View Full Version : Circuit setup help,please.

04-10-2010, 10:06 PM
Hello everyone. I've got an old basic stamp board that I've decided to put to good use. I want to create a wireless trigger for my camera flash. By day I'm a .Net programmer, but I know very little about how to make a circuit connect to another piece of equipment without releasing the smoke. This is where I need the help.

From the below site you can see I've got 5 connections I need to control and one ground connection.
kzar.net/wiki/Photo/CanonE-TTLProtocol (http://kzar.net/wiki/Photo/CanonE-TTLProtocol)

One has a trigger of 3-5 v, low being connected to ground.
Second connection low is 1.25v to ground, high is 3.2v.
Third, fourth and fifth connection is low at 2.2v, high being between 3.3v,3.7v, 5v.

So basically once I figure out the circuit I should be able to start working with the bytes being sent back and forth. I have a limited knowledge on circuit diagrams, but I can usually fumble through those decently well.

Below is another person's work, but this time with some clues for an arduino.

billgrundmann.wordpress.com/2009/03/04/ettl-interface/ (http://billgrundmann.wordpress.com/2009/03/04/ettl-interface/)

04-11-2010, 08:56 AM
What is it you would like us to help you with? How do you plan to implement the wireless part?

- Stephen

04-11-2010, 10:57 AM
Well the wireless part I'm going to use something like an xbee or the 433 mhz kit. The part I'm not sure of is what parts (resitors, etc) I need to put between my camera body and basic stamp so I don't smoke either one with I turn on the power. The other part is the high low piece with the low voltage being at 2.2 volts, but I think I can use a LM358 to do that for me and set it to something like 2.7 or 2.8 volts so I can check for high low easier. But again, I don't know how to wire it up without frying my camera or flash, both of which would eliminate the doing it myself to save a few bucks approach.

04-11-2010, 11:10 PM
You would have to find out if the pins that do not go to 5v can handle 5v or if that would damage them. It would be a good idea to read the link you sent and make sure you understand what is going on before you connect anything to the camera. Good luck with your project.

- Stephen

04-12-2010, 01:42 AM
I made an IR remote for my Nikon D80, using a small PIC powered by a couple of AA cells (it could be a Li coin cell). It works very well and has the advantage of not needing a direct electrical connection. Nikon sells an IR remote but mine only cost me about $3 to make. Adding wireless would be very easy. You might be able to do something similar with your Canon using the Stamp, if it has an IR sensor.

Leon Heller
Amateur radio callsign: G1HSM

Post Edited (Leon) : 4/11/2010 6:51:49 PM GMT

04-15-2010, 04:01 AM
The flash does have an IR sensor, but I would still need to connect the IR to the camera. Canon makes a piece that does this, but IR doesn't work well outside, its a known issue.

I found the LTC1298 on parallax's site. This looks like something I would need to figure out the commands coming from the camera. From my research and reading of those canon reference sites, if something would be better or cheaper let me know.

Data rate is around 104 khz. Can i use the Parallax USB Oscilloscope or is that to slow. I know its a 200 khz sample, but thats about it.
I've got 2 incoming, 1 outgoing data pins and 1 clock pin. The clock pin goes to ground (low is like 2v) to signal a preflash. So I need to hook this up to the LTC1298 and to the stamp, can I split the clk signal without any issues?
Can I hook up the LTC1298 to the current camera and flash and sniff the traffic without the Oscilloscope? Or will that cause issues?
I should be able to figure out myself to push 5v to 3.8, and 3.7 myself from my old physics classes.