My friend Alan Yates is currently working through all manner or particle detectors. His latest one is a Gas Electron Multiplier. It's basically a very two very thin plates with many tiny holes that electrons can go through triggering an electron avalanche between the two highly charged plates.
He was going to try using a piece of veroboard, when I said I'd make him something on the CNC.
Thanks to Tyson I have a good set of solid carbide PCB drills down to 0.25mm. Alan was only after 0.3mm and 0.5mm spacing so I easily managed that on the Widgitmaster machine.
Been playing with some code to convert images to GCode. Here is a test sample. Not bad I reckon. From 3 metres away it looks like a black and white photo. :)
I haven't been posting much lately because I've been busy helping out a friend with some handy little boxes of tricks.
The first one is a simple toggle button controller that uses an ATtiny13 to form a push-on push-off control button with LED and a dry-contact reset to turn the toggle off. The PCB was designed with gEDA PCB and the NC GCode was created with it's GCode export function. It generates passable GCode, but you do need to verify that the tool can make it through all the small clearance gaps otherwise you end up with bridged traces (especially around pads).
gEDA PCB GCode export also doesn't produce a very good outline code to route the board out. It for some reason includes all the drill holes etc etc. So I manually edit the file and remove all the unneeded stuff. I also have to manually add "tool diameter offset" with the G40 and G42 commands otherwise it will run the tool exactly on the outline and not compensate for the tools width. With the G42 command EMC2 will offset the tool width and cut the board out at the correct size. It's a bit of fiddling but the results are great otherwise
Also since I dialled out the backlash the machine is back to being accurate once again. My circular pads are circles again! Also the drill alignment is much much better.
Anyway, the second PCB (box still pending) is a two host to one device USB switcher. It's for a audio-visual automation system that requires to switch a device between two computer outlets. It takes a dry-contact to make the switch. The LEDs where added just to show the selection, otherwise they're not needed.
The board uses telephone grade 5V relays so the contacts should be more than adequate for USB. The device seems to work just fine with the box in line so so far so good.
Unfortunately I had to re-make the original board (the one shown in previous post) as I stuffed up and made the tracks just a little too small by setting the cut depth to deep with my v-shaped engraving bit. This makes the clearance between the traces larger and the tracks smaller. I had completed building four of the nine cells when I damaged the board with the tip of my iron building the fifth one. After a few minutes trying to fix the broken track I figured I could make a new one faster and not have this problem.
So a new piece of FR4 was put in the machine, and some eight minutes later I had a new board. Too easy!
Being sick today has had it's advantages (except for the runny nose and having to separate myself from my family), but I did get to spend a fair amount of time in the workshop fixing the things I haven't done in a while.
Firstly, I finally connected up an E-Stop to the CNC controller. After a few hair raising moments and scrambling for the keyboard today I thought I better finally put one together. It's actually been really handy and I'm surprised it took me this long to get it together.
The Bus Pirate I got from SparkFun is a nice bit of gear, but I didn't like the fact that it was floating around on my desk naked. I'd seen someone make a similar case with a Epilog laser and thought I could do a similar or better job with my little CNC mill. This is what I came up with!
It's an optical sensor to measure the RPM on my Wolfgang high speed spindle. It was made with said spindle, but I want EMC2 to control the RPM so that I can detect a bit break or slow the feed-rate when the bit starts to bog down.
(Mind the blobs of solder at the top. I bumped the crystal loose and tore the tracks off the board during the many attempts at removing the AVR as detailed below...)
The board engraved a treat and was flawless. Time to drill... oops! I forgot to set the Z height for the "Tool Change" home position, so helpfully the machine engraved a nice straight line across 3 tracks. DAMN! Ok, fix that... drill, drill, drill, DAMN does it again! This time only across one. Repair the tracks with a small piece of magnet wire and start assembly.
Well I finally did it, I've put limit/home switches on the Midi.
After playing with EMC2 for quite a bit (BTW it rocks!) I realised half my setup was homing axises, and with limit switches this would be done automatically. So I set to work!
You can see that I've cut down the tang of a standard micro-switch to fit in the small gap at the back of the Z axis. This works rather well. At the moment the switches are held on with super strength double sided adhesive strips but later on when I disassemble the machine for cleaning I'll drill and tap some 3mm holes in the back of the Z axis. These will do however for the time being.
For the Z axis I cheated a little, I've only added a home switch. Again I've cheated by using a miniature reed switch and magnet for the switch. It's super simple and seems to work perfectly well. The only downside is I cannot home the Z axis with the motor running because the reed switch gets switched by the motor randomly it would seem. EMC notices the switch behaving erratically and will cease the homing sequence, which stops the machine from crashing. Again I don't see this really as a problem because you'd only home the Z when the machine isn't running the spindle any how.
