MAP sensor

[Mark Pitts]

Anybody out there know who Stack is??? Well, they use those little =
squidgy yellow ear plugs as vibration mounts.. by all accounts they work =
REALY well! (but aparantly didnt save a data logger that went round the =
back wheel of a Kawasaki!). Ive used them in the past to mount my CD =
player in the Spitfire, as the ride is so harsh it wouldnt play.. 4 =
earplugs, end on underneath it, and no probs!

Just an Idea !

Mark


----------
From:  Darrell Norquay[SMTP:dnorquay at awinc.com]
Sent:  Saturday, September 14, 1996 2:51 PM
To:  diy_efi at coulomb.eng.ohio-state.edu
Subject:  Re: MAP sensor

At 08:19 AM 9/13/96 -0500, Tom wrote:

>Now, I'll just need to find out how much it costs,
>what it looks like, how it mounts, etc.

Typically, most OEM MAP sensors are little black boxes around 2x3x1", =
with
screw mounting holes built in, a small barbed hose fitting, and a plug =
or
short wiring harness with plug.

>The data sheets for these are on the Motorola web page,
>(http://motserv.indirect.com/) and they're listed in the Newark catalog
>for about $26.=20

The MPX4100 series have all the necessary signal conditioning built in.
They are simple 3 wire devices, voltage in (5V) , voltage out =
(.2v-4.9v),
ground.  Slap it in a waterproof enclosure and you're done.  They may =
not
like high vibration environments, so best to mount them on the firewall, =
in
the passenger compartment and run a hose to the manifold vacuum tree.  =
These
may be chaper than new OEM sensors, if you feel like doing the =
mechanical
bit yourself.  If you are doing an EFI circuit board, consider mounting =
the
sensor right on your PCB.  Vacuum hose doesn't pick up noise, whereas a
wiring harness might... One tip on these, the hose barbs provided on the
sensor are relatively fragile, one slip when pushing on the hose and =
it's
history.  Better to plumb this out to an external metal hose barb on the
box, to avoid the chance of breaking off the tit.

>Now, which to use -- and what does one do with the data re EFI ??
>Now, the frequency output of the OEM unit -- seems that
>that would entail either an F-V convertor and then A-D or an
>interrupt driven timer circuit that would return a number of counts
>proportional to the period of the sensor output.  Any suggestions?

Either unit will give you equivalent results, and probably don't require =
any
intervening components to interface to the processor.  If you have =
enough
analog channels on your micro, analog is probably easier.  If you are =
short
on analogs, and feel confident that you can write the code to measure
frequency (piece of cake on an 'HC11, but then so is analog) do it that =
way.
The frequency approach may have better noise immunity than analog.  =
Forget
the F-V stuff, it's not necessary or desireable.  For dinking around
purposes, you may be better off to get a used unit from an auto =
wreckers,
and see if it does what you want.  As far as what to do with the data =
once
you've got it, stay tuned...



regards
dn
dnorquay at awinc.com