Need to put a delay into circuit.

I am trying to fire a camera via a relay but I need to put a small delay (<0.5s) into the circuit.

There are three input pins to the camera. A common ground and two positives.
1. activates the Auto Focus (AF) and Meter
2. triggers the shutter release.

Originally I thought that closing both circuits at once would be sufficient but have since discovered that there is not really a potential between GND and 2 until GND and 1 is closed. There needs to be a delay between closing GND and 1 and then closing GND and 2 to fire the shutter otherwise it doesn't work.

I thought of putting in a RC circuit and SS relay to cause this delay but need some guidance on this. See attached images.

My questions are -
- would this be the correct / most simple way to introduce a delay?
- is the second relay necessary as they are really designed for heavy current and this is very small?

There was a similar thread about this awhile ago. Check out this thread and let me know if it helps.
https://www.electro-tech-online.com...meras-too-single-flash-a-delay-circuit.41491/

Hi Mikebits. I did look at that thread. Lots of different stuff was being suggested, but a final solution was never posted. I found some other posts and articles about the RC circuit and wondered if I was heading down the right path with that before I go too deeply into working out all the details.

I'm thinking there may be some alternatives to using another relay such as using a transistor.

You could use a 555 timer IC and a transistor instead of the second relay.

or

A resistor connected to the relay switch - capacitor connected to resistor and ground. Darlington (or high gain) transistor base connected to the junction of the R&C.

You can't power a delay circuit from the camera terminals. Excluding that, there many other ways to make a shutter delay.
Here is relay solution. Relays RLY1/2 can be small 12V reed relays. The delay is determined by the coil resistance, the capacitor size, and the relay's pull-in voltage. R1 discharges the capacitor after the trigger relay opens. The value is not critical, but it limits the time before the camera can again be triggered with a shutter delay.

Ken

KMoffett said:

You can't power a delay circuit from the camera terminals....

Click to expand...

Having said that, I wondered if you could. I thought the attached might work.

Not knowing what the circuit is inside the camera, I wonder about three possible problems:

1. The input impedance of the camera's trigger circuit may be too high to allow the capacitor re-charge between shots.

2. Unlike a relay or Schmitt trigger, the transistor passes through a linear phase as the capacitor discharges.

3. When the switch is opened, the AF is turned off immediately, but the Shutter remains ON until the capacitor re-charges.

Ken

flat5 said:

You could use a 555 timer IC and a transistor instead of the second relay.

or

A resistor connected to the relay switch - capacitor connected to resistor and ground. Darlington (or high gain) transistor base connected to the junction of the R&C.

Click to expand...

Thanks. I was hoping to avoid using an IC but I will look into the transistor option.

KMoffett said:

Here is relay solution.

Click to expand...

Thanks, most helpful. I think this might be the way to go because it's simplest for me to understand and only closes the cameras circuits which I see as the safest option due to having limited electronics knowledge. I'm a bit worried about connecting directly to the camera because if I get something wrong with a transistor, it could amplify the current right?

Also I will be able to test it just by listening. I reckon enough delay to just about hear the relays click separately will be spot on. The camera will still wait for focus and meter reading (if not using manual) to be acheived before firing the shutter, it just needs a slight delay to simulate pressing straight through a two stage button.

I may have some more questions in a few days regarding the correct values for C and R and relay specs if I get confused.

Many thanks,

Jim