Time lapse means pictures are taken at a specific interval of time. The time interval is adjustable over a wide range and it has an additional sensor, that interrupts the time lapse execution during the night, significantly reducing a large amount of black pictures. ;-)
What do you need:
a digital camera: Rollei 52 (although I guess it will work with most Rollei digital cameras)
a microcontroller (I used an Attiny24, but any other might do the same job)
a few electronics parts like transistors, resistors and connectors.
and a soldering iron like this one from craftsman for instance.
Step 1: Interface the Camera
Most big SLRs have an existing interface where you can plug in a control unit. Most small size digicams don't even have an external shutter release interface.
So we have to built this by ourself. But keep in mind that you loose the warranty if you open the camera.
But you can install the interface it in a way, that you can still use the camera normally.
Step 2: Disassemble
First unscrew all the screws on the side and the bottom and keep them in the right order.
Then lift up the front cover. The flash-light is still connected to the front cover, but you can unscrew it with two small screws if you want, or just leave it connected the front cover is not such a big thing.
After that you can unscrew the back cover from the inside, look at the pictures.
Step 3: Detecting the Function
The Rollei camera has on one pin of the ON/OFF-switch a high, while the other is low. When the button is pressed, the previously low pin gets a high signal and the camera is switched on or off. This also works if the high signal comes from somewhere else but the other side of the button, so we need only one pin (the previously low one) to control the ON/OFF functionality.
With the release button it is the same. When the camera is on, one pin is high, the other is low. When the release button is pressed, the previously high pin gets pulled down to low. So that's the second pin we need to control the shutter.
We are lucky, as we only need to drive these two pins to control the camera!
Step 4: Solder Wires to the Relevant Pins
First I used small coated copper wires for this job. They are only 0.15mm thick and are coated with isolating material. When you tin the ends, the isolation is removed and contact can be established. And they are thin enough to route them through a small hole or slit in the housing. Use them, if you still want to use the camera without the time lapse module.
After a while I noticed that these wires were to fragile to be handled and I used normally isolated wires.To get them out of the camera I removed the cover for the batteries. Now it's not possible to install batteries and use it normally., but I don't want that anyway.
On the outside, you can solder a small jack on the end of the wires or connect them directly to buttons or a microcontroller.
Step 5: Add External Power Supply
That is also the reason why I chose not to use batteries any more and use the battery case for the cables instead.
One dissadvantage of the Rollei compactline 52 is that the date is lost within a few minutes when you disconnect power. To cope for this problem, I soldered a supercap in the place where the battery used to be.
And because the camera is usually operated at 3V, I additionally added a diode in the power supply cable. At this diode we 'loose' 0.7V, so we can operate the camera with standard 3.7V Li-Ion batteries.
Step 6: Test Function Before Reassembling
Apply an external voltage or install batteries.
You remember which of the wire was for the ON/OFF? O.k., then connect this wire (white) to the positive power terminal or the positive supply wire (red).
What should happen is: The camera switches on, because we applied a high to the previously low pin. If you touch them again, the camera switches off again, but wait for this after the next test.
Now touch the other wire (blue) with the negative power source (black) for a short time and the camera should make a picture. To turn it off, just touch the first wire with the positive again. If nothing happens, then it is most likely that you installed the diode in the wrong direction. Then applying external power, the anode of the diode goes to the negative terminal of the camera! Try it first without diode and the with again.
That's it! That is the whole magic!
Now you could apply 1km of wires with pushbuttons at the end and make a remote control for the camera, but hey we want to make a time lapse camera, so go on to the next step!
Step 7: Use a Microcontroller for the Job
I once started off with a Picaxe 08M, which was more than enough for the control.
But later I wanted to add more functionality and started with the AVRs.
Now I'm working with an Attiny24, because it is small, fast and has a lot of other features that I wanted to have.
Step 8: The Functions
3. selection for time lapse interval
4. sensor for light (shutdown during night)
5. Indicator for function (LED)
7. Immediate release button.
8. Test for supply voltage and shutdown if too low.
The first two are mandatory, as the others are more or less optional.
