All About Circuits Forum  

Go Back   All About Circuits Forum > Electronics Forums > Homework Help


Homework Help Stuck on a textbook question or coursework? Cramming for a test and need help understanding something? Post your questions and attempts here and let others help.

Reply   Post New Thread
Thread Tools Display Modes
Old 05-13-2012, 04:07 AM
cly_1018 cly_1018 is offline
New Member
Join Date: Jan 2010
Posts: 2
Default IR Sensor using lm324

Hi All,

I need help on the IR Sensor circuit using lm324 comparator~the distance between transmitter and receiver is 20cm.
1) How to combine both circuit together? Is the circuit design correct?
2) How to measure the output voltage when the IR sensor is in blocking condition and non-blocking condition?


Reply With Quote
Old 05-13-2012, 12:26 PM
Bill_Marsden's Avatar
Bill_Marsden Bill_Marsden is offline
Super Moderator
Join Date: Mar 2008
Location: Dallas, TX (GMT-5 w/ DST)
Posts: 19,044
Blog Entries: 5

The design is flawed, seriously so. You have the - input connected to gnd. This will create a anomalous condition for the op amp, which you are trying to use as a comparator. With the input at ground there can never be a cross over of the voltages. There needs to be a small resistor to raise that level off the ground, as the + input can never go below the ground level.

You have another problem in using the LM324. This is an op amp, most op amps have a problem with their inputs going near either power supply level. Using a LM393, a true comparator, is a much better choice, though don't forget the pull up resistor (10KΩ typical) on the output.

When using 4 op amps or comparators do not forget to ground the unused components inputs, to prevent unwanted oscillations.

High Speed Op Amp Query

The LM358 is an op amp that is designed for its input to go very near ground.

Bill's Index
"Good enough is enemy of the best." An old engineering saying, Author unknown.

General info:
If you have a question, please start a thread/topic. I do not provide gratis assistance via PM nor E-mail, as that would violate the intent of this Board, which is sharing knowledge ... and deprives you of other knowledgeable input. Thanks for the verbage Wookie.
Reply With Quote
Reply   Post New Thread


Related Site Pages
Section Title
Worksheet Encoders and decoders
Worksheet CMOS logic gates
Worksheet Linear computational circuitry
Worksheet Positive feedback opamp circuits
Worksheet Negative feedback opamp circuits
Worksheet Open-loop opamp circuits
Textbook Operational amplifier models : Operational Amplifiers
Textbook Practical considerations : Operational Amplifiers
Textbook Negative feedback : Operational Amplifiers
Textbook Voltage comparator : Analog Integrated Circuits

Similar Threads
Thread Thread Starter Forum Replies Last Post
Using LM324 Quad Op Amp in PIC16F877A lloydi12345 Embedded Systems and Microcontrollers 2 11-04-2010 01:54 PM
IR Receiver triggering on power-up NZMikeV The Projects Forum 4 09-13-2010 09:53 AM
IR beam proximity sensor optimus9 The Projects Forum 0 10-18-2009 07:52 PM
Triggering an IR receiver from a white object/paint avz10 The Projects Forum 26 07-13-2009 02:43 AM
IR LED's and IR sensors/LDR Bear_2759 General Electronics Chat 8 02-22-2009 01:22 PM

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

All times are GMT. The time now is 01:57 AM.

User-posted content, unless source quoted, is licensed under a Creative Commons Public Domain License.
Powered by vBulletin
Copyright ©2000 - 2014, vBulletin Solutions, Inc.