Warning switch for lights

Post by **iddy** » Thu Feb 21, 2008 4:32 am

Is there an easy way for electrical dimwits like me to fit a warning bleeper to let us know when the lights have been left on. My other half forgot to turn the lights off last week (not for the first time)

She actually suggested the idea - "why can't it beep at me like the Focus?"
Cheers,
Iddy.

Post by **alex_holden** » Thu Feb 21, 2008 9:19 am

There's a fairly simple way to do this with a double pole automotive relay and a 12V buzzer. I'll sketch up a diagram a bit later.

Post by **bmcecosse** » Thu Feb 21, 2008 3:31 pm

Or just a light unit/buzzer connected between ignition and sidelights - with a diode to make sure it only lights/buzzes one way and not the other!

Post by **iddy** » Thu Feb 21, 2008 4:58 pm

Thanks Guys,

Remember, I did say electrical dimwit

Iddy

Post by **bmcecosse** » Thu Feb 21, 2008 5:08 pm

Maplins will sell you the buzzer and the diode!

Post by **bigginger** » Thu Feb 21, 2008 6:15 pm

iddy wrote:Thanks Guys,

Remember, I did say electrical dimwit

Iddy

I'm not, and it's not making much sense here either

Could you explain your idea, BMC?
a

Post by **bmcecosse** » Thu Feb 21, 2008 10:35 pm

If the sidelights are ON and the ignition is OFF, then a current will flow through the buzzer. Obviously the reverse would also happen (flow from IGN to sidelights making buzzer sound) - but if a diode is inserted in the circuit it will only buzz one way.

Post by **bigginger** » Thu Feb 21, 2008 10:54 pm

Aha - all becomes clear. Thanks
a

Post by **bmcecosse** » Thu Feb 21, 2008 11:00 pm

Of course - that only works when switching off ign while sidelights left on - which is something that may be wanted at night. So a switch to kill the buzzer could be added. Modern cars are much smarter and only buzz when a door is opened!

Post by **Axolotl** » Fri Feb 22, 2008 9:46 am

Modern cars are much smarter and only buzz when a door is opened!

Seems to me a relay-based solution as suggested by Alex could accomodate that feature too.

If you set up two relays, relay 1 closed when off, relay 2 closed when on, as follows:-

Relay 1 has ignition switched power to control the relay, so it is closed when the ignition is off, and open when the ignition is on. The "load" to this relay is the feed from the sidelights when they're on, connected to the control side of relay 2.

Relay 2 has the buzzer as its switched load fed from the courtesy light "on" circuit. This will sound if the sidelights are on, and the ignition is off (power from relay 1), but only if the courtesy light is on (power from that circuit drives the buzzer).

If you don't want to be warned about the sidelights, take the load feed for relay 1 from the headlight circuit, instead of the sidelights.

I think I might lash one up when I'm bored one day.

Post by **alex_holden** » Fri Feb 22, 2008 10:20 am

Axolotl wrote:Relay 2 has the buzzer as its switched load fed from the courtesy light "on" circuit. This will sound if the sidelights are on, and the ignition is off (power from relay 1), but only if the courtesy light is on (power from that circuit drives the buzzer).

If I understand your description correctly this will also buzz when you manually switch the interior light on while the sidelights are on, not just when you open a door. There is a simple way around this - circuit diagram coming when I have a spare half an hour to draw it!

Post by **Axolotl** » Fri Feb 22, 2008 10:54 am

this will also buzz when you manually switch the interior light on while the sidelights are on, not just when you open a door

Yep, I'd forgotten the manual light switch. Can't think how to get round that without adding a buzzer disable switch at the moment.

I look forward to seeing your solution and diagram.

Post by **Axolotl** » Fri Feb 22, 2008 1:07 pm

I can see how you can do it with a single relay, but I can't see you you can know whether the courtesy light has been activated by the door switch, or the light switch. It's the same piece of wire that gets earthed by either. Obviously, I'm not thinking laterally enough.

One 5 pin relay, as follows:

PIN 86 (Relay control) Ignition switched live.
PIN 85 (Relay control) Earth.

PIN 30 (Load supply) Side- or headlight power when lights on.
PIN 87A (connected to PIN 30 when PIN 86 Off) +ve side of buzzer.
PIN 87 (Connected to PIN 30 when PIN 86 On) Not used

-ve side of buzzer connected to earth via courtesy light switch. i.e. connected to Purple/White wire from courtesy light.

