# Syncing a camera and a pulsed flash light using a TTL signal

#### Biofluid Lab Biofluid Lab

Joined Feb 17, 2017
24
The resistor and capacitor work together to make the delay. Resistance (ohms) times capacitance (Farads) is called a "time constant". Doubling the resistance or doubling the capacitance will double tour delay. Doubling both will give you 4x the delay.
Thanks;
What about the op amp? Is it just to bring the voltage back up?

#### GopherT

Joined Nov 23, 2012
8,012
Thanks;
What about the op amp? Is it just to bring the voltage back up?
Which circuit did you end up using - I'll explain it.

#### Biofluid Lab Biofluid Lab

Joined Feb 17, 2017
24
There are no goofy questions.

1. It's Ground.

2. The shield of the cable is connected to ground, so as long as you connect everything up BNC wise, you'll always have a path to ground, like this:

View attachment 121004

3. You could, but a better idea would be to make R1 a rheostat. See 2.

4. R5 is the input resistance of the sparker and isn't part of the delay circuitry proper. Sorry for the confusion.
I used this one! Also attached to this post.
thx

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#### EM Fields

Joined Jun 8, 2016
583
Now that I was able to get what I wanted, let me ask you about more details on the delay board and what each components do.
So what is the main component causing the delay. I assume it is the capacitor, right? As far as I know, resistors cannot make delay to the signal; they only attenuate it, right? and that's why we used op amp to bring the voltage back up, right? Is it the only function of op amp in my circuit? Just to bring the voltage back up?

Thanks
Using the water analogy, let's say the capacitor is like a tank which you want to fill about half-full in a given amount of time, and that the resistor is like a pipe connecting the bottom of the tank to the water supply.
Assuming that the water pressure of the source remains constant, the tank's fill time will depend on the diameter and length of the feed pipe, the diameter of the tank's bottom, and the difference between the source pressure and the back-pressure exerted by the water column in the tank.

#### Biofluid Lab Biofluid Lab

Joined Feb 17, 2017
24
and the difference between the source pressure and the back-pressure exerted by the water column in the tank.
Thanks.
Is this section related to op amp function?

#### EM Fields

Joined Jun 8, 2016
583
Thanks.
Is this section related to op amp function?
I don't understand.