How hard can I drive an IR Blaster?

[EasyGoing1]

So I have one of these from a 2012 Samsung 3D TV ...



And what I wanna find out SAFELY ... is how hard can I drive this thing? I have a use for it in mind and if I could get it to invisibly light up my living room it could be useful to me .... muwhahahahahahaaaaa

[stj]

Re: How hard can I drive an IR Blaster?

forget it, those are just regular leds.

if your after secret lighting for camera's you need the IR version of the leds used in flashlights.

[EasyGoing1]

Re: How hard can I drive an IR Blaster?

forget it, those are just regular leds.

if your after secret lighting for camera's you need the IR version of the leds used in flashlights.

No I'm just wanting long reach for electronic equipment for IR repeating... Sorry if I was misleading in my initial post.

[stj]

Re: How hard can I drive an IR Blaster?

well most of the problem is going to be losses from filters & stuff like that, is this related to 3d glasses??

[eccerr0r]

Re: How hard can I drive an IR Blaster?

Most of the time the manufacturers are already driving it as hard as they can barring two thing: battery life (if applicable) and the LED must last longer than any possible warranty claim. So usually if you want to sacrifice one or the other, it usually is going as bright as it can without replacing the LED.

[EasyGoing1]

Re: How hard can I drive an IR Blaster?

well most of the problem is going to be losses from filters & stuff like that, is this related to 3d glasses??

No, it's an arduino project that relays IR codes to different equipment (TV, cable box, Roku etc.)

[EasyGoing1]

Re: How hard can I drive an IR Blaster?

forget it, those are just regular leds.

I took it apart, and discovered it has 5 LEDs in it... they are a little bit larger than a standard LED, and they are translucent with a blue-ish tint to them. They are attached to a small circuit board which connects them in parallel ... which means if one of them can handle say ... 200ma, then 5 of them in parallel can handle a full amp, right?

[Curious.George]

Re: How hard can I drive an IR Blaster?

I took it apart, and discovered it has 5 LEDs in it... they are a little bit larger than a standard LED, and they are translucent with a blue-ish tint to them. They are attached to a small circuit board which connects them in parallel ... which means if one of them can handle say ... 200ma, then 5 of them in parallel can handle a full amp, right?

Only if they are perfectly matched.

The better way to drive multiple LEDs (for greater luminous intensity) is to drive them in series. In that way, the output from each may vary (based on their individual characteristics) but you're sure that each will see the same "drive".

[The BEST way, of course, is to drive them individually to optimize output per device -- but, that's needlessly expensive]

Unfortunately, this means you need more voltage compliance in your (current-mode) driver. E.g., for 5 in a string, you're in the 15V range (losses in the driver).

So, you'd need 15V at 200mA (in your hypothetical example) instead of 3V @ 1A.

[EasyGoing1]

Re: How hard can I drive an IR Blaster?

Only if they are perfectly matched.

The better way to drive multiple LEDs (for greater luminous intensity) is to drive them in series. In that way, the output from each may vary (based on their individual characteristics) but you're sure that each will see the same "drive".

[The BEST way, of course, is to drive them individually to optimize output per device -- but, that's needlessly expensive]

Unfortunately, this means you need more voltage compliance in your (current-mode) driver. E.g., for 5 in a string, you're in the 15V range (losses in the driver).

So, you'd need 15V at 200mA (in your hypothetical example) instead of 3V @ 1A.

I'm driving this project with 19V because it also uses a stepper motor for volume knob control and i didn't have a 12v supply laying around ... but i've got several 19v laptop power supples in the drawer ... ive got it breadboarded and fully functional ... im driving the 5 parallel leds with 5v ... the Arduino Nano hits a NPN transistor base through a low value resistor, then the emitter straight to ground, and the collector feeds the cathode and the annode is connected straight to the output from a 7805 which is driven from the 19v supply ... no pullup reisistor at all. Its been running for a couple weeks and so far so good.

[budm]

Re: How hard can I drive an IR Blaster?

So you have all 5 LED connected in parallel with 5V power supply with one switched Transistor on the low side without out any current limiting resistors at all?
What is the current draw for EACH LED when you check?

[redwire]

Re: How hard can I drive an IR Blaster?

You always use resistors to limit LED current
The current-limiting is likely from the NPN switching transistor or 7805 or both having a large voltage drop. TX is only for a short burst.

So the LED's are getting unknown power. If they are 5mm LED's you can't push 200mA through them.
It would be better with the IR LED's in series (5*1.5V) to 7.5V and a resistor, or constant-current NPN switching transistor (add resistor), to the 19V rail.

