a rough cut, blow, or stroke. (the work was accomplished one hack at a time)
a quick job that produces what is needed, but not well (this code is a hack, but it works!)
Hack-A-Day is challenge to make complete one new project, from scratch, every day in November 2023.
Last year (2022), I set myself the challenge to make a software project every day, and met it. I had a ton of fun, and make a lot of cool video games and projects I can show off. This year I’m inviting the rest of the world to join me!
I’m a programmer, so I’m doing a new computer programming project every day. But you can do any kind of project, whatever you pick is great.
I’ve been pondering simple input methods for microcontrollers. One obvious idea is, a keyboard! But for some reason, my USB keyboards use a staggering amount of power compared to my microcontrollers–1W of power for my mechanical keyboards, maybe 0.1W for the regular ones.
Let’s look inside a commercial keyboard, and see if we can hook up to it:
Yikes. What’s going on? Well, let’s make our own little keyboard, and explore what’s going on. We’ll build it in three layers, or “index cards”:
The bottom layer has 6 vertical stripes. The top layer has 3 horizontal stripes. Each place they cross will be a “key” you can press.
In between them, we add a spacer layer (punched holes) so they keys are “up” by default, and you have to press them to make them connect.
This picture might help explain how they will go together:
Now we assemble:
The final keyboard has 6 x 3 = 18 “keys”. We write the hex digits plus a couple extra keys with marker.
If I attach alligator clips to the second horizontal screw terminal, and fourth vertical screw terminals, and wire a battery and buzzer with the terminals, I get a connection beep only when I press the key “A”:
In a real computer, we obviously can’t just move alligator clips around. Instead, we attach wires to all 9 posts–three outputs wires for the horizontal lines, and six inputs for the vertical lines. We output a signal on the first horizontal line, and see if we can read it from any of the six vertical lines inputs. Then we output a signal on the second horizontal line, and see if we can read it, and so on for the third. Assuming only one key is pressed (or none), we can identify the key. This “scanning” process could be done thousands of times a second, rapidly enough that it can’t miss our slowpoke human fingers.
Click to view interactive schematic (credit: Kragen)
And this is how most keyboards work. There are some special keys–Shift, Ctrl, Alt, etc might be on their very own line, since we want to detect key combos. And better keyboards can detect multiple keys being pressed at once (N-key rollover), which I think they do by having a completely separate wire to each key which multiple people tell me they do with a diode next to each key.
For the above project, I used:
Three index cards
A hole punch
Scissors
A ruler
A pen (NOT a pencil, since graphite is conductive)
9 screws, 9 nuts, and 18 washes. I selected #6 American Wire Gauge, which is about 4mm thickness
On some keyboards I’ve made, you have to press quite hard.
My multimeter takes a while to register a press. I think a microcontroller would be better.
You have to attach the terminals carefully. I think what’s going on is that you can actually put the screw exactly through the center of the washer which is actually making contact with the strips, so that only the washer is attached, and the screw doesn’t rub against the washer.
It’s of course fairly easy to mis-align anything. This is pretty easy to fix with care. I used the “spacer” grid to draw the centerpoint of the printed letters.
The screw heads are a bit thick, so it’s hard to press the keys in the column/row next to the screws. A piece of backing cardboard might fix this.
This was my third attempt. Here’s the second, using aluminium foil. It worked at least as well, maybe better, but it was harder to make. I just taped the foil down, taking care not to cover the contact points. I am told the aluminium will gradually oxidize, making it non-conductive.
And here’s one using graphite from drawing hard with a #2 pencil.. Graphite, it turns out, works terribly, and I couldn’t read a signal halfway down the index card. Despite what people have told me, I’m not yet convinced you can make a conductive wire out of it.
A friend of mine, Kragen Javier Sitaker has been designing something he calls the zorzpad (see link below). I can never remember the name, so as a joke my version became the “zorch pad”. We live on opposite sides of the globe, but we’ve picked up the same or similar hardware, and have been having fun developing the hardware and software together.
The basic idea of the Zorchpad is to have one computer, indefinitely. It should keep working until you die. That means no battery that runs out, and no parts that go bad (and of course, no requirements to “phone home” for the latest update via wifi!). This is not your standard computer, and we’ve been trying a lot of experimental things. One of the main requirements is that everything be very low-power. He picked out the excellent apollo3 processor, which theoretically runs at around 1mW. In general, the zorchpad is made of closed-source hardware.
Since I’ve realized this will be a long project, I’m going to post it piece-by-piece as I make progress. Below is a demo of the display.
The graphics demo shows, in order:
a title screen
a flashing screen (to show graphics-mode framerate)
a demo of font rendering. we’re using the fixed-width font tamsyn.
We’re using a memory-in-pixel LCD. The only manufacturer is Sharp LCD. You have have seen these before in things like the Pebble watch–they’ve very low-power except when you’re updating. This particular screen is quite tiny–240x400px display (which is fine with me), but only 1.39×2.31 inches (35x59mm). The only bigger screen available in this technology is 67x89mm, a bit lower resolution, and out of stock. As soon as it’s in stock I plan to switch to it.
According to the datasheet, the screen consumes 0.05-0.25mW without an update, and perhaps 0.175-0.35mW updating once per second. We haven’t yet measured the real power consumption for any of the components.
The most obvious alternative is e-ink. E-ink has a muuuch slower refresh rate (maybe 1Hz if you hack it), and uses no power when not updating. Unfortunately it uses orders of magnitude more power for an update. Also, you can get much larger e-ink screens. The final zorchpad might have one, both or something else entirely! We’re in an experimentation phase.
Datasheets, a bill of materials, and all source code can be found in my zorchpad repo. Also check out Kragen’s zorzpad repo.
I did a survey of the cost of buying hard drives (of all sorts), microsd/sd, USB sticks, CDs, DVDs, Blu-rays, and tape media (for tape drives).
I excluded used/refurbished options. Multi-packs (5 USB sticks) were excluded, except for optical media like CD-ROMs. Seagate drives were excluded because Seagate has a poor reputation.
Per TB, the options are (from cheapest to most expensive):
Tape media (LTO-8) at $4.52/TB, but I recommend against it. A tape drive is about $1,600 (twice that new). That’s a breakeven at 150-300TB. Also, the world is down to one tape drive manufacturer, so you may end up screwed in the future.
3.5″ internal spinning hard drives, at $15.00/TB. Currently the best option is 8TB drives.
Optical media, at $16.71/TB. 25GB blu-ray disks are cheapest.
3.5″ external hard drives, at $17.75/TB. Currently the best option is 18TB drives.
2.5″ portable spinning hard drives, at $22.00/TB. Currently the best option is 5TB drives.
SSD drives, at $42-$46/TB. Best option is 1TB.
USB sticks, at $59/TB. Best option is 128GB sticks.
MicroSD cards, at $62/TB. Best option is 512GB cards.
Changes since the last survey (4 months ago):
Amazon’s search improved. Less refurbished drives and sponsored listings.
Spinning drives: 22TB 3.5″ drives became available
Spinning drives: Prices for the previous cheapest option (4TB) rose, making 8TB the new cheap option.
SSDs: Prices dropped by about 30%.
MicroSD/SD: Prices dropped slightly.
Optical: The cheapest option (25GB blu-ray) dropped 30%.
Optical: I stopped gathering data on the cost of BR-RE
Tape: LTO-7 tape drives are now available used, halving the break-even point on tape.
I’m going to call this one a flop. There’s a good version of this project, but I ran out of time. Basically all it does is display info about a show, which is not very useful.
