Lm311

[parker]

Please help me identify the pin of LM311 from the circuit below!
Also need to understand on how this circuit works?

On which pin does the comparison takes place?
(e.g. pin A = 5V compare to pin B = 5V)
if both pins are equal where do i get the answer?

thanks in advance!

 

[ericgibbs]

Please help me identify the pin of LM311 from the circuit below!
Also need to understand on how this circuit works?

On which pin does the comparison takes place?
(e.g. pin A = 5V compare to pin B = 5V)
if both pins are equal where do i get the answer?

thanks in advance!

hi,
The -inp pin of the LM311 is at a fixed voltage [R1 and R2 form a voltage divider for the +5V]

The +inp pin is determined by what the voltage is at the junction of the divider formed by R9 and R9.

If the voltage on +inp is greater than the voltage on -inp then the LM311 output is high, else the output is low.....OK.?

 

[parker]

If the voltage on +inp is greater than the voltage on -inp then the LM311 output is high, else the output is low.....OK.?

i'm sorry eric i'm totally naive on this field kindly enlighten me more... what would be the output that i should expect is't CURRENT or VOLTAGE?

 

[ericgibbs]

i'm sorry eric i'm totally naive on this field kindly enlighten me more... what would be the output that i should expect is't CURRENT or VOLTAGE?

Hi,
Is this going to be used a battery charger circuit with auto cut off.???

 

[parker]

yes, and i'm planning to build this one but i don't really comprehend yet on how this circuit work?
do you have any better idea or better circuit that you will recommend? thanks again!

 

[ericgibbs]

yes, and i'm planning to build this one but i don't really comprehend yet on how this circuit work?
do you have any better idea or better circuit that you will recommend? thanks again!

hi,
It looks as though the LM311 input pins have been marked in reverse!! on the circuit, where did you get it.?

 

[parker]

It looks as though the LM311 input pins have been marked in reverse!!

from eleccircuit.com... i've notice that also when i compare the datasheet which i gathered but i'm not so sure...! and that's the reason why i ask for an expert help.

this is my 2nd project as a hobby and it's getting more interesting even though i don't have enough knowledge on this field, specially on how the circuits works...!
i really appreciate this forum, lots of expert share their wisdom

 

[ericgibbs]

from eleccircuit.com... i've notice that also when i compare the datasheet which i gathered but i'm not so sure...! and that's the reason why i ask for an expert help?

this is my 2nd project as a hobby and it's getting more interesting even though i don't have enough knowledge on this field, specially on how the circuits works...!
i really appreciate this forum, lots of expert share their wisdom

hi,
Look at this simulation of the circuit, I have added a few notes, also changed over the LM311 inputs.

The plot shows the V reference and V feedback from the battery.

 

[parker]

sorry eric i wasn't able to continue our discussion due to overnight power failure in our location.
what is the relay on this circuit, is't NORMALLY OPEN? and from the time the LM311 switch off the relay for how long it will stay on that mode?

 

[ericgibbs]

sorry eric i wasn't able to continue our discussion due to overnight power failure in our location.
what is the relay on this circuit, is't NORMALLY OPEN? and from the time the LM311 switch off the relay for how long it will stay on that mode?

hi
The diagram shows the relay as normally open.?
If you need to use a normally closed relay, you could just swop over the +/-inps of the LM311.

If you look at the plot I posted you will see that the relay opens [non charge mode] when the voltage at the junction of R4 and R8 rises to 2.85V and closes [charge mode] when the junction voltage falls to 2.58v.

The plot start shows the charge mode, as the battery sense voltage rises to 2.85v the relay opens and the charge stops.
As the battery voltage falls the sense voltage falls to 2.58v and the relay closes recharging the battery.

The ratio of the battery sense voltage is the divider R4 and R8 , 18K/[18k+86k] , so you can work out the actual battery voltage switching points from that ratio..OK.?

 

[parker]

@ junction R4, R8 and R3... what is the main function of R3? (also R9) kindly guide me more.

can i use LM339N of STmicroelectronics (i have it already) as a temporary replacement of LM311 cause i have not found it yet in my local distributor
will this one perform as LM311 if i use one of the comparator and leave blank the other 3?

i'm just curious what kind of program did you use to plot the diagram output?
i think it will help to progress my self study on electronics

thanks eric i'll keep you posted as soon as i finished this project.

 

[ericgibbs]

@ junction R4, R8 and R3... what is the main function of R3? (also R9) kindly guide me more.

can i use LM339N of STmicroelectronics (i have it already) as a temporary replacement of LM311 cause i have not found it yet in my local distributor
will this one perform as LM311 if i use one of the comparator and leave blank the other 3?

i'm just curious what kind of program did you use to plot the diagram output?
i think it will help to progress my self study on electronics

thanks eric i'll keep you posted as soon as i finished this project.

hi,
The simulation program is LTspice, which is a free download also join the Yahoo LTS user group for examples etc.

You can use an LM339, I will sim that circuit with a LM339 and post it.
I have attached the LTS *.asc file for that LM311 in case you use LTS for experimenting.

NOTE: you will have to get some of the model files [LM393 /LM339, relay] from the Yahoo user group [free]

Ref the R3 and R9,, quite often R2 and R7 have variable resistors so that the use user can 'tweak' the setting to give the required switching point.
As R10 and R2||R7 set the hysteresis feedback its a good idea to have a series resistor R9 so that the effect on the hysteresis is minimised when adjusting R2/R7.

Ref R4 and R8, again the user will often have a variable so the battery senses voltage can be tweaked.

In your project you could leave out R3.

As you are interested in comparators look thru this pdf for ideas.

 

[ericgibbs]

hi,
This is the LM339 version.

LTS.
**broken link removed**

 

[parker]

hi eric,

is there a required wattage for a trimmer to be series with R2 and R7?
what value of trimmer should i use?

 

[ericgibbs]

hi eric,

is there a required wattage for a trimmer to be series with R2 and R7?
what value of trimmer should i use?

hi,
The wattage of a trimmer is 0.125W, hardly any heating.
I would replace R7 with a 10K and connect the wiper to R9,, if you find the trimmer is set to close to one end of its rotation, change the value of R2 to say 6k8.

 

[parker]

hi eric,

do i need a regulated 14VDC?
what VA of transformer should i use? (if i wanted to charge a 12V 7AH and 12V 17AH)
what Ampere of diode should i use on rectification?

 

[ericgibbs]

hi eric,

do i need a regulated 14VDC?
what VA of transformer should i use? (if i wanted to charge a 12V 7AH and 12V 17AH)
what Ampere of diode should i use on rectification?

hi,
To answer your questions I need to know exactly what the purpose of the circuit is, what project, where used and is there anything else attached to the power supply etc...

 

[parker]

an auto shut off battery charger..
im doing the last circuit you gave me the version LM339...

 

[ericgibbs]

hi eric,

do i need a regulated 14VDC?
what VA of transformer should i use? (if i wanted to charge a 12V 7AH and 12V 17AH)
what Ampere of diode should i use on rectification?

hi,
If your batteries are SLA types, for cyclic fast charge its a constant voltage of 13.8V to 14Vmax, for a float charge approx 13.2V.

You require a mains to 15V transformer rated at 3 to 5 amps for a fast charge or a 15V rated at 1 to 3amps for a float charge.

After rectification of the 15V you will require a 5A or 2A, 14V/13.2V regulation circuit.

What type of charger did you have in mind.?

 

[parker]

the one that can charge a battery that came from a ups like maintenance free battery (is this the Sealed Lead Acid you mean?) and a battery of a car which need to refilled by distilled water...