Clean power from Dirty vehicle

[lonesouth]

I am about to start accessorizing my vehicle with some LEDs, not anything important, mostly ingress/egress. I have seen a number of posts about how dirty the 12v system is in vehicles and was hoping to create an easy to find post about how to get clean power from this, and why it is required.

With that in mind, what components are required to provide a clean 12v-14v from our dirty 12v-14v cars, and why do we need clean power?

Thanks!

 

[bshanahan14rulz]

For LEDs, current regulation is a must. Voltage regulation isn't a bad idea either. I used a sharp 12V regulator because it's simple (4 pins, in, out, ground, and an on/off pin that is switched by a variable duty-cycle PWM) and used resistors for each paralleled series string of 3 (they were white, higher vf).

 

[JohnR66]

Don't waste money and time on regulation for LEDs for this type of use. For my door light, I have three 20ma high flux LEDs in series with a 220 Ohm resistor. It gives plenty of light and limits current to around 20 ma at 14.4 volts. Voltage can vary widely without damaging the LEDs.

 

[MiniMag_Crazy_Greg]

I am about to start accessorizing my vehicle with some LEDs, not anything important, mostly ingress/egress. I have seen a number of posts about how dirty the 12v system is in vehicles and was hoping to create an easy to find post about how to get clean power from this, and why it is required.

With that in mind, what components are required to provide a clean 12v-14v from our dirty 12v-14v cars, and why do we need clean power?

Thanks!

I am also thinking of adding accent lights under my dash and aux area lamps in my cargo area of my truck. I am going to wire them into the dome lamp circuit so they come on when any door is opened. I found this: http://www.dealextreme.com/details.dx/sku.27376 and wondering if this will be a waste of $$.

Thanks for any tips!!

 

[lonesouth]

FYI, lm7805 voltage regulator will work with the following caveat:

I used an LM7805 with a 1050ma driver and an R2. I had the LM7805 and R2 mounted to aluminum 1" square tubing, a la amoeba light, mounted with DX thermal silicone. It worked fine, but upon powering from my vehicle, it immediately got hot, then it got very hot. It ran for about a minute until the R2 desoldered itself from the star mount.

So. Now i'm thinking using a dedicated 9-16v driver is my best bet. I'll post back if I find one that doesn't cost more than $5 each. I know that TaskLED has some, but I'm cheap.

edit:

I'm still happy that I haven't smoked anything yet :thumbsup:

 

[Steve K]

With that in mind, what components are required to provide a clean 12v-14v from our dirty 12v-14v cars, and why do we need clean power?

A good question, and something that should be a concern. As an engineer designing electronics for use on construction equipment, there are a lot of design guidelines that are followed. The most basic is regarding "power line transients", such as are defined in ISO 7637.

The basic idea is that the battery bus may carry large positive and negative transient voltages. You can block the negative transients by the use of a series diode, such as a 1N4004. The positive transients can be limited by a big zener diode, and followed by some filter capacitors. After that, add whatever regulator circuitry is needed to drive your leds.

The diodes and filter caps are pretty cheap, really. Probably under $1. It's cheap insurance compared to having to replace a few high power leds.

regards,

Steve K.