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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.
Thanks Matt for highlighting the cheap modules available.
So you’ve 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 = 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’t 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:
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.
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.
FWIW,
Charlie
On 1/8/2020 5:47 PM, Stephen Izett stephen.izett@gmail.com wrote:
Thanks very much Finn
Thats what I was a after.
As you mention, I’m 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.
Do you have the schematics for the EC2 and 3? & EM3?
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’ve 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’s temp issues.
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.
Being realistic, I’m 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.
Cheers
Steve Izett
On 8 Jan 2020, at 11:58 pm, Finn Lassen finn.lassen@verizon.net <flyrotary@lancaironline.net> wrote:
I thought about 3D printing a pressure multiplexer to be driven by a stepper motor.
Imagine an 8 point ignition distributor.
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.
Commercially available but much more expensive than buying 7 extra sensors.
Should be a fun Arduino project.
Finn
On 1/8/2020 10:17 AM, Matt Boiteau mattboiteau@gmail.com wrote:
Temp sensors are cheap, but pressure sensors are $15-20??each.
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