From: "Stephen Izett stephen.izett@gmail.com" <flyrotary@lancaironline.net>
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Subject: Re: [FlyRotary] Re: Using the EM3's EGT/CHT inputs for reading MPX10
 pressure sensors
Date: Thu, 9 Jan 2020 15:18:37 +0800
References: <list-13376875@logan.com>
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
In-Reply-To: <list-13376875@logan.com>
Message-Id: <FE3B1046-5C9F-4593-BF75-1F3FB8596F6B@gmail.com>

Hi Charlie

I was thinking of referencing everything to the aircrafts static system =
and reading air pressure (not pitot as in velocity) so as to determine =
the pressures around the cowl.
So perhaps various points in front of an exchanger cores and various =
points behind the cores.
This would then give us the flow through the cores.
=20
Thanks Matt for highlighting the cheap modules available.
So you=E2=80=99ve got me thinking:

Why not use a barometric sensor (absolute) unit with pressure and temp =
at the location your wanting to measure, rather than a hose back into =
the cockpit or micro.

As an example, the BMP280 has a pressure range  300-1100 hPa =3D 4.35 - =
15.95 psi.
So this unit can measure a pressure of 1.25psi above atmospheric at sea =
level and progressively higher pressures at higher altitudes.
They can handle up to 85C or 185F which I thought would be OK.

Unfortunately the units appear to have a fixed I2C address, so we =
can=E2=80=99t simply daisy chain them and address them in software.
It looks like they will require a hard Chip Select for each device.
So what about a small multicore from a micro (arduino or micromite etc) =
through the firewall to a node with connectors for any number of sensors =
to reticulate around the cowl.
Each of these connectors has its own Chip Select line from the micro so =
each is addressable.
Another of these units could be connected to the static of the aircraft =
to provide a local pressure reference for all measurements.

It looks like I could get 10 such boards for $20AUD on eBay.
Does this make sense?

Steve Izett


> On 9 Jan 2020, at 10:02 am, Charlie England ceengland7@gmail.com =
<flyrotary@lancaironline.net> wrote:
>=20
> On the subject of static source, are we talking about measuring =
cooling air *velocity* inside the ducts, etc? If so, I believe that =
you'll need to put the static source in the same air as the pressure =
('pitot') source.
>=20
> If you're looking for pressure ('piccolo tubes') differential, then =
I'd think you'd want a differential sensor with one port in the high =
pressure plenum area and the other in the exit plenum, which likely will =
also be at a higher pressure than the a/c's static pressure.
>=20
> FWIW,
>=20
> Charlie
>=20
> On 1/8/2020 5:47 PM, Stephen Izett stephen.izett@gmail.com wrote:
>> Thanks very much Finn
>>=20
>> Thats what I was a after.
>> As you mention, I=E2=80=99m not needing hi res data to understand =
whats happening in the cowl and ducts at various speeds.
>> Unfortunately I removed the data log option years ago (not enough =
space in that panel) and the Skyview logs the engine data well.
>>=20
>> Do you have the schematics for the EC2 and 3? & EM3?
>>=20
>> I thought it was just a question of whether I wanted to spend the =
extra time knocking up a string of amps for the 5 sensors I=E2=80=99ve =
got.
>> But after thinking about it overnight, displaying the data in the =
cockpit is no where near as helpful as logging and analysing the data on =
the ground.
>> I use a micromite system so the reading and writing to a mem card =
will be simple.
>> The benefit of building a little batt powered unit as you suggested =
Matt is we could use it to diagnose other=E2=80=99s temp issues.
>>=20
>> So you guys have been helpful as usual.
>> With my 5 MPX10DP sensors we could log airspeed and 4 pressure inputs =
referenced to the ships static.
>> Perhaps temps for each press input would be helpful as Matt =
suggested.
>>=20
>> Being realistic, I=E2=80=99m a bit slow, so I would need a week to =
fab it all up.
>> But it would be super helpful to me and possibly many others.
>> Only over the weekend we had a first flight of a lyc powered machine =
put down in a field adjacent to our strip due to overheating. =
Fortunately both pilot and machine were unscathed.
>>=20
>> Cheers
>>=20
>> Steve Izett
>>=20
>>=20
>>=20
>>=20
>>=20
>>=20
>>=20
>>=20
>>> On 8 Jan 2020, at 11:58 pm, Finn Lassen finn.lassen@verizon.net =
<flyrotary@lancaironline.net> wrote:
>>>=20
>>> I thought about 3D printing a pressure multiplexer to be driven by a =
stepper motor.
>>>=20
>>> Imagine an 8 point ignition distributor.
>>>=20
>>> You wouldn't have 8 real time pressure sensors, but I guess 1 second =
on each input should be enough for pressure to stabilize enough for =
measurement. So sampling all 8 inputs would take 8 seconds.
>>>=20
>>> Commercially available but much more expensive than buying 7 extra =
sensors.
>>>=20
>>> Should be a fun Arduino project.
>>>=20
>>> Finn
>>>=20
>>> On 1/8/2020 10:17 AM, Matt Boiteau mattboiteau@gmail.com wrote:
>>>> Temp sensors are cheap, but pressure sensors are $15-20??each.
>>>=20
>>=20
>> --
>> Homepage:  http://www.flyrotary.com/
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http://mail.lancaironline.net:81/lists/flyrotary/List.html
>=20
>=20
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