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Lm311 - How to use properly

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gjpollitt

New Member
Hi all

Read a post earlier about LM311 and how he couldnt get the circuit to work, well i have similar prob

Have posted my circuit here

Can anyone tell me why it works fine simulated but when i proto it on the breadboard the output (pin7) is .2 V and doesnt change regardless of the inputs?

i have pins 1 and 4 to gnd, 2 and 3 for inputs, 8 vcc, 5 and 6 tied together and 7 output

Thanks
Graham
UK
 

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Roff

Well-Known Member
Replace R1 with a piece of wire. Don't connect pins 5 and 6 together - just leave them unconnected. The output should switch between 0v and 5v(approx). R7 is unnecessary, and draws about 90ma from your 1.1v supply. What is the source of the 1.1v supply?
 

gjpollitt

New Member
The R7 is to load the battery being tested, the source of 1.1v is battery. The circuit is for me to test my batteries to see if they need charging or not.
I will try your ideas when i get home from work later
thanks
 

gjpollitt

New Member
cant get it to switch state, the led circuit is fine as can make switch between green and red manually with wire

the lm311 output just wont budge from .2v

could it possibly be that i have blown both chips i have? or is something else missing?

this circuit works fine in simulation but not reality :)
 

k7elp60

Active Member
LM311

You are right. In the configuration you are using the 311 is a voltage
sensitive switch. When the voltage you are comparing gets very close to the reference voltage, the output will change.
 
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