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Old Sep 30, 2007, 10:41 AM
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AmateurE's Avatar
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Camera Trigger/Stay Alive Circuit

Electronic Gurus, I'm looking for a trigger/keep alive circuit for my hacked Dakota disposable camera (I'm sure everyone else on the planet uses a much cooler camera) for aerial photagraphy use. Looking for a DIY project as opposed to some of the fine comercial products out there. Currently I utilize a servo/micro switch arrangement coupled to the ch.4 stick. The camera will go to sleep if there is no activity for a couple minutes. I'd like to use a component or TTL circuit (no PICs) as I have a well stocked parts bin. Something that would take a picture every 30 seconds with the ability to snap a shot with a wiggle of the left stick would be great. Thanks to any and all that might help.

Bob
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Old Sep 30, 2007, 12:49 PM
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How will the camera be triggered, ie can you just short two contacts? If so, a tiny relay is your best bet (no need to worry about polarity, voltage levels, etc etc).
555 timer (or if you're not too bothered about accuracy, a 7414 inverter with a resistor and capacitor) will time a few seconds, you can then divide that down with the digital stuff you sound familiar with.
I'm confused by your disposeable cam going to sleep, I thought the disposables were mechanical?
You can convert a servo pulse to something digital (very roughly) by averaging the signal and then going through a comparator. Or better and still not too complex: charge a capacitor during the high pulse and discharge during the low, then to a comparator again. Will need a bit of filtering after that.
That's probably enough for you to be getting on with.
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Old Sep 30, 2007, 04:37 PM
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Thanks MatC for the reply. The Dakota camera is a cheap one-time use digital (1.3M) unit that was hacked so one could download to your PC and reuse it. Not really sure if they even sell them anymore. $11 for a camera that I'm not afraid to send on a meeting with the dirt. Two contacts need to be shorted to take a picture. I stripped away the case so all your left with is a small board with the lens attached and a AA 2 cell battery holder. Ideally a 555 astable circuit (to keep it powered up) combined with a monostable trigger circuit (to take pictures on command) would work. I just haven't found a circuit that covers both needs.
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Old Sep 30, 2007, 04:47 PM
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Try this, I've heard that it works on some cameras: Fly with the trigger constantly depressed; that keeps the camera awake. Then, to snap a photo, release and depress again.
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Old Oct 01, 2007, 02:59 PM
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Joined Oct 2004
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Try servo circuit

You might think about using the circuit board from a small (micro) bad servo (gears striped, broken case, bad motor e.g.). With the TX control at one extreme the one of the servo motor leads should be at your RX battery voltage (about 5 volts, and at the other extreme about .1 volts or less relative to the RX pack ground (black lead) Very easy to connect a small 5 volt relay, possibly a SPST reed, to do what you need. Don't forget a small diode across the relay coil. I have some old servos from the late 70's early 80's that I wouldn't trust to fly due to possible erosion to the feedback pot or motor. I could send you one for the price of shipping (about a dollar) if you what one.

Glynn
AMA 30686
gfurr1@nc.rr.con
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Old Oct 01, 2007, 04:42 PM
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N.E. USA
Joined Oct 2003
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If your camera has a USB port,... this mod might work:
(powers camera up using USB port... as if connected to PC for download)
The electronic switch is simple... you'll need to determine whether the camera's trigger pin is active high or low (simply use other output on IC)

http://www.diyrc.com/aiptekmod.htm
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Old Oct 09, 2007, 04:53 PM
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Thanks guys for all the suggestions. Keeping the trigger constantly pushed didn't work on this cheapy camera, nor did powering thru the USB port. I ended up fabbing a 555 timer on a small circuit board whose output fed a small 14 pin dip relay for the contact/shutter closure. Its set to take a shot every 10 seconds, so I won't have remember to hit the left stick and take away any of my faculties from my crumby flying skills. Thanks for the link to the electronic switch, I may add something like this if the timed shots don't work out well. The circuit board is piggy-backed to the camera board with some plastic stand-offs. Compared to the slick, PIC based switches on the market today, mine looks like the 1970s.

Bob
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