I am an engineering psychologist who enjoys playing about with computer hardware and software.

I live in St. Leonards-on-Sea, on the South Coast of England, near where William the Conqueror landed when he invaded England in 1066.

My interests include amateur radio, electronics and computing, and motorcycling.

With a substantial business startup loan via the GRIST scheme, I am developing sports training aids using MEMS technology, in conjunction with the University of Brighton.

My CV is here.

I offer a fast, affordable electronics design service.

Further details here.

I use Pulsonix for my PCB designs, and find it excellent. See http://www.pulsonix.com/

I formed the Pulsonix Users Group: http://groups.yahoo.com/group/PulsonixUG. Apart from discussion of the software itself, and design techniques associated with its use, I see this group as being very useful for the exchange of user-generated parts and part libraries.

Philips has recently started shipping their new ARM MCU, the LPC210x. It is the easiest ARM chip to use, with fast on-chip flash memory and in-circuit programming via an RS-232 boot loader. Price is about $10 for small quantities. I've designed a simple prototyping PCB for it: go here for further details.

See http://www.EmbeddedRelated.com if you are interested in embedded systems.

I ride a 2003 Suzuki SV1000S high-performance 996 cc 90 degree V-twin.

Further details here: pic.html

Here are some notes on using the Taig/Peatol lathe.

Further details here: http://www.leonheller.com/

Wavefront DSP

I'm working on a DSP intended for audio applications using the Wavefront (formerly Alesis) DSP, ADC and DAC chips. Some details are here.

You might be interested in http://www.dsprelated.com.

Ubicom/Scenix SX28 MCU Prototyping PCB

I've had some SX28 chips lying around for some time, so thought I'd have a play with them. I accordingly designed a simple prototyping pcb.

Mini DDS

Details of my version of Jesper Hansen's DDS precision waveform generator are here.

The new dsPICs from Microchip are described as Digital Signal Controllers and can be regarded as microcontrollers with DSP capability. Here is a simple design using the dsPIC30F4013 for audio processing.

My callsign is G1HSM. I recently got interested in QRP (low-power) operation on the HF bands, and have a Yaesu FT-817ND transceiver which is used for SSB operation on the 20 m band. I've also got a Yaesu VX-2 VHF/UHF handheld transceiver and an FT-290R II. I've built a SoftRock-40 software-defined radio receiver using the kit supplied by AmQRP. I've recently acquired a Redifon R551N HF receiver, plus a second unit for spares.

If you are interested in using the Analog Devices AD9850, look at this web page of mine: dds.html.

It contains details of a simple Direct Digital Synthesis system, controlled via a PC printer port.

Here is a simple technique for designing and building a four-pole crystal ladder filter.

PCB designs are provided.

A simple noise generator circuit is here.

A simple high-performance DC receiver module.

A simple mixer module for an HF receiver is here.

A VFO/buffer for the above modules.

Now that Open Motif is available free, I've been playing about with it on my Linux system. These notes will be of interest to anyone else who is interested in Motif programming, and needs some help getting started.

Direct-coupled feedback pair amplifier design

A simple design technique for this useful amplifier is here.

Atmel AVR

The Atmel AVR range of RISC micro-controllers is very interesting, and has many advantages over the widely used PIC family from Arizona Microchip. I started with the 1200, and am now using the 2313 and the 8515 for several applications.

The 1200 is the ideal micro-controller for the newcomer. It is obviously intended for the same sort of applications as the Microchip 16F84, but is somewhat easier to use - the architecture is less esoteric and getting code into the device is much simpler. It is also a lot faster for a given clock rate. Here is the circuit for a minimal 1200 system, and source code to make it flash an LED connected to one of the I/O pins: 1200.html

The 2343 is one of the smaller members of the AVR family, and comes in an eight pin package. Here is a simple circuit to get you started with it, and a test program. 2343.html

The MSP430 range of micro-controllers has some very interesting features. Here is a web page to help you experiment with the MSP430F110: msp430.html

Here is a design for a little (just over 1" square) DIL module that uses the 'F11x1 or 'F11x in the SSOP package: msp_module.html

Microchip has put a lot of processing power into a small 18-pin package with the 40 MIPS dsPIC33FJ12GP201. I've designed a little prototyping board for this device: dsPIC33FJ12.html

A wearable computer or 'wearable' is a very small, low-power computer system that can be carried around in a pocket, or attached to one's clothing, and used whilst one is walking around, watching TV, or whatever. They typically use some form of keyboard that may be operated with one hand, and a head-mounted display. Gumstix are tiny computer modules based on the Intel PXA255 device running Linux and are ideal for use in wearable computers. Details of my Gumstix wearable are here: wearable.html

Here's a simple example of software using the full duplex hardware UART provided on the 2313 and 8515 devices: uart.html. Rather than an expensive RS-232 interface like the Maxim MAX202, I'm using an HCT14 to provide the necessary inversion for interfacing to the PC serial port.

Here is an Excel spreadsheet for calculating transistor bias resistors. Nothing particularly clever, but it saves a lot of time:Bias.xls

cpu.html

If you want to play with programmable logic devices, but are not sure of how to get going, here is something to get you started. pld_starter.html

A four pole crystal ladder filter is analysed here, with the SPICE simulator.

Here are the files for a DIY copy of the Altera ByteBlaster (schematic, Gerbers and drill files): blaster.zip.

If you would rather buy an improved version (SMD) ready-made and tested, see here.

Email: Leon Heller