The second project I managed to complete was a so-called “valve sensor” for the Camera Axe trigger I built three (!) years ago. This is connected to one of the sensor ports on the trigger, which can then open or close a solenoid-operated valve on the sensor, allowing water from a reservoir to flow through it. The trigger also controls timing of the camera shutter and a flash gun.
In sequence, the Camera Axe does the following:
- Opens the camera shutter
- Opens the valve for a few milliseconds to allow a single drop of water through the valve
- The drop falls into a dish of water below the valve, causing a column of water to rise from the dish
- Meanwhile, the valve releases a second drop of water after a delay that is carefully timed to ensure that the second drop collides with the rising column of water from the first drop
- Another fixed delay elapses and the flash is fired just as the collision occurs
Some experimentation is required to set the various timings to values that will create the collision and then capture it.
Here is the setup and an example picture: