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subot_robot
02-06-2006, 03:28 PM
Hi,
Can anybody please tell me how to connect CRO to the output pins of microcontroller and get the output on the screen. I am trying to get pwm waveform from PIC18F452 on CRO. When I connected the ground wire of CRO probe to the bread board containing pic circuit the pic stopped running. The moment I disconnect CRO probe it startsf running again. If anybody have connected microcontroller o/p to CRO please guide how to do it.
Thanks

Subot_robot

yogi
02-06-2006, 03:52 PM
i think PIC is not able to source enough current. I think u connect a buffer between them( either use an opamp as a buffer or IC74244 buffer). but i never done this before. When u connect the output to the CRO see the voltage on Vcc pins of PIC. It may be low which cause PIC stops running.



Bibin John
www.bibinjohn.tk

docel
02-07-2006, 12:52 AM
Hi,
You need Proffessional CRO Probes (1200 bucks), not the 'college'Probes (35 bucks audio pick-up probes!!).
The input should be hi Z ( high impedence); Try the x100 switched probe for minimum loading of the micro O/P. You can also try HF filter and TV switches on the CRO. This will prevent mutual coupling and interference.

Supario
02-07-2006, 11:53 PM
Hi,

If you just need the average value or the frequency of the PWM output and arent too concerned about the actual waveform, you could use the frequency counter and voltmeter functions of a multimeter itself. Otherwise try setting the probe on the oscilloscope to x1000. BTW the analog CROs in the upstairs lab arent very good, try using the digital ones downstairs.

Supario

devpriya
02-08-2006, 11:25 AM
Hey try putting 1K resistors in series, i hope that will work.

EmbeddedGuy
02-10-2006, 12:32 PM
Use high impedence and good quality prob. These types of proble will cost you more then Rs.1500/- the cost depends on make and quality.