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 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.
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.
This replacement thermostat for an old refrigerator offers LCD display showing temperature in C or F, 0.5C accuracy and allows target temperature to be set percisely. Uses ATmega8 controller and DS18B20 1-wire sensor.
The concepts behind direct digital synthesis (DDS) can be explained without the need for complex maths nor heavy-duty digital electronics theory. This tutorial describes how DDS works in simple and easy to understand terms.
A minimalist DIY programming and development board for the ATtiny2313 AVR microcontroller. Made on a piece of matrix board using point-to-point wiring.
A DIY build of VK2BTL's sensitive field strength meter circuit design, using parts from an old CB SWR meter. Ideal for testing antenna, radio control and handheld transmitters.