Moderator

What

A voting device, similar to edubuzzer but with the design-goal of being super-cheap.

Hardware

bare PCB, no container (yet)

MCU

STM32F100C8T6

Reasons:

• Cheap
• Powerful (up to 24MHz), Cortex-M3
• Lots of GPIOs
• Small (LQFP48)
• 3.3V levels

Alternatives:

• STM32F0xx
• Freescale Cortex-M0
• MSP430G2553
• RFD22301 (probably far too expensive, but it includes the RF stuff)
• ATmega328P @ 3.3V, 8MHz

RF

nRF24L01+ module

some info for using them with Arduinos

Reasons:

• Cheap
• Small
• Relatively low-power
• Easy to use
• Lot of libraries for it
• Supports point-to-point, broadcasts and multiple channels
• Special module versions available with ranges of up to 1100m
• Uses 3.3V levels

There are a lot of modules with that chip available. Most of them use a 2x4pin 0.1" connector with a standard pinout. There are also much smaller SMD modules available, but these are more expensive and do not seem to have a standard pinout or layout.

Alternatives:

• Bluetooth 4.0 Low Energy (nRF8001, BLE113-A, CC2541, …)
• 433MHz RF wireless transmitter module (one-way only!)
• 802.11b/g/n (CC3000, HF-LPB, …)

Display?

Nokia 5110 display

Reasons:

• Cheap
• Small
• Low-power
• Lot of libraries for it
• Can mount directly to the PCB, no expensive/rare connector required
• Uses 3.3V levels

Alternatives:

• Just some status LEDs (takes a lot of power)
• Sharp Memory Display
• Liquid Crystal display without a backlight
• Two flipdot-dots?

Buttons

5x5mm button

Reasons:

• Cheap
• Large enough for humans to handle

Alternatives:

too many to list

Leds

None

Reasons:

• LEDs require a lot of power
• Not a lot of expressiveness with them

Power

Coin Cell: CR2032, 3V

Reasons:

• Cheap
• Low self-discharge

Unsolved problems:

• Does not deliver a lot of power (~0.1mA per spec)
• Not a lot of capacity

Alternatives:

• AA battery (large, but cheap and easily available — only delivers 1-1.5V though)
• 2xAA battery for 2-3V (very large!)
• Lithium Polymer Battery (like the one used in the Magic Shifter)
• Solar Panel

BOM

Table here..

Basestation

RaspberryPi

NRF shield

Raspberry Pi-to-nRF24L01+-Module Adapter

Who

Overflo

anlumo