Arne's Electronics Series

Larson Scanner & Beyond

The Larson Scanner was thus named decades after its appearance on BSG and Knight Rider. It's the effect of a red light, or "Cylon eye" bouncing side to side, seemingly scanning. It's easy light up LEDs one at a time going in one direction using a 4017, but the bounce requires extra logic. It's of course trivial using a microcontroller nowadays, but back in the '80s 7400 and 4000 series had to be used. I found a schematic made in 1983 but didn't have the 74193 in my bins. Curious, I set out to see if I could solve the problem using what I have.

Now, to drive the LEDs I might need a special board to produce the soft afterglow effect of light-bulbs. I've been meaning to design such a board for a pinball machine project anyways. I found that two 2*47uF (~100) worked well with my white LEDs & 220 Ohm. I use a diode to make sure the cap discharges through the LED but there's something going on with the GND that I don't quite understand still. Also, I later added a transistor to drive each LED and maybe this makes the diode pointless?

I also tried to get a circular, 8-stage astable multivibrator to work as an experiment but because they're analog they're quirky, and they use two resistors and one cap per stage.


A 10 second delay circuit can be useful in alarm systems and such. A simple one can be made using a cap discharging through the base/switch of a transistor. But, transistors are analog amplifiers and not digital switches. I used a comparator here to produce a digital cutoff threshold (A-D converter), mostly to learn how they work. I think it's better to use a 555 for something like this.


Still waiting for a MCU-retro computer with BASIC.

I accidentally made a radio trying to ampilify something.

I wrote some more low-level port code for this USB Leonardo keypad just to complicate matters. Using the keyboard library a keypad is just a few lines. However, what becomes complicated is that different OSes use different key codes.

Photoshop Keypad symbols inspired by Alien.


A look inside my Amiga sound sampler. They were paranoid about reverse engineering or something else. Enclosure is generic. This sampler served me well though. It's strange to think about now... how much money it cost then to get basic functionality we take for granted now.

Blew up the bulk filter cap of a Dreamcast like a careless idiot.

Thought I'd make an egg-clock / timer using a 7-segment IC + 555, but it turns out most of my 7-seg displays are common anode and I don't want to use a inverters.

I'm old enough to remember disposable flash cubes for cameras. This relic that I found in the garage is older... maybe the '50s?

I played CASIO's Cosmo Fighter as a wee lad. I wish e-paper displays had better refresh rates and could be used for B/W LCD style games. Had to draw what I think it could look like. Analog stick, slider, 3D engine and colour overlay HUD. I suppose a B/W hires LCD screen could work but maybe they don't really exist... OLED might, but they're a bit more expensive.

Roccat Lua reconditioned. The surface finish had rotted so I took it off with steel wool. It leaves an uneven scratched finish but it can be hidden by a polish using a minuscule amount of hand creme.

Coffee machines can be a fire hazard if left on by mistake. I think there's a heating element inside which is powered more or less straight from the outlet, similar to a water boiler or soldering iron. So, maybe no regulation for the light integrated into the rocker switch. It's kaputt. My mechanical solution is what it is.


Photos/Art by Arne Niklas Jansson

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