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Circuit Notebook

Interesting circuit ideas which we have checked but not built and tested. Contributions will be paid for at standard rates. All submissions should include full name, address & phone number.

Replacement horn circuit for a car

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This circuit was devised to replace the horn contacts that were damaged after removing the steering wheel on a Mitsubishi Express van. It can be adapted to other models and the horn relay circuit could also be employed if there is a need to install extra horns in a vehicle.

Five tactile switches are installed on a section of Veroboard which is cut to shape to fit under the horn button. The tactile switches are wired to alternate tracks of the Veroboard and are all effectively connected in parallel so that as long as one of the switches is closed, the relay will be energised and the horn will sound.

The Veroboard and switch assembly is sandwiched between two sheets of thin plastic which can be sourced from the lids of take-away food containers.

Geoff Coppa,
Toormina, NSW. ($40)

Program variation for Digital Spirit Level

Back in October 2011, we published a program variation for the Digital Spirit Level (August 2011) which allowed it to read gradients as a percentage rather than in degrees. That was useful but readers commented that the auto switch-off is a nuisance in some applications. What was wanted was a variant like the G-Force meter (November 2011) which has a normal power switch.

Accordingly, a new version of the code has been created which eliminates the auto switch-off facility. It still reads degrees or percentage, as selected by pressing the calibrate switch for about five seconds and then the display will toggle between the two modes. A short press on the calibrate button will zero the reading, as in previous versions.

The calibration reading and the selected mode are stored in non-volatile memory so you do not need to select the mode each time you use the device. Hence, in the degree mode, the instrument reads from 0° to 360° in 0.1° increments. In percentage mode, it shows 0.0% to 99.9% gradient between 0° and 45° and between 180° and 215°.

Conversely, it displays 0.0% to -99.9% between 315° and 360° and between 135° and 180°.

The software, Digital Inclinometer Always, can be downloaded from the SILICON CHIP website.

Andrew Levido,
Wollstonecraft, NSW. ($70)

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