1. Connect the battery

2. Touch the battery and the 556 timer. If the battery or timer become hot, then there is a mistake in the circuit. Disconnect the battery and look for the mistake. Ask the teacher for help.

3. If the battery or 556 timer do not get hot, test the trigger. Touch the red trigger wire to the 1-megohm resistor (black-brown-green). See this photo. If the flash fires, test the delay next.

Notice that after the flash fires, you have to wait a few seconds before the flash will fire again.

Sometimes, you have to push down on the blue 1-megohm variable resistor so that the legs will make good contact with the breadboard.

4. Turn the blue 1-megohm variable resistor one way or the other to see how the time delay changes. See this photo.

5. Here's how the time delay is determined.

6. You can also control the amount of time that the circuit will not respond after a flash. This is called the trigger dead time. This is helpful if you don't want the flash to go off two or more times in a row in the same photo. Here's how to control the dead time.