Cheddar is a connected button based on the ESP8266.
Amazon created not a long time ago a connected button (called Dash button) that allows to make an order on Amazon just by pressing a single button facilitating the process of buying of household goods. It didn’t take a long time before hackers started appropriating the object and use it for their own purposes:
- Hacking Amazon’s $5 Dash Button to order Domino’s Pizza
- How To Use the Amazon Dash with IFTTT and Home Assistant
All that had to be done was to buy one, get the button ID through the Amazon app and encode that ID to whatever was listening to the incoming query. Amazon gave you a $5 connected piece of hardware, battery and case included that allowed you to do virtually anything with it.
As amazing as this might sound, the problems of those buttons are:
- You need an amazon premium account to purchase them and get the button ID.
- You can’t directly program them, which makes complex queries more difficult to run and embedding sensors impossible.
- You need a server running somewhere locally to listen to the incoming queries.
- You can’t wake it up from external events other than by pressing the button.
Why not create our own open source “Amazon Dash button”. It would also run on a battery, can be programmed and is Internet-connected. The ESP8266 microcontroller is used in a wide variety of projects and many frameworks are developed around + it’s also really cheap !
Powering an ESP8266 dev board (WEMOS D1, NodeMCU DevKit, Sparkfun ESP8266 Thing…) with a battery and waking it up when the button is pressed is quite a trivial problem and not fun. That’s why I chose to create a PCB to host the ESP8266 module. Although it has some requirements:
- Be able to program it and debug it from USB
- Can run on batteries
- Batteries should be rechargeable using the on board USB
- It should be power efficient
| Ref | Qty | What | Value | Footprint |
|---|---|---|---|---|
| Q1 | 1 | P-MOSFET | DMG3415U | SOT23-3 |
| U1 | 1 | USB-Serial converter | CH340G | SO-16-N |
| U2 | 1 | Battery charger | MCP73831 | SOT23-5 |
| U3 | 1 | uC + wireless module | ESP-12E | ESP-12E_SMD |
| U4 | 1 | Voltage regulator | HT7333 | SOT89 |
| D1 | 1 | Battery 100% LED | 1206 | |
| D2 | 1 | Schottky diode | 1PS79SB31 | SOD-523 |
| Ref | Qty | Value | Footprint |
|---|---|---|---|
| C1, C9 | 2 | 220uF | 1206 |
| C2, C3 | 2 | 22pF | 1206 |
| C4, C8 | 2 | 100nF | 1206 |
| C5 | 1 | 10nF | 1206 |
| C6 | 1 | 22nF | 1206 |
| C7 | 1 | 1uF | 1206 |
| Ref | Qty | Value | Footprint |
|---|---|---|---|
| R1 | 1 | 470R | 1206 |
| R3, R5, R6, R7, R8 | 5 | 10kR | 1206 |
| R9 | 1 | 100kR | 1206 |
| Ref | Qty | Value | Footprint |
|---|---|---|---|
| Y1 | 1 | 12Mhz | Crystal_SMD_3225-4pin_3.2x2.5mm |
| Ref | Qty | Footprint |
|---|---|---|
| J1 | 1 | USB_Micro-B_Molex |
| J2, J3 | 2 | Pin_Header_Straight_1x08_Pitch2.54mm |
| J4 | 1 | Pin_Header_Straight_1x02_Pitch2.54mm |
| J5 | 1 | JST_SH_SM02B-SRSS-TB_02x1.00mm_Angled |
| Ref | Qty | Footprint |
|---|---|---|
| SW1 | 1 | SW_DIP_x1_W5.08mm |