While working on our exam project, we decided to make a blog and share some ideas that helped us during our work. Our assignment was to make hardware configuration which measures heartbeat (puls), and body temperature. Hardware components which are included into solution are:
1) Arduino LilyPad chip
2) Heartbeat sensor
3) Temperature sensor
4) Bluetooth module (Bluetooth Bee + XBee Shield)
5) Devices that use Android OS (great thanks to our mentor from the faculty who provided us Asus Eee Pad Transformer TF101 to work on it and test software solution during project)
Arduino LilyPad chip
Basic hardware part of our configuration is Arduino LilyPad chip, which can be seen on picture 1.
Picture 1. LilyPad Ardino Simple Board
This is the LilyPad Arduino Simple Board. It's controlled by an ATmega328 with the Arduino bootloader. It has fewer pins than the LilyPad Arduino Main Board, a built in power supply socket, and an on/off switch. Any of our LiPo batteries can be plugged right into the socket. The Simple board is designed to streamline your next sewable project by keeping things simple and giving you more room to work and eliminating the need to sew a power supply. Some other usefull information about LilyPad chip may be found on http://arduino.cc/en/Guide/ArduinoLilyPad
HeartBeat sensor
Function of this module is to measure heart pulse. During our work we have found several solutions and finally decided for this:
Picture 2. Hardware arhitectureof heartbeat sensor
The sensor uses two simple components, an IR LED and an IR phototransistor. Both components are powered by the Arduino's 5V output and one analogue input reads the voltage across the phototransistor.
1) 10KOhm resistor
2) 220Ohm resistor
3) IR LED(ZD1945)
4) IR Phototransistor(ZD1950)
1) 10KOhm resistor
2) 220Ohm resistor
3) IR LED(ZD1945)
4) IR Phototransistor(ZD1950)
The main idea is that when your heart beats you have a quick fast rush of blood into tiny blood vessels close to your skin which makes it less transparent. This effect is easiest to observe on your finger tips or earlobe. So the IR emitter and phototransistor are placed next to each other (not much light goes through the side of the emitter!) and I put my finger on top. Light from the IR emitter illuminates my skin and is reflected into the phototransistor.
The phototransistor is connected to the Arduino in a similar way to a potentiometer. One lead is connected to +5V and the other to ground. The +5V lead is also connected to an analogue input on the Arduino. When the phototransistor receives more IR light it becomes more resistive and a lower voltage is detected by the analogue input.
The phototransistor is connected to the Arduino in a similar way to a potentiometer. One lead is connected to +5V and the other to ground. The +5V lead is also connected to an analogue input on the Arduino. When the phototransistor receives more IR light it becomes more resistive and a lower voltage is detected by the analogue input.
More information about this, can be found at this address:
Temperature sensor
Function of this module is to measure body temperature. Image of this temperature sensor is on picture 3.
Picture 3. LilyPad Temperature Sensor
Detecting temperature changes has never been easier. The MCP9700 is a small thermistor type temperature sensor. This sensor will output 0.5V at 0 degrees C, 0.75V at 25 C, and 10mV per degree C. Doing an analog to digital conversion on the signal line will allow you to establish the local ambient temperature. Detect physical touch based on body heat and ambient conditions with this small sensor.
LilyPad is a wearable e-textile technology developed by Leah Buechley and cooperatively designed by Leah and SparkFun. Each LilyPad was creatively designed to have large connecting pads to allow them to be sewn into clothing. Various input, output, power, and sensor boards are available. They're even washable!
More detail information (for example Datasheet, prices and users reviews, etc.) may be found on
Bluetooth modul
Bluetooth Bee is a simple breakout board for the Bluetooth Module, which designed to DIP model (http://www.sparkfun.com/products/8550), compatible with existing Xbee sockets, designed for transparent wireless serial connection setup. Bluetooth Bee can be configured to Master, Slave or Loopback three different modes(HC-06 just be Master/Slave, coulud be customized), and it will connect to or be connected by other devices that support SPP protocol per configuration, and it is a suitable substitute for most applications. Bluetooth Bee is an easy to use Bluetooth SPP (Serial Port Protocol) module, designed for transparent wireless serial connection setup. This is a fully qualified Bluetooth V2.0+EDR (Enhanced Data Rate) 3Mbps modulation with complete 2.4GHz radio transceiver. It uses CSR Bluecore4-external single chip Bluetooth system with CMOS technology and with AFH (Adaptive Frequency Hopping).
- HC-03/HC-05 could be configured to Master/Slave by user.
- HC-04/HC-06 just be Master or Slave when the factory, cann't be configured by user.
Picture 4. Bluetooth Bee module serial HC-05
XBee shield
The XBee shield provides 3 optional hardware interface, which determine how the shield’s serial communication connects to the serial communication between microcontroller (ATmega8 or ATmega168) and FTDI USB-to-serial chip on the Arduino board. So it is necessary to explain the XBee shield work mode first.
The XBee shield has 4 row jumpers figure2. DIN corresponds with Bluetooth Bee’s RX, DOUT corresponds with Bluetooth Bee’s TX, TX_H corresponds with Arduino’s TX(D0), RX_H corresponds with Arduino’s RX(D1), D2 corresponds with Arduino’s D2, D3 corresponds with Arduino’s D3. We select work mode by DIN and DOUT freedom match with TX_H, TX_H, D2, D3.
Picture 5. Schematic of XBee Shield
Bluetooth Bee direct use Arduino main board’s UART(TX/RX) connect to PC. If you want find out more information about this, visit (http://www.seeedstudio.com/wiki/Bluetooth_Bee).
Schematic - How to connect Bluetooth Bee with Xbee shield
Picture 6. Whole Bluetooth moduls connected
Well, that's all for our first post. In the next post we will try to explain software application which is run on devices connected to hardware configuration, also we will try to post an image which shows how Android Lilypad chip, temperature sensor, heartbeat sensor and bluetooth modul are connected to each other and make whole hardware part of our project.
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