Hello George,

We are writing in response to your letter describing a series of problems in your hotel. We have discussed it and we have found we can best help you with your problems with the dumbwaiter your patrons have been over filling.  We have devised a way for you to be notified of the status of the dumbwaiter. There will be sensors in the dumbwaiter that will measure the distance from the top of the dumbwaiter to the height of the stacked dishes. Those measurements will be interpreted and will light either a red, yellow, or green led. The red will mean the dumb waiter is overfilled and requires your assistance before it can be operated. Yellow will mean it may possible to operate but as it will be moving, things might shift and could possibly get jammed. Finally, green will mean the dumbwaiter is within the normal filling range and can be operated without worry. In order to have this feedback system working you will need to install sensors in the dumbwaiter and program an Arduino. We will walk you through the steps and will even help you understand how the system works. These instructions will give you a working prototype. We understand that you are busy and might not have the time to go through some of the set up required, so we also are working on a upgrade that would make the system wireless thus simplifying the set up and making the capacity indicator portable.

Here is a list of the parts you will need:

(2) Arduino uno
(1) red LED
(1) yellow LED
(1) green LED
(2) ultra sonic distance sensors
(1) breadboard
Hookup Wire / Jumpers  cables photo 249769E9-9E5B-4606-BEF4-AA77D06C8FB3.jpg

Here also is a more formal Bill of Materials (BOM).

 photo Screen Shot 2015-04-27 at 1.53.54 PM.png

Before we get started on the actual build you should familiarize yourself with the schematic for the build and what system will look like once completed, shown here.

 photo IMG_3776.jpg
The wiring may look confusing but it will all be made clear in the project schematic shown below.

 photo Screen Shot 2015-04-27 at 1.03.26 PM.png

Preparing Arduino Tx

Now that you’re familiar with the schematic, its time to build! It’s quite simple, it’s just a matter of connecting the components to the right pins on the Arduino. Fortunately we already wrote the code for you so you just need to follow our instructions and you will have a working prototype in a few minutes.

1.  First gather your 2 distance sensors and one Arduino, we will call it “Arduino Tx”. The sensors will have 4 pins you can go ahead and wrap a bit of hookup wire connecting the 2 middle pins(Trig and Echo), we will call this junction the signal pin. The other two are labeled Vcc and GND thats Voltage and ground respectively.

2.   We will begin by connecting the sensors to the Arduino Tx. Next connect the signal pin into pin 13, then Vcc to the 5v pin on the Arduino. On the second sensor, connect the ground pin to the ground pins on the Arduino, next connect the signal pin or trigger and echo into pin 12, then Vcc to the 5v pin on the Arduino. Because the Arduino only has one 5V pin use a breadboard to connect the two pins with the 5V pin like shown.
 photo b2fa5c95-2bb7-43cc-9ce2-cbb1b849ad82.jpg

3.  Now upload the code to the Arduino 1. It is now ready to send the distance information to the Arduino 2.
Here’s a link to the code.
 photo Screen Shot 2015-04-27 at 11.50.26 AM.png 

4.  On the other Arduino (Arduino Rx) we will set up the LEDs. Using a bread board connect the green LED’s anode to pin 7 and the cathode to the ground pin. Next connect the yellow LED’s anode to pin 6 and the cathode to the ground pin. Next connect the red LED’s anode to pin 5 and the cathode to the ground pin.
 photo da5c55eb-bded-471e-abd5-a7ec1bbf6117.jpg

5.  Now upload the code to the Arduino 2. It is now ready to receive the distance information to the Arduino 1
Here is a link to the code

 photo Screen Shot 2015-04-27 at 11.51.24 AM.png  

6.  Now wire for serial communication by connecting a wire from Arduino Tx pin 1 to Arduino Rx pin 0, and another wire from Arduino Tx ground pin to Arduino Rx ground pin.
 photo IMG_3775.jpg

7. Both Arduinos are ready. Simply power both Arduinos and the system will be functional!
On the transmitting Arduino(Arduino 1/Arduino Tx) its best to use 4 AA Batteries
The Receiving (Arduino 2/Arduino Rx) will work just fine with a standard 9V battery

8. One last thing we tested and designed this system by strategically placing the sensors on top of the roof panel of the dumbwaiter you described. If you want to change the placement to better suit your dumbwaiter the system will still work. we placed them evenly across the image shows the holes for the sensors from above. photo 7685B7D4-1DD8-4301-A1F3-AB4F1C8B0712.jpg

And there you have it, your fully functioning “Smart Waiter.” To improve this project even further you could set up multiple Xbee receivers i.e. one that you could carry around with you to let you know when the waiter is full or getting there. Another improvement would be to add more steps of “fullness” with some added code and more LEDs hooked up to the receivers. Last but not least, you could add an alarm or buzzer of sorts to not only give a visual warning, but an audible one to heighten awareness of the urgent and desperately dire issue that is the overfilled dumbwaiters. If your interested in making it wireless follow this link Thanks for reading.


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