IR Blaster, alternative transistors?

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IR Blaster, alternative transistors?

Unread postby ZacWolf » Sun Jan 28, 2018 7:52 am

Can someone recommend any other Transistors to use for the IR Blaster project: https://wiki.odroid.com/odroid-c2/appli ... io_blaster

I'm not finding a source for PBRN123Y (or any RETs for that matter).

I found an alternative diagram for Arduino at: https://electronics.stackexchange.com/a/205611/35218

I'd like to use three IR LEDs so that I can point in slightly different directions, as this is going in a coffee-table with a fixed location, vs a remote control pointed right at the receiver.

Also, would there be an issue driving 3 LEDs off the 5V pin, and still using GPIO #249? So using: Pin4/5V - Pin6/Ground - Pin7/GPIO#249?

THANKS!!!
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Re: IR Blaster, alternative transistors?

Unread postby odroid » Sun Jan 28, 2018 11:24 am

I think those transistors can work. But we might need to adjust the base input resistor(R-bias) value.
Since Arduino GPIO output is 5Volt while C2 is 3.3Volt, the transistor characteristics and resistor values should be different.
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Re: IR Blaster, alternative transistors?

Unread postby ZacWolf » Sun Jan 28, 2018 11:41 pm

Any recommendations for transistors in that kit (in the link?), and R1 values for using the 5V?

Or, Is there enough power capacity on the 3.3V Pin1 to drive three LEDs, so I'm not dealing with the cross-voltage values?

I tried http://tinyurl.com/y86majsq, and based on the simulation reading the transistor load values seem very low (which I believe is good?)? But is Pin 1 going to have any problem providing the 59mA?

I'm working with basic electronics knowledge from the 80's, so I'm rusty to say the least!

Would using the IRF520 N Channel Power Mosfet with the 3 LEDs in series be a safer bet (the 2nd diagram )?

THANKS!
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Re: IR Blaster, alternative transistors?

Unread postby mad_ady » Mon Jan 29, 2018 3:21 am

I built my blaster to drive 5 ir leds (part of a ir extender). I used the 5V line for power, 4 330 ohm resistors in paralel to make a 80 ohm resistor to limit the current that goes through the diodes and a 330 ohm resistor between the base of the transistor and the gpio pin. The transistor I used was a 2N2222, which should be common everywhere.
You can find the schematic and implementation details here: https://magazine.odroid.com/article/hom ... rs-relays/
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Re: IR Blaster, alternative transistors?

Unread postby ZacWolf » Mon Jan 29, 2018 5:46 am

Excellent!

Thanks, that's exactly what I needed!
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