BD649 DATASHEET PDF

Collector-base voltage (IE = 0). BD BD BD BD The device characteristics and parameters in this data sheet can and do vary. BD Transistor Datasheet pdf, BD Equivalent. Parameters and Characteristics. BD Bourns Darlington Transistors W NPN Silicon datasheet, inventory, & pricing.

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EEL Data Sheet – Transistor Footprints – ETSG – The University of Queensland, Australia

Discussion in ‘ General Electronics Chat ‘ started by roukeJul 21, Resistor values in flash slave Reply to Thread.

Jul 21, 1. Dayasheet 21, 7 0. I’m trying to make a flash slave as in the attached diagram. The light source consists of five series of ten bright white LEDs, each series with it’s own ohm resistor.

The unit works well, although not as bright as flash tube, but good for macro photography. I want it to be triggered by the camera’s built in flash, but I can’t get it daatsheet work satisfactorily. When I shine a torch on the photo resistor, it saturates and the LEDs light up bright, but when I try to activate the system with the flash, the LEDs don’t seem to work.

The photo transistor is probably an IR type can’t find a visible light onebut I expect a flash tube to emit a broad light spectrum including sufficient IR to saturate the photo transistor.

R1 is k and R3 is 50k. I’ve looked on-line and saw some diagrams without an R1 or an R2, but wouldn’t that blow the BD or the photo transistor when it saturates? Does anyone have any suggestions? Jul 21, dagasheet. Nov 13, Do you realize how short that flash from the camera really is? datasheef

What you want to do is allow the input power source to charge up a capacitor, and then datashest your light sensor senses the external flash, dump that cap into the LEDs. Generally a good job for an SCR. Jul 21, 3. Nov 30, 18, 9, I would start by re-designing this.

Measure the current through the opto-transistor in ambient light. Set R2 to allow that current to create not more than one volt. Lets try 30 ua in ambient light. Maybe on my second try. How are you with mosfets?

Will this work if you don’t have any way to stop the LEDs quickly? That’s what an SCR and a capacitor will do. You get the power in the capacitor datasheft you can’t stop the light until the capacitor is empty. The br649 can only allow. That’s not going to blow out anything. Jul 21, 4.

See where I’m going with this? Jul 21, 5. Jul 22, 6. May 27, 52 Jul 22, 7. Jul 22, 8. Jul 22, 9. Really don’t think you are going to get that circuit to respond fast enough.

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Hypatia’s Protege likes this. Jul 22, Sep 24, 2, OK, I’m going to open my mouth on this. I may be wrong – honestly, I’m not sure. But if your PT photo transistor is rated for 50 mS and you opt for one that is much faster, the next question is: Suppose the PT is 5 mS and the darlington is 20 mS.

That’s going to be 25 mS delay in the flash of the LED’s. Just playing devil’s advocate here. Mar 1, 3, 2, Mar 5, 1, OK thank you all for your thoughts on this. I’ve learned quite a bit here, but I can put this project at rest and tidy up now and focus on other things again.

Jul 23, Are you referring to R3? You suggested a 22k in series datashewt the trim pot meter, and none in series with the opto-transistor.

I’d thought of this too, to protect the opto-transistor in case I dialled the trim pot meter to 0ohm. But if it’s in series with the opto-transitor, it’s multifunctional.

(PDF) BD649 Datasheet download

I think there should be one in series with the opto-transistor, so I can adjust the voltage at the point to the darlington to be 0v at ambient light. Without it the current through the opto-transistor at ambient light is sufficient to saturate the base of the darlington, and the LEDs xatasheet always on.

But I think that’s what you’re saying albeit in other words ;- However, if R1 and R2 are high enough, the current through the base of the darlington would also be limited to a safe level.

So I guess my main question is, how do I calculate the size of R1 and R2 so it protects both the opto-transistor and the base of the darlington at 0.

NPN SILICON POWER DARLINGTONS

Have I got that right? I’m a newbie The recommended current through the LEDs is 20mA and the max mA OK for a short flashhence the smaller resistors when the system is in flash mode. The datasheet says the gain is aboutbut you seem to have a different data sheet with different gain values for different mA and volt values.

I guess it’ll always be 3 volt, and in my case. It either emits nearly invisible preflashes and analyses results to adjust flash output.

I’m working on the idea that when the built-in flash is blocked by a large macro lens at close range, the LED ring will compensate, and the camera will calculate from whatever it ‘sees’ through the lens. Whether that be from it’s own flash or any other light source. But yes, speed matters. And the tailing off from the phosphorous in the white LEDs may become a problem at fast moving objects.

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But that’s something I can olny find out when the electronics work. And it looks like they should work. Now, putting the opto-transistor right in front of the built-in flash? If the current assumption is that it receives too much light and we have to reduce it with the IR filter. As you could see from my pictures, the unit is a rectangular circuit board that slides in a Cokin filter holder with the LEDS facing forward and the opto-transistor mounted on the reverse side of the circuit board, facing the built-in flash.

So, yes I guess the IR filter might help, but the twisted pair is perhaps excessive? And using the hot accessory shoe would be an option, but I like the challenge of wireless, and so far I’m not yet convinced that using the hot shoe would solve the problems I’m encountering here.

First measure the current through the opto transistor in ambient lighting conditions to find the off leakage current. Then the adjustment leg is designed to develop less than 1 volt at that current, and some adjustability to compensate for ambient light.

You can not get to zero volts and you don’t need to. The Darlington transistor needs about 1. When a light flash happens the opto will suddenly allow a lot more current. You route that to the base of the transistor. You size R3 to limit the total opto current to 0. R1 should only be necessary if the adjustment leg will eat too much current when the flash fires.

BD Datasheet – General purpose NPN Darlington transistor from Power Innovations

Datashest resistor values in a mesh. Posted by striplar in forum: Solving for two resistor values in a resistor-divider network Posted by jerseyguy in forum: Resistor Values Posted by tquiva in forum: You May Also Like: One-Time Programmable Memory in Action: If you could build your dream bench, what would you put on it?

LEDs and Solar Cells Combine into Devices that Emit and Absorb Bd49 Researchers have developed double-heterojunction nanorods which can be biased to both send and receive light—in other words, a device that is both an LED and solar cell, capable of emitting and absorbing light. Your name or email address: Do you already have an account? No, create an account now. Yes, my password is: Quote of the day.