ECG simulator circuit is very useful in the medical community. Such as experimental research and development of biomedical imaging.
But we should do not use this with patients. Because we do not want that. The real purpose is to preview a heart rate only.
In general, measuring the rate of the heartbeat will get a waveform as Figure 1.
Figure1 the ECG waveform and feature of P to U
Start of all, we take the sensor to Attached to on the patient at various points.
Measurement results are the amplitude of approximately 1mV.
A heartbeat rate is between 40 Hz to 150 Hz.
The electronic medical use the letter P to the U to count the ECG wave is 1 time. We will see one waveform include the one peaks of spikes.
The working of circuit
The circuit consists of two standard logic ICs and a few parts.
IC1-CD4521 is a CMOS IC called a 24 stage binary counter. It has the frequency setting in the counter is X1-crystal at a frequency of 4,194,304 Hz.
The IC1 will divide frequency out of 16 Hz. Its output is a square wave to output Q18 (pin 10).
And, S1b is selector switch to choose the output frequency of IC 1 is a low frequency of 1Hz or 2 Hz.
Then, the 16 Hz output frequency is a clock signal. It gets into IC2, CD4017.
Which the 4017 is good at a Decimal Counter circuit. Next, see in the circuit at pin 15 of IC2 to divide frequency at output 10.
After that, The second signal will be filtered with R3 and C3. They are a waveform in spikes into pin 15 of IC2. Then, D2-diode will block a negative voltage not flow into pin 15.
And, IC2 will count to 9 and on hold this state. And, pin 11 connects with pin enable input (pin 13) to reset working. Which it is the wave conditions in the U form.
If necessary, you cannot find Crystal as specified. You may use 4MHz instead, but the frequency will be slightly distorted.
Also, we watch at the output devices. Which they get an output signal of Q1, Q4, and Q6.
By the first wave is a pulse that has been transformed into a P waveform, by the filter in integrator form. They include of R6 and C4. The C4 will charge from 0V to about 1V.
For T waveform, we get it from the integrator of R7 and C4. The R7 is the resistance of less than half of the R6. And the pulse waveform of Q6 will charge more up.
Which C4 are 2 times of the P waveform. C5 and R10 are put into an R pulse between 2 waveforms.
Then, The R8-resistor to limit the current to the charging of C5. And in at the same time, D5 allows the voltage to 3.8V via the C R9 and D3.
And, LED blinks while the R-waveforms.
Then, the spike waveform passed R13, R14 and R15 will convert the output voltage is 1V and 1mV as we need.
This circuit uses the 9-volt battery. And, The rate of consumption of the circuit about 2.5mA.
Before Build it
I publish this circuit. Because of the benefits of medical. But I never tried it at all. So I can’t confirm that Is it works? I sincerely apologize.
Okay, friends, You are smart! you want to try it for everyone.
I suggest you assemble the parts on a universal PCB. Then check all for errors after assembling them. Next, connect the wiring to the oscilloscope and the battery wire to the circuit. Just now already to use ECG simulator.
The component List
Resistors 0.25 W 5%
R3, R4, R12: 100K
R13, R14: 10K
C1: 82pF 50V, Ceramic
C2: 22pF 50V, Ceramic
C3: 0.22uF 63V, Polyester
C4: 0.47uF 63V, Polyester
C5, C6: 0.33uF 63V Polyester
C7: 0.1uF 63V Polyester
D1, D2, D4: 1N4148 0.75A 100V_Silicon Diode
D3: LED_in Super bright type
D5: Zener Diode_3V 500mw
IC1: CD4521__CMOS 4-stage Frequency Divider
IC2: CD4017__DECADE COUNTER/DIVIDER IC
S1: Slide switch in DPDT – Double – pole , Double-throw.
BT1: 9-volts battery
X1: Crystal__4.194304 MHz
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