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Turn indicator flasher

I have called this design the “Urban Indicator” and its purpose is to switch automotive or motorcycle turn indica-tors. A novel function of the Circuit (which I have used on a motorcycle for over a year) is that it switches the indicator lights out of phase, that is the rear one is on while the front one is off and vice-versa. The Circuit shown will oper-ate in this manner although it can be modified to operate as standard with the moving of two MOSFETs. It will also function as “hazard” lights with the addition of a suitable switch.

A 7805 IC is used as a current regulator for the CMOS chips, the supply linę being noisc filtered by the zener diodę. Switch SI is a centre off type with the

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centre connected to ground. When a turn is to be indicated SI enables a NAND gate oscillator operating at 1Hz. It also enables “left” or “right” through a 4071 or gate, whose output goes Iow switching on an optocoupler device which can be part of a quad package.

The optocoupler applies a vo!tage that is quite close to linę vołtage to the gate of a power MOSFET, which sw itches on one of the globcs.

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and available from VSI should use the metal case as a heatsink and can handle high currents. The 7805 can use similar heatsinking but must be insułated. The MOSFETs don’t need insulation if the metal case is isolated from the vehicle^łs body.

I hope others enjoy building and using this Circuit as much as I have.

Karl Stevens,

Willoughby, NSW.    W³

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TO PRiNTER STANOARD CENTRONICS INTERFACE

It is generally true to say, however, that the “dumber” the interface, the smarter the user needs to be. Especially with word processors, an intelligent interface ónły gets in the way.

The routine is not relocatable, so it must be changed if it is to bc used in a slot other than numbcr 1. Because of this, it is morę memory and time effi-cient than those routines stored on ROMS. It is also infinitely morę flexible as it can be changed from software.

Ross Donelly,

Lindfield. NSW.

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ELECTRONICS Australia. September 1987

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