Lights on alarm

[tweeky]

Hi,

Ive just fitted a buzzer to my indicators as I carnt hear the standard warning, and ist got me thinking about the lights.

 

Has anybody fitted a light on alarm, if so how do you go about it.

 

Many thanks

 

Mark C

 

[Colin Mill]

Hi Mark

 

I have not done this but I think all you need is to connect a buzzer via a diode between the headlight feed (or sidelight if you want it to sound even with sidlights left on) and the switched ignition feed to the ECU. If you like I could have a look at the circuit diagram and see if I can find some convenient places to pick these up from.

 

Colin

[Mick Day]

*idea*Why not a warning for when the engines been left on as well.

[JonathanP]

Might need one on the tin-top, but surely you always turn round to look at your 7 when walking away, or is that just me? 😬

[Drumster]

Battery master switch does the job for me

 

Chris Alston

1800 Supersprint here

Drive it like you stole it! but don't tell my pupils that 😳

 

[Chris W]

I just measured the resistance between my ignition lead and ground (with the ignition OFF) and its only 40 ohms. If it's about the same for your car, then this means you could connect a buzzer directly between the sidelight feed wire (usually RED) and the ignition wire (usually WHITE).

 

You need to use a buzzer that only works one way round (ie: it has a + and a - lead). Connect the + side to the sidelight feed and the - side to the ignition wire.

 

If the ignition is ON and lights OFF, the buzzer is effectively connected the wrong way round and won't buzz. If the ignition and sidelights are both ON, there is the same voltage on both sides of the buzzer and it won't buzz. However, if the sidelights are ON and the ignition is OFF, then the buzzer has 9 volts across it and will buzz. (see below for why it's 9v and not 12v)*

 

A suitable (and very cheap buzzer) can be obtained from Maplin on the webpage here

 

*The effective resistance of this buzzer is around 120 ohms, so if the resistance to ground is 40 ohms the total resistance is 160 ohms. The buzzer will therefore have 120/160 x 12 volts across it = 9 volts. So the buzzer will not be at full volume but it's cheap enough to try at only 99 pence! If the reistance of your ignition lead to ground is much more than 40 ohms I would guess that the buzz volume will be reduced too much. In that case, buy the 6 volt version of the same buzzer at £1.49

 

Chris

 

2003 1.8K SV 140hp see it here

 

Edited by - Chris W on 26 May 2006 00:28:53