Headlamp Modifications

[Vanny]

Well go on, what was the fault? You can't blame my top of the range original relays and not tell us what the fault really was

[mat_fenwick]

Prepare to be dazzled!
As for the fault - it turned out to be a combination of a connector that wasn't fully in its holder, and a fuse that looked intact but wasn't.
Now all I have to do is find a convenient space for it and wire it in. Should be sorted within the year...
(Vanny, your relays worked fine. In fact they're the best relays I've ever used, their clickyness is exceptionally good! Happy now?)

[electrokid]

Excellent - glad it's working

I went to check prices of relays today - went to Europarts - £8.49 so went to another factors - £3.49 but 1 week delivery time for 6 off - so I'm off to eBay in a mo.

It's worth mentioning - if fact I ought to put it on the drawing - that the relays used do not have internal diodes. These relays are available with an internal 'catching' diode also known as a 'snubber' - when a coil is switched off a large voltage spike is generated across the coil in the reverse direction to which it was energised - if there is an electronic component such as a transistor which is being used to drive the coil then this voltage spike is very likely tp pop it - unless a snubber circuit or catching diode is fitted across the coil. Coils operated by switches don't need the catching diode.

[mat_fenwick]

Are there any old style DIY removal scrapyards round your way? As surely it would be cheaper to pull an armful from a scrap car rather than buy new. That's what I tend to do with relays, fuses etc (and when I was a poor impoverished student, bulbs as well!)
BTW I was vaguely aware of diode equipped relays but not sure where they were needed so cheers for that.

Regarding the over-the-top batteries, I did get two of 'em for nothing and despite being fairly discharged they seem to be holding it fine once recharged. It'll give us a little more flexibility on holiday and allow us to run the fridge from the inverter for a couple of days should we run out of gas. The downside is if I do run them down it'll take a lot of driving around to charge them back up!

[electrokid]

Found some relays on eBay at £2.88 each including postage so I snapped them up - the seller also has some beefy cables as well - you'll be glad to hear he doesn't do them in green - eliteautomotive2010

Red is available - seems appropriate to me

[electrokid]

HA ! sent the diodes to the wrong Fenwick ! ! !

[mat_fenwick]

That line in your earlier post puzzled me a little too, as I didn't remember giving you my address (although I don't remember what I did yesterday half the time!)
Oh well, they say it's the thought that counts...thanks anyway.

The diodes I have used are probably over specced for the job in terms of current, but it should mean they are physically that bit more robust. (Wrapped in heatshrink now so I can't easily check).

[electrokid]

Oh well, they say it's the thought that counts...thanks anyway

My pleasure - sorry it went astray - as long as my Welsh relatives don't find out I confused North Wales with Kingston-upon-Hull

Relay coil current will be around 150mA so 1A diodes will be fine - the ones I sent were 1N4007 - not worth keeping stock of 4001, 4002, 4003 etc they are all rated at 1A. As a ball-park guide always use something rated at least 3 times the current you intend to use. The complex calcs are called 'derating' - the 1N4007 has a current rating of 1A at 20° C and 0A at 175° C and the relationship is linear. So if you run a 1N4007 at 750mA you'd think you'll be ok.

1N4007 at 750mA will have about 0.85 volts across is - so dissipation will be 0.75 x 0.85 = 0.6375 watts. Thermal resistance of the 1N4007 is 50° C per watt so the temp rise in the diode will be 0.6375 x 50 = 31.9° so the diode will run at 71.9° in an underbonnet environment of 40° - at which point the max current spec of the diode has reduced (derated) to about 665mA. So you'd be running it at 113% of its max spec not 75% as it looks at first glance. It will probably work for a little while but it will quickly die.

Heatshrink - excellent

[electrokid]

If anyone is following the headlamp mod discussion it's only fair to mention at this stage that there's a "Mark 2" on the drawing board.

I'll need to do some math and breadboard it before its ready for posting. It uses some electronics plus 2 relays and features adjustable brightness on dim-dip. I'm going to try and include optional bulb monitoring as well but I'll try to keep that as separate as possible so that it could be retrofitted to existing headlamps, the Mark 1 mod, or the Mark 2.

When ready I'll post as a new subject.

[mat_fenwick]

Oh you git!

You wait till I make it and then say there's a Mark 2 'new and improved' version being released.

I'll have a go at splitting this topic from the original and move it into the Technical section if there is a logical point, then you can add to it when you want.

[electrokid]

Oh you git!

Hahaha - you got your own back though - took me ages to find this under it's new title good idea though - thanks for doing that

You wait till I make it and then say there's a Mark 2 'new and improved' version being released

New - not necessarily improved - just a different approach - same functionality as Mark 1 except for the variable dim-dip brightness. Mark 2 has more to go wrong of course and is less serviceable 'in the field'. I still remember being on the Isle of Man with my Morris Minor with its duff OC36 transistor in the flashing indicators that I couldn't replace until I got back to the mainland. Fortunately the IoM is only 30 x 10 miles and you can get to everywhere with just right turns

Part of the challenge with Mark 2 is 'designing out' potentail failures - but whatever I do with it Mark 1 remains easier to fix if anything fails.

[Jaba]

I am dazzled by what you guys are doing by designing and installing new circuits for our BXs.
Can I put in a request for other mods ????

1. Variable intermittent front windscreen wiper. May be as simple as tweaking whatever gives the present interrupted first position wiping.

2.Interface to enable an RF keyfob for central locking. Maybe with indicators that flash once while locking as well.

But don't let me sidetrack you from sorting out the headlights first.

[Vanny]

Jaba, No2 already exists, a couple of Maplin components and a small mod to the existing central locking system. You might find it by a search, but Bob Smith did an almost step by step guide.

No1 i would LOVE! Its a simple as an adjustable delay timer which emits a 12v pulse to trigger the single wipe, i think. In my head this should be easy.

[electrokid]

Yes- search BXClub for central locking mods which are probably still around.

Variable delayed wiper is certainly useful - probably lots of ccts on the web so google it for now and post any interesting links here please so we can chose a decent one that fits the BX well and Citroënise it

[mat_fenwick]

When I was a lad I remember reading my Dad's Citroenian and in the BX column the writer had fitted a variable intermittent wipe. It was triggered by setting the wipers to intermittent, at which point the wipers would operate once. The interval was then set by flicking the wipers on to continuous briefly, from then on the delay was set at the time between first selecting intermittent and switching to continuous. It was a direct plug in replacement as well!
Does this tangent mean I'll have to split this thread as well?