I can't wait for the solution

Post by **MoggyTech** » Fri Feb 22, 2008 2:06 pm

http://www.elises.co.uk/diy/buzzer/index.html

Above circuit diagram is how it's done. Very easy.
Only slight variation is you use the sidelight feed on the Moggy, rather than the headlight feed. Diode can be an IN4001 from Maplin. Total cost inc buzzer about £3

Post by **Axolotl** » Fri Feb 22, 2008 2:26 pm

But that suffers from two issues:

Firstly, it will sound the buzzer whether the ignition is on or off.

I thought the idea was you only wanted it to sound when the ignition is off, i.e. when you are in danger of running the battery down. Otherwise, it is simply a "door open" buzzer that only works when the lights are on

. (Presumably on the basis that if it is daylight, you can see the door's open?)

Secondly, it suffers from the same issue as my solution(s), i.e. it will also sound the buzzer if you turn on the interior light using the manual switch, since that switch simply connects point A to earth, same as the door switch.

Come on Alex. Put us(me) out of our(my) misery.

Post by **alex_holden** » Fri Feb 22, 2008 3:27 pm

My first design would buzz when the lights were on and a door was open regardless of whether the ignition was off, so I've instead taken Axolotl's design and made a tiny change - add a diode in the wire from the courtesy light to the first door switch so the door switches can activate the light but the light switch can't activate the buzzer.

(1) Courtesy light.
(2) Diode. Needs to be large enough to handle the current the courtesy light bulb needs - a 1N4001 should be fine. Reverse it if your car is still positive earth. I recommend soldering the wires to it and then enclosing it in heat shrink tubing to avoid short circuits.
(3) Door switches.
(4) Buzzer.
(5) Small SPDT 12V relay. The buzzer is connected to the "NC" contact.
(6) Small diode. Only needs to handle enough current to power the buzzer (but another 1N4001 would work just fine). Reverse it if your car is positive earth.

Edit: Added a second diode to prevent the circuit misbehaving when the sidelights are switched off.

Post by **Orkney** » Fri Feb 22, 2008 3:36 pm

Ive had half the dash off of one modernish car trying to find the flipping speaker thing the noise comes from to no avail still couldnt find and destroy and the dash never quite seatd back correctly

Yes i know i havnt got a seatbelt on or a doors open or ive left the lights on its for a reason thanks and you Bong Bong Bonging at me doesnt help anything !
Dreading the day i ever get a car that speaks and tells you, that would just be the limit, although have heard some amusing satnav voices but its still tedious after about 3 mins.

Post by **Axolotl** » Fri Feb 22, 2008 4:01 pm

Orkney, I sort of agree, but it was a bit like Everest: a challenge, to see if it could be done and if so, how. Now you've suggested a voice, I'll have to see if I can get a voice-box instead of a buzzer.

What should it say?

Alex, thanks, I see it all now. A workable solution that meets all the requirements. I'll add a switch, so that if Orkney ever buys my car, he can turn it off without wrecking the dash

.

Off down Maplins to get the bits next week

.

Don't suppose you can suggest the easiest place to find and break into the courtesy light wire to link to the buzzer and install the diode? [Edit] I think I'd put the main diode just in the driver's side door switch wire, as you don't want the buzzer going off while your passenger gets in or out.

Post by **iddy** » Fri Feb 22, 2008 4:02 pm

iddy

Post by **alex_holden** » Fri Feb 22, 2008 4:14 pm

Axolotl wrote:Orkney, I sort of agree, but it was a bit like Everest: a challenge, to see if it could be done and if so, how. Now you've suggested a voice, I'll have to see if I can get a voice-box instead of a buzzer.
What should it say?

How about "muppet" on an endless loop? ;)

Don't suppose you can suggest the easiest place to find and break into the courtesy light wire to link to the buzzer and install the diode

I think the wire comes down one of the windscreen supports but I'm not sure which side. You could probably make up a diode with a short bit of wire and a round crimp connector on each end (male on one, female on the other) and insert it without cutting anything at the point where it splits off to the two door switches.

Note that I've added a second diode to the diagram - without that you'll get reverse polarity across the buzzer when the sidelights are switched off.