There's context?

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Um...yeah. "Why won't a 741 go below 12 volts of output?"
I don't think that was ever resolved.
In post #6, absf demonstrated that the chip will go to about 1.5V above the negative rail, confirming that the real problem is not the chip.

 

Ok, serves me right for roughing up a newbie.

 

You are designing a comparator circuit rather than an amplifier. Op amps are optimised as amplifiers so I would suggest you use a comparator that will swing between on and off on the output. TL331 for example.

 

In my time here I have noticed that *some* people love to rant against the 741 whenever it pops up, usually by noobs in countries that have not heard of Digi-Key. Yet despite its...issues, the 741 basically spoiled the entire analog design universe with its unity-gain-stable performance. This became clear when the NE5532 showed up a few years later requiring a compensation cap for gains under 10. People were actually offended that Signetics made them think.

ak

 

Um...yeah. "Why won't a 741 go below 12 volts of output?"
I don't think that was ever resolved.
In post #6, absf demonstrated that the chip will go to about 1.5V above the negative rail, confirming that the real problem is not the chip.

I suspected that the problem was how the 741 was driving the base of the mysterious transistor that drives the relay, so I gave the OP a road map to overcome the shortcomings of a 741 when used on a single supply. In good faith, the OP got a circuit that would work. If he was observant, he would have learned why the 741 is a poor choice for this circuit, even if I did gore someone's ox.

 

You are designing a comparator circuit rather than an amplifier. Op amps are optimised as amplifiers so I would suggest you use a comparator that will swing between on and off on the output. TL331 for example.

Also, the 741 has a current limit function. If you are drawing too much current in your load the output will turn off and may well sit at 12V which is mid-rail. You could do a test by removing the load, replace with a 10k and make sure the opamp is still working.