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Dennis Glaeser
Joined: 10 Jan 2006
Posts: 53
Location: Rochester Hills, Michigan
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 Posted: Sat May 29, 2010 4:45 pm Post subject: IVO Prop Electronic CB report |
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Bob,
I built the 'Prop Pitch Current Limiter and Electronic CB' circuit last week
and tested it today.
It works as expected, with one minor difficulty - the Amber LED doesn't come
on! It flashes briefly when the switch is released, but that's it. The
Green LED is lit when the motor is in operation, and the CB feature works
great - the motor stops when the current is a bit over 9 amps. The IRFP3703
barely gets warm, but the 0.2 ohm resister does get warm (not too hot to
touch - didn't measure).
What would cause the Amber LED to not come on? Could I have installed it
backwards? (I double checked, but Murphy's Law has not been repealed)
One of my EAA Chapter buddies has an O-scope I can borrow, so what (and how)
to check?
Thanks,
Dennis
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nuckolls.bob(at)aeroelect
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| Posted: Sun May 30, 2010 10:23 am Post subject: IVO Prop Electronic CB report |
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At 07:43 PM 5/29/2010, you wrote:
<glaesers(at)wideopenwest.com>
Bob,
I built the 'Prop Pitch Current Limiter and Electronic CB' circuit last week
and tested it today.
It works as expected, with one minor difficulty - the Amber LED doesn't come
on! It flashes briefly when the switch is released, but that's it. The
Green LED is lit when the motor is in operation, and the CB feature works
great - the motor stops when the current is a bit over 9 amps. The IRFP3703
barely gets warm, but the 0.2 ohm resister does get warm (not too hot to
touch - didn't measure).
What would cause the Amber LED to not come on? Could I have installed it
backwards? (I double checked, but Murphy's Law has not been repealed)
One of my EAA Chapter buddies has an O-scope I can borrow, so what (and how)
to check?
The amber light will illuminate only while the circuit
is POWERED UP and in a current limited mode. This is when
the voltage across the source shunts of Q114 exceed the
Vbe drop of Q115. Q115 collector goes low and does two things:
(1) it deprives Q114 of gate drive thus limiting total motor
current to some value that provides one Vbe drop of voltage
across the source shunts. This is where current limiting happens.
During this time, Q115 is in a linear mode of operation.
(2) Q115 also pulls down on the base of Q103 which should
switch it on "hard" . . . i.e. collector rises very close to
level of applied voltage. This causes C112 to charge through
R106 until the voltage reaches the magnitude of zener
conduction. When the zener starts to conduct, it pulls up
firmly (through 1K and zener) on the base of Q115 which
should turn it on hard (switch mode) and deprive Q114
of ALL gate drive, thus shutting the motor OFF.
As long as power remains applied, Q103 and Q115 should
remain turned on hard (Q103 collector near applied votlage,
Q115 collector near ground) and the amber LED should be
illuminated and the motor should remain un-powered.
As soon as you release the switch, the Q115/Q103 "latch"
should release. The capacitor discharges through R106,
a forward biased collector-base junction of Q103, R104
and R119. The prepares the circuit for the next operating
cycle.
A voltmeter or scope reading at collector of Q103 should show
a very low voltage (under 1 volt) while the motor is
running mid stroke. When the stroke limit is reached,
the voltage should jump to approximately applied
voltage and remain there after the motor shuts down
with the prop pitch switch still held. During this
time, the amber LED should be lit.
If you trigger the 'scope on the rising edge of
the voltage at collector of Q103 and use the other
channel to watch the gate drive to Q114, gate
drive should go away 100-200 milliseconds after
Q103 collector goes high.
Bob . . .
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Dennis Glaeser
Joined: 10 Jan 2006
Posts: 53
Location: Rochester Hills, Michigan
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| Posted: Sun May 30, 2010 5:57 pm Post subject: IVO Prop Electronic CB report |
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I discovered a wiring error in my circuit. Hopefully tomorrow I can fix it
and re-test.
Dennis
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Dennis Glaeser
Joined: 10 Jan 2006
Posts: 53
Location: Rochester Hills, Michigan
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| Posted: Mon May 31, 2010 12:29 pm Post subject: IVO Prop Electronic CB report |
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I corrected my wiring error and the circuit works perfectly! The amber LED
comes on when the current hits the limit (about 9A), and stays on as long as
the switch is held, but current to the motor drops to basically nothing
(measured with a clamp on ammeter on the ground lead). The IRFP3703 doesn't
even get noticeably warm (above the 90F ambient today!).
