4-minute circuit...

Superman

Hi,

I'm not sure if this is the right board cause i cant find an electrics/circuitry one.
I'm looking to make a circuit that will close every 4-minutes (preferably be able to change this).

I plan on wiring it into the remote for my digital camera so i can just set it up and let it take a pick every 4 min (4 min is how long it takes the sun to move 1 degree across the sky)
i'll be using this this shutter trigger.

I really just need to know how to make it but if anyone loves soldering anf wants to make it for me i can pay a couple of quid (but i'll need the shematics in case i brake it ).

backboiler

Is that just a mechanical button on a cable? Do you mind chopping it up or are you after a sort of "artificial finger" jobbie that would press the button every few minutes? (Not that it's make any real difference to the circuit, just solenoid+sellotape:p instead of relay).

What about this one? http://www3.telus.net/chemelec/Projects/Timer/Timer-1.jpg
Just substitute the relay contacts for the switch.

Note: This is just a random web find, not my site. See the instructions on that site first.

Superman

hmm looks impressive, thanks for your help i'm going to have a crack at it in a few days maybe

backboiler

Watch out for the way the pins are shown on that diagram though. They're the opposite from the usual layout, which is as seen from above. This diagram shows them from below, if you know what I mean.

david powell

You can buy timer-relays from the likes of radionics or some electrical wholesalers, you can set the on & off time for the contacts and they can provide various delays, from seconds up to hours, from memory you'll get something for about 30 Euro, this would probably be the simplest route.... Before Programable logic controlers ( PLCs ) timer-relays were very widely used...

Of Course the other option is to make something up with a 555 timer

backboiler

Another thing to consider is the accuracy of the timing. If the interval must be exactly 4 minutes then you'd be better off building a simple crystal oscillator and dividing the output from that. You could expect an accuracy of about 1/40 of a second or better without tuning. With resistor and capacitor the initial variance could be as much as 80% of the expected value and even after calibration, temperature changes will cause substantial differences in cycle time. This is especially true if you use a simple 555-based circuit with a large capacitor (for a long time constant). I mention this only because you're tying the circuit to sky movements so the accumulated inaccuracies in timing may not be desirable.

finnpark

If you can have a PC running you could use a simple software program to generate the delay for you . You would need to be able to access your parallel port or USB or something in order to do this. This can be tricky on a Windows machine although if you google for userport driver it will free up the parallel port for you.

If were doing this I would use a micro-controlled with a programmed timer to trigger the output line of the switch - assuming that it would have the current sourcing capabilities for the type of cct inside the camera . ie. at the switch.

You could use a web cam on your PC to take the picture for you - essentially then all you have is a simple software problem.

finnpark

After re-reading your post I think that using the USB port or a micro-controller is best way to go. If you can get yourself a realy with a built in timer then go for it.

As far as using a 555 timer: It could get very tricky due to the delay length