100 LEDs circuit !!! Advice needed !!! Very urgent please...?

Question

I just bought this LEDs http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ih=012&sspagename=STRK%3AMEWN%3AIT&viewitem=&item=220105849747&rd=1&rd=1

i want to make a flashlight with a 100 of this LEDs

The criteria or this project is :
- Using 100 LEDs
- operated in 6v or 9v
- using D cell batteries

Please your proffesional advice about how should i get this project done, my question is :
- should i use Parralel or Series connection for the led, or maybe any good combination?
- What kind of resistor i need to add (if any)
- If posibble i will like to use transistor and any other circuit rather than just resistor to supply the right voltage.

I have an advice to use 9V D cell Batteries and connect the LEDs with "50sets of 2 on series in parallel" and use resistor to fit the voltage needed.

I hope i can have more choice for doing this project

Thanks

Answer 1

Read the specs on the LED's at the e-bay web site.
Forward Voltage : 3.3v-3.6v
Forward Current : 20mA

The bulbs themselves operate on 3.3 V. If you put 100 in series, you would need 3.3 x 100 = 330 volts. That would be over 200 D cell batteries and reach lethal voltage levels.

Each LED has a maximum forward current of 20 mA. 100 x 20 mA = 2000 milliamps or 2 amps.

Two sets of "50 LEDs in parallel" placed in series would have a forward voltage of 2 x 3.3 = 6.9 volts. (up to 2 x 3.6 = 7.2 V) I realize there would be some voltage drop in the circuit, but a 9 volt supply might over power the LED's and burn the out. Adding a resistor would help, but the resistor would need to be rated for at least 3 watts. (1 amp x 2.1 volts = 2.1 watts, round up to 3 watts)

You can try things out using two LED's in series. If they work on the battery combination, then just scale things up by adding multiple LED's in the series/parallel combination.

Get yourself a perforated board to attach all the LED's. (Stop at an electronics store and ask for a "perf board". Ask them to show you how to use a wire wrap tool to attach wires to the LEDs without soldering.

If you want to make something even more temporary, ask them for a breadboard and some small gauge wire to make your own jumpers.

See links below for pictures of a perf board and a breadboard.

Good luck and have fun.

Answer 2

Well I believe you want them all to light up simultaneously....
These are the facts you need to consider:
a) You need to limit the current to about 15mA, the LEDs are not acting as "load resistors". So for 9 Volt, that would be a 560Ohm (standard value) resistor.
b) Each LED in series "steals" about 2 Volts away. So with a 9 Volt battery, you can only have 4-5 LEDs in a row.
With 100 LEDs, you therefore need 25 parallel circuits with each 4 (and a resistor each) in series.
You then need a transistor that can handle a 0.4 Amp collector current to switch the whole chain....

Answer 3

I hope you just dont want to light them together, you want to create some sort of display with them.
You can do that by arranging them in any rectangular pattern on a board say a matrix of 5 x 20. connect all the columns in parallel and the rows in series. then connect this thing to a micro controller chip. Now just program and reprogram this controller and create what ever design you want .(These controllers are easily available in the market).

Answer 4

Military Grade Tactical Flashlight - http://FlashLight.uzaev.com/?mvom