Playing with LEDs

[mudbuggy]

I went into our electrical supply house friday after work and asked if they had any led stuff. They handed me an led light and a lense all for $6. But they warned me not to put more then 3 volts into the thing or it will cease to work. Well I came home and had been racking my brain how I would reduce 12 volts to 3 then I looked up on my toolbench and saw a bunch of D batteries.

My original idiea was to add led light to the overhead lights for the map lights, but once I got the thing working, I started to think about making other lighting devices. Not spot lights for running down the road, but at least flood lights for when we are at the cabin after dark. Anyways here's the pictures from me playing around with my 6 dollar led.

Oh yea, they told me that this led is a .5 watt led, red in color and doesn't need a heat sink. Here's some pictures from playing with leds this afternoon.

 

[sweetk30]

to drop volt's for led's its called a resistor . . . .

cute build / play keep it going.

 

[mudbuggy]

Here's some idea of the light working in light and dark. The 30 foot shot was on the Eagle Globe and Anchor and the US flag. I guess I should have done the same on the 30 foot shot as I did with the 60 foot shot. Oh well, guess I could tomorrow.

 

[thatK30guy]

Does anyone make LED lights for our years of trucks in the tail lights, park lamps, side markers, roof, and tail gate lights?

 

[mudbuggy]

yep superbrightled.com google them, they will give you a vehicle app chart. You can figure it out from there.

 

[TheBeast_88K5]

I swapped my old tail light sockets for Honda Civic sockets.
Now, I can get replacement led bulbs at any autoparts store.

 

[NorCalKid]

Details please? I have been thinking of swapping out my front sockets to a newer model of something, just haven't had time to poke around the pick'n pull recently

 

[Fordum]

Thought I would give you a little information that might help. I suspect that you will not need it, because there are better things out there, but someone here might be able to use it.

You normally get more information about an LED than you posted, but we can work with what you got.
You say its a .5 watt@3 volts.
OK, that means you divide the watts by the volts to get the current it should draw.
.5/3 equals 0.166666666666667 amps.
Round that down because you do not want to cause it to draw more amps, and you get .16 amps.

The current in a series circuit is the same at all points in the circuit.
The way to look it a circuit like this is to figure voltage drop.

NOTE: For any electronics guys out there, I know what all I am leaving out and oversimplifying........

You start out with 12 volts at the positive terminal, and wind up with zero volts at the negative terminal.
So, you "lose" 12 volts around the circuit. You want to lose 3 volts of it across the LED, so you have to lose the rest of it across a resistor.
And that loss has to be at .16 amps.

So, you have to lose 9 volts@ .16 amps.
Resistance equals volts divided by amps.

9/.16 equals 56.25 ohms.
So, if you put a 56.25, ohm resistor in series with your LED, it would work on a 12 volt system.

NOTE: watts equals volts time amps, so the resistor will have to dissipate
9X.16=1.44 watts, so you are going to need a pretty heavy resistor.

All this sounds great, except there is a problem. A truck's electrical system is not 12 volts.
When you crank it, it goes up to about 14.5, and all the figures change.

The current across the diode goes up to a little over .19 amps, and the voltage goes to 3.62 volts, or .69 watts, which is bye bye .5 watt LED.

So, you can do the figuring for 14.5 instead of 12, which I have done in the distant past and got LEDs to work on car systems.

But, you are better off building a small power supply to control the voltage going to the LED, which will hold the voltage going to it no matter what the supply voltage goes to, and can be done with a resistor and a Zener diode.

But, better still, you can buy a premade voltage regulator for an LED which is much more stable.

However, all this work can be eliminated these days. I do stuff like this for a living and fun, and even I don't do it anymore.

Go someplace like this.
http://www.superbrightleds.com/cgi-bin/store/index.cgi?action=DispPage&Page2Disp=/1157.htm
There are tons of others if you don't like their prices.

Buy an 12 volt LED of the color and brightness you want, and it will have the circuitry built in to regulate it.

For instance, an 1156 replacement tail light bulb will be much brighter than the one you have, you can buy a single contact socket off that site, or get one from the taillight off an older car in the junkyard, and you are in business.

Playing with LEDs like you are doing is a lot of fun, and I sometimes still do it. But I quit doing it for actual use a long time ago.
Now I just buy off the shelf unless its a very special application.

