Oscilloscope Clocks

Posted on Feb 5, 2014

This oscilloscope clock project uses a PIC 16F876 and a DAC to generate X and Y signals to draw a clock on the oscilloscope. The original circuit and software was designed by OZ2CPU, which can be found here:. The clock circuit was slightly modified to use a different DAC from Texas Instruments. The 60Hz signal was obtained from the AC side of a

Oscilloscope Clocks
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12VAC (NOT DC) wall adapter and the current is limited with a 10K resistor. Below is the schematic of the minimal oscilloscope clock circuit: At first I didn`t bother building the entire oscilloscope from scratch because I had a handful of oscilloscopes sitting around. However, the only working oscilloscope I had with a Z axis input was the Tektronix 7704A, but experiments showed that the blanking signal from pin 26 of the PIC was not entirely necessary. The blanking is only used to supress any lines from appearing while the DAC quickly changes from a point to another point. It turns out that the vectors are drawn so quickly that there is almost nothing visible between points without the blanking signal. Omitting the use of the blanking signal makes this circuit more versatile for a wide range of oscilloscopes with simple X and Y inputs, including vacuum tube oscilloscopes! However, the graphics are stable and crisp with DC coupling to the oscilloscope. Most tube scopes use AC coupling, but if the deflection amplifiers are designed well then the graphics will look pretty good. The only downfall with AC coupling is a degree of image distortion and the image will drift around the CRT face, but the benefit of the drifting is a reduced risk of phosphor burn on the screen. The two switches (SW1 and SW2) sets the time, but I`m not sure which switch does what so you`ll have to find out. One switch will change the clock mode which...

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