Hi,


Your design seems very neat, I'd be very thankful if you send me the
code/schematics.

Thanks

Best Regards
Anders Eliasson



At 11:26 1998-01-14 GMT+0200, you wrote:
>Hi,
>
>If anyone would like to see the code and the schematic, mail me and I'll
>mail it to you.
>
>Regards,
>Niki
>
>> I think you project is neat!
>> Would you be willing to share your code (just for personal
>> non-commercial use).
>> tks
>>
>> Mike Montaigne
>> montaignem@aecl.ca
>>
>> >----------
>> >From:  N STEENKAMP [M.ING E&E][SMTP:STEENKMP@FIRGA.SUN.AC.ZA]
>> >Sent:  Tuesday, January 13, 1998 4:58 AM
>> >To:    PICLIST@MITVMA.MIT.EDU
>> >Subject:       Re: pic tachometer...
>> >
>> >Hi,
>> >
>> >> Once again I'm drawing upon the infinite wisdom of the PICLIST...
>> >>
>> >>   I'm building a simple pic-based automotive tachometer and would like
>> >> to count pulses from the primary lead of the ignition coil and display
>> >> the RPM on an LCD.  For peace-of-mind (and other reasons), I'd like to
>> >> isolate the input pin of the pic with a 4N35 optoisolator.  I can handle
>> >> everything but the connection to the coil...
>> >>
>> >> I have 2 questions -
>> >>
>> >> 1.  What is the maximum frequency that the 4N35 will reliably switch at
>> >> (will it keep up with the pulse train from the coil)?
>> >>
>> >> 2.  What do I need to do at the optoisolator's input to handle the
>> >> ignition pulses?
>> >>
>> >Just a comment:
>> >I have also constructed an automotive tachometer about a year ago.  I
>> >have found that counting pulses in a fixed period is not a very good
>> >approach, since the frequency of pulses can be quite low.  At 600 RPM it
>> >is 20Hz for a 4cyl engine.  That means that your counting period must be
>> >quite long to be able to get sufficient accuracy, which means a
>> >slow update rate of the display.  The method I used was to time the
>> >period between two pulses and calculate the RPM from that.  I
>> >wanted to keep the refresh rate between 5 and 10 times per second.  Since
>> >the higher the RPM's the shorter the period, I was also able to average
>> >samples at higher RPM's for a stabler display.  From 0 to 1200RPM's I
>> >used 1 sample, from 1200 to 2400 I used 2 samples.  From 2400 to 4800 I
>> >used 4 samples and from 4800 upwards I used 8 samples.
>> >
>> >The project uses a 16C54 running at 20MHz and the display is a 16x2 LCD.
>> >It has a resolution of 10RPM's.  In the top line of the LCD I display the
>> >RPM's in digits and in the bottom line I have a bargraph display (made by
>> >using the programmable characters of the LCD).  The display is
>> >really fast and responsive.
>> >I guess that using one of the PIC's with a capture and compare unit
>> >would have been easier, but I wanted to see what I could do with a 54!
>> >
>> >Regards,
>> >Niki
>> >
>>
>
>