LM311 | Electronic Project Circuits

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LM311 Oscillator

LM311 is a comparator,
It operates from single 5V supply or dual supplies, input current 150 nA, 50 V-50 mA output drive capability. TTL-CMOS compatible output.

The Output is open collector so it can sink current but cannot source, a totem pole output can source and sink. In this Circuit R2 is the source or pull-up.
The Output being high or low depends on which input is more dominant or positive. If + or non-inverting input is more positive than the – inverting input then output of LM311 is high impedance or high Z as output transistor of LM311 is turned off, but output goes high due to R2 pull-up 1K, so you can apply a load of 10K and above for source. When the – input or inverting input is more positive, output goes Low as transistor turns on, now a current of upto 50mA can sink here, a LED or Relay can be driven.

On turn on C2 capacitor is discharged and pin 3 the inverting input is at a lower potential than pin 2 the non-inverting which is at 2.5V. Hence output goes high and C2 starts charging thru R5, When C2 charges a little beyond 2.5V pin 3 is more dominant and output goes low now, this slowly discharges the C2 bringing the voltage at pin 3 again below 2.5V so output goes high again. This process goes on, hence it oscillates. The charging and discharging is at the rate of R5 * C2 approx. , R3 serves as hysterisis or feedback to ensure clean turn on and off.

Read More Source:http://schematics.blogspot.com/2004/11/lm311-oscillator.html
Thank you.

Be the first to comment - What do you think? Posted by admin - January 10, 2008 at 7:32 pm

Categories: Oscillator generator Tags: LM311, Oscillator generator

PWM DC Motor Speed Control with NE556,LM311

The left half of the 556 dual timer IC is used as a fixed frequency square wave oscillator. The oscillator signal is fed into the right half of the 556 which is configured as a variable pulse width one-shot monostable multivibrator (pulse stretcher). The output of the one-shot is a variable width square wave pulse, the pulse width is set with the speed control pot on the control voltage input. The variable width output pulse switches the IRF521 MOSFET transistor on and off. The MOSFET amplifies the current of this signal so that it is powerful enough to control a small DC motor. The 311 comparator is used to cut off the one-shot via the reset pin when the control voltage is below a certain threshold, the 311 is also controlled by the speed control pot. The cut off circuit is necessary because the 556 one-shot circuit will always put out a small pulse, even when the control voltage is at zero.
Read more Source:http://www.solorb.com/elect/pwm/pwm0/

Be the first to comment - What do you think? Posted by admin - September 9, 2007 at 10:03 pm

Categories: Electronic Control, Motor controller Tags: LM311, Motor controller, NE556, PWM-Speed-Motor

Auto Fast Battery Charger by LM311 for CAR

This is Circuit Auto Fast Battery Charger.Here is circuit Auto Charger battery 12V will quickly and easily charge most any lead acid battery. When the battery is fully charged, the circuit Relay switches off
Use IC 7805 for power supply here circuit. and IC LM311 control test volt battery .
Read detail in circuit.