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Ned to make an IR Blaster... with 30 transmitters...
^Faldo^ 
29/8/08 11:48:46 AM
God

Here she is: http://tinyurl.com/5p34re

Details:
5MM EMITTING DIODELooks like a 5mm LED & has a blue transparent lens.Specifications:- Forward Current (If): 50mA max - Peak forward current (Ip): 1.2A- Forward Voltage (VF): 1.2V @ 20mA - Reverse Voltage (VR): 5V max- Power Dissipation (Pd): 100mW max - Viewing Angle: 30°- Peak Spectral Wavelength(IR): 940nm @ 20mA * Spectral Bandwidth (DI): 50nm@20mA- Material: GaAs

Haven't tested the kit yet, that's for tonight after I solder in the last wire bridge. She'll be right, haven't built a kit yet that didn't work.

-DAVE.


Edited by ^Faldo^: 29/8/2008 2:42:41 PM

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freespace 
29/8/08 5:48:03 PM
Hero
Titan


Quote by ^Faldo^
Here she is: http://tinyurl.com/5p34re

Details:
5MM EMITTING DIODELooks like a 5mm LED & has a blue transparent lens.Specifications:- Forward Current (If): 50mA max - Peak forward current (Ip): 1.2A- Forward Voltage (VF): 1.2V @ 20mA - Reverse Voltage (VR): 5V max- Power Dissipation (Pd): 100mW max - Viewing Angle: 30°- Peak Spectral Wavelength(IR): 940nm @ 20mA * Spectral Bandwidth (DI): 50nm@20mA- Material: GaAs

Haven't tested the kit yet, that's for tonight after I solder in the last wire bridge. She'll be right, haven't built a kit yet that didn't work.

-DAVE.
Edited by ^Faldo^: 29/8/2008 2:42:41 PM

Ha, my calculation was pretty spot on, good!

It should be fine to power 30 LEDs, but you need to wire the transistor's emitter to Vcc using 2x10R resistor in parallel, instead of through the 150R. Then you should be fine connecting connecting the IR LEDs in parallel, as long as each has a 220R resistor in series with it.

Explanation:

The 2x10R in parallel will give you 5R equiv. in series with the PNP. This should provide enough current for all the IR LEDs:

30x220R in parallel is equiv to 7.3R

1.2V drop across the IR LEDs, 7.8V drop between Vcc and anode.

7.8/(7.3+5) = 0.58A, which is 0.02A less than what you should be drawing for 30IR LED (30x0.02=0.6), but should be alright, since everything has ~10% tolerance. So that should supply enough current, and also ensure you don't exceed the current rating for the PNP transistor.

Also, when I asked whether the kit works, I mean whether it works for the purpose for which you bought it :)

Cheers,
Steve

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