Multiple wires to power OR tap into a single wire

You are installing 4 LEDs in your car. You have a ground and a power source. Do you need to run a wire from each LED to the power source and ground? Do you need to run 4 wires to your switch?

You've got a basic setup with just 1 LED. Run 1 wire from your power source to the positive lead on the LED, and another wire from the ground of the LED to the ground/chassis of the car.

Quite simple. Like this diagram:


Now, you want more than just 1 LED. You copy what you did with 1 LED, but apply it to 4 LEDs.

It looks something like this:


That's a lot of wires! And if you're installing the LEDs in the very back of your car, things get messy quite fast. Wouldn't it be better to run a SINGLE wire from your power source to the location of your LEDs? Once that wire is at the location you want, you can "tap into it", "split it off", "tee it off", etc... As long as the metal connects, an electrical connection is made, and you can pretend it is a single wire.
This is better! Especially if the LEDs are a long distance from your power source.


Suppose you have a water spigot on the side of your house. You've got a brand new lawn and 4 brand new gophers. You want to give each gopher its own "gopher drinking fountain". You get a 4-way garden hose Y splitter and 4 100 foot garden hoses. You run them 100 feet away to your lawn.
Lots of hose


Is this really the best way spend your saturday? Running 400 feet of garden hose? Instead you would probably get a single 100 foot hose, and a few 5 or 10 foot hoses like this!
Less hose. Happy gophers.


Electricity is the same way!

Remember: you always need to fuse your lights.

You can run a wire from the battery (and put a fuse as close as possible - maybe 12 inches). Run the wire into your car, split it off to a few switches, and split off some lights to the other ends of those switches.

so the moral of the story is you always have to make your gophers happy????

great write up phil and quite amusing at the same time

That analogy worked suprisingly well.

I just took all the positive ends to the LEDS and attached them to one power wire from the battery utilizing an electrical screw top thing. WOrks wonders. I also did the same thing ffor the ground as well.

could you run a live power wire in a circle around your car and tap in to that with little wires? would that make the first led the brightest and the last dim?and then run the ground likewise?....just for accesibility?

i accidentally hit a gopher the other day.
=(
i think it was a gopher...

Don't forget the resistors...

What I want to know is (I have been searching)...Im working on a project where series wiring wont work (makes a difficult install)...so I have been resisting EACH led (there are 5 of them) although they all are coming from the same power wire.

For example...One power and one ground wire running to five seperate leds, all of the leds have a resistor.

It works well but I could cut down on a lot of soldering IF I was able to resist the power wire in line before the leds.

Like this "wire-resistor-split off to 5 leds"
Instead of like this "wire-split off to 5 resistors-soldered onto 5 leds"

I was trying to explain that so I wouldnt confuse you...I dont know if it worked lol

Culokin wrote:

What I want to know is (I have been searching)...Im working on a project where series wiring wont work (makes a difficult install)...so I have been resisting EACH led (there are 5 of them) although they all are coming from the same power wire. For example...One power and one ground wire running to five seperate leds, all of the leds have a resistor. It works well but I could cut down on a lot of soldering IF I was able to resist the power wire in line before the leds. Like this "wire-resistor-split off to 5 leds" Instead of like this "wire-split off to 5 resistors-soldered onto 5 leds" I was trying to explain that so I wouldnt confuse you...I dont know if it worked lol

thats simple to do, make you own voltage regulator.
http://www.oznium.com/forum/topic8468
it will regulate the voltage down to a preset voltage, and the you can add as much as 2amps of LEDS, which is about 100 LEDs at 20ma each. If you do run the regulator at 2amps then you better put a heat sink on that puppy or you will burn the regulator up.

Thank you. So there is no way to run one resistor to 5 leds?

The thing is I make lots of this particular product and im scared to try the voltage regulator because it looks easy for me to screw up and this will be going out to lots of people lol. I will stick to soldering in each resistor if I have to

well, you can put 5 LEDs on one resistor but you need to recalculate the resistor. The resistor you received from Oznium is not calculated for mroe than 1 LED, and wil start dimming the LEDs as more are added.

so use this to find which resistor is best for 5 LEDs, I've done this with 8 LEDs so I know it will work, but you have to have the right resistor.
http://led.linear1.org/1led.wiz

Wow I get lost with the diode forward voltage and diode forward current? WTF? lol

so...gophers like leds? and who wants gophers in their lawn?

alien... since he is wiring each led in it's own parallel circuit after the resistor he should be ok with the single resistor... or will the amperage kill the resistor?( i wouldnt think it would.... but it depends on how many leds he is putting onto one resitor)

he just wants to wire the leds in a series-parallel circuit having the resistor in the series end of the circuit before it splits off into the parallel.... instead of having the resistors in the parallel part of the circuit after the split from series

only time i would see that as a no no is when there are to many led's for the watt rating of the resitor

unfortunatly resistors aren't that simple. Yes they can handle multiple wattages, but the amperage and voltage are both controlled by the resistor. So if you don't want your amperage being cut short of where it should be, then you better recalculate the resistor. Amperage and forward voltages are both calculated into the resistor value, and if you get it wrong then you can cut your LED short of its much needed amerage and/or voltage.

