LED question (AGAIN!)

If I want to connect 4 LED in a row, controlled from one switch, coonect to a battery, do I need a resistor at the start of the wire (from the switch)?

And, if I have other NEONS running off seperate switches, from the same battery, does the 4 LED in a row, then need a different resistor?

Can someone explain to me how this works?

First you need to tell us which colour LED's you want to use because each colour requires a different voltage.

ALL BLUE

Adria,

Just checked out your site, EXCELLENT!!

What you've done to some of those cars is what I'm talking about (without the expense of course!).

if you want your LEDs to last longer you should always use a resistor, but which one? I don't know.

gezzzz

jeffpqld wrote:

Adria, Just checked out your site, EXCELLENT!! What you've done to some of those cars is what I'm talking about (without the expense of course!).

OK, let me see if I'm reading this right... you want to get the effects... without the expense. Damn - when you figure out a way of doing that please let us all know

Adrian,

Yeah! Everyone would like to know that one!! Ha ha!

Anyway, I know you have an Aussie distributor, but what is the price for the GEM Rough, and Flood (watertight) in pounds?

I have all my neons being connected next week, and would love to include these 2 above.

In the UK they are £39.50 & £51.50 including Vampire Added Tax

What did we find out for wiring the blue LEDs (Phil's LEDs)? I have the same question and cannot find the answer by searching. A quick answer instead of telling me to search again would be greatly appreciated.

OK. I'm bored - If the only current limiter is going to be a resistor it better be as high a value as possible. So I'd forget about wiring your LEDs in series ~ wire them in parallel each with their own resistor. Allowing 4V for the blue LED @ 20ma, and assuming 14V for your supply (engine running) the resistor needs to drop 10V. Using Ohms law, R=V/I = 10/0.02 = 500 Ohms. Nearest preferred value=510 Ohms.


And now for some ASCII Art... wire each LED like this:


+12V o-----------[510R]---------|>|-------------o Chassis


So why, you ask, have I seen more than one LED per resistor? Because some people like to cut as many corners as possible. But each shortcut costs you the life of the LED. This is becasue LEDs are very sensitive to over-voltage stresses and although many manufacturers count on there being 12V feeding them - this is more like 14 to 15 volts while your engine runs and in certain situations spikes of up to 100 volts or more can be found!

http://www.sto-p.com/pfp/pfp-transients.htm

Without doubt, all this extra voltage appearing through the usual current limiting resistor will shorten the life of a LED. The weakest ones will eventually blow-out at some point.

As far as I know, ICELED designs are the only ones to use a transistor circuit to maintain the current in EVERY LED to a fixed value - no matter what the supply voltage does. The controller also switches off automatically if it sees the supply go above 18 Volts (i.e. in the case where your altenator fails) This happened on my car and I know it happens on many other cars as well. Most other LED products will be toast in this situation. As if this wasn't enough, there are transient suppressors in the circuits as well