New to the site and Venturing into some LED work for my truck. Done the basics on the insturments and what not. But I would like to build some tail light panels to replace the stock bulbs.

I am planning on using HP Agilent Superflux diodes. VF=2.25v @ 30mA.

Ive read over Bill_Marsden's blog on leds and regulators (understood some of it) and was trying to put together a regulated circuit so as I would have consistent output weather the truck is running or not. The number of LEDs is not set as I still need to design the PCB for it, but if any one could give me some feedback on if i went with this many LEDs, would it work. Or if there is a better way to build this. Im all ears and would like to learn.


Here is the basic layout.

Thanks

 

oops.. new to the site but missed the rules.. (mostly because they are not very clear or easy to stumble upon IMO) but "No Discussions of Automotive Topics"
Just the mention of tail lights will lock this post. Should have said a "ring light for your amateur owl watching camera" or some other crap.. welcome though. please come again

 

Yeah well... Is the circuit right or not? Thanks though.

 

There is no need for the voltage regulator. It is just a waste of power. The leds will work fine at 12V.

You are going to have issues with Leds in parallel. Leds have different voltage drops. When they make those panels, manufactures buy leds in big batches. They then test and sort them so they get a matched batch per panel.

You would be better off getting three high wattage leds in series.

You would also be better to use a buck current regulator instead of the resistors. You circuit will consume less power.

 

Actually they are 3 leds in series. They just use a common ground. The leds I am using are sorted and matched from the manuf.

What is a buck current regulator?

 

Actually they are 3 leds in series. They just use a common ground. The leds I am using are sorted and matched from the manuf.

What is a buck current regulator?

No you have 20 sets of 3 leds in parallel.

 

Here is a 300ma one

http://www.ebay.com/itm/300mA-Curre...185?pt=LH_DefaultDomain_0&hash=item51a4a2a7c9

Of course you can build one. I think this one uses the pt4115 and is for ac but can easily be hacked.

 

Don't count on it. You should check the voltage drop of all of them yourself.

Oh and here is a better buck regulator.

http://www.digikey.com/product-detail/en/3021-D-E-350/788-1113-ND/3114429

They make them in all types of current ratings. They even make one or two that are adjustable. I use the 700ma adjustable in a lighting project. If you decide you want to control your light with an mcu, they have a nice 5V regulated output to power an mcu or digital circuit.

 

So am i just mixing the 2 configurations up?

And thanks for the info on the buck regulator. Ill look into that.

 

So am i just mixing the 2 configurations up?

And thanks for the info on the buck regulator. Ill look into that.

You have a combination of both of these above.

 

You should be aware that the danger of putting leds in parallel and using one buck regulator to regulate the current, if you loose one or two strings of LEDs, the rest of the leds could go too, due to too much current.

Another reason you are better with series only. If one goes out then the whole string goes out until you can repair it.

 

Thank you for all the help. Ive been looking at the BuckPucks and higher powered (700mA) quad led boards that may fit the bill nicely. And not to mention be a heck of a lot easier to wire up.

 

That is the one huge limitation of this forum. It misses out on a huge amount of great DC discussion because it bans Automotive discussion. I have heard the "Reasons", and they don't make sense to me. Just limits forum growth, and it's not my forum, so it is what it is.