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Latching fog lamp switch


Digsy
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Reading the one-touch window thread prompted me to post this about something I had been thinking about for a while:

 

Is it possible to wire up a converted rear fog lamp with a new-style switch that un-latches when the tail lights are turned off and on again (a'la most new cars these days).

 

Speaking as a pathological hater of people who leave their fogs on for days after the fog has cleared up, this technology can only be a good thing!

 

I wondered whether you could somehow loop the fog lamp feed back to the +12v side of the relay coil so that it would stay on even when the switch was released, thereby allowing you to use a momentary switch (yeah, I know it has to be illuminated - I'm working on it).

 

I need to draw the circuits out I suppose. Sounds like a good way to short something to me.

 

Any ideas, anyone?

 

Darren

 

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Yes. You need a double-pole-single-throw relay rather than the more normal single-pole-single-throw. It's then a matter of making your fog light switch a pulse generator rather than the main power control. You could achieve this part with a 555 family device in monostable mode.

 

 

What am I thinking? or you could use a PIC chip to provide all the intelligence and drive a standard single-pole-single-throw. Much more fun that way.

 

 

(Edited by Paul Booth at 6:19 pm on July 19, 2001)

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I understood most of that. Any chance of a circuit diagram?

 

I was thinking about this on the way home last night while I should have been paying attention to driving. None of the solutions I thought of would allow you to turn the fog lamp off again without flicking the tail lights off and on! Would your idea do this?

 

...and what's a PIC chip and why are they so much fun compared to a 555?

 

Sorry its not a very sexy subject, but I'm not a very sexy person.

 

Darren

 

(What no reply from Ash? Is he ill or something?)

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PIC chips are from Arizona Microchip. They're an incredibly cheap programmable MCU (can be programmed in an EPROM programmer or, better yet, in a board they supply which is connected via an RS232 port.

It's got to be the most primitive RISC processor ever. It has a dozen or so instructions and it's perfect where you want a slow state machine with a complex behaviour profile. You can get it down to an 8 pin device in surface mount.

There are variants with all sorts of nonsense built in and they started to release bigger devices intended to compete with the 8051 family of embedded MCUs, but I still prefer the 8 pin device with no extras.

I once emulated an RS232/Mitutoyo protocol converter using only the power available on the RTS and DTR lines to power the board.

 

Ign.   Fog   Side     Lamp Pwr

0        0       0           0      0

0        0       1           0      0

0        1       0           0      0

0        1       1           0      0 (?)

1        0       0           0      0

1        0       1           0      0

1        1       0           1      0

1        1     0->1       1      1 (state change, not steady state test)

 

So if the ignition, sides or fog lights are switched off, the fog enable output resets and only enables the fog lights when the ignition and side lights are on and the fog light switch changes state from off to on. It's basically what the 406 rain sense switch position on the wipers does.

 

One PIC, a few resistors to sense the switch lines, a power tranny to drive your relay and an indicator LED in the dashboard for the rear fog light.

 

I gave it some thought too. As I have a j-spec, my fog light switch only has one position. Cirrently I have it enabling front and rear fogs simultaneously. It is possible to have it cycle the fog lights, i.e., have it enable the front fog light when you switch it to on once and then both if you switch it off and on again within a time period. Reset clears that status too.

 

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How many variations are there on the theme of Fog light conversions for Jap cars?

 

I have a JIC conversion which puts a pathetic red bulb in my off side reverse lamp.

 

It glows red at MOT time  and that’s about it!

 

The other rear lamps on the Supra are very bright anyway, but I don’t want to get rear ended in the fog.

 

I have seen another car that uses twin filament lamps in one of the off side red lamps (not sure which one).

 

 

I think you may have to turn all my other lamps out to see the fog lamp in the dark :angry:

 

I also get fed up with people shouting  “ Mate do you know one of your reverse lamps is broken”

 

Anyone care to project some illumination on this subject?

 

 

 

 

 

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Whoever converted mine cut a rectangular hole in the bottom of my rear bumper and mounted a very bright fog lamp. It works well but looks crap.

 

It's my long term plan to use the stop filaments in the inner red lenses. Yes I know they're too close to the outer lenses, that's why I've been practising taking them apart and I plan to move the lenses around.

It will then work as the UK spec and hence my desire for the cycling fog light switch.

 

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Thanks for the information Paul! Probably a bit too in depth for me to bother with, though. I did think at one point that I'd figured out how to do it with a couple of relays, but you would need some kind of whizzy-double-pole-double-throw-double-momentary (illuminated) swich (or two separate momentary buttons, one push-to-make for "on" and one push-to-break for "off") but I still need to give it some thought!

 

As for the conversions, there seems to be three ways to do it:

 

1) Red lamp in offside reversing light a'la Phil. What are the comparative wattages of the reversing lamp, your red bulb, and a "real" fog lamp?

 

2) Inner brake light conversion.

 

3) "Halfords" fog lamp in the rea bumper a'la Paul.

 

(2) is technically illegal because of the 10cm minimum distance restriction between the rear fog and the nearest tail light (or brake light, I can't remember). I suppose for (1) to be strictly legal you should disable the inner tail / brake lights or have them switching off when the rear fog comes on - using even more relays!!!!

