Electronics – Imablog

November 21, 2022November 21, 2022

Power supplies on the workbench

I’ve got a number of power supplies that I can use to supply power to the various projects that I’ve got on the workbench.

There’s the obvious wall power and a variety of wall warts of different voltages and current ratings. I’ve got wall warts and power supplies ranging from 5V all the way up to big chunky 28V power supplies.

A power strip mounted to the side of a bookshelf with a 5V wall wart power supply and flashlight plugged in

For projects that require a beefier power supply I’ve got an unregulated power supply that gives me up to 30VDC or 25VAC. It doesn’t get used too often, but comes in handy when it’s needed. There are also a few 13.8V power supplies that I can steal from the radios in a pinch.

Power supply offering unregulated 0-30V DC and 0-25V AC

Most of my projects don’t have big current draws though, so more often than not, I’m just using batteries to power my projects. One that I use most often is a 12V battery pack made by wiring 2 quad C-cell battery holders together and putting a standard 3.5mm DC barrel connector on it.

A battery pack of 8 C-cells connected to a Sparkfun RedBoard

DC barrel connectors can be easily attached to those snap connectors used for 9V batteries providing another power source (here’s one from Sparkfun if you don’t want to make one).

A 9V battery connected to a Sparkfun RedBoard

Some battery holders I have also use those snap connectors, so I can have battery power sources ranging from 3V to practically as high as I need.

Batteries in a variety of battery holders

I’m often using mostly used batteries pulled out of other things like TV remotes, smoke detectors, etc. Usually they still have plenty of juice left to power my smaller projects.

While charging up some old sealed lead acid (SLA) batteries pulled from my battery backup UPSs, I got to thinking about how I could put them to use as an additional power source. I’ve got plenty of three terminal voltage regulators that would provide the voltages that I’d need.

I sketched out block diagrams for a couple of possible concepts. One would switch between several different voltages but provide just a single output, while the second would provide multiple outputs and have toggle switches turn to each one on or off.

Block diagram for a potential battery powered power supply with a variety of switched voltages

Block diagram for a potential battery powered power supply providing multiple voltages

Probably wouldn’t do 3.3V, but the others would definitely be feasible. 12V would probably be just a direct connection to the battery rather than going through a voltage regulator. Since I’ve got 2 SLA batteries, I could even put them in series for a 24V source and give myself a wider range of regulated voltages.

Still in the concept stage for this and haven’t started building anything yet. Seems like it could be a fun project.

May 18, 2022May 18, 2022

Pixel 6 X-ray

A radiograph of my new Pixel 6 phone. The Pixel 6 is a big chunky phone with a lot of stuff in it.

X-ray image of a Pixel 6 smartphone. 80 kV, 1 mAs

This one was acquired using a portable x-ray unit at 80 kV, 1 mAs, and the small focal spot. It’s raised up about 25 cm above the image receptor for a bit of magnification (about 1.3x) and cropped in from the original image.

March 23, 2022March 23, 2022

Soldering station upgrade

I’m finally upgrading my soldering station.

After many years of using my slow, inexpensive (but pretty reliable) Radio Shack soldering iron, I’m upgrading to a Hakko FX-888D!

I’m excited to start using the Hakko. I expect there will be a bit of a learning curve with the new soldering iron, but I think it will be a nice step up. The old soldering iron will go back to the garage to get used on projects there.

March 23, 2022March 23, 2022

RCA Victor 45-EY-3 vintage record player

On the workbench for some troubleshooting is a 1950s era vintage RCA Victor 45-EY-3 record player. It belongs to someone in my neighbourhood and came to me via a referral from a neighbour who’s familiar with my penchant for tinkering with electronics.

RCA Victor 45-EY-3 record player from 1950

The owner purchased this recently and had already replaced the tubes, capacitors, a few resistors and some of the mechanical bits before the record player landed on my bench. He said it was sort of working (some mechanical issues with the arm moving), but then stopped turning on. Fortunately, he had a printouts of the service documentation available to look over. On the electronics side, the circuitry is pretty simple consisting of three tubes: rectifier (35W4), amplifier (12AV6), and output (50C5).

After touching up a few solder joints, I found the power switch was kind of dodgy and would work if I tilted it a certain way. I also realigned the muting switch (S2) so that it was oriented the same way as one of the photos in the service manual. That got me to the point where records could play and sound came out of the speaker instead of just resonating through the needle arm. The sound volume was pretty low though, even with the volume pot turned up all the way and there’s also a lot of hum getting into the electronics too. Those are the two main things I need to work on, and the owner will work on the mechanical stuff.

October 12, 2021October 12, 2021

Lap joystick

The Atari 2600 joysticks were pretty much shot, so I picked up a couple of arcade joysticks and buttons thinking I’d build a couple of new ones to use with the Ataris.

My initial plan was to use a project enclosure to build a new joystick out of, but it turned out to be a bit too small and felt awkward. Then I looked around and saw an old lap desk that I wasn’t using anymore and thought “Oooh, that might work.”

The lap desk was originally designed to have a little pouch for carrying things like paper and writing implements in. Perfect for containing the wiring and components. The innards of the lap desk was accessible via a few zippers (two “pouches” contained inserts with styrofoam beads for padding and a middle pouch for stashing things in). Used a hole saw to make a few holes for the joystick controller and two buttons so that the “lap joystick” could be used left or right handed.

Joystick controller installed on the lap desk

The joystick controller and buttons went in very nicely.

To wire everything up, I started with a piece of copper clad PCB hot-glued to the back for a base. I thought some MeSquares would make good spots to wire up the joystick and buttons to the cable that connects to the Atari. A terminal connector was used for the common connection. I was originally going to just solder the common connections to the copper clad, but my soldering iron turned out to be too puny and ineffective for soldering onto a copper clad heat sink. The cable from one of the dead joysticks was used to connect to the Atari console.

Getting the joystick and buttons wired up

The wiring is pretty ugly and I’ll probably re-do it at some point to make it neater but the lap joystick works perfectly with the Atari, and it’s actually pretty comfortable to use. The cable out to the console ended up being kind of on the short side (it’s not that long to begin with), so the console has to be pretty close to play. When I re-wire everything, I’ll see if I can extend that out a bit.

I’ve got one more joystick controller and will need to get a couple more buttons to build a second lap joystick. I think I’ll see if I can find some shorter buttons to use.