shekhar_dandya Posted March 13, 2006 Report Share Posted March 13, 2006 How to make an RPM counter?Assuming you have some sensing mechanism,say a flywheel with a slit to pass the light beam that is sensed by a photosensor at reciever end and which is attached to a transistor driver that gives you square pulses for every cut.How to process the rest of the signal using a microcontroller?One way is to use interrrupt pin to interrupt the MCU every time the pulse comesand increment a variable in the ISR.use a timer to generate a delay of 1 min.read the counter variable before starting the timer and after 1 min.take the difference and display.Is there any more better way?How are commercial RPM counters/taechometers made?I feel they don;t wait for 1 min to gather the # of revs in a minute.How do they work? Quote Link to comment Share on other sites More sharing options...
pebe Posted March 13, 2006 Report Share Posted March 13, 2006 They use their timer to measure the time between two interrupts, then calculate the RMP from that. Quote Link to comment Share on other sites More sharing options...
shekhar_dandya Posted March 14, 2006 Author Report Share Posted March 14, 2006 This method will work for slower RPM, for faster ones?I think then one can measure no. of revs in say 10 sec and then calculate for 1 min?what do you say? Quote Link to comment Share on other sites More sharing options...
europus2002 Posted March 17, 2006 Report Share Posted March 17, 2006 Use a divide by N counter....say like CD4040 to divide yr input signal and then take to microcontroller OR..To avoid microcontroller , use CD4040 counter as divider , feed the divided output to Frequency to voltage convertor chip like NE565 PLL and display it using 3 1/2 digit ADC for display , the type used in DVM (ICL7137)......This division approach will allow you to feed input signal to very high RPM and still not jam yr circuit........I hope things are clear.........feel free to drop by in case of questions.... Quote Link to comment Share on other sites More sharing options...
fever16 Posted March 17, 2006 Report Share Posted March 17, 2006 i think magnetic sensors work efficiently at high speeds compared to IR sensors.u can uses a pair of magnet and halleffect sensor for calculating RPM.i dono much abt pic programming.but i came across such RPM counter while searchig for LED POV stuffhttp://www.raphnet.net/electronique/pov_leds/pov_leds.phpscroll down,and at v2.2 tag u'll find a rpm counting led pov. Quote Link to comment Share on other sites More sharing options...
Shahriar Posted March 19, 2006 Report Share Posted March 19, 2006 The best way for a RPM counter is What pebe Said.Imagine if you use a Devider or revs in say 10 sec and then calculate for 1 min this problem will happen!You should multiply the number of RPM in 10 seconds by 6 to achieve for 1 min. so the Number you achieve is alway = 6K. I mean : 6 - 12 -18 - 24- ... 6K (Sorry, I don't know the english name)So if you have a real RPM = 15 then your device will show 12 or 18 And another problem is your counter will be refereshed every 10 seconds. If you decrease this interval (10s) then you should multiply it with a bigger number and ..... :o :oHTH - Shahriar Quote Link to comment Share on other sites More sharing options...
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