With this device you are able to measure the velocity of a free flowing stream. The only thing that is necessary are Arduino and some basic crafting skills and, of course, a free flowing stream. It is not the most practical way to measure the velocity, but that is not the point. It’s just another fun way to determine flow velocity.

Step 1: The Things You Need.

There is a short list of stuff you will need:

- Particle photon

- Breadboard

- Connecting wires

- Button

- 10kΩ and 100kΩ resistor

- Led

- Continuous servo motor

- Electrodes

- Rope

- Wood

- Glue gun

Step 2: Electronic Setup

In the image above you see the complete setup of the electronics. Just replicate the breadboard and everything will work just fine! In the end it will look as follows.

Step 3: Construction of the Gutter

In the first picture you see the gutter in which the water will flow. In this case we used a pvc pipe that was cut in two pieces, but in fact you can use everything gutter-like as long as it does not have too much surface area to block the flow. Just use a glue gun to mount the two electrodes at the end. Make sure that they don’t touch each other so leave a gap of a couple millimeters in between.

Step 4: Construction of the Lowering Device

The lowering device consists of two parts. The first part is the servo motor attached to a coil which the rope wraps around. Also the breadboard will be placed with this. This part will be located on top of the second part. The second part is just the rail which will lead the gutter downwards.

Step 5: Mounting the Device

It is important that the whole construction is well mounted to the flow channel. We made it so that the device was hanging just above the free flow. This way the wooden rail wouldn’t interfere with the flow which would cause unnecessary forces on the construction. The bottom of the gutter can just rest on the bottom of the flow channel. This will stay nicely in place when the rail is precisely made following the radius of the gutter.

Step 6: The Coding

In this picture you can see all the code that is needed for the device to work. When the electronics are connected exactly like seen before, you are done. However, it’s much more fun to try coding it for yourself. It works as follows: you let the servo motor do steps of a quarter of the radius. Every time one step is done you let the program check if there is contact between the electrodes. Also it is important to count every step as this is the main parameter used for calculating the flow velocity. If there is no contact you do the loop over again. When there is contact, the program needs to use the number of steps to calculate the flow velocity. This will be send to the pc as your measurement. After that the servo needs to turn the other way around for exactly the same amount of steps. It is important that al the integers are set to zero again after doing a measurement. With these tips and a couple hours of puzzling you should be able to come up with your own code.