This is definitely the smallest and simplest PCB I’ve ever designed. It’s 14.6mm x 7.9mm. That’s it.
But why!? Well, if you saw the last post about the Pin Bender, this is the second part… once those pins are straightened out, we put the lil PCB on there.
These rotary encoders come with right angle headers, and they work great in a breadboard, but I often have to solder wires to the rotary encoder PCB. I used to solder wires directly to the pins, and then heat shrink them on. That was terrible!
After that I desoldered the pins to get to the holes to solder on wires. That was also terrible!
I need to solder wires onto these things often enough that designing a Pin Bender and getting some PCBs fabricated totally made sense from a cost & time perspective. The PCBs are super cheap because they are so small. They serve a specific purpose, and that’s great.
Each board comes out just under 9 cents. (Not including shipping which was almost double that cost, but I ordered three different PCBs in one order.) It’s worth 9 cents on a BOM to me for the time it saves, so I consider it a win.
The 1/8″ stereo jack on the left is where you plug in the Pocket Operator, and the 1/8″ stereo jack on the right goes to the device you want to sync up. (A Behringer RD-6 or TD-3 for example.) The ring/red is the audio side of things, the tip/orange is the click/sync signal put out by the PO, and sleeve/black is the common ground.
As previously mentioned, the Pocket Operators are awesome, and they can sync with each other, but can’t always sync with other devices. They put out a 1 volt signal for the sync track (the “click”) and most other electronic devices want something higher, like 2.5 volts, or 5 volts. The Behringer RD-6 wants over 2.5 volts, so you cannot sync it to a Pocket Operator, but now you can with this device!
This basically reads the 1 volt from the Pocket Operator, and then outputs 5 volts that the Behringer RD-6 can recognize as a sync in signal. While the RD-6 has a sync out port, there are reasons you may want to have the PO be the primary and the RD-6 be the secondary. There’s also the Behringer TD-3, which (oddly enough) does not have a sync out port.
A guy named Oscar got in touch and asked if this worked with the TD-3 and at the time I didn’t have one. Well, I have one now, and it works great. And since the TD-3 does not have a sync out port (!?!?) this is the only way (without additional hardware) to sync a TD-3 to a PO.
I built one (using a Nano, not an Uno) and I’m sending it to Oscar to test out. He’ll need to provide a USB power source and a splitter cable to get it working. (He’s got both already. Most Pocket Operator nerds probably do.)
I did make one mistake on this device… I actually incorporated labels into the enclosure. I for “In” and O for “Out” and when assembling it I didn’t notice I had it backwards until testing. Oops! So I just stuck some labels on the top, and now In is on the right and Out is on the left. If I make another, I’ll do it right next time. Oh, I also realized I could probably just build a splitter into it by adding another jack, so I may do that as well. (Though that will increase the size of the enclosure a bit.)
Things have been busy lately. I’ve been building a lot of electronic devices and since there’s soldering and assembly involved I’ve been looking seriously at my tools. In some cases I’ve bought new (and better) tools, and in some cases I’ve looked at making my own tools. Here’s a “Header Pin Snapper” that makes it easy to get a 14 pin header from a longer strip.
So I spent a few minutes making this simple device that can snap pin headers to a length of 14 pins. Exactly what I need, and it works fast. Working fast is often better than working slow. I didn’t need an adjustable one, or a customizable one, so this one fulfills my needs, but might not be useful for others.
It’s just three pieces of 3mm thick acrylic, and four 3mm x 12mm bolts along with four 3mm hex nuts. I’ve got plenty of small scraps of acrylic lying around so made two just in case I misplace one.
I’ve got a Behringer RD-6 Analog Drum Machine and it’s battery powered! I’ve seen a number of video reviews of this machine and the reviewer always seems to say “It’s not battery powered, so you can’t easily take it with you…” But I’m here to tell you that you can take it with you (just like Steve Albini did with his Roland TR-606) and below I’ll show you how.
A battery pack that will hold 6 AA batteries. Each battery is 1.5 volts, so 6 of them is 9 volts. (And no, a standard 9 volt battery won’t work due to the low amperage it can put out.) I had some lying around that were like this but some have connectors on them like these. As long as they have bare wires at the end, you’re good. If they do have a connector on the end you may need to chop it off. (More on that later.)
You’ll need a 2.1mm Barrel Power Jack. I usually buy a pack of them. You only need one, so find one, or buy one, or buy a bunch and have spares. (You won’t need the matching receptacle plugs. At least not for this project.)
Important! All of the barrel jacks I’ve purchased have positive in the center and negative on the outside of the barrel/sleeve. In the world of musical things (well, guitar pedals at least) negative is on the center/tip, and positive is on the outside of the barrel/sleeve.
Here’s the back of the RD-6. You can see the symbol showing negative in the center/tip. Note that it also shows 300 milliamps. A 9 volt battery is 500 milliamps, so it will work for a while, but not long. The power supply Behringer gives you is 670 milliamps, but it’s not a battery, it plugs into a wall socket.
Right so we need to… reverse the polarity! Luckily it’s as simple as switching the wires around. Normally red is positive and black is negative, but we’re switching those. Make red negative and black positive.
Here’s mine. Now, it’s worth noting that I checked all of this with a multimeter. I’d advise you to do the same. Double check your work. If you don’t know what you’re doing, ask someone for help. This probably voids your warranty, and I cannot be held responsible for what you do. On with the show!
Oh, you’ll also need batteries! Any AA batteries will do, but rechargeable are preferred, at least by me. I’m a fan of the Eneloop rechargeable batteries. I’ve got some I bought ten years ago that still work. Grab a charger and 4 batteries and, um… 4 more because you need a total of 6 batteries.
Okay, stick it all together and you get a battery powered drum machine. Boom. Tsk. Boom. Tsk. I haven’t testing how long a set of batteries will last, but I’ll add that to the list of things to do.
Now, it’s not as nice as internal batteries that are built into the case, and if I actually use this on a regular basis I might think about adding in some hook & loop to attach the battery pack to the side. It might be better to use two 3 AA battery packs wires together, since those would have a flat back that could be attached to the RD-6.
For many electronics enthusiasts there is a special place in their heart for knife switches. At least that’s the case for educators I’ve worked with the past decade or so. My guess is it has to do with the simplicity of the knife switch in explaining how a circuit works. Is the circuit opened or is it closed? A knife switch provides a visual demonstration of this like few other switches do nowadays.
Knife switches are not used for most modern day circuits as they have been replaced by switches that are safer at high voltages, but since we work with low voltage circuits in educational settings this DIY Cardboard Knife Switch is perfect.
I’ve talked to a few educators and heard complaints about how expensive the old style knife switches are. (You can buy new “cheap” plastic versions for about $2 per switch, but the ceramic ones are often $10 or more.) I thought I’d lower the curve by creating a cheap DIY version that can be made with Maker Tape.
There’s a template that can be used to make one from cardboard or other material that’s got some rigidity and thickness to it. Cardboard is great, foamcore could work, cereal boxes are too thin. The template expects some cardboard and a way to cut it, which could be an X-ACTO knife, some scissors, a razor blade, or even a laser cutter.
Once you have your four pieces you attach some conductive Maker Tape, poke some holes for the brass fasteners to go through, and you’re nearly done!
Assemble the four pieces using the brass fasteners to hold them together and to act as a pivot point for the lever and you’ve got a knife switch. It may help to pinch the top of the two outside pieces a bit narrower so the knife is guided into place a bit better. (You’ll see this tip and more in the PDF guide.)