Projects in the July 2002 issue of EPE Magazine

EPE Stylopic
- hand-held stylus-operated musical instrument. Remember the TV star Rolf Harris and the Stylophone - "the greatest little instrument of the century"? EPE brings Rolf's favourite right up to date with our PIC-powered stylus instrument that has many improvements over the transistorised original. Includes two full octaves with superb tuning accuracy thanks to a new technique previously unpublished in EPE.

For more background on the original Stylophone, visit

In August 2002's issue (P. 616), we said that on P. 490, Fig 2, an LM13700 can be used instead of an LM13600 if desired.

Infra-red Autoswitch
- intended primarily for use in kitchens, this unit will keep any worktop lighting powered on for as long as someone is using the worksurface. Waving your hand near to the IR switch turns on the lights for a preset period. Also, if you stay in the work area the unit will remain triggered.
Rotary Combination Lock
- using a smooth-action 360 degree rotary switch and some standard 4000 CMOS logic, this design emulates the action of a rotary combination lock, energising a solenoid latch when the correct number is dialled in. Offers approximately twice the security of a 4-digit keypad, it is also able to send a secret "panic" (duress) signal to another location. Presettable combination using wire link selectors.

Simple Audio Circuits (3)
This month we cover the techniques of successfully designing power supplies, loudspeaker systems, crossover networks and filters. The construction of a power supply and a Crossover/ Audio filter are described.

Special feature: using the PIC PCLATH command - how to access PIC addresses beyond 2K and place tables outside of the basic 256 byte block.

In August 2002 (P. 616) we said that in the PCLATH article, Figs 1 and 2 should be tranposed.

Also in this issue: Teach-In 2002 Part 9: Filters, Sampling, A-D Conversion, Sampling. Nuclear Radiation Sensing. New Technology Update - how holographic techniques could revolutionise computer data storage; Circuit Surgery examines bandgap voltages; Ingenuity Unlimited - readers' own circuits.