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 needed to output some debugging from a micro controller, usually this is easy. Just plug in a MAX232 and connect up a USB to Serial cable and you're away. But in this case I was using 3.3v making the MAX232 useless. I didn't have any MAX3232's in my boxes and I didn't want to fiddle around with resistors etc to make a rudimentary level converter. I needed something, and I knew it was something I would use time and time again in the future so I set out to make a LVTTL USB to Serial cable.
Looking at the various USB to Serial cables I had, I came across one that I could clearly see had a FT232BM. Looking up the data sheet for the FT232BM I found in the app notes that this chip can be configured to be 5V bus powered, 5V self-powered, 5V bus powered with 3.3V I/O and 5V self-powered with 3.3V I/O.
I've been working on a small project of late that utilises an ATMega32 and plays WAV files from a SD card. I'm using ELM Chan's Petit FatFS to do the FAT translation, but I was having issues with the SD card configuration and communication. Getting frustrated I started using my S3E development board as a SUMP Logic Analyzer for a while until I splurged and bought an Openbench Logic Sniffer which is based on the SUMP LA.
It cost me $46 AUD with free shipping from SeeedStudio. The "free" shipping took about 3 weeks to get from Hong Kong to Sydney Australia so I was less than impressed with that, but I'm more than impressed by the little board.
After setting up "the alternate" SUMP client and connecting up my SD card logic lines I soon had a sample of where my problems were. Also the SPI decoding build into the client was a joy to use and very very handy. The S3E version does have the advantage of the larger capture buffer (512K vs 4K) but using 115200bps serial as opposed to the 1Mbps of the OLS's USB connection this limitation is soon forgotten.
Having this board on my bench for a week or so, I was starting to worry about damage from things being dropped on the board while in use. So I set out to make a Perspex case similar to my Bus Pirate case. And here is the result...
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!
I managed to get my design over to the CNC mill today. I ended up using pcb2gcode to convert the gerber files. There was a bit of frig'n around but nothing to bad. I didn't change the spindle on the machine to my better low run-out Wolfgang. Instead I left the default Proxxon that has a bit of noticeable run-out when working at these sizes, that's why a few tracks are a bit thinner than I'd like (also the machine has a bit of undiagnosed backlash I haven't dealt with yet).
I found some time to finished the back-plate and the cabling of my controller box. It has worked out to be a very neat little device. I still have to mount the exhaust fan and filter in the lit, but it's pretty much completed now. I may actually put the exhaust fan in the front or the side, but we'll see when I get the sort of fan I'm after.
I've never been happy with the layout in my little CNC controller box. It was a little cramped hard to work on, plus I made a backplate for it but it was far to small and the connectors wouldn't fix. So, for the longest time I just had the cables and sockets hanging out the back.
So the other night I pulled the whole thing apart to see what I could do. I found a piece of plate aluminium that was the same size as the base of the box. I decided to mount all the internal components on this plate and mount that on six stand-offs in the base of the case making the whole assembly easy to lift out and work on. I also removed the rear fan and nibbled out the rear panel so that I can now fit the three Speakcons, one Powercon, four XLRs and a DB25 on a nice rear plate (I've yet to machine, chicken and egg problem) without having everything all bunched up together.
I've made a few little door signs for my nieces and nephews bedroom doors. They turned out pretty good I think. I've used my new version of VCarve Pro v6.0 for the first time and I really like the new features they've added. The new tool library and the toolpath templates are truly awesome and save a *heap* of time in creating a layout.
