Preventing reverse voltage @ 12VDC - which diode?

[Turntable_Terrorist]

Hey guys,

A really simple one (in theory to me, anyway) - I have an LED strobe-effect flasher connected to a pair of LED brake lights (on a car). The problem is that if the left-hand lamp has power applied, the right-hand lamp will also light up (the circuit is completed through the brake switch). As The flasher can be configured with alternating left/right patterns, I would like to know what kind of diode I can put in-line to the wiring to isolate the lamps from each other. It's all running at 12V DC and the current would never be any more than 1 amp.

Thanks for any help!

TT

 

[Dx3]

A 1n4000 series diode will carry 1 amp, but that's its limit. (1n4001, 1n4002, up to 1n4007)
You can get these at Radio Shack. It would be safer to ask for a 2 or 3 amp power rectifier diode.

 

[Turntable_Terrorist]

Hi,

Thank you for your reply.

I live in the UK so I had a bit of a search and found a supplier that stocks Vishay 1N4001-E3 rectifiers. Am I right in thinking these are simply wired in-line (observing diode polarity)?

Thinking about the load, it's not going to be more than a couple of watts, so I think smaller diodes would also cope.

Thanks again....

 

[Dx3]

Yes. A diode is like a flapper valve in a pipe. Flow only goes one way. Then end with the stripe is where the positive comes out. (I'm talking "positive" because you're talking about car parts, which are usually negative ground.) If you put it in backwards, the only thing that will happen is...nothing. Just don't put it in parallel. That would put it across the battery terminals and the battery would try to empty out in a matter of seconds, causing smoke and the crackle of exploding thermoplastic.

ps, there is a place to declare your country in the "profile", I think. Saves a bit of confusion.

 

[Turntable_Terrorist]

Thank you again for your help! I'm off to get some Zener's now and see how it goes. I'll post a video of the completed project once I have soldered them in.

I've also got twin LED VU meters to solder up too - they're being mounted in the rear tail-gate up each side of the window (as you do).. only the 25-core cable I am using for the LEDs only has a couple of strands in each core, so soldering is going to be so much fun. I need the steadiness of a brain surgeon!

I'll get my profile sorted to prevent further confusion.. I know there are plenty of other soldering projects on the horizon to be done as well, so I guess I will be here a little longer.

Thanks again.

 

[tvtech]

I'm off to get some Zener's now and see how it goes. I'll post a video of the completed project once I have soldered them in.

Thanks again.

.

Zeners??? Waiting in anticipation for the Video.

Cheers

 

[Turntable_Terrorist]

Not zeners? Well, whatever you call them (that'll teach me to try and be clever!)... as long as the part number is 1N40001-43 I think I should be spared a puff of smoke!

Microscopic soldering iron tips arrived this morning, so the VU meter project is GO! Not looking forward to it though, 12 LEDs per board - that's 48 tiny wires to solder (96 in total... aarrrgh). As I said, the 25-core cable (so the LEDs can be mounted 'remotely' in the tailgate) literally has 2 or 3 wisps of copper per core, so I'm going to have to solder in between breaths and heartbeats.. much like that guy who carves match heads and grains of rice!

Here's a short video (AVI, Zipped) of the current "covert" LED set up I have - a red/blue dash light, two grille LED strobes and the SHO-ME 11.1005SF solid state flasher that is wired up to the brake (top) and fog (bottom) clusters.



View attachment VW_Polo_Police.zip

 

[lilimike]

Looks neat! but it's a good thing the ocean is preventing you from diving this car all the way to North America because a first look from a police car and it would raise the cost of your project considerably!

 

[Turntable_Terrorist]

LOL!! Thanks.... Same goes for the UK (impersonation of a police officer or vehicle), I would definitely be feeling the stiff arm of the law if I was to attempt to use these lights on a public highway (and before anyone asks, no I have never tried it, nor will I - strictly shows only!). Actually, I got caught last summer for having German number plates (with a UK registration mark) - the policeman just didn't get why us Brits insist on putting German plates on our VW's! My argument was that I was indeed licenced, taxed and insured, plus you could clearly read my registration number; and I had not tried to disguise it in any way

Since our new government came in and abolished the crime targets for the police, I don't even get a second look.