Also, I know I could have done all the figuring for 14.5 to start with, but sometimes an alternator might put out more than that, plus if it quits, or the engine is not running, the LEDs will be dim.
But the main reason was I wanted to demonstrate the problems with using a straight resistor in that it does not adjust for different voltages.

 

[dyeager535]

Does anyone make LED lights for our years of trucks in the tail lights, park lamps, side markers, roof, and tail gate lights?

Yes. Go to ebay, search whatever bulb number you need (194, 1156, etc) and "led" and you will find likely thousands of them, sold directly from China where they are made. FAR cheaper than you can get them domestically, and I have a very hard time believing they aren't the same items. So cheap it's worth buying them just to play with.

Some pointers:

Universal facts: the more LED's, and the more directions the LED's face, the better. The bulb needs to be the same color as the lens. Green to green, red to red, clear to clear, etc.

The "festoon bulbs" (dome light bulbs) made with SMD's are far brighter than you can tolerate to look at comfortably with no lens. And brightness/less draw/less heat are the points of LED's, right? They do NOT do well behind the opaque lens that is stock (dimmer than stock), LMC sells clear ones for this purpose. Someone on here (apologies for not remembering who, Blue85?) made some lenses out of the fluorescent fixture diffusers you can get for dirt cheap...heat up a bit with heat gun, etc., bend to shape. IMO you REALLY need an actual diffuser to spread the light, even with SMD the spread of light is far less than incandescent. Also, the festoon bulbs I got to test are simply circuitboards soldered to the "caps" that contact the bulb socket. With vibration from bumps and perhaps light handling, the solder breaks free from the caps and the light no longer works. I re-soldered one of mine and it came loose shortly afterwards. Probably an easy fix to ensure vibration can't loosen the solder, but it's an issue.

You can't replace the 194's in the side markers with LED's. Obviously LED's can only be placed in a socket one direction (IE + to + , - to -) because thats how they work. The side markers that also blink (fronts) obviously switch polarity...meaning you can get an LED to either act as the marker, or the blinker, but not both. Brightness in these positions is not that different than incandescent. So they work ok for the rear position.

Replacing the "check engine" bulb didn't work for me. The bulb stayed constantly lit, albeit dimly. Brake and turn signals worked.

Amazingly, LED's are supposed to use PWM to dim them, however my Dad put LED 194's in the dash sockets, and the dimmer works to an extent. Our dimmers suck in general, and you can find 12V PWM controllers that are quite small and pretty cheap if you wanted to modify the dash wiring to take it.

The larger bulbs (brake, backup, etc) depend on position as to how they look. The brake ones work good, but again you must ensure that they have multiple LED's facing outward, not just backward. You will find many are circuit cards stacked on top of each other to accomplish this. That works good. Only way you can tell they are LED is the way they look as they blink on/off as the turn signal. Somewhere on the order of 32 LED's. I am unsure how the SMD's work in that position. One issue of concern is the bulb hitting the lens. Found that to be an issue with the 194 SMD's in the rear marker position, and the standard LED's in the brake position. It's VERY close, so the design is going to be the deciding factor here.

The reverse lights do NOT work good. I suspect much of that is due again to the opaque lens for reverse. The light is not as bright, and is too focused towards the side of the vehicle, and doesn't spread out enough to be of much use. With better condition lenses (or aftermarket clear) this may be less of a concern. But as always with the LED's, you need them to face the direction(s) you want illuminated.

In general, be careful with bulbs that have plastic covers. I've found them to not be affixed to the base very well...since you have to twist the bulb to remove/insert them from the socket, if the base doesn't move, but the top does, you have a problem.

Some of the 194 bulbs have pretty poor "legs" to contact the socket. I had one rust completely off. I'd use dielectric grease on that style. I'm not convinced yet that any of the LED styles will last long term, vibration, and corrosion since the housings aren't air tight, etc. But I've had some on there for over a year (little driving) and not had any failures except the one rust issue and the one festoon bulb. No tlike our bulbs are hard to change anyway, but it would be nice if they lasted as long as they should, which is probably forever.

All I bought were not damaged by inserting "backwards" (polarity) so they've gotten smarter in design of them.

I've got an electric flasher, so no clue if these would have worked with the original style flasher. I know that can be a problem with LED's.