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How to connect an Oscilloscope and Function Generator to a 555 Timer

How to connect an Oscilloscope and Function Generator to a 555 Timer

I am setting up a basic RC Circuit using a 555 Timer for a Lamp Dimmer.  I cannot figure out how to connect the Function Generator with an Oscilloscope to get Voltage and measure the frequency and duty cycle of the output voltage over the range of potentiometer resistance.  I have to get this to work in multisim!  I cannot find any information on how to do this.  I have no documentation on how to do this and was never taught how to use multisim.  We are required to use multisim in my engineering class but were never taught how to use it.  So now I'm trying to figure out how to use it considering we don't use live equipment and were not taught how to do with live equipment either.  I have included a copy of the lamp dimmer schematic in multisim. 


Please help!Capture.PNG

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Re: How to connect an Oscilloscope and Function Generator to a 555 Timer



A function generator is used to generate a signal, in this case you don't need it since the 555 timer can generate the signal.


The scope you selected has two channels, A and B which allows you to view two signals at the same time.  Each channel have two pins, a + and -.  The + pin should be connected to the circuit where you want to analyze the signal.   If you leave the - pin unconnected, Multisim assumes it reference to ground. If you connect both the + and - pin to your circuit,  you are analyzing the differential voltage ( Vpin+ - Vpin-) between the two nodes


Once you connected the scope to your circuit, double click on the scope to expand the instrument.  Under Channel A and B, you should see the Scale, and in the attached screen the scale is 5V/div represent 5V for each rectangle on the scope screen.   To find the frequency and duty, use the cursors located at the upper left corner, click and drag cursor to the risen or fallen edge of the wave.  The blue cursor is T2 and the red is T1, and on the scope T2-T1 tells you the time difference between the two cursors.  Use value from T2-T1 to calculate frequency, and you can use similar procedure to calculate duty cycle.


Tien P.

National Instruments
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