Negative problem

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Negative problem

Postby pic16 » Wed Mar 04, 2015 10:01 am

hi, everyone...

i have a small signal in mV need to amplifier to V, the amplifier i use need dual + & - supply, so the output will have negative as well, my problem is the output signal was go to MCU. How to allow the positive but stop negative signal go to MCU pin? Will negative V damage the MCU?(pic16f877)
i'm poor in english and just an electronic hobbyist.
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Re: Negative problem

Postby ober » Wed Mar 04, 2015 11:28 pm

Why don use diode?
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Re: Negative problem

Postby pic16 » Thu Mar 05, 2015 12:40 am

ober WROTE:Why don use diode?



may i know how? :P
i'm poor in english and just an electronic hobbyist.
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Re: Negative problem

Postby ober » Fri Mar 06, 2015 9:23 am

Can you share you setup ? Schematic or picture of actual hardware.
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Re: Negative problem

Postby pic16 » Tue Mar 10, 2015 2:22 pm

ober WROTE:Can you share you setup ? Schematic or picture of actual hardware.



hi,
just simply like this, pin 3 is +V input signal, pin 2 is -V input signal (Can't connect pin 2 and pin 4 to ground )
its output will be either positive and negative, but what i want is output was positive +V only, any method?
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i'm poor in english and just an electronic hobbyist.
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Re: Negative problem

Postby yonghui » Thu Mar 12, 2015 1:35 pm

why dont user single supply op amp like MCP601, MCP602.

if u still want keep using dual supply op amp, make sure the output from op amp does not exceed 5V for the PIC input. use a signal diode like 1N4148 to rectifier the negative half or the signal .

diode in between
op Amp output -------|>|-------PIC pin
thanks&regards,
yh
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Re: Negative problem

Postby pic16 » Thu Mar 12, 2015 3:18 pm

yonghui WROTE:why dont user single supply op amp like MCP601, MCP602.

if u still want keep using dual supply op amp, make sure the output from op amp does not exceed 5V for the PIC input. use a signal diode like 1N4148 to rectifier the negative half or the signal .

diode in between
op Amp output -------|>|-------PIC pin



the negative volt still go though it, in -mV
i'm poor in english and just an electronic hobbyist.
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Re: Negative problem

Postby ober » Thu Mar 12, 2015 5:20 pm

milli voltage should be no problem.
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