Wiring/Electronics Help Needed for Working Lights

[Hiroboy]

Guys, I need some help, on my 1:12 Skyline I want to add working lights.
2 off at the front for the headlights and 2 off at the rear for Tail Lamps.
But I bugger all about electronics. I will use the boot (trunk) space for the battery, switch etc.
What I want to use is
For the lights I will use LED's as they do not get hot, PP3 (9v) Battery and a Switch.
Can anyone help me get started. I would be great to get them all on a timer, say 1 minute on, 2 minutes off. would this be very hard.
As I said I know nothing about this stuff. so all the help you can give would be much appreciated.


Thanks in advance

[Vric]

this link can give you some basic idea

http://www.briansmodelcars.com/tutor...D=31&CurPage=1

[Jurva]

I think that if you use two super bright blue and two ordinary red, and mock up them in a series. That would require that 9v you mentioned.

I have planned this for a while for my aoshima vip hiace. Maybe I put the battery as a fridge.

[willimo]

I don't know what motivates you to want it on a timer, and it may just be because you want it that way. But instead of a timer, you could use a reed switch. A reed switch is a small switch that uses a magnet passed over it to open or close a circuit, and is often used by model railroaders to activate trackside animation when a particular rail car passes over a certain spot (the switch would be buried under the track). Using a switch such as this, you could turn the lights on and off without having a switch poke out or having to touch the car at all. Just an idea. And I would be very curious to see what you find out as far as this circuit goes, because I don't know squat about electronics either.

[008]

Google around for "circuit kits". A few months ago I was searching for something similar and came across a site that had tons of different kits and schematics for those things. They had blinkers, timers, sequential, etc and all on a miniature scale. Some even included the LEDs.

[Ferrari TR]

Somewhere in here I found a bunch of stuff on model lighting.
Starship Modeler
I wish I could be more specific, but I did'nt know there was going to be a quiz...lol

[moe171]

I have never put lighting into any of my cars but I do know about electronics. I work on electrical systems on Huey's and Cobra's in the U.S. Marine Corps. When I first started in electronics I was told that the basics of any system would be Source (being your power source), Load (In this case would be the Light) and Ground. We use a flasher relay to make our lights flash. Which would be way to big to be able to fit into any car.

[DSM-Mark]

I've done a bit of research into LEDs for making a flashlight or headlamp out of LEDs (for light-weight hiking). LEDs only require a voltage applied to them that is greater than their forward voltage to activate. So if the forward voltage is 4 Volts and you apply 9 Volts across it, it will activate. However, the way you adjust brightness and consequently life of the LED is through current. Most often, you want to have a resistor of some sort in the path to limit the amount of current flowing through the LED. Otherwise, the only resistance the circuit sees is basically the resistance of the wire, so it's sort of like crossing the terminals on a battery with just a chunk of wire.

Here is a link with some calculations you can do with LED circuits. THIS IS NOT MY WORK. I take no credit for it. http://www.freewebz.com/led_headlamp/

If you need help with some of the calculations, I should be able to help you out. Just let me know what you want for #s of batteries (1 or 2, I'm guessing).

Hope this helps.

[1ofaknd]

here's a small diagram...it's not as hard as you might be thinking...

[cyclone1410]

Originally Posted by 1ofaknd

here's a small diagram...it's not as hard as you might be thinking...

The only problem (and it is only a small problem) with the above diagram is it is dependent upon the voltage of the battery source and if the lights are in fact LED's. If the battery voltage is too high for LEDs it will blow them up. The diagram shows that the LEDs are connected in parallel across the battery meaning that each leg of the LED has a direct path to a terminal of the battery. Connecting LEDs in parallel is by far the BEST method as it is easier to fault find and provides consistent brightness across all LEDs.

Now assuming for a moment that the battery source is 9V and the forward voltage of the LED's is 2V a resistor is required to be placed in one leg of each LED - it can go in either the positive or negative leg (remember LED's are polarity conscious). The only other bit of info needed is the forward current of the LED. Typically this is around 20mA or 20 thousands of an AMP. To calculate the resistor size required we know that we have to drop 7V across it (9V supply minus 2V voltage of the LED) at 20mA (the forward current of the LED).

Formula V (voltage) = I (current) X R (resistance)

We can transpose this to become

R = V / I

R = 7 / 0.020 (20mA)

R = 350 ohms

The nearest regular resistor size is 330 ohms or 390 ohms. Alternatively you could use two 180 ohm resistors in series. The final figure will depend upon the forward voltage of the LED and the typical forward current of the LED.

I hope this helps. PM me if you need further info.

