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Basic Electronics » Laptop ground safety question

March 27, 2010
by ese
ese's Avatar

I don't have an oscilloscope; although I would like to get one. I do have some Python code to display Nerdkits output using tkinter canvas. I'd like to observe a 741 op amp. The plus and minus into the op_amp comes from two power supplies each going into a 7805 voltage regulator.

Powered up: can I safely hook points A and B (in the picture) together?

ground check

Good day to you.

March 27, 2010
by mongo
mongo's Avatar

Looks like you probably can.

As long as you do not ground the negative side of the second regulator, it should be OK. Technically, (A) is the ground. The OP AMP is running on a 10V supply but I would be wary of reading negative voltages though.

I would prefer to use a 7905 in the negative side however.

March 27, 2010
by ese
ese's Avatar

Looking at a 7905 data sheet:

7905 data sheet

I take it that the 7905 outputs a negative voltage (-5) with inputs of (-7-35). Is that (-7 to -35) or (-7 to 35)? Anyway I don't have one of those at this time.

I overlooked the possibility of a negative voltage on the ADC. I have no idea what that would do to the -168.

Thanks for the response.

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