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What sort of diode do I need?
kurt - 20/3/06 at 08:40 AM

I'm trying to wire up my supply for the hazards on my MK Indy R1 build. I have used the R1 loom and extended it, and hazards work fine when the ignition is on. If I wire up an additional fused supply from the battery to run the hazards when the ignition key is out, I will end up shorting out the battery, so it would seem I need two diodes, one to protect the ignition on hazard circuit from my additional supply, and one to protect the ignition off hazard circuit, when the ignition is on ( hope that makes sense.) I've looked on the Maplins website and there are loads to choose from. What do I use? Do Halfords do a simple automotive type diode?

Cheers, Kurt

britishtrident - 20/3/06 at 08:49 AM

Just supply it from a fuse that dosen't go through the ignition switch.

stevebubs - 20/3/06 at 10:05 AM

or a 2-way relay that flip-flops between state depending on whether the ignition is on or off.

When ignition is on, hazard circuit draws its power from main loom

When ignition is off, relay closes and hazard draws its power from battery. Rest of loom can't draw power as feed back to ignition-side of the loom is isolated.

Something like R20BC from VWP should do the trick.

Stephen

02GF74 - 20/3/06 at 11:30 AM

quote:
Originally posted by kurt
I'm trying to wire up my supply for the hazards on my MK Indy R1 build. I have used the R1 loom and extended it, and hazards work fine when the ignition is on. If I wire up an additional fused supply from the battery to run the hazards when the ignition key is out, I will end up shorting out the battery, so it would seem I need two diodes, one to protect the ignition on hazard circuit from my additional supply, and one to protect the ignition off hazard circuit, when the ignition is on ( hope that makes sense.) I've looked on the Maplins website and there are loads to choose from. What do I use? Do Halfords do a simple automotive type diode?

Cheers, Kurt


can you draw the circuit - I cannot see how you can wire it to short out the battery but from my undersanding, wiring in the second supply would mean the ignition is permently on.

Once I understand your circuit, I can advise on the diode and how to fit them or the relay version. You would want the relay to be (NC - normally closed when not powered so it does not draw power when ignition is off).

As Mike VVVV says below; you need a fairly big diode to power all 6 indicator lamps(4 main and 2 repeater flashing all at once); depending on the lamp wattage.


[Edited on 20/3/06 by 02GF74]

MikeRJ - 20/3/06 at 01:18 PM

1N4001 is only rated for 1Amp; typicaly indicators will have 12v, 21Watt lamps giving a steady state current of 3.5 Amps, and obviously a much higher inrush current as these are fillament lamps.

Even a 1N5401 would not be suitably rated for this, but would probably survive due to the relatively low duty cycle of the indicators.