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Help me wire a 741 opamp

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bobobano

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wireing a 741 opamp

greetings all,
ok heres the issue, I'm trying to build a light sensor for my robot, I have a pretty good desogn with a 741 diferentiator circuit, the only problem is that I want to have it from just a standard DC powers supply. However I don't know and can't find anywhere on how to wire it so I get the neccesary -9v on pin 4. All the wireing diagrams I've found just say to have a -v but dont actualy say how to obtain it.

sensor.jpg
 

Re: wireing a 741 opamp

It is possible to use operational amplifiers from a single supply but it involves a virtual ground at Vdd/2.

Search for "single supply operation".
 

wireing a 741 opamp

What kind of light sensor are you using? At what level are you going to set the comparator threshold? If the threshold is going to be above +3V, you shouldn't need a negative supply rail.

If you need a negative supply voltage for other parts of your circuit, you could use a charge pump inverter such as the venerable TC7660.

Consider using a comparator such as LM393 (it's also a very popular part).
 

Re: wireing a 741 opamp

And try to use the sensor in bridge configuration
see detalis here
**broken link removed**
 

Re: wireing a 741 opamp

Depending on what's the hatched rectangle, you could get very different circuits. I basically refuse to guess if the author isn't willing to give minimal information.
 

wireing a 741 opamp

sorry, forgot to label it, thats a light sensor. the LDRs I've found are too expensive and i got a bunch of solar lights during the last "everywatt counts" sale at home depot so I'm trying to use those.
Thanks for the tip about the single source opamp I found some good material.
 


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