[EasyGoing1]

Re: How hard can I drive an IR Blaster?

So you have all 5 LED connected in parallel with 5V power supply with one switched Transistor on the low side without out any current limiting resistors at all?
What is the current draw for EACH LED when you check?

I guess that would require that I actually check ... I would have to desolder to check just one ... would you settle for total current draw from all 5 and we can just divide the result?

[EasyGoing1]

Re: How hard can I drive an IR Blaster?

You always use resistors to limit LED current
The current-limiting is likely from the NPN switching transistor or 7805 or both having a large voltage drop. TX is only for a short burst.

So the LED's are getting unknown power. If they are 5mm LED's you can't push 200mA through them.
It would be better with the IR LED's in series (5*1.5V) to 7.5V and a resistor, or constant-current NPN switching transistor (add resistor), to the 19V rail.

Once I discovered that these LEDs are slightly larger than "normal" leds and that they clear with a blue tint, I googled around and saw that they were basically standard high output IR LEDs, which are typically rated at 1.2 volts at 100 ma. With a 5v supply and a sum total of 500ma, it would call for a pull up resistor of about 7 or 8 ohms ... I figured with the transistor offering SOME resistance and the fact that they will be switched on and off so quickly ... I didn't need to mess with the resistor.

So if I sourced the IR LEDs from 19 volts through a switching transistor, Id need about 35 ohms or whatever I have thats close to that value ... I could actually eliminate that 7805 if I did that because the only thing that regulator does is power those LEDs.... hmmmm... thats a good idea I havent ordered the PCB yet so I still have time to change the design.

[budm]

Re: How hard can I drive an IR Blaster?

I guess that would require that I actually check ... I would have to desolder to check just one ... would you settle for total current draw from all 5 and we can just divide the result?

When putting LED in parallel and they do not have matching VF, so they will not conduct with same amount of current, the one with the lower VF will conduct the most, the one with higher VF may conduct little or not conduct at all, and when the one with lower Vf is conducting as it is heated up it will lower the Vf so it will conduct even more and get into thermal runaway, that is why you do not simply put semiconductor in parallel unless you match them and also the thermal management has to be done correctly.
Current limiting resistor for each LED for parallel connection, that is why you are better off connecting LED's in series and drive them with PWM constant current.
https://www.arrow.com/en/research-an...ds-in-parallel

https://www.edn.com/design/led/44245...el-LED-strings

Using 7805 to drop 19V to 5V at 500mA, that means the 7805 will be dissipating 19V - 5V = 14V of Vdrops on the 7805. 14V x 0.5A = 7W of power dissipation on the 7805.

[EasyGoing1]

Re: How hard can I drive an IR Blaster?

When putting LED in parallel and they do not have matching VF, so they will not conduct with same amount of current, the one with the lower VF will conduct the most, the one with higher VF may conduct little or not conduct at all, and when the one with lower Vf is conducting as it is heated up it will lower the Vf so it will conduct even more and get into thermal runaway, that is why you do not simply put semiconductor in parallel unless you match them and also the thermal management has to be done correctly.
Current limiting resistor for each LED for parallel connection, that is why you are better off connecting LED's in series and drive them with PWM constant current.
https://www.arrow.com/en/research-an...ds-in-parallel

https://www.edn.com/design/led/44245...el-LED-strings

Using 7805 to drop 19V to 5V at 500mA, that means the 7805 will be dissipating 19V - 5V = 14V of Vdrops on the 7805. 14V x 0.5A = 7W of power dissipation on the 7805.

These 5 LEDs in parallel are a commercial product, manufactured by Samsung. There are no resistors, just a circuit board with five of these LEDs connected in parallel. When I send an IR signal into the LEDs with a 5 volt source with the configuration previously stated, and I look at the LEDs using a cell phone camera, all 5 light up fairly brightly...

[goontron]

Re: How hard can I drive an IR Blaster?

forget it, those are just regular leds.

if your after secret lighting for camera's you need the IR version of the leds used in flashlights.

Interesting. I picked a few cameras from the tip that have IR rings. Do they run in the same bands? Can i make an IR blaster from them for.. Say... A TV be gone?

[budm]

Re: How hard can I drive an IR Blaster?

These 5 LEDs in parallel are a commercial product, manufactured by Samsung. There are no resistors, just a circuit board with five of these LEDs connected in parallel. When I send an IR signal into the LEDs with a 5 volt source with the configuration previously stated, and I look at the LEDs using a cell phone camera, all 5 light up fairly brightly...

How about showing us good clear pictures of the whole top and bottom side of this Samsung board?