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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I would start by re-designing this. I’d thought of this too, to protect the opto-transistor in case I dialled the trim pot meter to 0ohm. 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.

Now, putting the opto-transistor right in front of the built-in flash? Hypatia’s Protege likes this. Posted by striplar in forum: Set R2 to allow that current to create not more than one volt. Yes, my password is: You route that to the base of the transistor. First measure the current through the opto transistor in ambient lighting conditions to find the off leakage current.

How are you with mosfets? Measure the current through the opto-transistor in ambient light. It either emits nearly invisible preflashes and analyses results to adjust flash output. Will this work if you don’t have any way to stop the LEDs quickly?

Mar 5, 1, Have I got that right? Jul 21, 7 0. See where I’m going with this? But yes, speed matters.


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? I’m trying to make a flash slave as in the attached diagram.

Are you referring to R3?


Catasheet the current assumption is that it receives too much light and we have to reduce it with the IR filter. Jul 21, 5. Resistor values in flash slave Reply to Thread. Discussion in ‘ General Electronics Chat ‘ started by roukeJul 21, Do you realize how short that flash from the camera really is?

I may be wrong – honestly, I’m not sure. You can not get to dataseet volts and you don’t need to. That’s not going to datasheeh out anything.

Does anyone have any suggestions? You size R3 to limit the total opto current to 0. Your name or email address: R1 is k and R3 is 50k. Suppose the PT is 5 mS and the darlington is 20 mS. No, create an account now.

The light source consists of five series of ten bright white LEDs, each series with it’s own ohm resistor. OK, I’m going to open my mouth on this. When a light flash happens the opto will suddenly allow a lot more current. Quote of the day. Do you already have an account?

But that’s something I can olny find out when the electronics work. Just playing devil’s advocate here. Maybe on my second try. 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 photo transistor is probably an IR datashfet 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 should only be necessary if the adjustment leg will eat too much current when the flash fires. The unit works well, although not as bright as flash tube, but good for macro photography.

Resistor values in flash slave | All About Circuits

And the tailing off from the phosphorous in the white LEDs may become a problem at fast moving objects. 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.

Solving for two resistor values in a resistor-divider network Posted by jerseyguy in forum: You get the power in the capacitor and you can’t stop the light until the capacitor is empty.

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