In or lamens terms, it matters a whole lot what amperage is going through the resistor, even from just 2 LEDs can hurt it.

diode forward voltage = LED voltage requirement
diode forward current = LED amperage 20ma for 5mm LEDs



quotes from a past topic http://www.oznium.com/forum/topic6255

alienyoungjr wrote:

the resistor you get from phil have been calculated for one LED not multiple so you can do it but you are hurting yourself cause you will loose brightness. Lets show you the evidence on the change to a resistor if you add an LED and calculate the right resistance for those LEDs Single LED 12v power 4v LED input 20ma load = 470 resistor Double LED in parallel 12v power 4v each LED input 40ma total load of both LEDs = 220 ohm resistor The change in amperage is the main causing factor and will cause things to change such as brightness. PLEASE PLEASE PLEASE do't do that cause you paid good money for a bright LED and why waste that with a silly mistake as that.

alienyoungjr wrote:

The function of resistors is to restrict the flow of electric current, for example a resistor is placed in series with a light-emitting diode (LED) to limit the current passing through the LED. Change the current by adding more LED's in parallel and the resistance value of the resistor must change to compensate the change. If you still don't believe me then ask you physics teacher and he will comfirm that I am correct or even ask Adrian cause he knows way more than me.

I say make this a sticky!

hmmmm.... definitly confused now...

i can understand how you would need a smaller resistor if the leds were in series after the resistor... but with the parallel circuit.... the amount of current through the reisistor would go up from what i understand....


wait a sec... in order for you to get more current..... if the resitance stayed the same... availible power would have to go up...... and since it does not change in your vehcile.... current drops... led's not as bright...


it's weird cause i just wired some led's into my window/lock panels in my truck... one side i soldered a resistor to each led.. and then another in series to actually dim the 3 leds that had 1 resistor each( it wasway to brite for driving at night) on the other side i used two resistors attached to each other to bypass soldering a resitor into each led... and both sides are the same brightness



i know this stuff.... but having only 8 hours of sleep in the past 3 days doesnt help... and well it's been a little over a month since i was in my basic electronics class (attending uti for auto tech)


so basically a regulator would be best for everything.... but cost wise it is not the best way to go... thus resistors are used... but they "use up" the volts and amps that they restrict... where as a regulator allows you to control just the volts allowing amps to flow "freely" atleast that's what it is in a since right?

CrashKing wrote:

hmmmm.... definitly confused now... i can understand how you would need a smaller resistor if the leds were in series after the resistor... but with the parallel circuit.... the amount of current through the reisistor would go up from what i understand.... wait a sec... in order for you to get more current..... if the resitance stayed the same... availible power would have to go up...... and since it does not change in your vehcile.... current drops... led's not as bright... it's weird cause i just wired some led's into my window/lock panels in my truck... one side i soldered a resistor to each led.. and then another in series to actually dim the 3 leds that had 1 resistor each( it wasway to brite for driving at night) on the other side i used two resistors attached to each other to bypass soldering a resitor into each led... and both sides are the same brightness i know this stuff.... but having only 8 hours of sleep in the past 3 days doesnt help... and well it's been a little over a month since i was in my basic electronics class (attending uti for auto tech) so basically a regulator would be best for everything.... but cost wise it is not the best way to go... thus resistors are used... but they "use up" the volts and amps that they restrict... where as a regulator allows you to control just the volts allowing amps to flow "freely" atleast that's what it is in a since right?

correct, a voltage regulator only controls volts, and has a max amp output of 2 amps, and they requires a heat sink. Resistor controls both amps and volts, but 2 LEDs will not show a drastic change, but keep adding more and watch the brightnesses drop.

alienyoungjr wrote:

CrashKing wrote: hmmmm.... definitly confused now... i can understand how you would need a smaller resistor if the leds were in series after the resistor... but with the parallel circuit.... the amount of current through the reisistor would go up from what i understand.... wait a sec... in order for you to get more current..... if the resitance stayed the same... availible power would have to go up...... and since it does not change in your vehcile.... current drops... led's not as bright... it's weird cause i just wired some led's into my window/lock panels in my truck... one side i soldered a resistor to each led.. and then another in series to actually dim the 3 leds that had 1 resistor each( it wasway to brite for driving at night) on the other side i used two resistors attached to each other to bypass soldering a resitor into each led... and both sides are the same brightness i know this stuff.... but having only 8 hours of sleep in the past 3 days doesnt help... and well it's been a little over a month since i was in my basic electronics class (attending uti for auto tech) so basically a regulator would be best for everything.... but cost wise it is not the best way to go... thus resistors are used... but they "use up" the volts and amps that they restrict... where as a regulator allows you to control just the volts allowing amps to flow "freely" atleast that's what it is in a since right? correct, a voltage regulator only controls volts, and has a max amp output of 2 amps, and they requires a heat sink. Resistor controls both amps and volts, but 2 LEDs will not show a drastic change, but keep adding more and watch the brightnesses drop.

yeah i knew it all.... just not at that point in time... lol

i actually saw a big difference saturday when i was changing my dash lights out.... 3 led's in each one.... i tried one led+resistor on a 9 volt(i always test them after i do something to it...)... then the 3.... def a difference

Yea water is a good analogy to electricity, i forget some times after all this MECP drilled into my head, some people are still starting at the basics, don't be afraid to ask, or try anything guys, just research and ask first!