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Wireless ECG

Wireless ECG

Monitoring cardiac signals with ZigBee

The combination of electronics and biology always yields interesting projects. The system described here is easy to build and enables the wireless monitoring of cardiac signals. ZigBee modules are used for the wireless link.ZigBee technology is an ideal choice for this application in terms of cost, ease of use and low power consumption. The data transmission rate of 250 kbit/s is sufficient for applications such as transmitting ECG signals, which have a narrow bandwidth.
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Extra info, Update

Features

* ECG resolution 10 bits
* ZigBee wireless data transmission
* Range 100 m (300 ft) (outdoors)
* Based on XBee modules
* No programming necessary
* Serial computer interface
* Identical PCBs for acquisition and receiver boards

 

Updates & Corrections

January 6, 2011

- R12 should have a value of 3.3k (not 33k), the indicated gain of 142 is correct.

- In Figures 1 and 2, the gain of IC4 shoud be shown as 15, not 7.

Components

Acquisition board
Resistors (SMD 0805)
R1,R19,R20 = 10kOhm
R2,R11,R14 = 1MOhm
R3 = 470kOhm
R4 = 240Ohm
R5,R9 = 27kOhm
R6,R7,R13,R16 = 33kOhm
R8 = 360Ohm
R10 = 8.2kOhm

R12 = 3.3kOhm (correction w.r.t. orignal publication)
R15,R17,R18 = 47kOhm
Capacitors (SMD 0805, ceramic, except C1,C7)
C1,C7 = 47µF 10V, SMD, Kemet B45196E2476K409
C2,C4,C8,C9,C11,C12 = 100nF
C3,C6,C13 = 10nF
C5 = 3,3nF
C10 = 1µF
Semiconductors
D1 = 1N4148 SMD Minimelf
D2,D3,D4 = dubbeldiode BAV99 (SOT23)
IC1,IC3,IC5 = OPA237NA/250 (SOT23-5)
IC2 = MAX6120EUR+T (SOT-23)
IC4 = AD623ARZ (SOIC-8)
IC6 = LM317LM (SOIC-8)
Diversen:
K1,K2 = 2-pin pinheader, lead pitch 0.1 in. (2.54mm)
K3 = 5-pin pinheader, lead pitch 0.1 in. (2.54mm)
S1 = pushbutton, make contact, PCB mount, 6mm, e.g Multicomp type MC32830
XB1 = XBee module, ZB ZigBee with chip antenna, Digi type XB24-Z7CIT-004
A = no wire link
Receiver only


XBee-module, Digi type XB24-Z7CIT-004
USB-to-TTL cable, 3.3V version, Elektor # 080213-72
R19,R20 = 10kOhm
K4 = 6-pin pinheader, lead pitch 0.1 in.(2.54mm)
S1 = pushbutton, make contact, PCB mount, 6mm
A = wire link
PCB # 080805-1

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