hye everybody, sorry for bothering all of u here. i would to ask for heLp from anybody here. i having a problem with my mini-project which i have to design a Round Per Minute (rpm) METER using 7segment display which it will count the rotation of a DC Motor. to count this rotation, i need to use an infrared sensor. all this is hardware are suppose to be controlled by 8051 micro controller. i got 2 weeks to make all this,,, could anybody here help me?? about the schematic, hardware and assembly language of the 8051 for this project.i am really having no clear idea how to fix all this thing in such time.

 

Here is a link that may help - http://www.circuitstoday.com/optocoupler-devices-and-application

That is revolutions per minute.

Set up the optocoupler, count the pulses for a period, display the count.

 

thanks for the info about optocoupler. i had read that explanation, but i wonder may i make a custom made optocoupler using that schematic??
if not, then how do i gonna place my DC Motor to let the opto device detects the rotation of the motor shaft??
another problem is which part of the output of the opto device that i can connect to 8051 microcontroller?? thanks for your consideration.

 

Your DC motor should be coupled to a disc with a slot. Use the disc/slot to block the light to your optocoupler as the motor turn.

The output of the opto coupler can be fed to any digital IO of your 8051. Use the 8051 timer to time the duration between each pulses.

 

thanks to beenthere and arm n legs.