This page lists some hardware posts, tools and projects I've created.

Feel free to adapt any of the open source designs here, bearing in mind that they come with absolutely no warranty, and should be treated as potentially dangerous given that I am not a chartered electrical engineer. Some of these circuits are capable of sourcing large voltages with enough current to kill. You've been warned! That being said, if you do find any of these designs useful, please drop me an email so I can get a warm fuzzy feeling!

In addition to the designs below, I designed most of the Razorbill Instruments RP100 high voltage power supply and amplifier for their line of stress and strain cells. It has many cool features, including USB control via some software. Buy one!

Standard resistors

Resistors, capacitors, inductors and zener diodes come in standard values. There's a lot of logic behind the choices of these values. More information, along with lookup tables of series and parallel combinations of standard resistors, is provided here.

Resistor types

There are various different types of resistor, each with different appropriate uses. See this post for more information.

High voltage polarity switcher

This circuit is designed to flip the polarity of its input, controlled via a signal between ±10 VDC. The input can have up to ±1000 VDC per conductor. Have a look.

High voltage filter

This is a circuit which removes ripple and noise from a power supply up to around 400 V. It uses a "Maida-style" high voltage floating regulator, and is based on a design by Pete Millett, but using a different MOSFET and suitable for higher voltages.

Contec digital input and output interfaces

These circuits map 32 electrically isolated, bipolar CMOS-compatible input or output channels to a Contec PIO-64/64L(PCI)H digital I/O card.

High voltage amplifier

This is a quad-channel, low noise, 0 to ±375 V source/sink, high voltage amplifier for driving capacitive loads.

Magnetometer readout

This board lets undergraduates conducting the geomagnetic storm detection laboratory at the University of Glasgow observatory quickly understand and build a simple closed feedback loop with which to detect fluctuations in the Earth's magnetic field due to changes in solar activity.

Negative impedance converter coil damper

This board super-charges the damping performance of so-called eddy current dampers used on suspended optics for gravitational wave interferometry experiments.

Ethernet environment sensor

This is an ethernet connected dust, temperature, humidity, pressure and light sensor.

BOSEM fieldbox

This circuit is a specialised circuit to drive "BOSEMs" used to sense and feed back to suspended test masses used in laser interferometers.

Mains waveform monitor

This circuit measures the lab mains waveform for data quality purposes.

Point of load Raspberry Pi Zero power supply DC/DC converter

This circuit provides a DC supply to power a connected load (such as a Raspberry Pi) and attached peripherals. This is useful for applications where one needs to power a Pi (which needs 5 VDC) alongside some other device such as a 12 V relay, but where for practical reasons there should only be one supply (the higher voltage). The on-board switch mode chip converts the higher voltage down to 5 VDC for the attached Raspberry Pi, for which the board's header is fully compatible.

Automatic plant watering system

This page describes my automatic plant watering system. It's a valve controlled by a Raspberry Pi, with a systemd service and timer to control its operation.

Wireless energy sensors

...when I finish testing them.

Op-amp noise and parameter tester

...when I can be bothered to write about it.

Networked coil drivers using Arduinos

...when I can be bothered to write about it.