Donegan OptiVisor

Donegan OptiVisor DA-5

I’d been ummming and ahhhing about getting something like for years. Would it work? Would it work better than my existing magnifying lamp? I had some credit on, so I finally bit the bullet and purchased it. I also had Prime one-day shipping (purchased to watch the the Grand Tour), so it came the next day without any additional shipping charges. In fact they originally offered to ship it same day when I looking online mid-day, but I waited until the evening to order as I knew that Mrs Boffin would be home the next day when it arrived. So after settling in to watch the latest “The Reassembler“, what should appear on the screen, but James May sporting pretty much the same thing. Perhaps I was James May in a previous life, I’d like to think so (or maybe it’s my future life?).

How does it work? It’s superb for close-up work. Amusingly, the first task I put it to use with was putting a new screw back in my distance glasses, after it fell out yesterday. Tweezers, small screw, small screwdriver. Success, first time. Run, don’t walk and buy one of these, you wont regret it.

Focal distance is about 20cm which is close, but not so close that it gets in the way of the soldering iron, which means I did well when I chose the 2.5x version; the higher magnification ones having a lower working distance. The stereo eyepieces (glass on the DA version) seem nice and sturdy, and I splurged the extra $13 for additional “OptiLoupe” flip down magnifier which gives another 2.5x for a total of 6.25x for very close up work. With the extra magnifier flipped down, I can easily read part numbers off SMD parts; worth the extra dollars.

Wow, the flash really makes my short haircut look like I'm bald.

Back to work on the nixie project I thought I’d try it out this evening making a second nixie back-plane like last weekend’s, mostly just to see what it’s like to solder with it on. I really like it. There’s only one small complaint and that is the bottom edge of the headband is sharpish plastic and is a little uncomfortable on my ears, but other than that the headband works well, it’s not heavy at all, and doesn’t feel unstable or awkward in any way. I’ll probably just put a little piece of fabric on the headband, and that will completely solve any annoyance.

Lastly, and completely unrelated, I of course mucked up somewhat and made a mistake soldering, so dug out some solder-wick to fix it. I had this cheapo roll of Chinese wick from Ali Express and I thought I’d give it a try (normally I use the 25 yr old roll of MG). Anyway, the Chinese stuff was useless, and would pick up nothing. Until, that is, I wetted the wick with an MG Flux pen. If you’re not using wick without a flux pen first, you need to run, not walk, and go buy a good flux pen (keep it in a zip-lock when you’re not using it).




Bare Nixie Board

I had been thinking about doing a little project with nixies for a long time, but hadn’t really gotten around to it. They have a great old-school (old-fart?) vibe, and I found an old board on eBay with 7 nixies on it for cheap and decided that was a good place to start. It arrived (from Belarus), and I quickly realized how much faster this would go with a proper vacuum desolder tool, rather than just a sucker and some wick. Anyway, after much futzing around, I managed to get the little tubes off the board in prep for the next step. There are still some high voltage drivers left on that board I wouldn’t mind scavenging, but the board has a coating, and those intial 7 tubes just about killed me.

Nixies need 170V or so, and I didn’t much fancy the idea of rolling my own high-voltage power supply, so a quick check of the interwebs and sure enough there are a ton of them on places like eBay and Tindie. However, one that caught my attention as a better solution was a guy down in the states with a website Not only did he have some nice inexpensive (and tiny) power supplies, they also sell a very very nifty I2C nixie driver board. I had originally thought I might build a two digit module with the shift registers and drivers and sell it on Tindie myself, but wow, this is much better supporting direct addressing, shift modes, clock modes and even dimming. The density is crazy, with tiny SMD high voltage drivers, and a PIC controlling it all.

Like all good projects, all this stuff arrived months ago, and sat on my desk while I goofed off and did other things (Oscilloscope episode, coming soon !), and finally this weekend I decided to hook some of it up. First task was to make a mounting board that held four nixie modules (I only have two right now – I need to order more), so I cut up some advanced-vero-substitute (which really brings back old memories of Vero offcuts @ Greenweld), and build that into a mount that holds four digits, and strings together the necessary power (170, 5, GND) and I2C (SDA, SCL) lines.

A little cutting, filing, and some 0.1″ headers soldered to the board and it works out pretty well. Eventually I want two boards of four, but for now I’ll get the first one hooked up, and then spend some time playing with the I2C interface. I tried really hard to get some action shots of the soldering but that’s pretty hard without an assistant, luckily Mrs Boffin was close at hand, so I did manage to capture at least one action shot.

In the end I decided to also add a couple of 0.1μF capacitors as well on the 5 volt rail, but it all went together fairly well, all I need to do now is repeat it on the second board. It really is nice to have a stock of things like the 0.1″ headers and caps, which I buy cheap in bulk from China/AliExpress.

