555 timer DSLR time lapse shutter release

I've tried to use a Velleman timer kit for time-lapse photography with my Pentax DSLR camera but the single relay output isn't enough.

The Pentax-made *manual* cable release is terminated in a standard

2.5mm stereo jack plug. When the button is pressed, the centre contact on the plug is shorted to the one nearest the body (triggering autofocus etc) and when the button is pressed further in, these two contacts remain shorted but the contact furthest from the plug's body is then also shorted to trigger the shutter release.

What's needed for the 555 time-lapse circuit is second relay whose Normally Open contacts close as well, a fraction of a second after the first one. All 3 connections were shorted at this point when I checked the manual cable release with a continuity tester.

I've considered adding a single transistor triggered by the 555's output but with a simple RC time delay, e.g. its base taking a finite time to reach a sufficiently high voltage to turn the transistor on, and consequently activating the relay.

I'd be grateful for any suggestions to achieve this result. It's been years since I've done much with a soldering iron and electronic construction. Maybe I should be using a thyristor instead of a transistor, or a Darlington or something. I want to keep it simple.

Thanks in advance, Dave. 3000 photos especially Edinburgh & Scotland. + 3D rendered art, old ads etc. Délété david for email; watch the spam filters.

Reply to
Dave
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I\'m not sure that\'s such a good way to do it because it won\'t
unshort the contacts in the same sequence the manual cable release
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Reply to
John Fields

I'm not sure what your velleman kit does. Presumably this: ------------ | | ------- --------- (autofocus etc) T0 T1 T2

And you need this?

------------ | | ------- --------- (autofocus etc) T0 T1 ---- T2 | | ----------- ------ (shutter) T0 T1a T1b T2

In the absence of any specs, and if you have a bunch of relays, you could try this:

Vellman Relay n/o Contact RY1-1 n/o RY1-2 n/o |>| |>| |>| +12 ---o o----+---o o---+-----+ +---o o---> auto- | | | | focus +-----+ [RY2] [D2] | | | | |a | [D1] [RY1] +-----+ +---------> Camera a| | + | | | common +-----+ [470uF] [10K] | | | | | Gnd ----------+---------+-----+ +---o o---> shutter |>| RY2-1 n/o

When the Velleman relay transfers, it energizes RY1, which takes a few mS to transfer. When transferred, it energizes autofocus, and energizes RY2 through the charging current of the 470 uF cap. RY2 takes a few mS to transfer, which provides the delay between autofocus and shutter. When transferred, it activates the shutter. RY2 drops out when the 470 uF cap is charged and stops drawing current through RY2. The

10K will discharge the cap when RY1 drops out.

The circuit doesn't have a lot to recommend it, except that it will give you a few mS delay, and is "spec-less". It might work. You can try it until you develop specs for what is really needed for the timing.

Ideally, it would be nice to have a circuit with adjustable times for T1 to T1a, T1a to T1b and T1 to T2 and that can be designed if we know the specs.

Ed

Reply to
ehsjr

Have you tried simply shorting both the center & tip to ground at the same time? Your shot will probably be delayed by however long it takes the AF system to achieve focus, but that'd be true with any other system as well. Alternatively, you could use a positive output from your 555 to drive the bases of 2 NPN transistors, with the collectors connected directly to the tip & center connections, & both emittors wired to ground.

Reply to
Lionel

On Wed, 21 Feb 2007 14:55:37 -0600, John Fields somehow managed to impart:

I've copied the circuit diagram to:

The supply voltage is 12 volts. There is no start button, just applying power starts it. The length of the shutter release sequence is probably roughly 1 second in manual use, whether using the cable release or the button on the camera, i.e. press the button half way, wait for autofocus / autoexposure to kick in, there's a beep to confirm it's focussed then you press the button all the way to open the shutter and take the photo.

Thanks to everyone for their suggestions. I reckon I'll dig out my old 'breadboard' and try a few things out...

Dave. 3000 photos especially Edinburgh & Scotland. + 3D rendered art, old ads etc. Délété david for email; watch the spam filters.

Reply to
Dave

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Sorry, I forgot to ask how long it\'ll be between triggers.
Reply to
John Fields

On Fri, 23 Feb 2007 11:29:26 -0600, John Fields somehow managed to impart:

[snip]

I think I'm on the way to a working circuit. The output of the 555 turns on the first relay and also turns on an NPN transistor with a

100K resistor as a collector load. This goes low and triggers another 555 in monostable mode. After a delay of say, between 500mS and 1S, the second relay should close and fire the shutter.

I've got the trigger working - and I *did* have the monostable working but I need to take a rest because of the need to keep changing my spectacles as well as using a jeweller's eyeglass. The eyesight ain't what it used to be. I'm glad I don't have to fix CRT monitors and laptop mainboards any more!

Dave. 3000 photos especially Edinburgh & Scotland. + 3D rendered art, old ads etc. Délété david for email; watch the spam filters.

Reply to
Dave

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