In this week, I have to look back at circuit diagram before buying it. Below is the circuit diagram for muscle simulator and timer.

                                                          Figure 1: Timer circuit diagram

                                                      Figure 2: Muscle stimulator circuit diagram


Figure 1 shows the timer circuit. It uses IC NE555 wired in monostable mode. Initially, when press switch S2, the monostable triggers and its output goes high for 10 minutes. Thereafter, its output goes low to give a beep sound from the piezobuzzer and lights up the red LED (LED2) indicating that muscle stimulation time is over.

Figure 2 shows the circuit of the muscle stimulator. IC 7555 is wired as an astable multivibrator to generate about 80Hz pulses. Potentiometer VR1 can control the intensity of current sensing at the electrodes. The brightness level of LED1 indicates the amplitude of the pulses. To increase the intensity level, replace the 1.8 kohm resistor with 5.6 kohm or higher value up to 10kohm.

Above is a little bit description for each circuit. I already had a discussion with my supervisor about these circuit and there is a few things need to be considered before buying all the components. As for the output of this circuit, a suitable electrode need to be connected to the output of this device. After do some research, I found that ECG electrodes is suit for the output of this device. Next week will go and buy the components.