Have you ever wanted to remotely activate your Nikon camera? Maybe you already own the optional keychain remote but find it to be lacking in features? How about complete hands free remote triggering? Yes, our "Clap Snap" project will not only allow hands free operation, but it has a continuous 10 second time lapse feature built in as well so you will never have to mess around with the camera menus or be caught pointing that keychain at the lens in your photos! This project feeds the output from an audio amplifier into the analog to digital converter on an inexpensive microcontroller that decodes three sharp sounds and then issues the infrared signal to the camera to take a photo. This project works on all of the Nikon SLR cameras I have tested, and may work on others as well. Modifications to the design to support different features and makes of cameras would certainly be easy as well.
The Clap Snap program is designed for an AVR ATMega-88 microprocessor, but is simple enough to fit into just about any low end 8 bit microprocessor with a little code reworking. The source code is presented in assembly and the HEX file is included in case you simply want to program the microcontroller and not make any changes to the pin configurations or program operation.
Figure 1 - The original prototype was built on a solderless breadboard
It took some time to decode the pulse train that came from the original Nikon keychain remote control, but in the end it was found to be very similar to most of the VCR or TV remote controls; using a series of on and off intervals of a 40 KHz carrier signal. This old and time tested protocol is actually called "RC5" and although it varies from one manufacturer to another, it is basically a modulated 38 KHz to 40K Hz carrier wave. The Nikon was found to use a 40 KHz carrier wave as per the pulse train measured on the output of the optional Nikon keychain remote control system.
I use my Nikon cameras a LOT, and often I find myself pecking at the menus to get that self timer activated. The issue I have with the self timer is that not all of my Nikon cameras allow more than a single shot to be taken and by the time I get back into place, the timer seems to already be taking the photo! I also have the keychain remote, but again, it forces me to point at the camera and then attempt to set up the shot with the remote in my hand. I wanted hands free operation as well as a continuous 10 second time lapse system that would offer a hint of warning before each shot so the "Clap Snap" project was born. My goals were to have three claps, snaps or sharp sounds trigger a shutter release while ignoring most background sounds. I also wanted to have a nonstop 10 second timer mode. A low cost ATMega-88 was chosen as it had more than enough power for the job and would run from its internal oscillator.
Once I had the timing parameters for the pulse train that the Nikon cameras needed, I created a very simple amplifier system that would send a voltage spike to the analog to digital input on the microcontroller. The amplifier responds very well to a short and sharp sound, but does a fair job of ignoring any ambient background noise. Further processing done in the microcontroller will allow some "intelligent" listening to happen, making the camera only respond to three sharp claps or snaps in a row rather than false triggering every time the background noise level is high. To allow some feedback on operation, three visible LEDs are added to the circuit. A red LED shows the sound spikes on the input of the ADC, a blue LED indicates that claps have been heard and that the "window of opportunity" is active, and a green LED flashes when the system has heard three claps and is about to take a photo. Control of the Nikon camera is through an invisible infrared LED, just like the optional factory made remote control.
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