5V delay switch

[figure1a]

How can I make a simple contraption that consists of a switch that when pressed would delay for 41 milliseconds then output 5V DC current for 5 milliseconds? Is that something I could make with simple capacitors/resistors/transistors type of stuff?

 

[Brevor]

Yes you could do it with a couple 555's or a logic gate. Someone for sure will ask how much current the circuit needs to supply, if it's more than a few milliamps you will need a transistor on the output. It also matters how precise the time delays need to be.

 

[figure1a]

Thanks for the reply. The time delays don't need to be 41 milliseconds exactly but it needs to be consistent. How would I go about figuring out what parts to get and what specs should I look for? Is this something someone could sketch up really quickly?

 

[colin55]

How much current does it have to deliver for 5mS

 

[figure1a]

How much current does it have to deliver for 5mS

A few milliamps will do. It is going to trigger a camera in the shutter release socket. I haven't measure how much current it needs yet.

 

[carbonzit]

I think this circuit might work; I simulated it (in LTspice), and it generates a ~1mS pulse, about 5 volts, about 12mS after power-on. You could probably tweak it to get closer to your specified timings.

**broken link removed**

So can anyone here tell us how to improve this? It doesn't exactly produce a square wave. What's the easiest way to square up the output? make sure the transistor is driven into saturation? (LTspice file attached below.)

 

[colin55]

You had better measure the current first.

 

[carbonzit]

Well, that aside, am I on the right track here? Can anyone come up with a simpler solution? (For my money, I'd like to see something without an IC like a 555. This is such a simple function that it seems to only need BJTs and such.)

 

[ericgibbs]

Well, that aside, am I on the right track here? Can anyone come up with a simpler solution? (For my money, I'd like to see something without an IC like a 555. This is such a simple function that it seems to only need BJTs and such.)

hi cz,
One way is to add a second transistor and invert the action of the first transistor.

 

[carbonzit]

So you'd, what, make Q1 an emitter follower and Q2 a common-emitter stage?

By the way, here's the trace I get from this circuit (somewhat modified, new LTspice file attached). Not too bad. A little wider than 1mS, but should be fine to trigger a camera with, I'd think.

 

[Reloadron]

A few milliamps will do. It is going to trigger a camera in the shutter release socket. I haven't measure how much current it needs yet.

I may be way off base with this, and if yes, I am sorry for questioning. I have a few DSLR cameras a Canon EOS 10D and a 7D. Both of these cameras as well as many other DSLR cameras I have worked with involve using a logic low signal for external or remote shutter release. The shutter release on my own cameras has a 3 pin connector. Two of the 3 pins are held at a logic high of 3.3 volts. They are held high through an internal pull up resistor. Placing either pin to logic low will fire a function. One pin is the AF (if used) and the other is shutter release. I just want you to be sure that an external positive pulse of 5 volts is what you want.

Ron

 

[carbonzit]

Well, if that's true, my simple circuit could certainly be tweaked to produce a negative-going pulse. But it's a good question.