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.
A quick-start guide to getting a cross compilation environment up and running on Ubuntu Linux.
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.
Made by bending a coat hanger, this antenna is for 70cm and can be scaled for UHF CB. It works well, especially considering how quick and easy it is to make.
An interactive map showing Australian amateur radio repeaters. Navigate as required and click on a repeater-site icon to display frequency, ctcss and other details and notes. Display all repeaters or select by band.
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 half-wave end-fed for 2m is built from PVC pipe and a couple of meters of RG58 coax. This easily reproducible design from VK2ZOI can be made quickly and performs well. The addition of some tinfoil and sticky tape turns this into a dual-band 70cm collinear.
A self contained programming adapter for PRM80 series radios that is built into a DB9 to RJ45 convertor using a miniature MAX3232 module for level convertion. Power is obtained from the radio via the programming cable.
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.