Hand machined mechanical pencils



LM317 adjustable current source/regulator A linearly-adjustable current source based on the LM317 regulator, useful for things like laser diodes

Linear power-supply potentiometer feedback Ensuring a linear response and protection against loss of wiper contact


Modifying a power supply for variable voltage Converting a 12V fixed supply into an adjustable 5-15V supply

SSR relay switched mains socket A twin-gang mains socket with an inbuilt solid-state relay

Current-fed inverter advantages An overview of current-fed inverters and why they're better (in my opinion) for resonant loads like induction heaters

Celtic/Pictish circuit board drinks coasters Some really cool drinks coasters made using normal PCB processes


Gate drive transformer testing Making and testing toroidal gate drive transformers

Oscilloscope probe contact tips Making a low-inductance connection to a probe tip

Planetary mutiturn potentiometer A rather strange multiturn potentiometer which uses a planetary reduction mechanism

Old TV tube neck Deflection assembly from an old TV tube neck. Found chucked in the bushes...

Inductor design: energy-storage inductors Some practical steps for designing an energy-storage inductor (e.g. flyback, buck, boost etc)

Brushless motor driver Using a fan driver IC to run some disk drive motors

Mitutoyo SPC Digimatic interface An analogue readout unit for my digital indicator


High-current shunt resistor Making a 100µΩ current-sense resistor from some aluminium bar

RMS and average values of waveforms Derivation for sinewave, half- and full-wave rectified waveforms

Desoldering using a custom "iron" A big lump of brass works well for desoldering multi-pin components

IC decapping Decapping a USB isolator chip

Laser wire stripping Quick way to strip ribbon cable

Laser-cut transformer bobbin Bobbin made from laser-cut 3mm hardboard using finger joints

Resonant charging equations Charge time, peak current, peak inductor energy

Salvaging ferrite cores Removing the cores from SMPS transformers by heating in an oven

USB connector panel insulator A little plastic part which provides electrical insulation and mechanical support for a USB connector

Geiger-Müller tube detector circuit Simple circuit to power a G-M tube

Desoldering SOIC device Removing an SOIC chip using a wire under the pins to pull them away from the board

Pick-and-place Turning my CNC router into a pick-and-place machine

EasyPIC5 ICSP connector and programming jig Adding a pin header to the EasyPIC5 board, plus a progrmaming jig using pogo pins.

Making PCBs My own experiences with making PCBs

Read-modify-write problem Be careful when using tri-state PIC outputs!

Flyback HV supply Some photos of my old high voltage supply

High-value resistor mixture Using a mixture of Aquadag and PVA glue to make high-value resistors

High-speed photodiode Detector using a BPX65 photodiode


Load resistance on PIC's programming pin If a load resistance is present between the MCLR/VPP pin and ground, programming may not work correctly

Fixing a transformer thermal cutout Repairing the transformer in a small desk lamp

Improving ADC resolution by adding noise Deliberately adding noise to an analog signal can improve the resolution achievable

PCB via size test Checking to see how small a via I can make with home etching

Small variac transformers Two small variacs I picked up a while ago - one has an isolated low-voltage secondary, which is a bit unusual.

Large Brandenburg flyback transformer A huge flyback, unfortunately with a cracked winding

Series HV trigger Simple circuit for series triggering of spark gaps, arc lamps etc.

Inductor properties A quick look at how inductor properties (inductance and saturation current) vary with turns and air gap

High-voltage diode stack A potted stack of UF4007 diodes to make a 48kV dual diode

Hot air gun circuit and operation The insides of a cheap Clarke hot air gun

Inductor tester Simple circuit for measuring the saturation current of inductors

Wide-range adjustable pulse generator A circuit to produce pulses anywhere from 200ns to 500ms

Modifying a rotary switch Converting a 4-pole 3-way switch into a 1-pole 12-way version

Film capacitor dissection Removing the ends of a film capacitor to expose the metallising, and then soldering directly to it. Idea for better cooling of the capacitor.

Using an external coil with an induction cooker Winding a coil to fool an induction cooker into thinking it's running its original coil

Resistor colour code chart High-resolution chart of resistor colour codes

1000x capacitive high voltage probe A high voltage oscilloscope probe suitable for measuring fast HV pulses

Removing ground/earth from site transformer This mod allows a site transformer to be used as an isolation transformer with a 110V output.

Triggered spark gap A triggered spark gap using stock hardware


Faulty PCB pin header connectors Not all 0.1" PCB pin header connectors are created equal. A particular intermittent fault was traced to bad connectors.

Bayonet bulb plug adapter Plug to make electrical connection to a light socket

Large resistor model Painted wooden model of a ¼W resistor

TV CRT Tube Socket Socket for TV CRT necks

ICSP adapter for EasyPIC5 Making an adapter cable to allow PICs to be programmed externally

Potentiometer end-stop modification Altering a cheap carbon potentiometer to obtain smooth adjustment at the end of the wiper travel

Making a current-sense resistor How to make a low-ohmic sense resistor using a short piece of resistance wire

40-400V, 20W power supply General-purpose high-voltage power supply for experimenting with Nixie tubes and the like

Surface mount adapter boards Allows SMD devices to be used on a 0.1"-pitch breadboard

Spark radiation detector Spark detector for α particles

Power ultrasonic driver Inverter power supply for a 28kHz ultrasonic tank transducer

High-voltage trigger and capacitor dumper This arrangement was originally designed as an attempt at pulse arc welding, but is useful where a high-voltage, high-frequency trigger pulse is required.

TIG welder with HF start This is not my work, but is a backup of a page I found on another site. It describes the construction of a 180A TIG welder with high-frequency start.

Planté rheostatic machine A completely mechanical means of charging a string of capacitors in parallel and discharging them in series to obtain increased voltages

New 3V camera supply A better 3V supply for my digital camera, this time built in an ATX supply case.

Double-sided exposure alignment jig A useful jig for exposing double-sided things, such as for PCBs or photochemical etching.


Large IC model A 10x scale wooden model of a 555 timer IC

Excellon to G-code converter Program to convert Excellon drill files from Eagle to G-code suitable for running a CNC machine. Also performs geometric transformations to correct for distortion in the board.

Digital Kirlian photography Using a digital camera to take Kirlian photographs.

Nixie tube counter Simple counter circuit to drive a Russian IN-8 nixie counter tube using a PIC. Also interfaces to a telephone rotary dial.

LED on conductive glass A surface-mount LED mounted on a piece of conductive glass.

Laser-cut solder stencil Trial of making a solder paste stencil using transparency film cut with a CO2 laser.


Dual AA battery eliminator If, like me, you have a little digital camera which runs from two AA batteries, then you probably will be fed up with using a lot of batteries when you're taking pictures or videos around the house. This little circuit is a simple 3V adjustable regulator which runs from a 5V supply. I made the adaptor to fit a Nikon L2 camera, but it should work with anything.


PowerPAD™/MSOP-8 heatsink Small copper-foil heatsink for PowerPAD™ IC packages to allow hand soldering

Surface mount component soldering arm Useful tool for holding surface mount components in place whilst soldering

PCB drilling viewer Gadget to drill PCB boards by optically aligning the underside of the board with the drill axis


Induction cooker Brief investigation of the waveforms in a 2kW induction cooker.