Auto Tachometer

Archiver

TC-

When I did the math I got an answer that tells me a difference of 5
RPM corresponds to ~ 0.166 tach pulses per second, which says you
can't get there from here by counting pulses over a small interval
like 1/2 seconds.

Have you considered PULSIN instead of COUNT? The resolution
available to measure the duration of the pulses--or the duration
between pulses--rather than their frequency may be more useful.


Regards,

Steve

Archiver

Can someone help me make a code for a BS2 to read a car's tach? I
have a V8 Chevy. I know a few things about motors, the distributor's
RPM is 1/2 the crank's RPM. But the RPM is how many times the crank
goes past a certin point in one Min. And the tach output is on the
distributor. so RPM(from distributor)*2=RPM at crank.

I got it to somewhat work, got it to read in 15RPM incramints with
the count camand using 1/2 sec. then take what the count was then put
in a formla: "RPM=(RPMTemp*2)*60" but that is no good. I nead 5 RPM
incramints. 1/2 sec. is about as slow as i will go.

I was thinking of using a Freq to Volt conveter then sending the Volt
to a A/D converter then to the stamp. Please help me. Have not got
much sleep from my little (little pain in the a$$) project.

Thanks,
TC

Archiver

If you want to make an auto tachometer a I have a some
good ideas.
First you can make an encoder disk with 60 holes on
it.
Then just make the disk rotate trhough a
optotransistor and then meassure how many pulses you
get in 1 second, you can do that with the COUNT
command for Basic Stamp. Then you will read RPM
directly. Another way is to use a laser pointer and a
LM567 tone decoder to get the reflect transitions from
a mini mirror ( I prefer this because you can use only
one laser pointe in the shaft of the car to meassure
the torque, speed and cinetic movment one at a time).

I dont recommend you the pulsin command because is not
fast enough so you will lose some pulses.

Another good option is to convert this frequency into
voltage with a LM2907 freq-volt converter ($6.00). You
can calibrate the IC to get 10mv per revolution,, is
very easy to do that.


Another way that I suggest is to use a external
counter like ICM7217 from Intersil and the ICM7207 to
generate the gate timings, store and reset.

But first try one of the below.



--- S Parkis <parkiss@e...> wrote:
> TC-
>
> When I did the math I got an answer that tells me a
> difference of 5
> RPM corresponds to ~ 0.166 tach pulses per second,
> which says you
> can't get there from here by counting pulses over a
> small interval
> like 1/2 seconds.
>
> Have you considered PULSIN instead of COUNT? The
> resolution
> available to measure the duration of the pulses--or
> the duration
> between pulses--rather than their frequency may be
> more useful.
>
>
> Regards,
>
> Steve
>
>
>
> Your use of Yahoo! Groups is subject to
> http://docs.yahoo.com/info/terms/
>
>


__________________________________________________
Do You Yahoo!?
Yahoo! Auctions - buy the things you want at great prices
http://auctions.yahoo.com/

Archiver

[font=arial,helvetica]i do a lot of work with stamps in auto applications to measure rpm, e-mail me
your contact info and i will call you tomorrow.


sdavis6969@aol.com[/font]