I am trying to build a simple seismic circuit to measure the amount of vertical motion in the floor as people walk by my cubicle at work. I bought a geophone (a magnetic sensor that measures resistance between two magnets and thus measures vertical motion.) I want to interface this with my PC and so I am thinking of using either the Parallel Port, Serial Port, or possibly Game port of my PC to send in the data. At first I wanted to simply use the game port and connect the geophone as the Y axis of a joystick (since a joystick is simply a potentiometer that goes from 0 - 100K ohms). This did not work so well because the geophone at 5V only measures about between 1-2K ohms of resistance. I found a circuit on the net that converts the resitance to DC voltage between 0 - 5V.
**broken link removed**
However, the PC interface costs $100 bucks and is not very cool. I wanted to build myself and so bought a ADC and found another circuit that converts the voltage to a binary number between 0 and 255. (8bit ADC)
http://www.iguanalabs.com/adc2051.htm
I am having trouble getting the ADC converter to work with my PIC 16F84A, but I think that I can figure this one out on my own. I was wondering if anyone new of a circuit that acts as a resitance multiplier so that if the output from the Geophone is only between 1k OHM and 2kOhm the resulting output of my circuit would be between 5K - 10K ohm or possibly 50K - 100K ohms??? I am a software guy and pretty new at hardware. I know how to program the PIC and I think that I can get it to work with my PC Parallel port once I figure out how to get a 10Mhz clock connected to my PIC in order to send the data from the ADC to the PC within 10us which is the time out for a read from the LPT data port.
Thanks for any help!!!
**broken link removed**
However, the PC interface costs $100 bucks and is not very cool. I wanted to build myself and so bought a ADC and found another circuit that converts the voltage to a binary number between 0 and 255. (8bit ADC)
http://www.iguanalabs.com/adc2051.htm
I am having trouble getting the ADC converter to work with my PIC 16F84A, but I think that I can figure this one out on my own. I was wondering if anyone new of a circuit that acts as a resitance multiplier so that if the output from the Geophone is only between 1k OHM and 2kOhm the resulting output of my circuit would be between 5K - 10K ohm or possibly 50K - 100K ohms??? I am a software guy and pretty new at hardware. I know how to program the PIC and I think that I can get it to work with my PC Parallel port once I figure out how to get a 10Mhz clock connected to my PIC in order to send the data from the ADC to the PC within 10us which is the time out for a read from the LPT data port.
Thanks for any help!!!