SMPS)

See Also:
Parallax 7345 Repair Tips

A friend had a Parrallax 7345 power converter for a RV that didn't work. We know what happened, It's designed for 120VAC only and somehow got hooked up to 240VAC. So it released some of it's magic smoke. (and probably made a big BANG noise I imagine)

Basic Info:

• The big heatsinks may have 300VDC+- on them, Be careful! (obviously if it's on the heatsinks, it could be anywhere, like those 2 big caps) It doesn't just go away if it's not plugged it either.
• 45A@13.8VDC (7300 series 45A)
• 120VAC input
• Despite the fancy "converter" name it's just a big Switch Mode Power Supply (SMPS)
• Schematics are not available (Parrallax has on their page "We do not give schematics to anyone perod", or something to that effect), as with most things in the RV universe, they are expensive to replace and don't expect any help repairing them.

The Diagnosis:
It was pretty easy to locate the fault, as there was black stuff all over one spot. (Note: I'd already removed the heatsink from the bridge rectifier in the first picture and cleaned to bottom a bit when I took the second picture)

I looked it over good. It seems a MOV (metal oxide varistor) is missing (vaporized in fact), but that wouldn't prevent it from working, it just shorts the ac line together when they reach a certain voltage, with it gone it should power up, unless something else is broken. Sure enough the line filter next to it had melted a wire clean off, I didn't see it at first because the MOV had left a bunch of residue that hid it.
The other black spot on the circuit board (far left) is under the output resistors, they work fine, but must run a bit hot under prolonged load.

I bridged the broken wire on the filter, sheilded my face and plugged it in. It powered up nicely, made a moderately loud buzzing noise (no load), so I unplugged it and connected it to a 12V battery. Absolutely quiet now, but putting an amp or so into my battery. The battery is connected to an inverter I use for emergency power, so I plugged a toaster in and it jumped right to 45A. I ran a couple toaster cycles then let it fully charge my battery and all seems well.


The Repair:
I couldn't find an exact replacement for the filter, so I had to make a few mods to the board for the one I found. I had to guess on the MOV, I used a 175V MOV (datasheet said 150VAC max) I still have no idea what size would have been right, I even spent a couple hours trying to find how to choose the voltage and still didn't come up with an answer.

But a new MOV and line filter later it's back in service. The good news it the MOV did it's job, protecting all the electronics after it, it should have had a fuse in the AC line and the MOV and line filter may have survived. There was some minor damage to the traces around the line filter and MOV, but nothing too bad. The owner was instructed "Don't hook it to 240 again!", but I think he already knew that.

The other side of the board, nothing wrong here, just in case you want to see it:

Update:

I picked up a broken 55A version of this unit. As far as I can tell it's exactly the same board. I'm going to do a post and probably a video of diagnosing and repairing it, but that may be a while. 

I was going to post the correct value of the MOV, but it doesn't have one. The MOV footprint is not populated. I have the numbers off the filter, but google hasn't helped my find anything about it, so it may be a wild goose chase. In case it helps someone:

Filter:

06847475-000 843TC6

AXM EIA-17-0315-1A

ArduinoISP

Intro:
If you read Part 2 of my Sanguinololu Build you saw my arduino ISP (in Circuit Programmer) built on a breadboard to burn bootloaders my 1284p's. It worked really good, but I had to be really careful not to bump any wires loose or pull them out accidentally.
Some day I may buy a proper ISP, but until then it would be nice to have something that would work on the rather rare occasion I actually need one. So I decided to make something more permanent but not require a dedicated Arduino either.

The Project:

• Connect an Arduino to any 6 pin AVRISP header
• Include status LED's
• Be completely removable (mounted on headers)

There you have it, 3 led's (Pulse, Error, Data?) Schematic was figured from the Burning the Sanguino Bootloader using Arduino as ISP page.  LED's are dead bugged on the header, not sure if you even need the cap. just plug in the 2 headers, the 6 pin ISP plug and burn away!

Seems to work so far, Tried it on my other arduino, not really extensive testing, but seems to work.I'd like to make a couple pcb's for various chips with the 6 pin ISP header on them, but that's all for now.

UPDATE:
Just built a second one, decided to move the ground from the power side to the io pin side, that allows selection of 5v or 3.3v on the VCC wire. or you can leave it disconnected if your target is self powered.