Diodes

[Jack]

I'm planning some wiring work on the Celica involving the rear lights. I need to add a diode to some of the wires, but what voltage/wattage etc diode should I be using?

The bulbs are standard 21W dual filament jobbers (i.e. tail/brake). Should I get one thats 12v 21W or does it not work like that?

[phazer]

They come in a variety of 'sizes'. Reverse voltage and current (amps) handling is what you need to consider. All but the smallest surface mount will do voltage wise.

In the hazard mod I specified a 1N5402 (maplin code QL83E 26p). This has a reverse voltage limit of 200v and a 3A current handling which should be waaay more than you need for your rear lights (unless you're going for some ebay china specials? lol)

[C612DNM]

I wonder what you're planning???

I use a varied pile of diodes in my work on cars (blues & twos etc..), and we tend to use a bridge rectifier for most light tapping jobs - they're better at handling current, and having four diodes within (where we only use two - with three of the lucas spade type tabs), plus the benefit of being able to bolt it to the bodywork for heat dissipation. Good enough for flashing main beams, or rear fogs.

I use 1N5402's or similar, for some signal taps where I want some reverse voltage protection.

So, what ya up to dude?

[Jack]

I'm converting my rear lights to semi-JDM spec - i.e. instead of one tail/brake and one fog on each side, I'm changing the fog to a tail/fog... like this:

http://www.celica-club.co.uk/wiki/images/3/30/Tail.jpg

The wiring is simple, its just I'm not up on technical stuff like diodes... lol

[16v Nova Kev]

is it so your bulb warning shiz dont come on.

[Jack]

No, mine's a UKDM car so doesn't have that gubbins :)

[16v Nova Kev]

not sure why you would need a diode or a resistor. am i being really stoopid or would you not just piggy back the wires.

[Sloth]

sametype as tanias lights jack? i can have a look how hers is done?

[bazil]

I'm converting my rear lights to semi-JDM spec - i.e. instead of one tail/brake and one fog on each side, I'm changing the fog to a tail/fog... like this:

http://www.celica-club.co.uk/wiki/images/3/30/Tail.jpg

The wiring is simple, its just I'm not up on technical stuff like diodes... lol

uk spec lights have a silver backing for the fog light, so your extra brake lights will be brighter than the standard ones,

[Jack]

sametype as tanias lights jack? i can have a look how hers is done?
No, JDM have different looms to allow for the dual tail/stop as standard. I need to modify my UK loom


uk spec lights have a silver backing for the fog light, so your extra brake lights will be brighter than the standard ones,
These are JDM lenses :thumb: Sorry, should have explained that - UK car, UK loom, JDM lenses.


not sure why you would need a diode or a resistor. am i being really stoopid or would you not just piggy back the wires.
Actually, now that you mention it... I'm not sure I do need a diode. Its mentioned on the notes I have from CCUK, but thinking about it why would I need one?

At the moment, lamp 1 is tail/stop. Lamp 2 is fog only. I want to swap Lamp 2 to a dual filament bulb and holder; then connect the 21W wire to the fog +ve, and splice the 5W wire to the stop +ve from lamp 1. The notes say I need a diode on the splicing wire, and another on the fog +ve. I don't reckon I would though, as what current is going to go back up those wires?

[Sloth]

jack i may be able to get you a jdm rear loom....

[mowgli]

vw tourans have some sort of dimmer arrangement so the brake/tail lights are a single filament 21w bulb.. but i really don't know where the circuit board is for it..

[Jack]

jack i may be able to get you a jdm rear loom....
Might as well just mod my existing one as I have all the stuff here to do it (except the diodes, which I don't think I now need lol), its just as imple case of joining a couple wires up.

[16v Nova Kev]

you could leave your existing lights in stiu and wire up the new ones in the boot as a trial then nothing has beed disturbed

[Jack]

Yeah, but I need to cut the loom to switch the bulb holders round (changing single filament for dual filament).

Here's the diagram I'm working off btw:

http://www.celica-club.co.uk/wiki/images/2/2f/4STOP2FOG.jpg

The connection from tail to fog, and from stop to fog are the new bits. That makes both lamps become tail/stop, with one also being used as fog. The wiring isn't a problem, its just whether or not I need the diode on the fog +ve (as I know looking at that I'll need the stop-to-fog one), and what diodes do I want to do the job.

[phazer]

and what diodes do I want to do the job.

If you need them (I can't see the diagram), then check the first reply to your thread lol

[Jack]

lmfao, I got sidetracked explaining what I wanted them for

I'll give the maplin ones a try :thumb:

[mowgli]

can't you do something with relays?

[phazer]

lmfao, I got sidetracked explaining what I wanted them for

I'll give the maplin ones a try :thumb:

lol, I did wonder! Oh and cheers :thumb:

[C612DNM]

Using relays with a solid 12v battery feed will ensure consistent voltage at the lamps. We often use relays to ensure that flashed headlights get full juice as diodes induce a 0.707v drop.

[phazer]

Cars don't produce a solid 12v though, it's somewhere between 9 and 15v depending on the engine being started/not started and the alternator output. If a solid and stable 12v was important then you'd need to introduce a regulated power supply.

Besides a lot of automotive relays have 'flyback' diodes fitted so you suffer the same drop anyway.

[C612DNM]

The "flyback" diode is to stop back feeds (which may effect the system that's being used to engergise the relay, so it's across the coil, not the contacts.

When I say a "solid" 12v, I mean battery voltage, full juice, the whole lot, not Vb-Vd=dim lights.

[Stuart]

ohhh 0.7V down on a filament bulb is going to make SOOOOOOO much difference lol

[Jack]

http://sphotos.ak.fbcdn.net/hphotos-ak-ash2/hs561.ash2/148301_496013978884_667958884_7301686_6082628_n.jp g

Well I'm halfway there - Maplin only had two diodes and I thought I could get away without putting one on the fog wire, but it seems even though my diagram reckons its relay controlled it still made the warning light come on. D'oh lol

Gotta wait for them to get more in stock now before I can finish off. They do have 15V Zener diodes in though - would these be Ok to use? As I can't see any more than 15V going down the wire!

Still, on the plus side, Jap wiring is SO much better to work on than the Nova stuff... I could unplug the loom and work on it in the warm and dry inside, rather than the Nova rear light loom which is all in one with the car loom lol


[edit] That is normal brightness tail lights in the pic BTW, its just the crappy camera makes them look really bright lol

[Stuart]

Zener is no use to you really