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Topic: IR transmitter - questions! (Read 258 times) previous topic - next topic

PSteward

Hello,

I'm looking to make various IR transmitters (38khz to control TV/AC/Lights etc..) and am seeking the best designs to increase transmitter power.
Variables include the quantity of LEDs (1-6) and the voltage (3.3/3.7/5V/6V etc).

Ideal designs seem to have a constant current design including a 2N2222/2N3904/BC337 transistor and respective resistors to control the base voltage among other things.

They are all similar but slightly different, and some definitely "seem" more powerful then others (why can a TV-B-Gone pull off 150 ft, but a poorly directed basic IR transmitter can't get the signal to the receiver 5 ft away)....

I'll be using Vishay TSAL6100/6200/6400.

Thanks!

INTP

Most people don't read the data sheets and realize those 5mm IR bulbs can take upwards of an amp at the duty cycles typical of modulated signals.
You just don't see people providing that kind of power.

PSteward

Good Point!
The Vishay's surge max is 1.5 amps, you think exceeding the 200ma peak is fine for this application? Not sure of the duty cycle for the varying signals....
If I started with a 5V / 6 LED design, what design will get the most current into the LEDs without damaging them or the output pin? It's also possible I wouldn't need 6 LEDs if the signal can reflect (like my damn Harmony remotes with two LEDs).


INTP

I'm not sure what 200ma peak you're referring to.
Maybe you should first declare what your goals are instead of picking '5V 6LED' arbitrarily and then try to build around that random foundationless design choice.

PSteward

#4
Mar 21, 2018, 01:38 am Last Edit: Mar 21, 2018, 01:43 am by PSteward
The datasheet for the Vishay LED in question : https://www.vishay.com/doc?81011
Peak forward current is 200 mA.

5v is USB voltage, as I'm using an Arduino it seems a good place to start.

6 LEDs seemed like an ideal starting place for a multi-angle IR emitter. Even the Logitech hub sports 6 as well as some other designs I've seen: https://github.com/zmoteio

Since it appears I have a "random foundationless design choice", why don't you elighten me?

And to clarify, I am looking to design IR emitters for varying applications with varying voltages. Ultimately the designs I've tests are limited in strength.

INTP

You won't be powering LEDs from your Arduino, and you've made no mention of what your power source is going to be. The Arduino running on 5V is then hardly relevant.

Still not sure what your actual goal is. Are you adding IR functionality to those devices, or are you trying to control devices that you already know use 38kHz IR?
If you are trying to add functionality, RF is a better option. If you have an AC unit already, it probably does use RF and not IR.

So if I play along and just assume you know what you want, and what you want is to flash 6 IR LEDs, then you can start by figuring out how much current you want each of them to see and explain how you'll provide that current. The part with the Arduino is cake. It's just diddling the base pins. But you will want transistors that can handle whatever current you decide to go with.

Wawa

You can use two IR diodes max in series on a 5volt supply (Vf ~1.45volt@200mA).
Six LEDs in series @200mA peak, plus the driver, need a 12volt supply.
An active CL drive stage is needed if you use the diodes close to their max current.
Post the diagram of the 6-LED setup, with values.
You can work out the max safe current from the pulse train you're trying to send.
That could well be more than 200mA (see graph#3 in the datasheet).
Leo..

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