For the first two we need only output pins. To limit the current and to protect the micro controller we use an 4.7k-Ohm resistor in line.
The third point might be solved a thousand ways. I chose a simple button that increases a time variable each time it is pressed.
For the fourth point I used a light dependent resistor. Its resistance varies by the amount of light that falls on it, which can be measured by the micro controller and so night could be detected.
The fifth point needs an digital output too, that's rather easy.
The reset-pin is fixed to one specific pin of the uC, so we just have to add a button there.
For the seventh point we exploit the external interrupt ability of the microcontoller. That means, if the button is pressed, any time no matter what the microcontroller just does, it interrupt the normal execution and goes straight to the interrupt routine, which tells him to take a picture. I call this the naked button. Just image you sitting somewhere and taking a time lapse and a naked is running by. So just press this button and wow, got it!
You'll thank me when it happens!!! ;-)
The eighth point also makes use of the ADC functionality of the uC.
3 digital outputs (On/Off, shutter, LED)
3 digital inputs (Reset, naked-button, interval)
2 ADC-inputs (LDR, supply)
That's quite a lot, but the AVR Attiny24 is sufficient for the job.
Step 9: Make the Circuit and the Layout
From the functions I described in the last step, it is very easy to set up an electronic circuit. Just look at the one I provide, if the picture is too small try the pdf which is zoomable.
To save space and make it as small as possible I used some SMD parts. These are surface mounted devices. They are not as hard to handle as you might think. in fact, once you get used to, they are much easier, because you don't need to drill the PCB for them! ;-)
Two of the three top layer routes are realised as wires on the bottom side and the last one is realised as wire on the top side. I don't like double sided PCB as this is quite a hustle and three air wires are not enough to justify this.
You can use the provided board layout to etch a custom board by yourself or build the whole thing up from scratch on breadboard.
Step 10: Power the Micro Controller and Camera
We can use 3x 1.2V NiMH batteries or one Li-Ion-cell of 3.7V.
If we want to power it with a larger range of power sources we can use an LF33CV in a TO220-case. This device provides up to 1.5A at 3.3V at any input voltage from 4-20V. Ideal for the use with a lead-acid battery or solar power panel.
I will publish an instructable for this soon.
Step 11: Program the Microcontroller
Step 12: Debugging
In bright light the reading is zero, but when switching the light off the reading rises.
Covering the PCB with the hand would cause it to rise even further.
I detected a good value for the night shutdown to be around 7D, which I finally used as the limit. When you look at the code, you will see, that the reading from the LDR is multiplied by 4 and then compared to 500. The exact value also depends on the LDR you use. I used a Perkin Elmer A905014, which has 3MOhm after 5s of darkness and around 15kOhm in 100lux light intensity (bright daylight).
Step 13: Operating Instructions :-)
But o.k. I give you a brief summary:
When power is applied, the LED flashes quick two times.
Then you can adjust the time lapse interval with the interval button. Following table shows how many pushes produce which time:
0 no switch off, taking picture after picture. (one picture every four seconds)
If you press more than 11 times, the counter starts with zero again.
After you found the right time, press the interrupt button. Then the LED flashes as often as you pushed the button. You can count the flashes to control the setting. Then there is a pause of 1s and a long last flash.
After that the time lapse starts. Camera will be switched on, a picture is taken, camera switches off again.
Remember: If a naked is rushing by, press the interrupt button and pictures will be taken immediately as long as you push the button! ;-))
If the voltage of the power supply drops below 80% of the initial voltage, the micro controller enters power down mode and stays there until you replace the power supply (i.e. the batteries).
Step 14: Have Fun!
Ever missed that beautiful sunrise because you wanted to sleep another few minutes?
That's no problem any more now, just place the camera outside the window in the evening and when you wake up see what you have missed....
Or ever wanted to know who park on your place when you are away?
The embedded video shows some example for a time lapse that was recorded with the Rollei 52.
The last word: If I had a laser cutter, I could make me a water proof housing for it! So please vote for me at the epilog challenge!