I need an advice for building a self-timer for an old camera. The concept is quite simple - the camera has two small holes next to the shutter button. Those two holes were used for an original remote shutter release that was just two wires (that fit into those holes) and a button switch. When you press the button on the shutter release, the two wires are connected and the camera takes a photo.
So, what I want to do is to control the connection between those two wires via Arduino. So I can create a simple self-timer. It should work like this:
You press a button connected to an Arduino, the Arduino waits 10 seconds (or any predefined time), then creates a circuit between the two wires (for about 5s) and after that it disconnects the circuit.
Should I use some basic transistor or relay? The camera has its own circuit, so I don't want pass any electricity from the Arduino. I just wanna make a timed connection between two wires. And the whole thing should be small (I want to use some super-small Arduino compatible board).
Could anybody draw a simple circuit for me how to do that?
You probably want to use an opto-coupler instead of a relay. Most relays are bigger and meant to switch more current, and the mechanical relays also tend to make a sound as the relay is switched open/closed. An opto-coupler is an enclosed chip that has a tiny LED in it, and a tiny photo sensor. From the Arduino you activate the LED, and when it is activated, the photo sensor completes the circuit. Here is one such wiring setup that I found via google: Optocoupler
I tend to like the CNY-74 opto-coupler since it provides two independent circuits, and it works well with both 3.3v processors like my Teensy 3.x and 5v processors like my Uno. On my Olympus cameras, you can control the 1/2 press of the shutter with one circuit, and the full shutter release with the second and first combined. I use it with my steampunk camera setup where pressing the telegraph key starts the focus action (1/2 press of the shutter) and when you release the telegraph key, it then tells the camera to take the picture. Here is a US based ebay seller of the CNY-74: http://www.ebay.com/itm/160881206628?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649
This page describes the pin out for various shutter releases: www.doc-diy.net :: camera remote release pinout list. In general, if your camera does not take a standard audio 2.5mm/3.5mm connector, you would either buy a cheap remote release for your camera and hack up the wires, or you buy an appropriate cable for shutter releases that use 2.5mm/3.5mm audio jacks to support multiple cameras.
This store for instance sells cables that connect to the pixel shutter release/remote flash setup: Security Measure
You probably want to use an opto-coupler instead of a relay
I thought of that also, but most circuits require a voltage across the photo sensor?
Maybe not? if not then that's an option.
In most/all of the electronic shutter releases, the shutter release merely connects the ground to the focus and fire wires, and the camera provides the voltage via its battery. There is no separate battery in the simple wired shutter releases (in the wireless and timer shutter releases you need a battery to do the extra stuff). You can verify this by connecting the wires directly to see that it fires.
Some cameras need the focus/ground connection to be on before the fire/ground connection fires the camera, some the focus and fire are completely separate, and you can connect the fire/ground wires to fire the camera without connecting the focus/ground.
In the 3.5mm/2.5mm cables for shutter releases I have used, the band next to the sleeve is the common ground, the middle band is for doing the 1/2 press of the shutter action (focus), and the outer band is for firing the camera. If you don't care about the distinction between focus and fire, you can wire them together. Some of my older cameras need a longer period to focus when the camera is in live view mode, so I do need to have separate controls.
Since the camera is normally powered via a battery, the camera's ground is independent of the Arduino, so you probably would not want to use a transistor.
If your camera does not support a wired shutter release, you have several options:
It might support an infra-red shutter release, and there are programs to allow the Arduino to act as an IR shutter release;
If you are willing to open the camera and void any warranty, you can add additional wires to where the shutter button connects;
You can use a servo to press the shutter release.
Some of my Olympus cameras support a wired shutter release, but will not use the shutter release to start/stop movies. Instead to take movies you need to press a separate button, and if you wanted to do that, you would need to rig up a servo to press the button.
martinsnajdr:
So, what I want to do is to control the connection between those two wires via Arduino.
I would be a bit careful about this. I have a JYC controller that will do just about everything you can think of, plus a few you probably won't, and I'm sure it cost a lot less than an Arduino.
Secondly, unless you are already certain of what you are about, you might question what those holes are for, or at least advise us what the camera is, as a single jack is more or less de rigueur. I have never seen an electric release socket that has two holes, but my Graflex has a three hole socket for a combination release and flash. If you really mean old, the shutter release will more likely be mechanical and part of the shutter button, and two holes is more likely for the flash contacts
Thank all for your answers. I'll buy that opto-coupler and try to play with that.
It's a classic Polaroid SX-70. Those two holes are just behind the shutter button, so from what I know the holes just work as an optional way to trigger the shutter button.
Nick_Pyner:
Ah well, there you go. Trust Polaroid to do it differently............
The SX-70 predates the modern cameras that take electronic shutter releases, and I believe the original versions did not have automatic focusing, so it didn't need the 3rd contact to do the 1/2 press action to get the camera to auto focus (evidently later versions had sonar autofocusing). Of course given that there are something 10-20 different cables for shutter releases, with several manufacturers having different cables for different models, I think it is unfair to say they did things differently. In the area of shutter releases, there is a lot of variety.
