Category making things

Well, the prototype power 5V switching power supply that I cobbled together seems to be working. Up there you can see it powering the first nuxx Audio Input Switch, just to give it some sort of load to work on.

Here is a photo of the bottom of it. It’s clearly hacked together, just sort of built up on the board so I could have solder connections and reasonably short wires. When I tried to breadboard it things didn’t work quite right, which I blame on switching power supplies being touchy about long rows of bare wire.

It’s pretty much a reference implementation (some variances in parts) and it produces what appears to be nice, clean power. I can’t see any noise on my scope. Granted, my scope is pretty crappy, but it does seem to show some noise when it exists. (I can’t afford a new scope yet…)

I’m happy with how it is working thus far. I need to put a bit more load on it, but that’ll be done over one of the next random couple of days. For now I can say that it had no problem giving me an even 5.000 VDC while powering the nAIS above and being fed 6.073 VDC. If I cranked the input up to 35.93 VDC (the highest I can get my benchtop power supply) the power supply was pushing out 5.074 VDC. Pretty good, I think.

Danielle’s TV-B-Gone
(Click for full res photo…)

Tonight I helped Danielle put together her first electronics kit, one of Limor Fried’s open-source TV-B-Gone kits. She’s soldered a bunch of stuff before from when she briefly went to Kettering, but this is the first functional kit. And, of course, it works!

Well, it at least turns off my TV almost instantly… I imagine that it’ll work pretty well on whatever other ones. At $20 it’s a good, and useful first kit… Imagine actually being able to turn off all those annoying TVs in places like the doctor’s office waiting room, school hallways, and (hopefully) the advertising things on gas pumps.

Well, there’s that. It works.

I need to finish wiring everything else up and then pursue the group buy idea…

[Later, before I could hit post]

It’s too bad I’m finding problems with the design. Bah.

Transducer in the head of a Toothy Tunes Musical Toothbrush
(Click for more photos (photo gallery retired)…)

As mentioned earlier I had hoped to stop on the way home and pick up a Tooth Tunes Musical Toothbrush. Well, I did. For US$8.99 I grabbed a Tooth Tunes which plays Queen’s We Will Rock You. While I can’t stand that song, it was one of the few recognizable songs on the available brushes, with most of the others being tweenpop.

After eating dinner and playing a bit of E4 I decided to dig into the toothbrush. It definitely wasn’t designed to be easily taken apart, with a metal rivet holding the O-ring sealed bottom in place, and the solid plastic pieces ultrasonically welded together. This meant that most of my disassembly was pretty destructive, but I was able to keep all the electronics inside intact and poke around with them a bit.

The only real problem I ran into is that the IC which holds the audio (and can presumably be reprogrammed) is potted, so it’ll be very difficult to get to. The transducer itself is pretty nifty, and pressing it against my teeth or head or the workbench made the audio quite audible. It doesn’t sound too great, but it at least works.

Anyway, if you’d like to see photos which have better descriptions than the little glossed-over stuff above, just take a look here: Tooth Tunes Musical Toothbrush Dissection (photo gallery retired)

PICkit 2, ZIF socket from ICD2 clone, and cobbled together cable.

Well, it’s no gang programmer, but with that cable being reasonably solid I should have no problem using that setup there to program all the PICs for the forthcoming nuxx Audio Input Switch group buy. See, I’ll be offering up PCBs and programmed PICs to whoever wants them (and reserves them within a limited window) at cost as a favor to the DIY audio stuffs community and I want programming the PICs to go as easy as possible.

When I got home from work I cobbled together this cable from a spare 1×6 .100″ header, some 2 place Molex KK connectors, and an old piece of CAT5. With the PICkit 2 software now featuring a function to program (and verify) the part when the button on the programmer is pressed, so I should now be able to just drop a chip in, hit the button, wait for the box on the computer to turn green, then do it again. Even doing 100 parts (if that many people are actually interested) shouldn’t take very long at all. Yay!

[This is a cross-post from here at diyAudio Forums:]

Well, the first five PCBs were ordered from PCBEX.COM a few minutes ago. The biggest changes since yesterday were moving the smoothing capacitor before the voltage regulator to 1000uF (13mm diameter, 5mm lead spacing footprint) which required a good bit of shuffling of parts in the power supply. (Some configurations, particularly those not needing to use the 5VDC output, can use a much smaller cap here. I’m recommending this value as a best-fit.) As part of this I also ended up moving all of the connectors to the front edge of the board, which I think is a rather good thing.

The boards are five-day turn, so I figure they’ll ship sometime around the end of next week. As PCBEX.COM batches their boards out to China I expect it’ll be another week or so before I have the boards.

Here’s how the part prices from Mouser breaks down:

All parts, except PCB, heatsink, relays, and audio terminals: US$10.46
5x 4PDT Omron relays and 5 place Phoenix terminals: US$57.10
5x DPDT Omron relays and 3 place Phoenix terminals: US$25.45
1″ Tall Heatsink: US$1.14
1.5″ Tall Heatsink: US$1.06

Of course, you can cut these prices down if you do things such as not fitting the boards to switch all five inputs, leave out some of the onboard power supply parts, etc.

The PCBs cost about US$16/each after shipping from PCBEX.COM. If I were purchasing for a group buy or something I imagine the price would be a good bit lower, although that obviously depends on the quantity.

So, I guess that’s about it for now… There is more info over at the main nuxx Audio Input Switch (as the device is now known) page.

One final question for everyone: Are any of you interested in purchasing some of these PCBs in a group buy?

I figure that I could probably handle doing a group buy for some folks. I’d provide a PCB and programmed PIC, and you’d just have to order the rest of the parts. Everything in there is very standard, so even if you can’t order from Mouser you shouldn’t have a problem sourcing the same (or compatible parts. I’m not in the position to offer kits or assembled boards.

Off the top of my head I’d estimate the total cost at being around $20, to cover the blank PCB, PIC, packing stuffs, PayPal fees, etc.

Anyway, that’s it for now…

1) I should be in bed.
2) The vent on an electrolytic capacitor is called that for a very good reason. That said, I’m surprised how long the 470uF 25V Nichion audio cap worked for while backwards. It even somewhat worked while backwards, which is probably why I let it go for so long. Whoops!

nuxx Audio Input Switch on a Breadboard

Well, that’s that. The nuxx Audio Input Switch is coming along nicely and things are working as expected. Except for not realizing that MCLR has to be externally pulled high (or disabled), causing me about half an hour of head scratching, the software has worked as hoped for.

I had to learn a bit more about how the driver works and thusly redraw parts of the PCB, but I think it’s all sorted out now. If you’d like to see the board layout, just take a look here. Of course, you’re also welcome to read through the nuxx Audio Input Switch page, which currently has a fair bit of misplaced / inaccurate information in it.

Here, have a PCB layout that I think it almost complete. I need to validate some parts and be sure the drivers work as I expect, but beyond that it should be all set.

Now I’ll be able to switch inputs on a headphone amp without plugging / unplugging things. Yay!