I recently wanted to use my DE-5000 LCR meter, but the 9V battery that was inside had died. I then had to waste time going out to buy a 9V battery, as I didn’t have the right wall plug adapter. After I was done with it, I remembered Mike Harrison’s video on “USBCing all the things” and decided to do the same.
I did not want to modify my LCR meter internally, in case I decide to sell it later on, so the obvious solution was for the adapter to have a barrel plug, instead of a jack. Annoyingly, the DE-5000 doesn’t use that standard 5.5x2.1/2.5 barrel, but a thin one, 3.5x1.35 (dimensions in mm). Since I used the WCH CH224A integrated circuit, the schematic and PCB were simple enough to do. I decided to use solderable jumpers for the config pins, in case I want to change the output voltage later for other purposes.
You can see the schematic below, courtesy of Kicanvas. Unfortunately, the table with the jumper options doesn’t render correctly, so check out the PDF schematic if you’re interested in that.
The only thing that is missing is some overvoltage protection. I wanted to keep it simple, however my friend Steven mentioned that Vishay’s SIP32440 would be a perfect fit, and he is totally right. If I ever do a revision, I’ll definitely add that in. Alternative, you can use the STMicroelectronic STUSB4531, which has VUSB monitoring and undervoltage / overvoltage protections included, but it’s not as simple to use as the CH223.
Below you can see some pictures of the PCB assembly.
I also decided to use a piece of shrink tube over the board, and the yellow matches perfectly with my LCR meter.
That’s it, enjoy!