Close to GND isn't the problem. LMV331 inputs can go 0.1V below GND, but it will only work when the inputs are more than 0.8V below the positive rail.

Ron H -- you missed my point. I admitted to not checking his component, and in quickly looking over the design I ASSumed it was an opamp and a switch.

The problem is, when people come up with designs that are so far from being technically correct or operational, it is hard to provide "good" advise without spending a lot of time looking into design parameters to redesign and redraw most of the circuit. Therefore, I sometimes just add a note or two to try to get the person to move forward with what they have done (note I suggested looking into datasheet applications).

Studying datasheet applications for reference comparator circuits, and understanding the function, would help this person considerably; rather than just throwing him a fish. I can almost predict that the next question will be "what is hysteresis?"

 

Ron H -- you missed my point. I admitted to not checking his component, and in quickly looking over the design I ASSumed it was an opamp and a switch.

The problem is, when people come up with designs that are so far from being technically correct or operational, it is hard to provide "good" advise without spending a lot of time looking into design parameters to redesign and redraw most of the circuit. Therefore, I sometimes just add a note or two to try to get the person to move forward with what they have done (note I suggested looking into datasheet applications).

Studying datasheet applications for reference comparator circuits, and understanding the function, would help this person considerably; rather than just throwing him a fish. I can almost predict that the next question will be "what is hysteresis?"

I just thought that the reference to the inputs going close to GND was an unintentional red herring, so I wanted to make it clear that that was not an issue in this case.
When appropriate, I resort to "Google is your friend", which has pissed off at least one guy.
Nevertheless, if he asks about hysteresis, that will be my response.

 

lol, i got it i'm not going to ask what is hysteresis! thanks for the help, i did read the datasheet and got it, ^_^ thanks all for the help

 

...i'm not going to ask what is hysteresis!...

You will eventually!

Ken

 

You will eventually!

Ken

lol, come on! i just want to let u know that i got it.
also i realized that, i could done this thing using Arduino microcontroller. with less mess, because i will have several sensors and a screen. after all it's good to have the knowledge.

 

lol, come on! i just want to let u know that i got it.
also i realized that, i could done this thing using Arduino microcontroller. with less mess, because i will have several sensors and a screen. after all it's good to have the knowledge.

You have negative feedback. Hysteresis requires positive feedback.

 

i can barely do nothing.
thanks ^_^