 

Consensus, anyone?

 

Darren

 

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I will look at bulbs and post ratings later today.

 

I have never bothered to look to be honest.

 

The stock rears seem so bright they penetrate fog very well.

The conversion is just there for MOT and not much good as a safety feature.

 

What happens in Japan in the fog?  

 

Do they all start rear ending each other?

 

Perhaps they realise that visibility is reduced and slow down.

 

Not like some nutters over here, who seem to think that if they have fog lamps on they can go just as fast as in perfect conditions.

 

 

 

(Edited by Phil Wall at 9:34 pm on July 23, 2001)

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Fog lamp conversion.

 

My bulb is 21 watts, the correct rating but  covered in a very dark red coating more like maroon.

 

It does not look right, nothing like the red of the other lamps.

 

The coating on the bulb is very thick, too thick in my opinion.

This is cutting down the light that can get out of the bulb.

 

I will be looking for an alternate. Hopefully in a more traditional fog light colour.

 

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They are created by using a normal bulb and red bulb paint. The only coloured bulbs I've ever seen have been indicator orange.

 

I've been mulling over the foglamp issue for a while. The switch-side I sorted by using the UK dash panel and switch. But I do rather like the look of the 4 rear lights which has put me off fitting the UK rear clusters.

 

I have the red bulb in place of a reversing lamp mod that was performed by the dealer. I don't like it because the red of the bulb shows through. What I might do at some stage is to wire a switch somewhere that will switch between normal reversing light and foglight. Then simply change the bulb for the MOT. I never use the blo*dy forglamp anyway. To my mind trying to find provision for one is a PITA.  

 

Yours,

J

 

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After checking my fog light  in the dark last night. I don't think it will pass the MOT as the coating is not giving a uniform red light. Too much white showing.

 

I made a few inquires at local accessory shops, including one where all the young lads go for there bits. Plenty  of amber bulbs but no reds.

 

One guy said try a disco supplier!!!!!!

 

There must be someone some where.  

 

I know there is a standard mod on a Nova to give twin fogs and reversing lamps using coloured bulbs and left hand drive rear clusters. I will get my son to post on his Nova group site and see what he comes up with.

 

If  I can locate a supply how many members may want a 21 watt red coated bulb?

 

I guess most people who bought an import from JIC.

 

 

 

(Edited by Phil Wall at 10:19 am on July 24, 2001)

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I might have missed it but nobody seems to have mentioned Pete Betts fog light system. He basically used 2 relays linked into the brake lights so that while the fog light is off you get the 4 brake lights, and while the fog light is on the inner 2 lights become fog lights and the outer 2 remain as brake lights. Not strictly legal as detailed below due to the proximity of the brake light to the fog light, but I have had no problems passing an MOT.

 

JB

Shop!!

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Yes I may have to go down that route.

 

Just slightly concerned that it is yet another doubtful issue for the MOT.

 

If some tw*t hits you up the rear in the fog, some sharp brief may end up blaming you, using the proximity of the lamps as his clients get out clause.:sad:

 

 

 

 

(Edited by Phil Wall at 10:28 am on July 24, 2001)

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Yes, Pete Betts has an excellent description of a braking light type conversion on his website.

 

How do the birghtnesses of the brake lights compare to that of a fog lamp?

 

If the fog lamps are brighter, then the other concern with using a fog lamp wattage blub in the brake light position is that it may overload the wiring.

 

I dread to think that the "Halfords" fog lamp may be the best technical and legal solution!

 

Darren

 

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I've got no idea who these guys are (except they are in Ameriica) but a quick internet search turned this up:

 

http://www.sherco-auto.com/minilamp.htm

 

If you can get them over there you must be able to get the over here!

 

Found another website (still across the pond).

 

http://www.lightlens.com/coloredbulbs.htm

 

Darren

 

 

 

 

(Edited by Darren Blake at 12:11 pm on July 24, 2001)

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Having taken Darren's question, regarding having fog lights which have to be positively asserted and don't just come on when you turn on your side lights becuase you forgot to switch them off yesterday, the relay option is difficult to achieve (not unachievable). This assumes you care about that (I do).

 

By moving to a UK spec rear end and retaining the stop/tail lighting, you can maintain a 4 tail light configuration, albeit with a slightly larger gap between the tails (might be even nicer in the dark). The stop filament in the inner light can then be used to provide the fog function when required.

 

This to me seems to address everyone's desires.

 

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Don't know. I intend to do what I did to repair my high-level stop light.

 

The plastic joints are held together with a fairly mild adhesive and by cutting key-ways into the jointing surface with a Dremel, I found I could stress the joints with a large flat screwdriver into parting, leaving 98% bonding surface to re-assemble and seal.

 

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Ah! You are talking about swapping the coloured lenses around to separate the two tail lights? Sorry if I misunderstood.

 

So would that put the reversing light between the two tail / brake lights, overcoming the 10cm barrier?

 

How are the lights in a UK car arranged (including the fog light)?

 

Darren

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