WetRuler--Kitchen Helpers for the Visually Impaired
Introduction: WetRuler--Kitchen Helpers for the Visually Impaired
I have worked most of my adult life with patients with vision problems in Alaska and pondered building a helpful device that would enable a more defined way of metering out fluids in a kitchen if users had no central vision. There are devices already for defining the limits of a cup with two wires that form a circuit at a set level but none actually measure different fluid levels. Most people just end up putting a finger into a hot liquid as its poured.
The sensors in these devices turn on with a button push and immediately read a baseline atmospheric pressure in a thin measuring tube. The sensor tube is then placed in the liquid whose depth you want to read and algorithms calculate how deep the tube is. All design considerations are based on size including the ATTiny85 for the microcontroller, small PCB, and a coin cell battery for power. The beeping sensor transmits its information by modulating its call for each inch of depth and the "smart" funnel slowly increases its yodeling as the tip goes deeper into the liquid. I designed these two little guys for fun but the inherent applicability of the design can be used for a variety of circumstances where fluid level cannot be well visualized and a tiny brain could help you.
The devices are made with silicon tubing and food level stainless steel straws at their sense apertures but the maker is left to his own devices for of food safety.
Step 1: Gather Your Materials
There are just a couple components that are needed for this build. The heart is the MP3V5004GP-ND sensor that costs about $13. It is great for measuring small volume changes in water height and have found it to be an adequate analog sensor even for AD convertor inside the ATTiny. The buzzer is generic --you just want something with a low current as there is no transistor in this circuit and the tiny must provide all the power. The demands of this circuit are small---only being on when needed with the pushbutton and the output signal will be turned off right away so the coin cell battery is appropriate. The circuit design can be easily modified to include other power supplies or switching--even solar.
1. MP3V5004GP-ND get at Digikey for $13
2. Push button -- generic $0
3. Battery holder CR2025 --WMYCONGCONG 30 PCS CR2032 CR2025 Coin Button Cell Battery Amazon $0
4. ATTiny85--Original Atmel Dip-8 ATTINY85-20PU Tiny85-20Pu Ic Chip Pack Of 5Pcs $2
5. Dip 8 Socket -- for ATTiny $0
6. 440
Silicon tubing 2mm inside diameter $1
7. Stainless Drinking Straws -- $0
8. Battery coin cell CR2025 -- $1
9. Buzzer --BNYZWOT Electromagnetic Active Buzzer Long Continous Beep Tone Alarm Ringer for Arduino $0
Step 2: Wire It
The above is a screen shot from Eagle design file. It is the companion PCB design system that works with Fusion 360. I have included the files necessary for ordering your own boards that make this project so tiny. It was the easiest thing to order this summer--$5 for 10 boards and they came in about 5 days from China...it still amazes me. (PCBWAY--I don't make $ from anyone I mention).
The wiring is totally simple. Power from the battery goes to the switch and from there to both the ATTiny and the sensor. The sensor analog wire goes to the AD convertor on the ATTiny (A1) and the output from the ATTiny (0) goes to the + lead of the buzzer and the ground in the system goes to ATTiny, Sensor, and Buzzer.
You can easily build this unit without the need for a PCB by dead-bug wiring. Most of the early testing was done this way. The PCB just makes it a lot neater for inclusion in the case. When wiring the PCB make sure you add all the components before you place the battery holder on the back as it covers up some of the solder spots--a consequence of making it smaller in size. You might still want to place the sensor on a PCB of its own just for stability sake.
Step 3: Print It
All design work is done in Fusion 360. Both designs use the same box framework that have identical matching front plates. The frontispiece can be changed to accommodate larger buttons and On/Off switches. It is held on by snap fit attachments and is designed for easy replacement of the CR2025 battery. The smart funnel has an extruded tube that is contiguous with the funnel drain and allows the silicon tube of the sensor to be parallel to it. 996