Heart Rate Monitor Schematics and Source Code for the ATExpo 2007 EASi Line




For the second year in a row, we have designed the give-away hardware for the EASi Line demonstration at ATexpo. We would like to share with you the design, source code and binaries, so that those of you who are interested can learn, make modifications, or come up with some other useful purpose for the give-away. Essentially, what you received is a 4 digit display controlled by an Atmel Tiny2313 processor. The board also contains a differential amplifier, power supply, and various other electronics to detect a person's heart beat. The board is powered by a 9V battery and has an auto-off feature to power down after a conversion is complete.

If you like your pulse reader board, you decided to use our project files to make your own or derivative project, or just have a comment in general, please send us an e-mail and let us know!


Project Details
Board Specs Design Considerations
Heart Rate Monitor Schematics Heart Rate Monitor PCB Layout
Heart Rate Monitor Silk Screen Mechanical Layout
Parts List / Bill of Materials Instructions on how to use
Heart Rate Monitor Source Code Reprogramming
Further Resources & Disclaimer



Board Specs   [Back to Top]
Here are the specifications for the LED Readerboard.
  • Processor: Atmel ATTiny2313
  • Power Supply: 9V Battery.
  • Clock Speed: Internal 1 Mhz Oscillator
  • Minimum Power Requirements: 6.4V
  • Current Draw when On: ~ 120 mA
  • Current Draw when Off: 0.0001 mA
  • Programmable with Atmel AVR tools & AVR Studio 4.12 or higher
  • 6 Pin Program Header, Not included
  • Code: C Source Available
  • 4 digit LED display
  • Pushbutton On
  • Auto-Off
  • LM324 quad amplifier configured as a very sensitive differential amplifier


Design Considerations   [Back to Top]
The Heart Rate Monitor was designed to be a give-away at the Assembly Technology Expo, and therefore had to meet a number of requirements. The following is a short list of the project design goals:
  • Low cost
  • All components on one side of the board except the battery
  • Support for in-system programming
  • At least one or two through hole parts to demonstrate various equipment on the EASi Line
To keep the device even more useful, we added a few design contraints of our own:
  • Must draw very little or no current when off to extend battery life when not in use
  • With only one momentary push-button switch, system must be able to turn itself off after a period of time
  • Use common parts to help facilitate quick prototyping, and make purchasing for the show simple
What we ended up with is the design you'll find here.



Heart Rate Monitor Schematics   [Back to Top]
Page 1
Page 2
Page 3


Heart Rate Monitor PCB Layout   [Back to Top]
Front
Back


PCB Silk Screen   [Back to Top]
Front


Mechanical Layout   [Back to Top]


Parts List / Bill of Materials   [Back to Top]

35 Resistors

 

 

Quantity:

 

References

 

Value

 

Value2

 

Package

 

PartNum

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

6

 

R1, R2, R9, R11, R33, R35

 

10K 5%

 

.1W

 

0603

 

ERJ-3GEYJ103V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2

 

R3, R12

 

0 ohm

 

.1W

 

0603

 

ERJ-3GEY0R00V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

6

 

R4, R6-R8, R10, R16

 

100K 5%

 

.1W

 

0603

 

ERJ-3GEYJ104V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

R5

 

4.7K 5%

 

.1W

 

0603

 

ERJ-3GEYJ472V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3

 

R13-R15

 

10M 5%

 

.1W

 

0603

 

ERJ-3GEYJ106V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

8

 

R17-R24

 

120

 

.1W

 

0603

 

ERJ-3GEYJ121V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

7

 

R25-R29, R32, R34

 

1K 5%

 

.1W

 

0603

 

ERJ-3GEYJ102V

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

R30

 

240 1%

 

.06W

 

0603

 

CRCW0603240RFKEA

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

R31

 

715 1%

 

.06W

 

0603

 

CRCW0603715RFKEA

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

21 Capacitors

 

 

Quantity:

 

References

 

Value

 

Value2

 

Package

 

PartNum

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

C1

 

470pf

 

50V

 

0603

 

ECJ-1VC1H471J

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

11

 

C2, C3, C8, C9, C13, C14, C17-C21

 

.1uf

 

50V

 

0603

 

C1608X7R1H104K

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

6

 

C4-C7, C10, C11

 

10uf

 

25V

 

1210

 

GRM32DR61E106KA12L

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

C12

 

1uf

 

16V

 

0603

 

EMK107BJ105KA-TR

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2

 

C15, C16

 

18pf

 

50V

 

0603

 

ECJ-1VC1H180J

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

3 Integrated Circuits

 

 

Quantity:

 

References

 

Value

 

Value2

 

Package

 

PartNum

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

U1

 

LM324DR

 

 

 

SO14

 

 LM324DR

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

U2

 

ATTINY2313-20SU

 

 

 

SOP20.375

 

ATTINY2313-20SU

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

U3

 

LM317LDR2

 

 

 

SO8

 