[appleseed]

actually, if you want to maintain brightness in any one LED, you would not go parallel but go in series. first off, for the electronically inclined, parallel ckts maintain a constant voltage across the legs of the LEDs. however, in this case, the brightness of the LEDs are current dependant which means you want the same current flowing through each of the elements. that is where a series ckt would work out best.

in the case of the parallel circuit, you can still get this to work but you don't need a resitor at each leg, just put a resistor in series to the source and that would give you the same voltage drop across each parallel LED element.

the only thing i would say here is that LEDs are very forgiving with respect to voltage. LEDs have a min and max operating voltage with the typical voltage listed on the package. you'll have to look at the spec sheet of the LED element itself.

i posted something a while back but don't know if it still exists here anymore...

i would suggest buying a breadboard from radioshack and a couple of diodes and play with them until you find the setup that you need.

a

[Future Boy]

Having the LED's in the car, you could also use fiber optics for other lights or guage lights

[cyclone1410]

Originally Posted by appleseed

actually, if you want to maintain brightness in any one LED, you would not go parallel but go in series. first off, for the electronically inclined, parallel ckts maintain a constant voltage across the legs of the LEDs. however, in this case, the brightness of the LEDs are current dependant which means you want the same current flowing through each of the elements. that is where a series ckt would work out best.

in the case of the parallel circuit, you can still get this to work but you don't need a resitor at each leg, just put a resistor in series to the source and that would give you the same voltage drop across each parallel LED element.

the only thing i would say here is that LEDs are very forgiving with respect to voltage. LEDs have a min and max operating voltage with the typical voltage listed on the package. you'll have to look at the spec sheet of the LED element itself.

i posted something a while back but don't know if it still exists here anymore...

i would suggest buying a breadboard from radioshack and a couple of diodes and play with them until you find the setup that you need.

a

From an electrical engineering perspective the parallel circuit is still the best. It also allows you to individually switch groups of LEDs on and off independently of others. It also makes fault finding easier in that if one LED goes faulty it doesn't stop the others from working as would be the case if they were in series. As LEDs are manufactured in great numbers and the consistency of silicon doping on each LED is identical the brightness does not vary to the naked eye. The variation comes between types and/or colours of LEDs but since you would have the same types at each end of the car this variation between colours is not a problem. If you don't believe me just have a look at the LED taillights on BMW's and other European cars and the LEDs used in traffic lights and at level crossings - they are usually in parallel. How do I know - I designed LED units for crossing installations for a company in Australia.

Regards

C

[675datsun]

Steve, I know this goes completely against the "scratchbuilt" them but if you're as lazy as I am how about picking up one these 1/24 scale die-cast kits with lights in them?
This is an S15 with a push button on the bottom. The stay on for 5-7 seconds. Really bright too.

front. There are 2 blue bulbs for th headlights. 2 underbody lights and 2 for the amps. Taillights are not lit.

2 AA batteries

body off

wiring
You could easily wire the tailights instead of having the underbody lights...maybe use the amp lights as an interior courtesy light/backlit gauges
Well if you need more close-ups of the wiring or a couple more shots let me know.
go to the "S15 lights" album for a few more shots
http://community.webshots.com/user/alving08

[appleseed]

Connecting LEDs in parallel is by far the BEST method as it is easier to fault find and provides consistent brightness across all LEDs.

i agree with this statement wholeheartedly with the caveat of it providing consistent brightness across all LEDs. a series ckt would achieve this better than a parallel one as each element is guaranteed the same current. i also understand that when one element goes out in a series ckt, they all go out thus making it a headache to find the fault. however, when we talk about consistency in brightness, few can argue against the fact that a series ckt is superior to a parallel one.

in real world applications, such as that of your tail lights, the parallel circuit is indeed better as redundancy plays a dominant role... one goes out, the others stay on. with the added incentive of high electrical troubleshooting costs, parallel is the way to go.

given, parallel circuits ensure that each element is delivered the same voltage. however, this constrains you to working with LEDs which operate with relatively the same operating voltages. some will still go on outside their optimal operating voltage but be either brighter or dimmer depending on the LED. this is where dropping resistors would come into play. however, 1/24 models are small and interior space is tight and limited making incorporation of resistors less than ideal.

parallel ckt design is undoutably the best way in the practical world but not necessarily so in the scale modeling world where the batteries are limited in size, voltage, and current (parallel circuits are more demanding on the source in that respect). i know you understand my perspective and by no means do i doubt your engineering prowess. i am merely stating that with such constraints and limitations in our wonderful, yet sometimes frustrating, hobby, the series circuit may be worth a second look.

cyclone, great post and thanks for your insight!

a.