dropControllerV4: Loop Page and Delta Values

To get drops to collide and then photograph the collision at exactly the right time can be very challenging. The drop start times have to be timed exactly right, the drop sizes have to be just right, and the shot has to be taken at exactly the right time. To do this with most drop systems is time consuming and can be frustrating. Wouldn’t it be nice if you could loop the drop sequence and move the flash trigger time slightly every loop. Or, make the drops start at different times every loop. Or, make the drop sizes larger or smaller. Using the dropController and Loop Mode you can.

Loop Mode is the heart of the dropController series of controllers. There has been a version of Loop Mode in every controller built, including the very early prototypes.


Loop Mode Control

Loop Mode is activated using the Loop Mode control on the main Drop Data Page.

Clicking the Loop Mode control button cycles through the various options; OFF, BUTTON, TIMER


Loop Mode is off and Single Sequence Mode is used.


Loop Mode is active. To start each drop sequence the Loop Page START button has to be clicked.


The first drop sequence is started by clicking the Loop Page START button and then subsequent sequences are started when the TIMER reaches 0.
The TIMER time is in seconds,

When Loop Mode is OFF, Single Sequence Mode is used. When Loop Mode is ON, clicking the the main START button opens the Loop Page

When BUTTON is selected. Each drop sequence is started by clicking the Loop Page START button and after each sequence is finished, the app will wait for the user to click the START button again.
In between sequences the sequence number will increase and any delta values will be added or subtracted.

When TIMER is selected a timer is displayed. The first sequence is started by clicking the Loop Page START button. After the first sequence finishes the app will start the timer and when the timer reaches 0 the next sequence will start automatically.
In between sequences the sequence number will increase and any delta values will be added or subtracted.

Here is a 3 drop sequence with delta values on drop 3 and the Flash Trigger.

Click START to start the first drop sequence. While the drops are dropping the START button changes to ACTIVE and is disabled. The EXIT button remains active though.

When the drop sequence completes, the START/ACTIVE button changes to STOP and the TIMER starts to countdown.

When the TIMER gets to zero the next sequence is started automatically.

and when this drop sequence has finished the TIMER starts again.

While the TIMER is active, the START button changes to STOP and the RESET button becomes enabled.
Clicking STOP, stops the TIMER. Clicking RESET resets the sequence back to 1.

After STOP is clicked the TIMER is cancelled and the app waits for the START button to be clicked.

Timer Delay

You will need to experiment to see what time suits you. I generally use around 10 seconds. This allows time for the water in the tray or bowl to settle and also allows time to move any bubbles out of the way. If you find you are constantly removing bubbles or adjusting things then it is probably better to use the BUTTON option and manually start each sequence.

I find it generally better to use a slightly longer delay than a short one. For example, 4 seconds does not give enough time for the liquid in the nozzle or the water in the bowl to settle and results in inconsistent results.


Using Loop Mode

The easiest way to show how Loop Mode works is probably to use a simple example. Below is a 2 drop sequence where I want to let the first drop fall, create a Worthing Jet, and then have the second drop hit the Worthington Jet. An easy way to do this is to start the second drop later than actually required and then reduce the drop start time until the drop hits the Worthington Jet. Using a manual system this would take quite a while to achieve. Using the DropController it takes a few minutes at most.

Two drops:

First drop
– Start time = 100ms
– Size = 35ms
– No delta values.

Second drop

– Start time = 250ms
– Size = 30ms
– A minus(-)5ms delta on the drop start time

The Camera Trigger is set to SYNC.
The Flash Trigger is set to 550ms no delta.
Loop Mode: BUTTON is selected.

The first drop does not have any delta values, therefore, its properties will not change. It will always start at 100ms and the size will always be 35ms.
The second drop does not have a delta on the size, so the size will not change, but there is a delta of minus(-)5ms on the Start Time. This means the drop will start 5ms earlier every loop.
The Camera Trigger and Flash Trigger times are fixed.

When the START button is clicked, the Loop Page opens

From here you can either start the first sequence by clinking the Loop Page START button or click EXIT to return to the Drop Data Page

The Loop Page has 3 main sections:
– Sequence number + drop data
– Trigger data
– Controls.


Sequence Number

The sequence number is displayed at the top. While looping, the sequence number will increment by one every loop.


Drop Data

The drop data shows the current times based on the delta values and the sequence number. On the first sequence, the delta values are not used and so the times are the same as displayed on the Drop Data Page.

Delta values are shown inside square brackets

To start the sequence, click the START button.

While the drop sequence is active the START button changes to ACTIVE.

After the sequence is complete, the ACTIVE button changes back to START ready for the next sequence. A few other things change as well.

1 – The sequence number increases
2 – Values with delta values are recalculated and the new value shown
3 – The RESET button becomes active
4 – The COPY button becomes active

Drop 2 Start Time delta value has been deducted from the drop start time. The new start time is now 245ms.

Clicking the START button again starts sequence 2. After the sequence finishes the Loop Page is updated to show the drop times for sequence 3.

and again, the drop times are updated to taking the delta values in to account.

The drop 2 start time is now 240ms.

You can use the Graph to see what is happening to the second drop.

On the Graph Page, click the + and buttons to increase and decrease the sequence number.

Clicking the + button increase the sequence number. Every time the sequence increases the second drop start time decreases by 5ms.


By using a delta value on the drop 2 start time you can very quickly capture a series of photos like the above.

Note: Each of the above photos is from a different sequence. They are not rapid fire shots from a single sequence.


The RESET button sets the sequence back to 1.


The COPY button copies the drop times from the current sequence to the main Drop Data page.

In the above example, clicking COPY after sequence 2 (and before sequence 3) would copy the drop 2 start timer of 240ms to the main drop data.

For a detailed guide on how to capture a sequence of shots like the one above see the dropControllerV4: First Drops Guide