The pulse collection device is now working, however my PC’s audio card is refusing to accept as an audio device. One thing that could be a cause is that I may need a second stage amplifier. I came to the conclusion after using a multimeter to measure the voltage. The multimeter seems to respond to me when I hit the piezo film however the output voltage is very low. This is a major set back in my project as I need a working device in order to collect pulses for my report.
I have completed my 2nd meeting with my supervisor. The outcomes of todays meeting were:
- Power and test the device.
- Do some research on pulse and its uses.
- Start design specification for the report.
- Decide on date for next meeting.
My plan is to complete the power on of the device by 30th of august. Complete research on pulse by 7th september and complete the first draft of my specifications by 14th september.
I have constructed my design for the collection device on a bread board. I will power it on later. So far all the connections seem all right.
Today I have completed the design for pulse collection device. I have used an LM 386 amplifier to amplify the raw signal coming out off the piezoelectric element. I will be using this device to collect pulses and study the effect of various things on the wave form of the pulses. So the first things I will be studying is how the wave form of the pulse 12 changes when people drink coffee.
I have ordered the parts and the parts have arrived. I have got a piezo electric sensor. I have also got an Arduino, ATMega8 and an LM386 op-amp. I am now experimenting with these to see which is most appropriate. The Arduino uses just a USB port for communications and power while the LM386 uses the audio jack for an output. The ATMega8 can be interfaced with a serial interface this can then be converted to a usb interface. The LM386 also requires a seperate power supply. On the other hand, an Arduino costs US$29 while the LM386 cost 1RMB(US$0.12) and the ATMega8 cost 8RMB(US$0.96). Overall the LM386 is most cost effective. On the other hand the ATMega8 does not cost so much and can be neatly interfaced with a serial interface. The ATMega 8 can also be programmed to analyze the pulse on the spot.