Look at that user interface, looks pretty usable isn’t it? But it’s not - adjustment timeout is so short that manual sweep is impossible and making adjustments to voltage or current requires a lot of button presses just to start. [End of rant]. Anyway, I wasn’t planning to do much manual control. Automation FTW!
To achieve automation I need to look at the back of the device and follow the data from the USB port.
Inside I found a dedicated board for USB communication.
The RS232 side of the board is not populated but the USB side is. And it even has data line isolation with optocouplers.
Chip for USB to RS232 conversion is CP2102 - very common in cheap USB-RS232 adapters.
After figuring out that I'm dealing with a simple UART I prepared an ESP01 module with the same connector used in the device.
For more details on the preparation of this module see this post: https://makerspacelt.tumblr.com/post/624341530736459776/wifize-everything
After preparing the module, came the time to install it into the device. While following wires going from the USB board I discovered a very convenient 4 pin connector on the mainboard which contained exactly what I needed - RX TX Vcc and GND.
So the installation was extremely simple. I've just unplugged wires going to the USB board.
And plugged the esp module in the same socket.
After that, it's just a simple task of finding a place to put the module itself without a metal case interfering with WiFi signals.
At this point I thought it’s kinda done, just close the case, put the screws back and the project will be completed!
Unfortunately, communication wasn't working and I reconnected the original USB board just to figure out if it is a hardware or software problem.
As the original USB communication wasn't working either it was clear now that the problem is software-related.
Documentation is kinda simple and I chose the simplest command to test on `*IDN?` which should return the device's model. Sadly enough device did not respond to any command on any baud rate with any line ending.
Long story short - I accidentally sent characters `\` and `n` instead of new-line character and the device responded. Not sure how much more time I would have had to spend to try this intentionally :D
So in general it was a pretty easy project, hardware part simply begging for this upgrade - I didn’t even need to cut or solder anything in the device.
I also did a presentation about this project on the Hack and Tell #38 at Kaunas Makerspace.
Long awaited addition to the electronics lab - an adjustable power supply. It maxes out at 26V and can deliver 3 amps. Construction is simple, of the shelf charging buck-boost converter with voltage and current limits and a panel meter to show voltage and current. Power comes from laptop charger found in the parts bin. For controls we used 10-turn pots.
