# DIY Intervalometer using TI-83 Calculator



## anthony.grimes (Aug 22, 2008)

So I have been interested in doing star photography, and from my understanding the most common method is to take numerous ~30s exposures and merge them.However, I didn't feel like standing out side and pressing the shutter button every 30 seconds for two hours. I found a really good tutorial online about how to turn you TI-83 graphing calculator into an intervalometer.

All you do is write a custom program for your calculator (code is below), when the program is run it will ask you to enter a value. This value is the time interval in between shots in seconds. Then connect the calculator to your  cameras remote shutter connection via the 2.5mm cable provided, and sit back and enjoy.

The original article can be found here.
http://www.instructables.com/id/Turn-a-TI-Graphing-Calculator-into-an-Intervalomet/

I edited the code so that the value input was in seconds. My code is as follows:

Prompt A
A*212.7 --> A
While 1
For (H,1,A,1)
End
Send(A)
End

**The 212.7 is the scaling factor to convert your input into seconds, this may vary based on calculator.

If you have any questions feel free to ask...


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## tkaat (Aug 22, 2008)

did you try yet and if you did how did the photo look 
And what gear are you using


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## anthony.grimes (Aug 22, 2008)

I have not tried with star photography yet, I live in the city so it is rather difficult. But I have tried the intervalometer and it functions properly. I use a rebel xti. My friend has a rebel xt and it works fine as well. The program will also work on a TI-84.


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## jamesino (Aug 22, 2008)

Can the TI also be used as a remote shutter release?


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## anthony.grimes (Aug 22, 2008)

yes it can, the program listed could actually function as a remote shutter. All you would do is enter the time delay and start the program, then stop the program after the first shot. You could code up a different program to act as a remote shutter, if you so desired.


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## jamesino (Aug 22, 2008)

Thanks for sharing =) Unfortunately, my TI-84 did not come with a 2.5mm to 2.5mm unit-to-unit connector, it only came with a usb cable and a usb unit-to-unit cable. 

Does anyone know which stores in North America, I could find a 2.5mm to 2.5mm cable?


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## photogincollege (Aug 22, 2008)

Would just like to say thanks for posting, im gonna give it a try.


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## anthony.grimes (Aug 24, 2008)

jamesino
I used my cable with a friends TI-84 and it worked fine, so if you can find a cable you should be in luck. I would check radio shack, I assume that they would have it. If not, I know you can find them online.

photogincollege
Let me know how it works. Be sure to post up some pictures when you are done!


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## Josh66 (Aug 24, 2008)

How would you write that in BASIC?  The only programmable calculator I have (Casio CFX-9850GB Plus) uses BASIC instead of whatever Texas Instruments calculators use.

I know it has to look sorta like this:


> 10 *write something here*
> 20 *write something here*
> 30 *write something here*
> 40 *write something here*
> etc...


...but I have no clue what commands I have to use.


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## tmckee1691 (Aug 26, 2008)

I really like this idea but I shoot a Nikon D80 and the remote shutter release cable is not a 2.5mm jack. Does anyone know where I can find a cable that will work for this setup?


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## anthony.grimes (Aug 27, 2008)

I know that you can splice one yourself, however, I have not done it with that specific cable so I am unsure as to the proper method.


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## jamesino (Sep 4, 2008)

I'm not sure what you did for the conversion factor.

A*212.7 --> A

I can't find a "-->" arrow on the calculator, so I just entered in "A x 212.7" and when I try to run it, it says Syntax Error


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