Help with triggering a camera with light?

[peps1]

Just increase the 4k7 up to about 220k and it should be over 10 X more light sensitive. It's just to keep the NPN off with a bit of ambient light, you might be able to go right up to 1 or 2 Meg if the ambient light is low enough.

Think you, I will breadboard it up with a big trim pot and see how it goes! 

(thank you for all the help)

Just to double-check....like this?

[StillTrying]

Yes, but you might have to move the collector of the phototransistor to the other side of the 2k2.

Because when the NPN is on/closed there's still 0.7V across its emitter-collector, with the photo's collector moved directly to the + the 0.7V should drop to less then 0.1V.

[peps1]

Thank you, that makes sense. 

[peps1]

Yes, but you might have to move the collector of the phototransistor to the other side of the 2k2.

Because when the NPN is on/closed there's still 0.7V across its emitter-collector, with the photo's collector moved directly to the + the 0.7V should drop to less then 0.1V.

No joy with using or bypassing the 2K2 resistor on the phototransistor or with a resistor up to 2M between the Base and emitter of the transistor.....100% sure I'm doing something really stupid on my end at this point!

[magic]

Keep in mind I'm using a Fluke 101 meter as I'm poor, but I'm getting 1.4v at the camera 1.3V after the resistors (switch open) 0v (switch closed).

Is this supposed to mean that the Fluke has at best 0.1V resolution on DC volts? Well, that wouldn't be my first choice of a budget DMM for breadboard circuits...

I gather it all means that the test current from the camera is so low that when the switch around 39kΩ is closed, there is less than 100mV voltage drop across the remaining 2.2kΩ resistor. If the camera requires this drop to be less than 0.7V then you have got a problem. No Darlington configuration of any sort is going to work.

What may possibly work is to go back to just two resistors and then connect the phototransistor right across the camera terminals, bypassing all resistors. Or experiment with smaller values instead of 2k2.

If the Panasonic guys have any brain, the camera should not be harmed even by a short between the two terminals. Indeed, such short often occurs during insertion of that kind of jack into the socket or it could happen due to cable damage or similar reasons. And your phototransistor doesn't seem capable of conducting much current anyway.

[peps1]

Is this supposed to mean that the Fluke has at best 0.1V resolution on DC volts? Well, that wouldn't be my first choice of a budget DMM for breadboard circuits...

Yes, that's what I mean...its not my choice I really only have it as a backup in my kit bag, and only really get uses as a continuity tester, would be interested in what you pick would be as my Extech EX330 just died after many years.

I gather it all means that the test current from the camera is so low that when the switch around 39kΩ is closed, there is less than 100mV voltage drop across the remaining 2.2kΩ resistor. If the camera requires this drop to be less than 0.7V then you have got a problem. No Darlington configuration of any sort is going to work.

Thank you for explaining this, my experience with Darlington configuration has been limited to audio applications.

What may possibly work is to go back to just two resistors and then connect the phototransistor right across the camera terminals, bypassing all resistors. Or experiment with smaller values instead of 2k2.

I like this idea, fewer parts and just swapping resistor value, now we are at my level of skill!

If the Panasonic guys have any brain, the camera should not be harmed even by a short between the two terminals. Indeed, such short often occurs during insertion of that kind of jack into the socket or it could happen due to cable damage or similar reasons. And your phototransistor doesn't seem capable of conducting much current anyway.

Oh, I'm 100% sure I shotted them together when working on the first switch as my previous experience had been with Canon cameras that just use a short to trigger.

Thank you so much for taking the time to help me out with this, its sincerely appreciated and teaching me a fair bit too!

[StillTrying]

I can't think of a reason why the photo and NPN versions don't work, a few 100mV across the phototransistor and 2k2 should be enough to provide base current into the NPN, I would think it's quite likely a bad connection on the breadboard.

[magic]

The 100mV across the photo plus 600mV across the NPN base-emitter junction may not be low enough for the camera to trigger.

I suspect this is why.

[StillTrying]

In Reply#23 he gives the voltage across the +&- contacts as 1.4V when the switch is open, which is 34uA through the resistors when the switch is open, it would have to be >320uA through the 2k2 when the switch is closed to give enough voltage left for the base and photo.
If he gave us another voltage such as the voltage at the +&- contacts when the switch is closed we could work it out.

Of course a 1.5V battery would do, or possibly even using the +&-'s own 1.4V to recharge a small capacitor ready for the next trigger.

[peps1]

I can't think of a reason why the photo and NPN versions don't work, a few 100mV across the phototransistor and 2k2 should be enough to provide base current into the NPN, I would think it's quite likely a bad connection on the breadboard.

I thought this too so moved the circuit around the breadboard to a few locations and even tried different components and got the same result.

If he gave us another voltage such as the voltage at the +&- contacts when the switch is closed we could work it out.

Of course a 1.5V battery would do, or possibly even using the +&-'s own 1.4V to recharge a small capacitor ready for the next trigger.

My meter was showing 0v with the switch closed. but think this is due to the limitations of the Fluke 101 I have been using the last couple of weeks, new meter should be here today so will report back.

Did find omitting the resistors increased sensitivity with regards to the range it would trigger, but had the side effect of not triggering if the light was too close/bright. 
 

[magic]

Well, it obviously looks like your camera accepts a narrow range of voltages and not  too close to zero.
Not sure if there is much more you can do without using additional power supply and more complexity.
Pick some series resistor value that works best with the light you have
You could try some Schottky diode too but it may not work at all or only prefocus.

[peps1]

Yeah, think that's my best option, 98% sure I can get something working in the range I have to work with, been testing with a torch, so the real test comes tonight when I try with the acctual UV array! Figers crossed... 

And, you guys have been amazingly helpful, sincerely, thank you!