I had already tested out the power supply just on a bare nixie tube, and had learned that you needed a 47k voltage setting resistor as well as an enable jumper, so it was simple to put the power supply module on a little Arduino shield, along with the I2C pullups, and then I can just use that as a test jig. Amazingly the PSU works great from 5 volts with enough oomph to drive a couple of tubes, although I suspect in the final circuit with eight nixies, I’ll probably need to run the PSU from 9-12V.

Now the simple part, right? A little Arduino sketch that outputs the data to the tubes. Of course by this time it’s 11pm, and while it seemed straight forward from the Wire library in Arduino-land that this should be simple, things rarely are.

After everything was hooked up and on the board I was having all sorts of problems. Hey! This should be easy, set the address, send a register value, send a digit value. Not so fast bucko. First I managed to bend a pin on the bottom of the shield that connects it to the Arduino. Did I bend just any pin? No… I bent the ground pin, on the far side, bent into the middle, so it was impossible to see until I finally flipped the shield upside down, followed by a facepalm moment. Still with all of that working again, I could see that there was I2C data being sent, but nothing was showing up on the digits.

This should send a 5 to the first module:

Wire.write(0); // register
Wire.write(5); // value

Nope, still no output on the tubes. After much head scratching, (and a 2nd glass of ginger beer), I decided it was time to dig out something that could actually decode what was going on on the I2C bus. So into the tool chest and out with the Analog Discovery USB oscilloscope I bought a couple of years back. I had picked this up off Kijiji from a student at USask that didn’t grasp the concept that the $100 student price he paid for it was WAAAY less than the $275 street price for us normal people. I see two or three every year going cheap this way. Anyway, it’s a fine tool, and while the bandwidth isn’t going to win any awards, it has built-in I2C  decoding on the 16 channel logic analyzer. Hey, what’s all that extra traffic happening? I didn’t put that there. Turns out it the module was set in clock mode (as opposed to address mode). WTF ?  The answer is that when they say “0 0 0 0” for the DIP switches, they really mean “ON ON ON ON” because they’re shorting to ground on pulled high inputs. OK, now we’re cookin’ with gas. Set it up to the self test setting, voila! It’s counting from 0-9. Set it back to the 1st address (0x10), but still my simple sketch isn’t doing the business, why not ?  I’ve set it to the correct address, I now understand the switch settings, why? why?  Well after playing with the sketch for different addresses, I discovered that when they say address 0x10 in the docs, they really mean half of that (I2C addresses are 7 bits and they were counting from the MSB apparently), Changing the address from 0x10 to 0x08 and it’s working YAY!

Once I got everything working, you can see clearly that the I2C address (at least from the Analog Discovery/Waveforms software) the address is and should be 0x08, not 0x10 for the 1st address. Easy fix in the code, and now I’ve got this sucker counting from 00-99 under my control.

Well, that was a weekend of 60 second fixes taking hours to find. Anyway, the first couple of digits are working, now to get 6 more modules (I’ve already got the nixies), and the 2nd carrier board built and we can move onto the next stage of the project.

Auction find; LED Sign

I pickFull RGB displayed up three of these interesting full RGB display signs from a local government auction; and while I haven’t done a lot of picking apart just yet, it looks like it’s completely tied to proprietary software. The company that built it the internals appears to be an Australian company that’s no longer in business. It’s beautifully bright, all the LEDs seem to work, and it’s powered by a very impressive 40 amp 5 volt power supply.  

All sorts of IO.  Ethernet (no I haven’t hooked it up to the home network just yet), RS232 (there’s a 485 in/out not shown in this photo as well). Some custom peripheral port, and weirdly there’s an audio input that goes to the logic board, but it doesn’t contain any audio display; I’m guessing there’s some software based way of having it do sound triggered/modified displays.

There’s a main CPU board, that drives a secondary board, and then three identical LED driver boards. Anyway, this will be my next project, and if I don’t get anything else out of it other than a 1000 bright RGB LEDs and a 200W 5V power supply, I’m still ahead.


LED Driver
One of three LED driver boards
Main CPU
The whole contraption

Update to the Serial Gauge

It’s been 8 months since I started selling on Tindie, and in that time I’ve managed to sell more serial gauges than I expected. I have received a little feedback from some of the purchasers, and based on that I’ve updated the software that drives the gauge to enhance a couple of things. The library now contains optimizations to use direct port mode, and main software has an option to set an initialization point. If you’ve got an old gauge, you can download the updated code from GitHub.

I’ve been thinking is there anything I want to add to this project?  Should I start a new project? What should I build? I know no one reads this blog, but if you’ve got ideas, please pass them along.


