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Monday, June 30, 2008

Using TI-83 as camera intervalometer

Found a really cheap solution for hands-free operation. Introducing the handy TI-83 graphing and programmable calculator (emphasis on programmable). Told about this link regarding time lapse photography while surfing for a commercial solution. A good colleague turned me onto this; Geoff is a real jack-of-all-trades sort. Turns out the remote shutter jack on my Rebel XT camera is a 2.5mm audio jack. The data port on the TI-83 is also a 2.5mm audio jack. By programming a routine to time mirror lock up and shutter release, the TI-83 send() command is used to pulse the data line...the same way a remote shutter control pulses the camera. The only difficulty I encountered was locating a male-to-male 2.5mm cable. Only thing I could find was online at BoxWave.


This is so cool! As I type this, the camera is outside working on 200 exposures of M17 tonight. No need for a laptop and cabling, now I'm free to grab the binoculars, star map, a beer, or two. The picture below is a little fuzzy, but you can see my messages printing to the screen as it operates the shutter release.


I programmed the calculator with the following:

[7/13/2008] Thanks to Craig on Andy's Shot Glass site, I've corrected listing. You MUST use the programs menu to enter commands, and remember to use the STO key to assign values to variables (the -> notation):

300->T
Prompt I
Prompt E

T*5->M
T*I->S
S+(T*3)->R
T*5->P

For(N,E,0,-1)
Disp N
Disp “MIRROR”
Send(I)
For(D,M,0,-1)
End

Disp “SHUTTER”
Send(I)
For(D,S,0,-1)
End

Disp “BUSY”
For(D,R,0,-1)
End

Disp “PAUSING”
For(D,P,0,-1)
End

End

Disp "DONE"



Voila!

4 comments:

Geoff said...

I'm glad that is working out for you. I'm still thinking of designing a microcontroller system to do similar just for the fun of designing the hardware and software.

Andy said...

Thanks again for the link, Geoff! I'll make sure I update the post with your credit, wasn't even thinkin'...too darned excited, been waiting to try this since you copied me on the link.

I would bet you could do this all with just hardware. This could be a marketable product for astro imagers using DSLRs. You could even offer a variety of cabling for different Canon, Nikon, and Olympus remote shutter ports.

Mle said...

Call me a noob but what do I put in for I and E? What does each do?

Andy said...

The variable I is the number of seconds for each exposure. I use 15 when prompted. The variable E is the number of exposures to take. So, to shoot 250 15-sec frames, you enter 15 for I and 250 for E.

Note, the measurement of time is simply based on delay of the for-loop, so its not very precise. If you enter 25 for I, each exposure would be roughly 25 seconds.