[NEWB. I have programmed for some general arduino circuits and controlling steppers but only ever used existing designs. No proper understanding of electronics on my part should be assumed.]
Thanks in advance for any help with this question:
PROBLEM SUMMARY
PROBLEM DESCRIPTION
QUESTION
[The full internal camera circuit can be posted, if required.]
PROBLEM SUMMARY
I want to activate the shutter on my film movie camera using Arduino. I want to take single frames and to specify the interval between them. Later I will expand the system beyond using Arduino as interavalometer alone.
A circuit (as has been used for dSLR shutters) using a 4N25 optoisolator as switch does not work with the camera. The circuit has been tested with LED and works. Camera shutter does not fire.
PROBLEM DESCRIPTION
To connect to the camera I am using the manufacturer's external interavalometer built for the camera, a Leicina.
Although I have the manufacturer's interavalometer I want to control the camera from an Arduino so I have more precise control and later I will also want to control a number of other things at the same time.
I am connecting via the external interavalometer because I can find a DIN connector more easily than the custom 8 pin plug that goes into the camera body. The interavalometer connects to the camera from the first of its two DIN sockets and I am using two pins in its 2nd DIN socket that was designed for an optional radio control. These pins can be used to trigger the shutter. If I short across the two pins the shutter is activated.
The interavalometer supplies power to the camera from 5 x 1.5v AA batteries. These are used instead of the camera's internal batteries which must be removed when the interavalometer is attached.
I have built and tested an Arduino (Uno) + circuit on breadboard using a 4N25 optoisolator.
The test circuit works to turn on and off LED resistor powered by a 9v battery on the other side of the optoisolator. (The code is simple.) But if I connect the two lines from the interavalometer DIN socket 1 + 8 (with no battery on the breadboard), instead of the LED/resistor then nothing happens.
It strikes me that although the circuit design may work fine for a dSLR, my camera is a cine camera with a motor involved. Perhaps the circuit inside the camera needs more current than can be passed through the optoisolator?
QUESTION. Can the 4N25 ever work for my needs? What kind of switching can I use? I guess the most responsive switching solution will be the better as I'm doing stop motion.
Crossroads, thanks for your suggestion. Do I need to work out what the resistance should be ? And how would I do that? My resources include a cheap meter.
How should I work out the specs for the MOFSET (or other component)?
I've attempted this question before in general electronics, but now I have more information and think I can make my question more explicit (and hopefully easier to answer). Hope this is the correct forum.
I want to control a switch in an external circuit that operates a cine-camera. The camera uses its own DC power supply.
I have posted the simplified camera circuit.
The total camera circuit runs off 5 x 1.5v AA batteries.
I measured approx. 38mA through the circuit's external switch pins (see diagram pins 1 and 8 in red) on single frame activation and 90mA on continuous mode.
How can I make a circuit to do this with an Arduino Uno, please?
The camera circuit and diagram for external socket:
Have you tried connecting the output of the 4N25 (pins 4 and 5) to the camera both ways round?
How much current are you driving the 4N25 with? Maybe you need more than you are using. Try reducing the series resistor. 100 ohms is about as low as you should go.
If you still can't get it to work, try a reed relay instead of an opto isolator.
Have you tried connecting the output of the 4N25 (pins 4 and 5) to the camera both ways round?
How much current are you driving the 4N25 with? Maybe you need more than you are using. Try reducing the series resistor. 100 ohms is about as low as you should go.
If you still can't get it to work, try a reed relay instead of an opto isolator.
Yes.
I'm using a 220R. That's the lowest I have at the moment.
Thanks for the suggestion. I'll look into a Reed Relay.
Grumpy_Mike:
The problem is that it all depends on the sort of circuit at the camera end which we know nothing of.
I had hoped the simple circuit schematic would be enough to solve the problem. I do have the complete and detailed circuit diagram for the camera internals. problem is that I'm under instructions from the person who let me see it not to post it online at the moment (!). I'd have to go back to the lender and ask whether I can – maybe if the reed relay doesn't work out. Otherwise I might be able to isolate the parts of the circuit that are important to the problem and redraw them....
The Reed Relay 5V SPST that Maplin sells (order Code: JH12N) will be just fine. You can drive this relay direct from an Arduino pin, because it only takes 10mA @ 5V. I suggest you connect a 1N4148 or preferably BAT43 flyback diode (both available from Maplin) in parallel with the coil, even though you can get away without it (because the flyback current will be conducted by the other transistor in the output buffer, unless you switch the pin mode from output to input while the relay is energised).
dc42:
The Reed Relay 5V SPST that Maplin sells (order Code: JH12N) will be just fine. You can drive this relay direct from an Arduino pin, because it only takes 10mA @ 5V. I suggest you connect a 1N4148 or preferably BAT43 flyback diode (both available from Maplin) in parallel with the coil, even though you can get away without it (because the flyback current will be conducted by the other transistor in the output buffer, unless you switch the pin mode from output to input while the relay is energised).
Maybe a couple of these - connect the two sides as needed, 50ohm resistance when powered from 5V.
Lots of other switches exist too.
crossroads. many thanks for the suggestion.... I think I'm going to try the reed relay first as it sounds the most promising to start there. cheers . Simon
