When I first started flying rockets, I always thought getting pictures during the flight would be great fun. Sort of a trophy from a successful flight. I did fly a rocket with an X-10 video camera in it over a year ago. It worked, but the transmitter lacks the range to record the entire flight. I actually pulled out the X-10 again, hooked it up and made sure it was still working, it was, but it didn't make much sense flying it again if it would only transmit several hundred feet. I bought a small factory rebuilt digital camera some time ago. The idea was to fly it in a rocket, I kind of liked the camera and hated to take it apart and put it in a rocket. But, simple digital cameras are so cheap now, I decided it was time to send it skyward.
The problem now, was how to trigger the shutter release in flight. I considered triggering it manually, using a small electric motor with a cam on it, pushing a rod that in turn pushed a lever on a pivot to push the shutter button. I wandered around my shop for a while, looking for likely parts. After a while I decided against the motor and lever idea, it just seemed clumsy, and destined to fail.
So I went back to my original idea of electronically triggering the shutter. I had opened up the camera before, and it looked like I should just be able to put another switch in parallel with the one in the camera. But what kind of switch? A 555 timer chip should work for timing, and a transistor would probably work to open and close like a switch. I decided to go with a small relay instead of the transistor. I wasn't sure if a transistor would work properly, it may, but I had the relay anyway and I knew it would work.
I tested the camera in the 640x480 mode, to see how much delay I would need between pictures. About 1 second was the minimum. Now I needed a 555 timer circuit to open and close the relay every second or so. I did a search on the web, and found a circuit that looked like it should work. So I built the timer circuit on my bread board and plugged it into a 9 volt battery. I used a piezo buzzer for output. After a few tries I found the right combination of capacitor and resistors to give me about a 1.5 second delay. I then wired my relay into the circuit, and it didn't work. For some reason, the circuit wasn't putting out enough power to drive the relay. So I doubled up the batteries and went with 18 volts, the maximum the 555 can take. The relay then worked perfectly.
The digital camera uses (4) 1.5 volt batteries for 6 volts. There wasn't much sense in adding an extra battery pack, so I decided to use a LM 317 voltage regulator to drive the camera. I was hoping there would be enough room on my little circuit board for everything, as it turned out, it was an easy fit.
Above is the schematic for the 555 timer based shutter release. It is viewed from the the bottom, or solder side. I didn't include the LM 317 part of the circuit, as that will vary from camera to camera.
Parts List:
1.5"x1.5" PCB
9 volt Mini Relay Radio Shack #275-005A
555 timer
47 uF Electrolytic Capacitor
22 uF Electrolytic Capacitor (a ceramic should work here also)
68K Ohm Resistor
1K Ohm Resistor
All the wiring was done on the bottom of the board using point to point wiring. I used 22 gauge solid wire.
Above is a picture of the camera mounted on a piece of PVC body tube. I decided the easiest way to mount it would be to cut a section out of the electronics bay, and screw the panel with the camera onto it.
I drilled a 1" hole through the PVC for the lens to poke through, I had to hot glue the lens focus ring in place, as it moved freely without the camera body in place. I roughed up the inside of the PVC, then hot glued the main camera board to the PVC. There is another smaller board with the switches on it, I hot glued it above the main board. The 555 timer/relay/LM 317 board is mounted to the PVC by way of 2 plywood blocks cut to fit the curve on one side and flat on the other, then screwed in place.
Above is a photo of the camera. The bottom board has the lens on it, you can see the USB connector at the lower right. The board on the left (on top) has the LCD display, function switch, mode switch and very top left is the shutter switch. The shutter switch had two positions, when you started pushing the shutter release part way in, the camera would display the number of remaining pictures. When the button was pushed in all the way the shutter would trigger. I found both switches needed to be activated, so I wired both together going to my relay.
Above is a close up of the timer board. Top left is the 555 timer chip with one capacitor above it and one below
it. To the right of the 555 are the 2 timing resistors for the 555. To the far right is the LM 317 voltage regulator.
Below the LM 317 are the two resistors used to adjust the regulators output. On the lower left is the mini relay.
I think I will mount the batteries on the other side of the electronics bay, just to balance the weight. The entire camera system you're looking at above, including the PVC weighs 151 grams. The two 9 volt batteries weigh about 70 grams. After everything was in place, I tested it to make sure all was still functioning. Upon installing the batteries, the camera started clicking away, I let it roll until it had taken about 40 pictures. I uploaded them to my computer, to check the results. The photos turned out fine, so I was just about done.
Above is the camera from the outside. On the top is the camera lens, then 2 screws to hold the timer board, then the pull pin shutter release and last the relay power switch.
The camera has a nice feature of staying on for 30 minutes before the power saver turns it off, many cameras turn themselves off after only 30 seconds. So, that would give me time to turn the camera on, and install the camera on the rocket in plenty of time to launch.
I discovered the entire camera system uses a fair amount of power, so to save power I installed a small slide switch on the outer shell. This switch powers off the relay, but still provides power to the LM 317 powering the camera.
The next thing I needed was a way to start the camera, so I installed a pull before flight 3.5mm jack. The jack has normally closed contacts, when the plug is installed the camera will not be taking pictures, when the plug is pulled the shooting starts. I'll probably just use a string to pull out the plug just before ignition of the rocket.
I'm not sure if I'll use a mirror to shoot down directly below the rocket, or just let it point straight out. I may do both, try it first without a mirror, then with a mirror. With the camera ready, I need to get a rocket ready to fly it in. I'll post the results to this page soon.