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Subject: RE: [FlyRotary] Re: EWP - series pumps and wacky ideas
Date: Wed, 15 Oct 2003 10:42:03 -0400
Message-ID: <0B27ED95697C4D4CBC82D79E790FE5678B09F1@exchange.rfgonline.com>
Thread-Topic: [FlyRotary] Re: EWP - series pumps and wacky ideas
Thread-Index: AcOTJ6ofTGXQJomMTPKpqFQn3USwBQAAiEfQ
From: "Robinson, Chad" <crobinson@rfgonline.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>

Current sensing can be done in one of two ways. One way is what you =
already do for your ammeters - you use a shunt designed to produce a =
small but measurable voltage drop across the line. Most of these are =
designed to produce "full scale" drops of 50mV for their rated current =
flow, and can be had in a variety of=20

A voltmeter would then allow you to measure current flow. If you want to =
"trigger" at a certain voltage, a comparator will allow you to do this. =
Two useful books if you just want a bunch of useful circuits are those =
by Forrest Mims sold by Rat Shack, and the "Encyclopedia of Electronic =
Circuits" volumes (there are like 6 or 7 these days). Both a 555 timer =
and an op amp, both sold by Rat Shack, can be used to make these.

Let me know if you want a schematic. I haven't looked into the specs to =
see voltage and current flow, so if you want me to draw one up I'll need =
to know the expected run voltage (is it 14V, or regulated, like to 12V =
or similar?), the full-scale current flow (what was this, 7 amps?), and =
the trigger point (the amount of current flow you want to trigger =
something). The easiest thing would be to light an LED - you can drive a =
relay for other tasks if you please.

The second way is more complex, but not invasive. You wrap a coil of =
wire around one of the power feeds to the motor, and use inductive =
measurement to determine current flow. This isn't really hard either, =
but it's hardER, so you may as well go for option 1 above if it's =
possible.

> -----Original Message-----
> From: Jim Sower [mailto:canarder@frontiernet.net]
> Sent: Wednesday, October 15, 2003 9:23 AM
> To: Rotary motors in aircraft
> Subject: [FlyRotary] Re: EWP - series pumps and wacky ideas
>=20
>=20
> A device like that would be interesting to have in a lot of=20
> places.  Like
> measuring current to fuel pumps as a take on their state of=20
> repair.  Wouldn't
> it be nice to have several of these and other sensors working=20
> in "background"
> on another "page" of my engine monitor that I could peek at=20
> from time to time.
> Ain't technology wonnerful ... Jim S.
>=20
> John Slade wrote:
>=20
> > > It would be relatively trivial to design a circuit that=20
> uses current
> > > sensing to detect pump failure. Current to the pump that=20
> falls either
> > > above or below the design window can be used to trigger=20
> an alarm or
> > > activate the backup. Response would be nearly instant.
> >
> > Relatively trivial to you, perhaps. Current sensing sounds=20
> like a great way
> > to spot a fuel or water pump failure, or even potential for=20
> failure. I
> > managed to build an RST intercom that sorta works. Could I=20
> build one of
> > these gizmos? What would be involved?
> > John Slade (electronically challenged, but keen to learn)
> >
> > >>  Homepage:  http://www.flyrotary.com/
> > >>  Archive:   http://lancaironline.net/lists/flyrotary/List.html
>=20
> --
> Jim Sower
> Crossville, TN; Chapter 5
> Long-EZ N83RT, Velocity N4095T
>=20
>=20
>=20
> >>  Homepage:  http://www.flyrotary.com/
> >>  Archive:   http://lancaironline.net/lists/flyrotary/List.html
>=20