PhotoTransistor Problem - Electronic Circuits Projects Diagrams Free

anita1984 · 25th October 2009, 12:33 PM

Hi Forum ,i am using a laser module, phototransistor SFH309-5, and 74HC14N (Circuit in the attachment) to detect the speed of the motor. On the Vout2 i measured frequency up to 2,8KHz when the speed of the motor is 28 000 RPM (because 6 reflected beam every rotation). But when i increase the motor to 32 000 RPM the frequency on Vout2 is 500Hz , and it should be 3,2KHz , what can be the problem ?
Thank you in advance ,

colin55 · 25th October 2009, 06:05 PM

What voltage is Vcc?

MikeMl · 25th October 2009, 07:09 PM

R2 looks low to me. Try several higher values up to 20K.
R1 looks low, too. Check that the current through the LED(I doubt that it is a "laser") is within spec.

palmtree · 25th October 2009, 07:29 PM

MAYBE YOU HAVE TO REPLACE R1 BY ANOTHER ONE LARGER to protect the laser module

12345678901234567890 · 25th October 2009, 08:00 PM

Are you able to check it (the interuptor module),with another pulse counter?

anita1984 · 30th October 2009, 12:11 AM

thanks for all , i change the value of R2 , it's now 10K , it's working well
Have a nice day

palmtree · 30th October 2009, 07:00 AM

congratulations anita

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25th October 2009, 12:33 PM	#1
anita1984	PhotoTransistor Problem Hi Forum ,i am using a laser module, phototransistor SFH309-5, and 74HC14N (Circuit in the attachment) to detect the speed of the motor. On the Vout2 i measured frequency up to 2,8KHz when the speed of the motor is 28 000 RPM (because 6 reflected beam every rotation). But when i increase the motor to 32 000 RPM the frequency on Vout2 is 500Hz , and it should be 3,2KHz , what can be the problem ? Thank you in advance , Attached Thumbnails

25th October 2009, 07:09 PM	#3
MikeMl	R2 looks low to me. Try several higher values up to 20K. R1 looks low, too. Check that the current through the LED(I doubt that it is a "laser") is within spec. __________________ Mike ML.

25th October 2009, 07:29 PM	#4
palmtree	MAYBE YOU HAVE TO REPLACE R1 BY ANOTHER ONE LARGER to protect the laser module

25th October 2009, 08:00 PM	#5
12345678901234567890	Are you able to check it (the interuptor module),with another pulse counter? Last edited by 12345678901234567890; 25th October 2009 at 08:03 PM.

30th October 2009, 12:11 AM	#6
anita1984	thanks for all , i change the value of R2 , it's now 10K , it's working well Have a nice day

30th October 2009, 07:00 AM	#7
palmtree	congratulations anita Last edited by palmtree; 30th October 2009 at 07:02 AM.