LM317LDR2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

6 Transistors

 

 

Quantity:

 

References

 

Value

 

Value2

 

Package

 

PartNum

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

Q1

 

MMBT3904

 

 

 

SOT23_MMBT3904

 

MMBT3904DICT

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

Q2

 

MMBT3906

 

 

 

SOT23_MMBT3906

 

MMBT3906DICT

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4

 

Q3-Q6

 

MMBT3906

 

 

 

SOT23_MMBT3906

 

MMBT3906DICT

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

11 Miscellaneous

 

 

Quantity:

 

References

 

Value

 

Value2

 

Package

 

PartNum

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2

 

DISP1, DISP2

 

DISP_A-562G

 

 

 

DISP_A-562G

 

DISP_A-562G

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

J1

 

9V-CLIP

 

 

 

CONN PCB 9V

 

9V_CLIP (special order)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

J2

 

AVR PGM

 

 

 

CONN-DIL6

 

Not stuffed

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

J3

 

CONN-H10

 

 

 

10 PIN EDGE CARD

 

PCB feature

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

SW1

 

SPST

 

 

 

B3FS-1002P

 

B3FS-1002P

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4

 

TP1-TP4

 

TEST_POINT

 

 

 

TEST_POINT

 

Not stuffed

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

 

X1

 

1.8432mhz

 

 

 

SMT_CSM7

 

Not stuffed

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


Instructions on using the Heart Rate Monitor   [Back to Top]
To being, press the Start button on the bottom left corner of the unit The Display will now show the word "Hold".



Next place your thumbs from each hand on the metal contacts in the upper left and right sides of the unit. Place your index fingers on the back side and grasp the unit with even pressure. You do not need to squeeze firmly, but a constant pressure is needed to get a good reading. Make sure you are not touching any other traces or electronics on the unit. This will cause a bad reading. Also to improve accuracy, make sure right index finger is touching the pad on the back side of the unit. Also putting as much of your thumb on the pad as possible, will maximize your heart rate detection.



After a short period of time, the word hold will disappear, and a dash will appear on the display. This dash should pulse on and off with each heart beat detected. Remain still during this time.



The amount of time it takes to detect your heart rate varies depending on how strong the signal is. After the conversion is complete, the abbreviated word "pulse" will appear on the display followed by your heart rate. After this alternating message has been displayed several times, the unit powers down. You can press start switch again to check your heart rate again.



Heart Rate Monitor Source Code / Pulse Monitor Source Code   [Back to Top]

C Source:
  • Main.c

    Binaries:
  • C Binary


    Reprogramming the Atmel ATTiny2313 AVR Processor   [Back to Top]
    In order to reprogram the board, you'll need to purchase an appropriate programmer and you'll need to use either the AVR Studio assembler or appropriate C compiler. Assembling or compiling the source is beyond the scope of this document. Your output should be in Intel hex format. We recommend the Atmel JTAG ICE mk-II debugger/programmer, with which you can use Atmel's AVR Studio software to reprogram the board. Reprogramming the board once you have this device is easy.

  • First, attach the 6 pin program header to the 10 pin header attached to the mk-II device. Pin one is the pin on the 6 pin header marked with an arrow.
  • Solder on a six pin header block to the PGRM labeled J2 through hole connections on the device. Pin 1 is the bottom right hand pin.
  • Match this up with the pin one from the header (arrow) and attach the mk-II to the board.
  • Power the board with a 9V battery. Continue to hold the button down to provide power to the board. Do not use a power supply as the floating grounds may blow your mk-II board.
  • Launch AVR Studio and connect to the mk-II device through the Tools->Program menu.
  • Click the Program tab. Choose the ATTiny2313 device.
  • Choose the Board tab and select an ISP frequency of 125 kHz. Write this value to the programmer.
  • Click the Advanced tab and read the Signature Bytes. You should get 0x1E 0x91 0x0A
  • Click the Fuses tab and read the fuses. You should get 0xFF 0xDF 0x64. Do not attempt to reprogram unless this information is accurate.
  • Choose the Program tab again and set the device to Erase Device before programming. Choose your hex file with the "..." browse button.
  • Click "Program" to reprogram your board.



    Further Resources & Disclaimer   [Back to Top]
  • Assembly Technology Expo

    Disclaimer: This is not a medical device. This educational device has touch plates that directly come in contact with the human body. A nine volt battery is used as a power supply to operate this circuit. Modifications to the power supply, connecting probes that can enter the blood stream, or attaching this device to other powered equipment, can create a hazardous condition resulting in death or bodily injury. If you plan on experimenting with this device with the purpose of connecting to a human body, take time to educate yourself on safety issues related to this. Also, those individuals with known medical issues relating to the heart or circulation system should not be experimented on by non-medical individuals. Use and modify this device at your own risk. CPU Ready Consulting makes no claim this device is safe either before or after modification.





    • Copyright 2007 CPU Ready Consulting Inc.
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