My name is Sonny and together with Nico, we made a salinity measurement device. We used the fact that items with a density less than water float. The difference between the densities of the water and the float is related to the upward floating force of the float, which can be calculated/measured. This is used for this device!
First we will explain how to make the device and after that we will explain how to set up the pressure measurement device!
Step 1: Tools
First, gather the tools we will use. The list below is an overview of the items in the picture above!
- 22mm drill for holes
- 4mm drill
- 7mm drill
- screw bit PH2 with adapter for the drill
- wood glue (maybe it's a material but i regard it as a tool)
- measuring tape
- safety glasses
- round file
Step 2: Materials
Now you can gather the required materials. In the picture above is a part of everything you need. In our device we also put 2 grips on top, so if you want this too, you need to get a grip! (haha) Below is an overview of the items in the picture.
- 5 liter measuring cup (not in the picture!)
- 4x equal length floats (i used dried bananaplant-trunks)
- weight (i used a copper pipe filled with lead)
- piece of iron wire
- 4x 6mm diameter wood sticks (i used the sticks you use to keep plants standing upright)
- 16x small tyraps (tie wraps/ tie rips)
- 20mm diameter 15cm long wood stick
- 2x iron rings with screw-thread
- 2x small screws
- 1x slightly bigger screw
- 1x plank (around 2cm thick, big enough to cut out 2 circles of 16cm diameter)
- 1x thin piece of plywood (big enough to hold your floats!)
Step 3: Assembly
Alright! Now you can begin making the device. First make the float (the sandwich in the picture):
- Draw 2 circles on the plywood (i used 13 cm diameter, but you can make it smaller if you have a smaller float)
- Use the jigsaw to cut them out
- Drill a 16mm hole in the middle of one circle
- Attach the 20mm diameter woor stick to the other circle (without the hole!), using the bigger screwUse wood glue to attach your floats to the bottom plywood circle
- Use wood glue to attach the plywood cirlce with the hole in it to the floats (slide it over the 20mm diameter stick)
- Screw the two metal rings in the top of the sandwich (this is to keep it from falling down later!)
Now make the body parts (these are white in the picture above!).
- Draw 2 16cm diameter circles on the thick plank and also a 10cm diameter circle in one of the two circles.
- Use the jigsaw to cut them out. (you get one circle and one ring, these are the upper and lower body parts (white parts in the picture!)
- Drill 4 holes matching holes in the body parts using the 7mm drill. Through these holes, the wooden sticks will be put)
- Drill a 22mm hole in the middle upper body and use the file to make it smooth.
- Drill 2 4mm holes in the upper body
- Put the sticks through the 7mm holes in the ring and use the tyraps to keep them in place (woodglue is also possible, both is best!)
- Put the float between the sticks
- Attach the upper body to the sticks, again by using tyraps/woodglue
- Put the metal wire through metal rings and 4mm holes in the upper body, so that the 20mm stick rests exactly a tiny little bit under the top of the upper body
- Screw the 2 smaller screws in the 4mm holes to fix the metal wire to the upper body
- Attach the grips (if you have them)
You're now almost ready to measure! The only thing left to do now is setting up the electronics in the next step.
Step 4: Setting Up the Particle Proton
To make the electronics for this device, you need the following items:
- Pressure sensor
- 10 kΩ resistor
- 1 kΩ resistor
- 1 four pin button
- 1 particle photon
- 1 micro usb to usb cable
- Some wires
Connect all the electronic components as indicated in the first figure above.
Now we must programing the electronics as follows:
The script shown in the second figure above (script) can be used to measure the voltage over the pressure sensor and thus the pressure on the sensor. The button function that is built in can be used to only measure when the button on the breadboard is pressed. This script needs to be uploaded to your particle using the particle photon web site. The event that is published indicates how high the pressure was when the button is clicked.
The last thing to do is put the pressure sensor on the 20mm stick, which stick through the upper body. Fix it in place with a piece of wood.
Step 5: Measuring
Good luck measuring salinity of the water! You need to make some trial runs first with tapwater to know what the startingvalue is of the device.