I was recently given this old bench multimeter after it sat in a box unused for some twenty or more years. With some modification to the power supply it is now back in service as as worthwhile addition to my workbench.
Using ⅛" stereo plugs, sockets and cables is a convenient way of connection RS232 serial lines between PCs and micro-controllers. Here is a simple little dongle incorporating a USB-to TTL-serial module, a max2323 and an ⅛" stereo jack. TX and RX lines are configurable via jumpers.
A simple but useful co-operative multitasking for AVR microcontrollers.
A variable gain hybrid-cascode amplifier stage followed by separate feedback amplifier stage, as used for amplifying the output from AD9850 DDS module as the basis for an HF signal generator.
An ESP8266 WIFI module interfaced to a relay allows for a 1000W/240v swimming-pool filter pump to be remote controlled. It turns on and off automatically depending on how much energy is available from the solar system. Software includes NodeMCU general-purpose telnet server, and Perl client utility.
A quick tutoral guide to setting up a Linux development environment for the ESP8266 WIFI enabled microcontroller. Intended for someone who might have just taken delivery of their first module and is wonder where to start. Covers hardware, firmware, C SDK, and NodeMCU Lua.
Suitable for morse code beacons, repeater idents and the like, this library is implemented as a state machine and hence allowing for other processing to be done whilst the morse is being set.
Some experimentiing with a cheap PAM8403 Class D Audio Amplifier Module results in a very compact and efficient stereo amp with very reasonable sound quality.
Eight 1-watt LEDS, a couple of cheap eBay modules, some salvaged hardware, and an ATTINY13 make for some very effective workbench lighting. A speed-controlled fan keeps the electronics and LEDs (and potentially the worker) cool.
A command line utilty that allows a Raspberry Pi to control a HD44780 based LCD via i2c.
A Raspberry Pi, USB hub and USB HDD are mounted in a box to make a neat little low-power server. Runs from a 12v battery charged by solar power. Uses around 6W as compared to 30W or more of the laptop that it replaces.
A utility to monitor a Sunny Boy 4000tl solar inverter via its Bluetooth interface. Uses a cheap tl-wr702n wireless router, but should work with any Linux system and with other Sunny Boy inverters.