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Fitting a "lights on" alarm to a V8
Alan Turner (Damask 0663) from Devon posted a note on the V8BB and in passing mentioned a useful modification. Here he sets out how to make the device. (Mar 05)

Alan recently acquired his V8 and comments "Isn't it strange, when returning to a classic for everyday transport, that you miss those little "insignificant" things like central locking, electric windows and headlamp warning alarm". Not wishing to get stuck with flat batteries by leaving my lights on, I decided to find an alarm for the side/head lamps. A search though Maplin's catalogue revealed a kit available for £7.99 plus postage. I found it was out of stock but put on a back order and eventually it arrived.

The kit is K3505 Car Headlamp Indicator order code VF24B and is on page 495 of the latest Maplin Autumn/Winter 2004/2005 catalogue. The kit comprises of a small printed circuit board of good quality with two mounting holes for M3 studs, 10 diodes, 10 resistors, 7 capacitors, 2 integrated circuits with sockets, a transistor and a buzzer. Most of the components come on a tape, which are in fitting sequence, there is also a booklet with information of board layout, circuit diagram and resistor colour codes.

Building the kit was the easy bit as far as I am concerned, but I am an electronics test engineer. It took a couple of hours to complete.

Alarm on its board alongside a 10p coin to illustrate the small size of this unit. (Photo: Alan Turner)

The connections to the outside world are ground, ignition and sidelights. I fitted a jumper across J2 to prevent a warning when ignition is switched on without lamps on (required in some countries). So the kit has two possible configurations. The kit was wired up for test and worked first time.

A small plastic box was found and the board mounted inside to protect it from damage. I marked and drilled


the holes for mounting before fitting the components to the printed circuit board populating the board, Two M3 countersunk screws with nuts fitted to space the board off the box. Remember to drill a hole in the box line with the buzzer or it will be very quiet.

Now to find somewhere to fit the box, secure it and get the required feeds to it. Well there is a square section tube running under the dash which had already been used to mount the fan override switch and the box would fit nicely with a couple of cable ties around this tube section. A feed was taken from the ignition, a white cable near a bullet connector under the steering column, the light switch was carefully prised from fascia and the sidelight feed cable is red with a green tracer. Piggy back connectors were used for both of these feeds and a eyelet crimped to the ground cable and a suitable position found. Job done.

The alarm sounds when the ignition is switched off when the lamps are still on for a few seconds and then repeats a couple of times and is then silent, so sidelights could be left on if desired.

A few notes worth mentioning perhaps:
o A multimeter (DVM) is useful to trace feeds, but a test lamp could be used.
o Static precautions should be taken when handling semiconductor electronic components.o If using cable ties, do cut the surplus off really flush or a very sharp edge can result, which can cause cuts especially when working in a confined spaced. There is a special tool available for this task

Tools required are a soldering iron (25 watt), side cutters, long nose/ round nose pliers, and a small flat blade screwdriver. You will also need solder and connecting wire/connectors.

Footnotes:
Integrated circuit is an electrical component consisting of many semi conductor devices encapsulated in one package, usually having a minimum of eight legs.
Static precautions usually take the form of a wrist strap which is connected to an earth point (on a 13 amp mains plug) with a 1 ohm resistor in the line. The concern with static is the person handling the components can obtain a high level of charge which could be discharged through touching an earthed unit. The earth strap and resistor lets this discharge. We are all familiar with the small shock when touching a door handle in dry weather, well this is the static charge on you discharging to the handle and not the handle being charged. So if you were to charged with static you could discharge through a semi conductor device, integrated circuit or transistor and the device could be damaged or its life reduced. In practice you often get away with it.
Small plastic box - you can get these from Maplin or Farnell.