time to switch between 0 and 1 and viceversa

Forum 2005-2010 (read only) Hardware Troubleshooting
1

Hi,

I made a simple lightning detector that triggers my EOS1000D via cable.

To save time I use the mirror lockup feature of the camera.

The problem is that to use this I have to trigger the mirror, keep the focus "pressed", depress it, "press" the shoot, and then re press the focus and the shoot to re-trigger the mirror.

I made some experiments, and if the time between the focus depress and the shoot press is less than 25ms, the camera doesn't sense it.

The question is: is the camera unable to detect more rapid events, or does it take so long to the arduino to drop a HIGH to LOW?

Unfortunately I don't have an oscilloscope...

The arduino is wired the following way to the camera:
Digital Pin out goes to a series of one 220ohm resistor and 2 diods (one is the led that indicates if it's "pressing" or not, the other is the led inside the optocoupler). On the other side of the optocoupler the camera is wired directly.

Any hints? Tnx!

2

25ms is a lot of time. The Arduino is definitely fast enough. This looks like an issue with you camera.

Udo

3

Thanks Udo, if the camera is the limit there's no way I can fix it :frowning:

Anyway I'm confident it's fast enough. Only 30ms slower than my modded small digital canon (due to the "forced" 25ms delay I have to set), and with the little one I took nice shots. A lightning is 200-250ms long, so I lose 10% or so (compared to the compact).

Let's wait the first spring storm;)

4

Hi.

Are you using manual or auto focus?

I am working in a similar trigger and use the camera on manual focus.
That way, i do not have to wait for the focus to be confirmed/attained.

I pulse the trigger output once to raise the mirror, and then pulse the output again to release the shutter when the event occurs.

Cheers.

5

25ms is a lot of time. The Arduino is definitely fast enough. This looks like an issue with you camera.

I'd say 25ms is quite fast for a digital camera - probably does last minute focus check and then powers a servo to set the aperture before enabling the CCD. If you can arrange to manually set max aperture that might help, but I'd pretty certain responding to lightning detectors was not a design requirement for even a top flight DSLR!

Worth hunting through the manual to see if there are other clues. Unfortunately lightning detectors give no advance warning since radio and light waves travel the same speed!

6

Deepz, I use manual focus. Tried with time priority, aperture priority and full manual.

If I press the shoot and release it, it remains locked only for 15 seconds or so. A solution would be counting 15 seconds with the arduino, then retrigger. But if for some reason I miss one, it starts triggering the mirror when it should shoot and vice versa, that's why I opted for this solution.

Which camera are you using? It'd be interesting to see how behaviour differs among cameras...