Today's Message Index:
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1. 10:17 AM - Re: Re: Thermocouples: grounded or ungrounded (Robert L. Nuckolls, III)
2. 10:37 AM - Re: OAT Probes for Garmin Transponder (Robert L. Nuckolls, III)
3. 01:03 PM - Re: OAT Probes for Garmin Transponder (andymeyer)
4. 05:52 PM - Re: Re: OAT Probes for Garmin Transponder (Jared Yates)
Message 1
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| Subject: | Re: Thermocouples: grounded or ungrounded |
At 04:04 PM 7/8/2022, you wrote:
>Bob
>I agree with what you are saying concerning the
>ideal method of monitoring the coils.
>However I need to work with what I have and I
>don't think I can monitor 12 individual
>coils with the tools at my disposal.
Previous examples of failure involved but a single coil of the
5. Correct me if I'm wrong, but I seem to recall that Revmaster
presently splits the TEN alternator stator poles into two groups . . .
rated at 18A each.
Okay, this is the first photo I recall seeing of a total-toasting
of all 5 coils on the Revmaster alternator. This suggest a different
failure mode. Bad R/R? Too much system loads? Probably
something different than conditions the precipitates
a single pole conflagration.
The difference in coil failures suggests at least two,
different operational stresses.
It would be interesting to know the rational behind the
'dual alternator' decision. History shows us that capability
of the individual half-alternators is marginal.
Has anyone considered a single winding spread over all
ten pole pieces wound with fewer turns of heavier wire
to produce a single alternator of say 20, 25A . . .
or more?
If the two existing windings are reasonably matched,
they could be operated in parallel as a single winding.
Watts dissipated is proportional to I(squared) x R. So
dropping current in each winding by one half reduces
heat generated in that winding by 75%.
That offers greater value in stress reduction than
adding cooling air.
I do plan on using your idea of the rotary switch
and I appreciate the schematic.=C2 I thought all
might be interested in a picture of the stator
after removal.=C2 The one coil suffered
catastrophic damage with the phenolic spacer
completely destroyed by the heat.=C2 I have
machined the case to allow more ventilation and
will add two blast tubes directly at the coils.=C2 And hope for the best.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 2
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| Subject: | Re: OAT Probes for Garmin Transponder |
At 09:06 PM 7/9/2022, you wrote:
>I've been working with a Garmin GTX 335 transponder installation.
>There is an optional outside air temp probe that enables a handy
>density altitude feature.
>
>I found one reference that says the transponder is looking for this:
>OUTSIDE AIR TEMPERATURE PROBE STANDARD 2-WIRE THERMOCOUPLE WITH 1
>MICRO-AMP PER 1 DEGREE KELVIN RESPONSE. SUITABLE MODELS ARE: EDMO
>655 AND DAVTRON C307PS.
>
>I tried an extra Dynon OAT probe that I had sitting around, and it
>indicated 175 degrees F. So I can rule out that one.
>
>The extra transponder feature is cool but not really cool enough to
>spend $150 on one of the above probes. Does anyone know what kind of
>thermocouple will produce 1 microamp per degree kelvin? Seems like
>making something up might be a fun experiment.
I believe those probes are based on the Analog
Devices AD590 temperature to current sensor chip.
https://tinyurl.com/2mqyzbtj
You can probably craft a substitute probe from one
of these available from Digikey and elsewhere
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 3
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| Subject: | Re: OAT Probes for Garmin Transponder |
Use this: AD592 from Mouser
https://www.mouser.com/ProductDetail/584-AD592CNZ or
https://www.mouser.com/ProductDetail/584-AD592ANZ
Much less expensive and higher accuracy component - newer version of the AD590.
It has three terminals, but only two are used. I've used these with my GTX330ES
and my uAvionix AV30E with excellent effect - both accuracy and weight of my
wallet!
On my LongEZ, The probe is wrapped in 2 layers of heat shrink and RTV'd in the
gear well with about 3/4" protrusion.
ANZ is +/- 2.5C, BNZ is +/- 1.0C and the CNZ is +/- .5C.
The Davtron probe is +/- 2.5C (AD590KH)
Andy
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=507438#507438
Message 4
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| Subject: | Re: OAT Probes for Garmin Transponder |
Thanks everybody, this is a big help! I read further and found that the
Dynon probe is resistive, whereas these little ICs are a current source.
On July 10, 2022 16:07:12 "andymeyer" <meyerkc135@gmail.com> wrote:
>
> Use this: AD592 from Mouser
> https://www.mouser.com/ProductDetail/584-AD592CNZ or
> https://www.mouser.com/ProductDetail/584-AD592ANZ
>
> Much less expensive and higher accuracy component - newer version of the
> AD590. It has three terminals, but only two are used. I've used these with
> my GTX330ES and my uAvionix AV30E with excellent effect - both accuracy and
> weight of my wallet!
>
> On my LongEZ, The probe is wrapped in 2 layers of heat shrink and RTV'd in
> the gear well with about 3/4" protrusion.
>
> ANZ is +/- 2.5C, BNZ is +/- 1.0C and the CNZ is +/- .5C.
> The Davtron probe is +/- 2.5C (AD590KH)
>
> Andy
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=507438#507438
>
>
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