What electrical components are needed for an op-amp circuit?
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I am doing a project where we are to build a micro-generation wind turbine at college. The turbine is constructed, but we need to carry out certain tests. One of these test is to attach a piezo electric vibration sensor to it and record the vibrations. However, the readings we are getting are too small to put into any real form of graphical result. My lecturer has asked that i build a simple op-amp circuit so that i can amplify the readings being produced by the vibration sensor. What components would i need to do this? i know i need resistors, but how do i tell what size the resistor should be?
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Answer:
It depends what op amp you're planning on using. I would do a google search for a 741 op amp data sheet, it'll probably have some example circuits on it. http://www.technologystudent.com/elec1/opamp1.htm
Craig at Yahoo! Answers Visit the source
Other answers
I like to use a TLC27C2, it will run very well on a single 5V supply and you can get gain in the thousands if need be. The front end will depend on the sensor, but you should be able to do it with a few resistors. Look at Digi-Key as they will have data sheets on all the devices.
protoham
A simple voltage-follower circuit has an op-amp IC like a 741 and 2 resistors. Google image "op-amp". If you need high-impedance you can use the non-inverting circuit.
adaviel
You need the specifications of the sensor. With those you can design the opamp circuit needed.
billrussell42
Taking the example in the link below: The sensitivity is around 26mV per g, which is gravity acceleration (9.81m/s/s). This particular sensor covers from 1kHz to 20kHz. The minimum capacitance is around 800pf and the minimum frequency 1kHz so the amplifier needs to have an input resistance at least 1 megohm so it doesn't attenuate frequencies around 1kHz. A much higher resistance may allow operation at lower frequencies than specified. This could be a non inverting op-amp as in the second link. I don't know what acceleration level you want, this sensor covers from 0.1g - 400g, and with 1g the signal is 26mV RMS, and about 70mV p-p (peak to peak). At 400G it would be 400 times this, around 28V p-p. If the amplifier has +9V and -9V supplies the maximum input and output is about 12V p-p. Using an LF411 op-amp with dual +/- 15V supplies it may be around 22V p-p which I expect easily suits your highest need. It makes sense to have a voltage divider using 2 * 1 megohm resistors at the input if high g is expected. The gain might be adjusted to suit a data measuring system, maybe 1V p-p for 1g acceleration. The voltage gain for that case would therefore be 100mV/70mV = 14.28 times. This would be 100K for R2 and 2 * 15K in parallel for R1 in the link below. Note there are 2 separate supplies, which could be two small batteries to provide +9V and -9V. Notes: Piezo sensors often use "charge amplifiers" because they are capacitive in nature. It seems this one uses a normal voltage amplifier, so already has a built in 1 megohm resistor. If the signal seems inappropriate, try adding a load resistor of 1 megohm or higher across the sensor, and if still not suitable, try a charge amplifier, which you can look up. Use an op-amp with jfet inputs like the LF411. This will provide some protection against over-voltage if the sensor is dropped etc.
Ecko
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