Are you talking about the voltage on the gate or the voltage on the drain to source?


No I wrote 5us on and 100us off, but not that I know what the duty cycle is for these pulses anyway I have changed it to what Ronv said 10us high(on) and 90us low(off)

Okay, is 5 us on enough to light the LED. Do I read the data sheet wrong? It looks like it suggests 100 us on and 1 ms off. But that would not explain blowing up transistors.

 

Maybe slow the blinking down (and at a lower current like300 mA) so you can see it working, then increase speed and current in increments.
How do you tell if the LED is blinking if you don't have a scope? Neither the camera or the eye can detect blinking at even 100 Hz. Even if you used the controller and an IR sensor you are limited by the speed of the software routines.

 

Okay, is 5 us on enough to light the LED. Do I read the data sheet wrong? It looks like it suggests 100 us on and 1 ms off. But that would not explain blowing up transistors.

I would imagine it means that I cant exceed 10% duty cycle and maximum pulse width of 0.1ms at 1amp.
For my application the Low(off) is very important it must be between 90us and 110us other wise my camera does not pick the leds up, the High(on) can vary a bit from 1us to 50us.

How do you tell if the LED is blinking if you don't have a scope? Neither the camera or the eye can detect blinking at even 100 Hz. Even if you used the controller and an IR sensor you are limited by the speed of the software routines.

Well the algorithm on the camera is made to pick up the modulated leds.
So if the leds are blinking correctly I can see them on the camera.
But this is neither here or there(not the issue)
It is to get the most current through my leds to get them the brightest as possible at my pulse rate.

 

I would imagine it means that I cant exceed 10% duty cycle and maximum pulse width of 0.1ms at 1amp.
For my application the Low(off) is very important it must be between 90us and 110us other wise my camera does not pick the leds up, the High(on) can vary a bit from 1us to 50us.


Well the algorithm on the camera is made to pick up the modulated leds.
So if the leds are blinking correctly I can see them on the camera.
But this is neither here or there(not the issue)
It is to get the most current through my leds to get them the brightest as possible at my pulse rate.

Super! What kind of camera are you using that lets you see the blinking?

 

Are you talking about the voltage on the gate or the voltage on the drain to source?


No I wrote 5us on and 100us off, but not that I know what the duty cycle is for these pulses anyway I have changed it to what Ronv said 10us high(on) and 90us low(off)

On IRLB8721PBF, it's 10V on Vgs. Vgs(th) is not the same thing. That is referring to the range in which tranconductance starts (1.35 to 2.35 Volts). The trick is in learning how to read datasheets-- most people don't know how (and this is intentional on the part of manufacturers).

 

On IRLB8721PBF, it's 10V on Vgs. Vgs(th) is not the same thing. That is referring to the range in which tranconductance starts (1.35 to 2.35 Volts). The trick is in learning how to read datasheets-- most people don't know how (and this is intentional on the part of manufacturers).

I don't think it is intentionally deceptive. How else would you describe them but as gate to source voltages?