Jon Thomasson's Build Log


Great video! Love the stuff Destin does, especially when there are highspeed cameras


That’s a good point about the POV inherent in charlieplexing. I hadn’t considered that. And that video was great! I liked that it detailed not only how POV works from the circuit side, but went further to explain why it works with the way we see light.


I got my boards back earlier in the week and I finally got a chance to put everything together. I ran into a few snafu’s initially. I failed to put in the right size footprint for the attiny85. I had thought in the datasheet it specified the thinner 3.9mm soic package, but the one I received from digikey was the wider 5.3mm variety. Fortunately I was just able to bend the leads a bit to get them to fit within the footprint. After that I had everything soldered up, inserted my coin cells, and checked for voltages to make sure that part of the circuit was working. Unfortunately I wasn’t getting the 3 volts from the batteries. I figured out that I needed to tin the ground pads that sit underneath the coin cell batteries so that they make adequate contact to the battery. I should have figured that out before soldering everything together, but I guess I was too excited to just get everything put together that I wasn’t really thinking straight. After overcoming those initial obstacles, I finally managed to upload a simple blink sketch to the board to test the leds. Unfortunately I had misread the cathode markings on the led packages and managed to solder them all on backwards! I guess murphy will get you every time on projects like this. After soldering the leds on the right way I was finally able to load a simple hello world script onto the board. Here’s some pics from the finished board:



hello world


Looks great! Is there video of it anywhere?


Thanks Chris! Here’s a little snippet of it in action:

I think if I were to do a version 2, I’d add a hall effect sensor under the cap to measure rpm. I’d also like to add one or two buttons for putting the spinner into different modes, or maybe provide the ability to add text via morse code.


Woo! Look at that thing go! Looks reasonably well balanced too!

Any chance you could sky-wire in a button to change the text? Or are you actually planning that rev 2?


Yeah I was pleased to see it balance so well. I may try to bodge in a button or two at some point. The led side of the board could actually use a little more weight so that might be where I end up adding them.


Looks awesome. Maybe you have started a new fad too a Bodge Spinner!


Thanks! Bodget spinner’s, I like the sound of that! :smiley:


Here’s another little project I’ve been working on recently. It’s a portable solder fume extractor built from a recycled 80mm psu fan. Previously I had used the fan hooked up to the 12v rail of a computer power supply, but due to a recent move I wanted to build something a little more lightweight and portable. For dramatic effect I call it the Solder Sniffer 9000. It’s pretty simple in its design. There’s basically two main circuits, a charging circuit and a voltage booster circuit.

The charge circuit consists of a micro usb port, an MCP73831 li-ion charge controller from Microchip, and a protected 18650 li-ion battery. I used the schematics for this Adafruit charger to get a start on the initial design: It basically follows the application circuit from the datasheet, except Adafruit uses a nifty way of charlieplexing the status leds to provide both a red(charging) and green(charged) status indicator. Here’s the finished schematic for the charge circuit:

The boost circuit was needed to boost the 2.6-4.2 volts output from the 18650 to the 12volts expected by the fan. For the booster circuit I used the Semtech SC4503 step-up switching regulator. I chose this regulator because it seemed to have a nice compromise between peak efficiency while also meeting the load current demands of my particular fan. The datasheet provided many application circuit examples, so I adapted one that was most similar to my needs and used it. Here’s the finished circuit for the boost converter:

And here’s the finished PCB:

Here’s the finished product extracting some fumes:

The backside with an activated carbon filter:

Of course I haven’t really had many chances to use it yet, but I’m hoping it provides at least a little relief from fumes in the projects to come.

Alex's Linear Power Supply Build Log

That’s a really awesome setup, smart to put it on the side of the fan. I might have to steal this idea.

I don’t do a lot of Soldering either, but I really like the idea. :slight_smile:


Thanks! Yeah, feel free to copy the design and make one. Here’s the github page with the project: Actually, I have 9 pcbs left if you want one of those just send me a PM with where to send it and I can send one off to you. I’m hoping to get my bill of materials uploaded as well either today or tomorrow.


Oh wow, that is a generous offer, look for a PM.

I was wondering if you had a BOM, since I know nothing about batteries/battery holders.

Really awesome either way.


That’s a super clever design using the dimensions of the fan and battery with branding and everything. I’m jealous of your creativity, I don’t think I would have thought of doing that in a million years.


Thank you for the kind words @ALeggeUp! If I come up with something creative it’s usually by accident or it’s inspired by something cool someone else has done. The stuff you and others on this forum are doing are what help to drive any semblance of creativity I have.


I got the bom all setup. Some of the components could be substituted probably to get the cost down a bit more. Usually with the capacitors and resistors if you buy 10 or more the cost goes down dramatically. Right now the BOM, minus the 18650 battery and the fan is at $8.58 for a one off. For the battery, really any protected 18650 should work. The reason it should be protected is that although the MCP73831 provides some level of overcharge protection, there isn’t any over discharge protection. And then really any 80mm fan should work. Here’s the link to the bom: which can be uploaded directly into a digikey shopping cart.


Just want to make sure that this is a battery that would work (from my understanding it is): Protected Battery.


Yep that looks like it should work. It looks like it’s the same dimensions as the one I bought: . Fortunately when I bought mine it was half off due to a lightning deal.


Awesome, Gonna order the parts now. Stoked for it since I have nothing better to kill some time with at the moment that is short and easy to do. And a fan is always nice.

Where did you get the charcoal filter? Amazon as well?


Yeah it’s funny, I’m just using mine as a fan to cool me off right now! It’s been going for nearly 2 hours so far. I got my filters off Amazon: Then I just cut them to fit the fan size. There’s a ton of options for filters, any of these should work:

Then the only other thing is if you’re adding the filters, you’ll need a grill or something to hold them on the fan. Or maybe 2 rubber bands would work? I just used the grill from the power supply, but you could probably just get that on Amazon too. Something like this:

That looks pretty similar to what I have. I had to be somewhat gentle when threading the screws through the pcb. I don’t know if I was being paranoid or not, I just wasn’t sure how much force the pcb could take. So I used 6 screws in total for my setup - 4 for the grill and filter and then 2 for the pcb.