So I decided to play with one of the Cheap Yellow Displays ("CYD") and thought to myself “man, this would look cool as an old-style CRT monitor.” A few hours later I was printing version one, and the next morning I made some changes and printed version two, which I'm happy to present!

Parts

• A CYD - technically an ESP32-2432S028R. I ordered this one and for whatever reason got some that also had a USB-C port on them but hey, it worked! $13/ea
• A TP4056 charger with boost module (specifically the black one for the mounting holes. $1/ea
• A snap-in USB-C jack like these. $0.33/ea
• A 3.7v LiPo battery. I picked a 1Ah from MakerFocus since I hate buying batteries on Ali. $4.75/ea
• 1x micro flashlight switch. $0.13/ea
• 1x M3x10 bolt
• 4x M3x5 bolts
• 2x M2x5 bolts
• Any old mSD card (I used an old no-name 2Gb card from a pile)
• OPTIONAL - some PH2.0 connectors to be able to unplug things. $0.32/pair

Buildin' It

Start by following the instructions on setting up XTouch on your CYD. Build your config.json, format your mSD to FAT32 and copy it over. Make sure it boots and works. Once assembled you'll be able to carefully wiggle the mSD in and out but will not have access to the USB ports without unscrewing your CYD.

With all your parts printed, start soldering. I started by putting PH connectors on the output and battery contacts of the TP4056, then inserted the USB-C snap-in to the print and soldered it's wires directly to the contact pads on the bottom of the TP4056.

That done, I soldered the micro switch between the CYD V+ and TP4056 (this part had a PH connector I added). I chose, for no particular reason, to solder my power leads on the CYT to the exposed back of it's JST connector, but you can do this any number of ways - using the leads they provide, cutting up an old USB cable, etc. Do whatever you're comfortable with, just leave enough wire to be able to move things around.

*** IMPORTANT ***

Connect your battery to the TP4056 and then power it up. Take a multi-meter to the output leads, make sure it's 5V! Out of the bag mine tried to output 4V which wouldn't have worked, but I've had others before turned way up that would have put out enough voltage to cook your CYD! Follow your vendor's instructions, usually it's just turning a little dial with a micro screwdriver and monitoring your multi-meter until voltage is shown as +/-0.1 from 5V.

From this point, I used a little double-sided tape to secure the battery, inserted the switch in to it's retainer, screwed in the CYD (4x M3x5) and the TP4056 (2x M2x5 - easiest to put one screw in a little bit, line up the module, then add the other screw and tighten both down). The side TP4056 will rest on the little standoffs.

Tuck your wires away and snap the front and back together. For the base, screw the M3x10 a ways then line up the base and the disk from the display. Tighten the bolt down (it'll be snug) until it starts to grab the disk to provide a frictional resistance. Too loose and it'll just flop, too tight and it won't move (which may be desirable).

That's it!

A 1000mAh 3.7V LiPo battery should provide anywhere from 1.5hr to 4hr life. This depends on screen brightness, how long the screen timeout is set, and if you keep it awake.

The battery has a 3.7Wh capacity (3.7V * 1000mAh)

At full brightness I observed a 1.8W draw on average, so adding an ~80% efficiency on the boost module:

3.7Wh * 80% eff. 5V boost ≈ 3Wh / 1.8W = 1hr 40min life

While idle I saw it consuming about 0.7W on average, so:

3.7Wh * 80% eff. 5V boost ≈ 3Wh / 0.7W = 4hr 20min life

So enough to be mobile, but probably want to keep it near a plug unless you want to jam a bigger battery in there. Since the switch simply disconnects the CYD from the battery, you can let it charge without it being turned on.