It will be next weekend at the earliest that I can get the Oscilloscope and
take the readings you described, but I would bet the readings will be as you
predict 
An implementation question: Are the values of R105 and R107 (the 1K
resistors in series with the LEDs) critical? The reason I ask is that I
have a couple of ready to mount LEDs that already have resistors built-in
for 12V use. I don't know what values they use for the resistors. My
suspicion is that they would work fine, but I don't want to spoil a
perfectly good recipe!
Thanks again!
Dennis
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nuckolls.bob(at)aeroelect
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| Posted: Tue Jun 01, 2010 10:52 am Post subject: IVO Prop Electronic CB report |
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At 02:42 PM 5/31/2010, you wrote:
| Quote: |
<glaesers(at)wideopenwest.com>
I corrected my wiring error and the circuit works perfectly! The amber LED
comes on when the current hits the limit (about 9A), and stays on as long as
the switch is held, but current to the motor drops to basically nothing
(measured with a clamp on ammeter on the ground lead). The IRFP3703 doesn't
even get noticeably warm (above the 90F ambient today!).
|
This is to be expected. The transistor is switched on hard during
normal motor running conditions and therefore dissipates very little
heat. When the system DOES go into current limit, the dissipation can
jump into the 100 WATT class . . . but for only the few milliseconds
it takes for the circuit breaker function to react. So total energy
turned into heat is low.
| Quote: | It will be next weekend at the earliest that I can get the Oscilloscope and
take the readings you described, but I would bet the readings will be as you
predict
|
I'd be pleased to hear the results of that measurement.
| Quote: | An implementation question: Are the values of R105 and R107 (the 1K
resistors in series with the LEDs) critical? The reason I ask is that I
have a couple of ready to mount LEDs that already have resistors built-in
for 12V use. I don't know what values they use for the resistors. My
suspicion is that they would work fine, but I don't want to spoil a
perfectly good recipe!
|
Your supposition is probably correct, but let's leave the
1K resistors in place, eliminate the LED's and then tie
your off-the-shelf indicators in PARALLEL with the 1K
resistors. VERY low risk there.
I'm wrapping up a couple of busy consulting projects
but with nothing coming over the visible horizon. Aviation
sucks as a career when there are folks actively engaged
in disrupting an otherwise successful, spontaneous order.
I'll be putting some time into the development of about
a dozen new AEC products. Your assistance in doing the
proof of concept work on this project suggests that
perhaps the IVO Prop Electronic CB should be one of
those products.
I appreciate your time and interest in this activity.
Bob . . .
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sportav8r(at)gmail.com
Guest
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| Posted: Tue Jun 01, 2010 11:47 am Post subject: IVO Prop Electronic CB report |
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Is one of them the AEC9004-1 IR alternator controller? Inquiring minds about to re-do their ship's electrical system want to know!
| Quote: |
| Quote: | > I'll be putting some time into the development of about
a dozen new AEC products. <<
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[quote] Bob . . .
[b]
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Tue Jun 01, 2010 12:38 pm Post subject: IVO Prop Electronic CB report |
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At 02:45 PM 6/1/2010, you wrote:
| Quote: | Is one of them the AEC9004-1 IR alternator controller? Inquiring
minds about to re-do their ship's electrical system want to know!
|
Yes it is.
Bob . . .
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Dennis Glaeser
Joined: 10 Jan 2006
Posts: 53
Location: Rochester Hills, Michigan
|
| Posted: Tue Jun 01, 2010 7:04 pm Post subject: IVO Prop Electronic CB report |
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| Quote: | An implementation question: Are the values of R105 and R107 (the 1K
resistors in series with the LEDs) critical? The reason I ask is that I
have a couple of ready to mount LEDs that already have resistors built-in
for 12V use. I don't know what values they use for the resistors. My
suspicion is that they would work fine, but I don't want to spoil a
perfectly good recipe!
|
Your supposition is probably correct, but let's leave the
1K resistors in place, eliminate the LED's and then tie
your off-the-shelf indicators in PARALLEL with the 1K
resistors. VERY low risk there.
---> I decided it is just as easy to stick with the original design. I also
have some LED mounts that are more compact and will provide a cleaner look.
I'll be putting some time into the development of about
a dozen new AEC products. Your assistance in doing the
proof of concept work on this project suggests that
perhaps the IVO Prop Electronic CB should be one of
those products.
---> I certainly agree! I'll bet the folks at IVO would be interested.
Everyone who has an IVO should be interested!
I appreciate your time and interest in this activity.
---> Well, I was the one who asked for help. And within a week I had an
operational solution in the reed switch. Now I have an electronic solution
that is operationally foolproof. A pretty good investment in time and
interest in my book, and a lot of fun to boot!
Thanks,
Dennis
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