Amazon Dash Replenishment Pens Using Arduino

A pen holder that determines when there are two or less pens and triggers an Amazon pen set replacement.

Things used in this project

Hardware components

Arduino MKR1000

Crayola Air Dry Clay

OpenBuilds Micro Limit Switch

Software apps and online services

Arduino IDE

Amazon Web Services AWS SNS

Hand tools and fabrication machines

Soldering iron (generic)

Story

I used the Arduino MKR1000 as the microcontroller to create my Pen Replacement system. I used the MKR1000 because it is wifi enabled and there is a great resource for connecting to Amazon DRS with an internet connected Arduino. Make sure that the Arduino software is updated completely before adding the AmazonDRS, AmazonJSON and Wifi101 resources. When I ran it with an older version of the Arduino software, I got a bunch of errors that prevented me from compiling the code. MKR1000 PINOUT

tutorial

The tutorial on the website: https://github.com/andium/AmazonDRS is very helpful but there are a couple notes that isn’t mentioned that caused me some frustration. Within the Security Profile>Web Settings, make sure that you add https://www.getpostman.com/oauth2/callback to Allowed Return URLs. When it gets to the part about AmazonTokens.h, you need to remember to clear the refresh_token, the authorization_grant_code and the access_token before you run the authCodeGrant code to get the refresh_token. Besides that, the github resource is very well written and concise that covers almost everything that you need to get Amazon DRS setup on your MKR1000. setup Amazon DRS on the MKR1000

Resource that I used to setup Amazon DRS on the MKR1000 slotId

This was where the slotId was located. slot onto the Amazon DRS device

I only added one slot onto the Amazon DRS device setup for the Device Details

This was my setup for the Device Details. The image was chosen randomly but Amazon requires there being an image. Security Profile should look like

This is an example of the what the Security Profile should look like

Security profile. Make sure that the URL is added to the Allowed Return URLs SNS dashboard

SNS dashboard that is referenced in the GitHub resource

Limit Switches

Before I set it up for the limit switches for my project I tested it with what the exampsuggested which was a single pushbutton onto pin 12. This was found in the examples under amazonDashButton example.

This is the first try to verify that the Amazon DRS portion of the code worked correctly. Another picture of the layout for the example

Another picture of the layout for the example.

I wanted to use limit switches instead of photoresistors or a mass sensor for a couple reasons – photoresistors require analog inputs so if I wanted to scale the device to detect 24 pens instead of 5 then I would need a lot more analog inputs. Photoresistors would also require me to autoadjust the system based on outside light. If the system was in a drawer or someplace very dark, the photoresistor wouldn’t do it’s job very well. I didn’t use a mass sensor because if a user stacks a bunch of stuff on top of the pens (like in an office environment) then there would be no indication about whether it was random stuff or something specific.

I bought some limit switches online that require 5VDC, ground and outputs a normally closes signal. Normally closed signals give a 5VDC signal when the limit switch isn’t pressed and 0VDC when the switch is pressed. There is an LED on the switch to indicate when the switch is pressed.

Limit switch not pressed

Limit switch not pressed Limit switch pressed. Light turns on.

Limit switch pressed. Light turns on.

I used five limit switches and put them in a row so that each one lines up with a pen. I used quick drying clay to make a shape that would line up the pens with the limit switches. The limit switches were larger than I had initially hoped so because of that, I decided that this project was more of a proof of concept rather than a fully fledged project idea.

This is what it looks like plugged into the five limit switches

This is the clay mold that I used. The pens line up over the limit switch so when you place the pens there, the switches depress.

This is what it looks like when the system is turned on. Notice that the lights are on for the pens that are placed.

What it looks like when four pens are pressed down.

Modified Code

See the modified code that I wrote and the comments in the code for how my logic works. Below are images of the results are from running the code.

running the code

After running the code, it connects to the system and if it’s two or less pens, a replacement starts Better view of the code

Better view of the code

It displays the number of pens

It displays the number of pens. I started with four pens and started taking them away until the replacement triggered code

In order to not have multiple replacements, I had the code wait until I had more than 2 pens before having the option to replenish

When the system requests a replacement, it asks Amazon to send an email to the user to notify them that the replenishment is being ordered and is on its way.

Email notification that came through. I set it up to just be an example so there’s no real arrival date

Schematics

Schematic layout for Pen replacement

Code

#include <AmazonDRS.h>
#include <AmazonTokens.h>

#include <WiFi101.h>

#include "AmazonDRS.h"

AmazonDRS DRS = AmazonDRS();

//WiFi creds ----------------------------------------------------------------------------------
char ssid[] = "WiFi"; //  your network SSID (name)
char pass[] = "password";    // your network password (use for WPA, or use as key for WEP)
//------------------------------------------------------------------------------------------------------

#define slotNumber 1 //This will vary for multi slot devices - dash buttons typically only serve one product/slot

int y = 0;
int x = 0;

int input0 = 6; // pin for the first input
int input1 = 7; // pin for the second input
int input2 = 8; // pin for the third input
int input3 = 9; // pin for the fourth input
int input4 = 10;// pin for the fifth input

debouncing
static String slotStatus = "true"; //boolean which depicts if slot is available for replenishment
static String slotId = "abddw91c-cdd1-3asd-b937-bef481699f5d";     //unique slot id ex: 0a5038b7-7609-4b81-b87e-3e291f386324
int status = WL_IDLE_STATUS;

void setup() {
  Serial.begin(115200);

  pinMode(input0, INPUT); // set the first DI/DO as an input
  pinMode(input1, INPUT); // set the second DI/DO as an input
  pinMode(input2, INPUT); // set the third DI/DO as an input
  pinMode(input3, INPUT); // set the fourth DI/DO as an input
  pinMode(input4, INPUT); // set the fifth DI/DO as an input
  
   #ifdef ESP8266 
   WiFiClientSecure client;
   #else
   WiFiSSLClient client;
   #endif
   //Start up DRS
   DRS.begin(&client);

  //connect to WiFi
  Serial.println("Initializing DRS... connecting to WiFi");
  while (status != WL_CONNECTED) {
    // Connect to WPA/WPA2 network. Change this line if using open or WEP network:
    status = WiFi.begin(ssid, pass);
    Serial.println(".");
    delay(3000);
    status = WiFi.status();
    
  }

  Serial.print("Connected to ");
  Serial.println(WiFi.SSID());

  //initialize slots
  DRS.retrieveSubscriptionInfo();  //check slot statuses

  slotStatus = DRS.getSlotStatus(slotNumber);
  slotId = DRS.getSlotId(slotNumber);
}