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nuckolls.bob(at)aeroelect
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 Posted: Sun Nov 05, 2023 9:48 am Post subject: OVM14 MkIII, rev P6 |
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An update on the project . . .
I was scheduled to be receiving boards last Friday along with
parts-not-in-inventory.
While crafting the parts order, I had discovered a mis-match
between the semiconductor package used on the layout and
that of the SCR we were going to evaluate. Further,
I've not crafted an ECB using an SCR in too many years.
I was kinda 'locked' into dozens of recent layouts for
power handling MOS-FETS. Oops! The signal input pin
(gate) for the two devices are reversed. Be cautious
as you age . . . hitorical 'grooves' may feature
more pot-holes than you're aware of!.
Managed to stop the board order before they fabricated
and shipped $90 worth of trash. I've modified the
layout to fix the error -AND- to configure pads that
will accommodate a constellation of devices and
packages.
Further, while working the parts order, I discovered
an SCR with more attractive ratings. Don't know
why this device didn't surface during earlier
queries to Digikey's exceedingly capable search
engine.
I've upgraded to the more attractive SCR. Oh yeah, had
to use vias (top to bottom conductor transitions)
under the SCR heat sink pad . . . I've got some kevlar
tape that makes a nice insulator under power components
that suffer this shortcoming. Hat tip: Eric
Picked my environmental test chamber. Needs
a bit of refurbishment but it shouldn't smoke
when I plug it in! Looking forward to paying
homage to Jack Thurman's circa 1980 qualification
tests for OV management systems.
So . . . we're only set back one week. Be that as
it may, the board has been fixed. Any efforts to
validate my work product are most welcome.
Latest drawing package:
http://aeroelectric.com/AEC_Legacy_Products/9003/AEC9003%20MkIII%20Check%20Drasings%20P6.pdf
Bob . . .
////
(o o)
===========o00o=(_)=o00o=========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
=================================
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
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Eric Page
Joined: 15 Feb 2017
Posts: 245
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| Posted: Sun Nov 05, 2023 12:09 pm Post subject: Re: OVM14 MkIII, rev P6 |
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Lucky catch on the backwards footprint. It all looks dandy to me now.
I'd be very interested to read what you have planned for temperature testing.
I had a PCB screw-up recently too. I failed to notice the fine print on the board fab's website stating that they don't support blind vias. I ended up with a four-layer board that had via-sized pads top and bottom that weren't connected to the internal planes. Fortunately, it was a very small board and therefore a cheap mistake. Unfortunately, I didn't catch it until after I soldered all of the parts to it and found that it didn't work. Oops!
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user9253
Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan
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| Posted: Mon Nov 06, 2023 4:37 am Post subject: Re: OVM14 MkIII, rev P6 |
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There is a typo in the file name: draSings.
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Joe Gores |
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nuckolls.bob(at)aeroelect
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| Posted: Mon Nov 06, 2023 5:21 am Post subject: OVM14 MkIII, rev P6 |
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At 02:09 PM 11/5/2023, you wrote:
| Quote: | --> AeroElectric-List message posted by: "Eric Page" <edpav8r(at)yahoo.com>
Lucky catch on the backwards footprint. It all looks dandy to me now. |
Thanks
| Quote: | | I'd be very interested to read what you have planned for temperature testing. |
One of Uncle Jack's qualification tests for OV
management relays was to conduct 50 simulated
trips in a row . . . about 10 seconds apart as
I recall. In this case, the issue being resolved
was the ability of relatively small (5a) relays
to break the very inductive alternator field
feeder without trashing the relay contacts.
In our case, I'm interested in demonstrating
the SCRs ability to crowbar the 5A breaker
multiple times in a row with the ECB assembly
at 160F (typical under the cowl temperature).
I'm not worried about it being capable but
it's nice to have a documented demonstration
for skeptics. The other consideration is
consistent trips at say at 0F or perhaps
even lower. Trigger requirements for SCR
go up at lower temperatures. We've got a
trade off in this circuit wrapped around
pull down capability of the LM383, pull-up
capability of R14 and SCR needs at temperature.
Of course, voltage and trip delay stability
can be evaluated as well.
| Quote: | | I had a PCB screw-up recently too. I failed to notice the fine print on the board fab's website stating that they don't support blind vias. I ended up with a four-layer board that had via-sized pads top and bottom that weren't connected to the internal planes. Fortunately, it was a very small board and therefore a cheap mistake. Unfortunately, I didn't catch it until after I soldered all of the parts to it and found that it didn't work. Oops! |
hate it when that happens!
I had a query from a Lister about the test fixture.
I used this technique for measuring pulse-width
on a study many moons ago on a hospital patient
. transporter device I was working on. Readers
might be interested in this on-line, RC
calculator at:
http://www.learningaboutelectronics.com/Articles/Capacitor-charge-calculator.php#answer
If we trip a device under test with an
input voltage of 17.0 volts and measure
the voltage across a 10.0uF capacitor
charged through a 150K resistor, we'll get
a voltmeter reading that is roughly
proportional to width of the output pulse
as follows:
100 mS 1.1 V
200 mS 2.12 V
300 mS 3.08 V
400 mS 3.97 V
500 mS 4.81 V
etc.
The capacitor provides a kind of sample
and hold effect when observed with a high
impedance voltmeter (10M or more). Of
course, the voltage bleeds off but slow
enough that one can observe the after-event,
peak value and then discharge the cap for the next
test.
Kind of a po' boy's timer for short,
single and widely spaced events.
Bob . . .
////
(o o)
===========o00o=(_)=o00o=========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
=================================
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
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