Some VSS info&questions

[Terry Sare]

     1. Avoid DA and AD if possible -- they have a host of other gotchas 
     and are not worth the cost and effort. If in digital domain, try to 
     stay there.
     
     2. Divide by N counters are available -- don't have data books handy 
     to look them up right now -- TI web site has ttl parts listed. Also, 
     CMOS part, 4xxx series, will work on 12V. A flip-flop does a divide by 
     2 each time. Most counters are simply flip-flops cascaded together -- 
     a 4 bit counter will divide by 16, 5 bit is 32, 6 bit is 64, 7 bit is 
     128 and a 8 bit counter is 255. ( I think :-) need more coffee!)
     My Digikey catalog show CD4018 (divide by n), CD4020 (14 stage 
     counter), CD4029 (counter), CD4060 (Counter), etc. They don't like 
     static electricity so handle with ground straps only.
     
     3. PIC Stamp would also be a useful part for this. Easy to change the 
     ratio when you change your gear ratio. 
     
     I am going to face the same problem when I update my 68 to modern 
     transmission so this mechanical info is verry helpful to me.
     
     ts


______________________________ Reply Separator _________________________________
Subject: Re: Some VSS info&questions
Author:  diy_efi-owner at esl.eng.ohio-state.edu at dell_unix
Date:    3/4/1998 8:56 AM


If you are doing a Camaro - P245/50R16 tires that rotate 811 times per mile. 
With a 40 pulse per driveshaft rev sensor and a 3.42 axle ratio, the output 
is 110,944.8 pulses per mile.  Aren't there simple counter chips that can 
divide by 55 to get 2018 pulses per mile?  (you can tell I'm an ME).   If 
you have different tires or axle ratio, put in your own data.  Tire revs per 
mile is 20,800/dia(in).
Gary Derian <gderian at cybergate.net>
     
-----Original Message-----
From: Andris Skulte <askulte at emerald.tufts.edu>
To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu> 
Date: Wednesday, March 04, 1998 1:57 AM
Subject: Re: Some VSS info&questions
     
>You got it exactly right. I'm getting rid of my mechanical T5 and going 
>to the electrical T56. I solved the speedo drive by using an electrical 
>firebird speedo and VSS buffer box. I still need to convert the 40 p/rev 
>to 2000 rev/mile. Someone mentioned using a frequency counter chip, 
>changing it to voltage (another chip), adding an adj resistor to change 
>(calibrate) voltage, and finally convert it down to frequency (third 
>chip). I think I got it right... What parts do I buy (i.e. numbers) TIA! 
>:)
>
>Andris