# Help with LED circuit

Discussion in 'The Projects Forum' started by Xpeditions, Feb 13, 2009.

1. ### Xpeditions Thread Starter New Member

Jan 29, 2009
2
0
Hello Everyone -- I'm building a small project to create an LED lighting panel. The only issue I have is power. I know I'll need one resistor per leg of LED's but have been out of the electronics arena for over 12 years and can't recall how to calculate the resistor value based on the devices I'm using.

I plan to run this from 2 9 volt batteries unless someone has a better idea. This is meant to be portable, thus battery operation.

I plan to only run one set at a time - either all white or all IR, which would be determined by a switch.

One bank of 6 devices is a bright white type. The other bank of 6 is IR. There are 2 rows of these, for a total of 12 white and 12 IR.

I planned to series connect each row in series. I am sure each row will need their own resistor.

This will be housed in a medium sized camera flash I recently found (it didn't work) and gutted for the project.

The needs of the white LED's is different from the IR devices.

The IR devices are part #: 1N6266

The white Part # is: LTW-2S3D7

I would be very grateful for any help in figuring out the resistor values.

Many Thanks
Jerry

2. ### Wendy Moderator

Mar 24, 2008
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Apr 5, 2008
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Hello,

As far as I can see the 1N6266 has a Vf of 1.7 Volts @ 100 mA.
and the LTW-2S3D7 has a Vf of 3.3 Volts and can handle max 75 mA.

To calculate the resistor there are several sites.
For example ledcalc : http://ledcalc.com/

Greetings,
Bertus

4. ### Audioguru New Member

Dec 20, 2007
9,411
896
In about one hour, the voltage from the tiny 9V batteries will be so low that the LEDs will turn off. You will see them dimming as the battery voltage runs down.
You need 6 or more AA rechargeable Ni-MH cells to power the LEDs for a few hours.

5. ### Xpeditions Thread Starter New Member

Jan 29, 2009
2
0
A big thank you to everyone who contributed. I really appreciate your efforts to assist me. I have all I need for now.

Best Wishes
Jerry