Simple LED wiring what do I need?

greasyspoon · Post by **greasyspoon** » Fri May 29, 2009 3:24 pm

I know this is basic stuff but I have never one it before. I am wanting to wire my Cylon raider but I am not sure what battery type, and resistor to use. This will be just a simple one off no blinking lights or anything.
I purchased some Phillips Christmas tree light to get the LED out of them.
I want 4 blue LEDs (engines) and 2 Orange LEDs (front).
I believe the voltage is 2.2 (blue) and 3.8 (orange) and assuming @ 20ma
My friend suggested 4 AA batteries as a source (should be 6 volts) and with an 150 ohm resister with a switch after the battery. Does this sound right?

If not what would you use if you wanted to run 6 LEDS off of batteries?

What would I use if I just wanted the 4 blue LEDs?

I figure the circuit would look this:
Battter ----- Switch --- Resistor ---- Blue—Blue----Blue –Blue -------Orange – Orange (wire back to battery to complete the loop)

Sorry for the simple questions I don’t remember my physics classes from college to well. I will get my parts a radio shack if you know of part numbers.

Thanks for any help I can get.
Jon

Umi_Ryuzuki · Post by **Umi_Ryuzuki** » Fri May 29, 2009 3:47 pm

Your wiring set up as written needs about 16.4 volts.
As written, you have wired the LED in series.

If you want to use 6 volts, you will probably may need
a 1/4 watt resistor in there at at least 150ohm, and all the
LED should get their own positive and negative leads once
the power enters the model. That is called wiring in parallel.

greasyspoon · Post by **greasyspoon** » Fri May 29, 2009 4:04 pm

so what type of Batteries do I need to get and How many?

macfrank · Post by **macfrank** » Fri May 29, 2009 4:29 pm

You can use this single LED calculator.

if you have more than 1 LED of a single type, you can use the more advanced serail/parallel LED calculator.

One way of simplifying your circuit is by using only white LEDs and colored filters to produce the colors you want (use clear colored paints to make the filters).

greasyspoon · Post by **greasyspoon** » Fri May 29, 2009 5:09 pm

I have looked at the LED Calculator, but I am not sure what my voltage should be either. I had a friend tell me 6, while it was posted here to use 12.

USS Atlantis · Post by **USS Atlantis** » Fri May 29, 2009 5:53 pm

greasyspoon wrote:I have looked at the LED Calculator, but I am not sure what my voltage should be either. I had a friend tell me 6, while it was posted here to use 12.

If you run your LEDs in series - as your circuit diagram above shows - ADD the voltages of all the LEDs together - Blues are usually 3v, Oranges are usually 2v

So the 4 blues and 2 oranges would total 3+3+3+3+2+2= 16v total to run that string

I would suggest running parallel
/ - resistor - Blue - \
| - resistor - Blue - |
| - resistor - Blue - |
Battery(+) - switch | - resistor - Blue - | - Battery(-)
| - resistor - Orange - |
\ - resistor - Orange - /

That way you only need 3v to run the entire circuit

macfrank · Post by **macfrank** » Fri May 29, 2009 5:58 pm

greasyspoon wrote:I have looked at the LED Calculator, but I am not sure what my voltage should be either. I had a friend tell me 6, while it was posted here to use 12.

The minimum voltage is going to be the minimum required to light the LED up, which varies from around 2V to 4.5V or so, depending on the LED.

The power supply you use depends on whatever you can find that is convenient. No point in using a 12V power supply when you have a 6V (or 5V) supply handy (as long as it can provide the current).

For example, using the typical values for a white LED (as listed on the LED calculator page; your actual numbers may be different):

Forward voltage: 2.2V
Forward current: 20ma
6 diodes
6V power supply

The power supply should deliver 120ma, minimum. In this case, a 200ma or 250ma 6V wall wart should do the trick.

greasyspoon · Post by **greasyspoon** » Mon Jun 01, 2009 9:16 am

SCC-7107 USS Atlantis wrote: I would suggest running parallel
/ - resistor - Blue - \
| - resistor - Blue - |
| - resistor - Blue - |
Battery(+) - switch | - resistor - Blue - | - Battery(-)
| - resistor - Orange - |
\ - resistor - Orange - /

That way you only need 3v to run the entire circuit

What size resistors do I need? Would the blue resistors be a different size vs the orange?

Thanks,
Jon

USS Atlantis · Post by **USS Atlantis** » Mon Jun 01, 2009 5:45 pm

greasyspoon wrote: What size resistors do I need? Would the blue resistors be a different size vs the orange?

Thanks,
Jon

If you're supplying 3v

No resistors needed for the Blue's

For the Oranges - if you get 2v ones - 56 ohm

Resistor value is based on the following calculation

(Vs-Vd)/A

Where
Vs is the supply voltage
Vd is the device voltage (2v for the Orange, 3v for the Blue)
A is the current draw of the device (20ma (.02A) for both)

That calculates out to 50 ohms - but 56 is the next higher standard rating - ALWAYS go higher, never lower