Wow, I should post more

power supplyTime sure flies.  I haven’t posted here in a while, but I thought I’d upload a few pictures of the most recent hack around the bench.  Took my old Radio ‘Battery Eliminator’ (12V, 3A), and converted it into a constant voltage/constant current supply using a little module I got from China (link here)

Moved the transformer inside the power supply back to make a little more room, and added a supply line fuse (it had an output fuse already).  Once that was done, I hacked the front to make the new module fit and added a couple of binding posts, making sure of the 0.75″ spacing (unlike the last time I hacked something like this), and I think it turned out rather well. I may still add an internal fan if it gets too warm, but I don’t use enough current out of it for that to likely be a problem.



power meter

I had also heard that these things weren’t particularly accurate, so I was curious to see how close it really was.  I hooked up an LED bulb (supposedly 2W, but closer to 1), and the current showed 94mA and the meter (Yes, the BM235 from EEVBlog) shows 96.1mA so about 2.5% off, but that’s close enough for the stuff I do.  It will be nice to be able to limit current, and also to have a quick current display to glance over at, rather than having to hook up a meter when I want to read it.

Of course the picture also shows my 1970s vintage Weller W-TCP-L, which is still going strong 40 years on. I’ve bought new tips (mostly use a 700 small chisel – for PCB work, and an 800F larger chisel – for bigger work), and it’s a champ.

Now to get back to what I came downstairs to do, pack up a Tindie order.  THANKS GUYS for all the support.  I’m not getting rich selling on Tindie, but it’s still a thrill to get an email saying “you have a new order!”

DIY hi hat controller for electronic drums

EDrum HiHatAbout 8 months back or so, I decided that I needed to learn how to play the drums. I’ve played the guitar for over 23 years, but needed something new, however, living in a condo I opted for a good, used electronic drum kit. As a fan of hard rock and heavy metal, one of the first things I bought was a double kick pedal to learn to play double bass. The one thing that was lacking however was the hi-hat cymbal’s controller could not be set into a fully closed position without my foot being on it – therefore, playing the hi-hat and double bass drum at the same time became not the best sounding or easiest thing to do.

A while ago, I got the bright idea to do some research around the internet and see if there might be any sort of electronic drop clutch that I could add onto the hi hat. After finding out how simple the hi hat controller foot pedal was (it’s essentially just a fancy potentiometer) – I realized what I had to do… make my own.

Continue reading “DIY hi hat controller for electronic drums”

Tindie – here I come

parts includedWell; I finally put the rest of my little stepper motor gauge project together and listed it on Tindie. Once they approve it, you should be able to find it by following the link at the top of the page to our Tindie Store.

The serial gauge driver allows you to retrofit any gauge mechanism with a simple to drive (any serial signal, it’s opto-isolated even) serial command stream.

Finished cleaning

The new parts drawers

I bought myself a birthday present, even more parts drawers. You can see the original ones (lower set on the left) as they’re a slightly different blue, but I decided what the hell, I’ll just buy the local distributor out of the last of their stock. There were a couple of casualties in shipping (mostly the really big drawers), but only had to toss one (and deal with cracks in one other).

After much sorting, labelling, divider gluing and generally going “what the heck should I call that”, I’ve emptied all my little flip top bins, and now have well over a 100 little drawers of awesomesauce (yes it’s a word, just added to the OED).

I’m sure I’m the only person that stresses about what kind of label (Avery 02209; removable) to use, or even what font (Source Code Pro, lower case). Have to say I’m glad I hunted for the right label. They’re the right size, and as they’re the removable style, easy to peel off if you make a mistake.

What does your parts cupboard look like?


Decided I would re-purpose some drawer units I had in the garage into the electronics storage. Quite a few things I own are too big for my existing method of flat storage boxes; especially some of the nuts/bolts/screws type items which I kept in the garage anyway.

Cleaning Storage Drawers

So, I relocated the drawer units in from the garage and gave them all a good wash. It’s amazing how dusty/cobwebby (is that a word?) it is in the garage. 20+ yr old labels needed cleaning off, but they seem to come off with some soaking. Some of the drawers I’ll continue to use for their original purpose (small nuts/bolts/screws/standoffs/grommits), but there are a few things that just don’t fit in my flat boxes very well (heatshrink, feet, stuff like that) that I’ll transition over.

These [Integrated Plastics Add-a-Drawer] really are the best drawer units I’ve ever come across, and I’m still kicking myself for having given away a bunch of them to the local college when I moved 12 years ago; oh well. Apparently Tenaquip still sell them even though the original company that made them is long gone; maybe I’ll buy another unit to add to what I have already, for now I’ll just keep an eye on Craigslist/Kijiji in case someone is selling some. If anyone does have any and they’re interesting in giving them up, give me a buzz…

A Start

sna·fu – snaˈfo͞o – NORTH AMERICAN informal
  1. a confused or chaotic state; a mess.
    “an enormous amount of my time was devoted to untangling snafus”
    synonyms: muddle, mess, tangle, jumble, confusion;
  1. in utter confusion or chaos.
    “our refrigeration plant is snafu”
  1. throw (a situation) into chaos.
    “you ignored his orders and snafued everything”