electrics help...surface mount relays n stuff

[steveo3002]

found this on a german site , they're headlamp relays but built into this niffy little water tight box

id like something like that as ive had probs with damp and i like things neat n tidy

is this something i could do myself ...I'm sure i could assemble it if i found the parts

[prey]

soldering surface mounts isn't a problem - just tin one pad on the board, slide the component in with tweezers then solder the other end - just have to be a bit more careful not to overheat them but it's not difficult

[steveo3002]

i mean finding the parts etc more so

I'm fairly confident i could assemble it if given the parts

[adamwatson]

Cpc.co.uk will probably have all the bits you need

[cobblers]

Those are through hole relays (not surface mount) and they are dead easy to solder. you wouldn't need to put them on a PCB though, they are just normal 5 pin relays - That PCB has some protection diodes and what looks like a couple of transistors on it, not sure what their purpose is, but they aren't required for normal headlight relaying purposes.

Getting small relays like that, that handle 25/30 amps is more expensive than using a normal relay - If you have water problems, just put the normal sized relay in a watertight box and jobs a goodun.

To be fair though, if you bosh some grease round the terminals and bottom of a normal relay, unless you are actually submersing it or putting it in a direct stream of water then you shouldn't have any issues

[steveo3002]

hmmm do you really think they're up to these nasty damp days where everything sits damp n wet?

I'm a fussy curse word and want it to look neat /factory made , i liked the fact that the one i posted about could be tucked away and hidden almost

by using 4 relays worst load would be 10amps ish for 2x 55watt bulbs ...plus whatever saftey margin id need to allow

[scruff]

I'd get a set of standard automotive relays, a neat little realy box with a cover, the right tools for factory style uninsulated crimps and make it up out of that.

It'll look factory if you hunt for a decent looking relay enclosure and it's more than man enough for the damp conditions. A dab of grease on each terminal as above will ensure it all stays lovely and grot free indefinately.

No need for all that complexity either I'm sure, a couple of standard 30A relays fed +12v by heavy cable and operated by the existing wiring would be fine. Won't take up much room either.

Trouble with relays like that is that if they go mammaries uppermost you need to get the soldering iron out.

I'd also not build a watertight box, because if water gets in (Condensation for example) it can't get out.... water resistant is better.

[Clamity]

I think if I were going to that sort of effort I would ditch mechanical relays and separate fuses and use automotive grade high side switches. They're a bit pricier - I think ones man enough to switch headlights will be about five quid apiece, but you get the advantage that you can truly fit and forget about it. And they often have a status signal on them so you can have a tell-tale on the dashboard for blown bulbs (or shorted wiring) if you care about that.

I've used BTS432's for switching a pair of radiator fans and they worked just fine. The metal tab is live on those so if it's going in a metal box you have to make sure it can't touch the sides by using a neoprene washer or something similar.



In order the legs are: ground, input (connect via a resistor divider to the existing switch), +12V, status output, load.

edit: Went out and found the fan switch I made. Excuse the rubbish tin box, I made that without the benefit of a press brake. It was watertight though after smearing a bit of mastic around the inside of the seams. Also, it was mounted with the wires on the underside.

[honeymonster]

Interesting. Thanks for that info Calamity. Saved for future use!

[jonw]

A bit of veroboard, wire, resistor and relays and you could make somthing similar.

Get it working, make a box and pot it in. No more moisture. You will need to be sure it work though as once potted, it will never come out!!!!

[steveo3002]

thanks for the help so far folks

ive looked for a tidy cover ...aint seen nothing that suits yet , plus i have 3 cars to do lol

[joostvdw]

I'm guessing most people would already know this, but the standard H4 headlight sockets have the same configuration as standard automotive relays. So by using this you can make the relay easily replaceable if they go south (never actually happened to me) and it looks very tidy.

You can also grab a relay board from a random car in the junkyard and mount this somewhere.

Also the "not water tight, make it water resistant" statement is very true, almost nothing is truly water tight so better design it so that is doesn't mind a bit of water.

[g40jon]

reason for the diodes is apparently because the relays can cause a reverse voltage which cooks the high beam led in your clocks (a problem on certain vw models.the mk2 polo being one of them)

z8.invisionfree.com/POLO3/index.php?showtopic=14304

oh and my other tip... for the trigger wires taken from the original headlight plugs, rather than cut the plugs off, I have used spade crimps. This gives you a fail safe option should the relayed loom fail. simply un-plug and go back to using the std headlight wiring. Dim lights is better than no lights!

[steveo3002]

never heard of the led problem...ive got 2 golfs mk2 and a polo 2 ...had em relayed for years but trying to redo em now nicer

[cobblers]

Older VWs use a normal bulb with a blue cap over it for the high beam light, since blue LED's weren't commercially available until about ten years ago (Which is why your Polo and golfs were fine).

The relay coil releases a spike of reverse voltage when it's turned off - I wouldn't imagine it's anywhere near enough to really damage normal bulbs (since it's such a short spike), but LEDs are fairly sensitive. Anything up to a mk3 golf uses normal bulbs, maybe even MK4 too (I've never had the clocks apart). A protection diode is easy to fit though, and pence.

[Clamity]

Nov 25, 2011 19:35:08 GMT cobblers said:

Older VWs use a normal bulb with a blue cap over it for the high beam light, since blue LED's weren't commercially available until about ten years ago (Which is why your Polo and golfs were fine).

Was going to say the same thing, though I did once have an '82 Polo Coupe with an orange LED for the main beam which I guess would have been a bit more fragile. As you say, It's always good practice to fit back EMF diodes anyway just in case something fragile gets added on later.

That reminds me, didn't Nissan have to do a wide ranging recall fairly recently because of this? Some innocuous relay with a built in protection diode with a tendency to go wonky was causing problems with something else on the same circuit which was safety critical.