Today's Message Index:
----------------------
1. 05:54 AM - Southbridge Airport Tornado Damage. (Eric M. Jones)
2. 09:44 AM - PTT buzz (Dan Billingsley)
3. 12:01 PM - IvoProp current limiter -revisit (Mike Welch)
4. 12:28 PM - Re: IvoProp current limiter -revisit (Robert L. Nuckolls, III)
5. 01:23 PM - Re: PTT buzz (Dan Billingsley)
6. 01:49 PM - Re: PTT buzz (Robert L. Nuckolls, III)
7. 03:05 PM - push to test circuit for differing loads (pmnewlon)
8. 04:06 PM - Re: push to test circuit for differing loads (Jeff Luckey)
9. 05:33 PM - Re: PTT buzz (Dan Billingsley)
10. 06:15 PM - IvoProp current limiter -revisit (Dennis & Anne Glaeser)
11. 06:59 PM - Re: IvoProp current limiter -revisit (Mike Welch)
12. 07:06 PM - Re: PTT buzz (Robert L. Nuckolls, III)
13. 07:24 PM - Re: IvoProp current limiter -revisit (Robert L. Nuckolls, III)
14. 07:45 PM - Re: IvoProp current limiter -revisit (Deems Herring)
15. 07:55 PM - Re: push to test circuit for differing loads (Robert L. Nuckolls, III)
16. 08:21 PM - Re: IvoProp current limiter -revisit (Mike Welch)
17. 08:32 PM - Re: push to test circuit for differing loads (Vern Little)
18. 09:15 PM - Re: IvoProp current limiter -revisit (Robert L. Nuckolls, III)
19. 09:15 PM - Re: IvoProp current limiter -revisit (Robert L. Nuckolls, III)
20. 10:00 PM - Re: push to test circuit for differing loads (Jeff Luckey)
Message 1
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| Subject: | Southbridge Airport Tornado Damage. |
I finally went up to the airport and spoke to Jim Latour, the manager. The tornado
destroyed 15 airplanes, not including an almost completed and not-insured
RV that just went into the new hangar...now totally destroyed. There had been
a lot of cleanup in the week since the twister.
I live a couple miles from 3BO, and there was hardly a breath of wind. Hummingbirds
were happy at the feeder.
Great sadness. The path of destruction was very narrow. A block away from the path
was unaffected. In the path, oak trees two feet in diameter were broken like
match-sticks....shredded by a billion HP weed-whacker.
See attached.
--------
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones@charter.net
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=343630#343630
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I just finished wiring the Ray Allen G205 stick in conjunction w/ Garmin SL40 radio
and the intercom PM1000 (PS Engineering). Turning it all on and headphone
jacks connected...I talk into mic and hear loud and clear. When I key the PTT,
I immediately get a pulsating buzz. I release, it goes away.
Could this be a ground loop? don't know...never heard this b-4.
Thanks,
Dan B
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| Subject: | IvoProp current limiter -revisit |
Bob N=2C
Quite a while back I built and installed the IvoProp current limiter circ
uit you desgned.
By all account=2C it appears to work=2C with one significant exception=3B i
t cuts out very quickly
when cycling in either direction. In other words=2C the blades barely move
at all.
Yes=2C the LEDs light up=2C and all other aspects of the circuit appear t
o function properly.
The only weakness is the extreme shortage of blade movement. I know the ob
vious=2C question
is=3B do we know if the blades are free to mover properly? As far as I kno
w=2C yes=2C they
used to work just fine=2C prior to the installation of the current limiter
circuit.
Bob=2C is it possible to "vary" the circuit's current limitation. Exampl
e....if the present resistors
that control the circuit's current to "top out" at such and such amps=2C wo
uld it be reasonable to
redesign the circuit to allow for 'differing" overloads. Do you get what I
'm trying to say?
By watching the entire system (circuit=2C prop blades/motor=2C etc)=2C th
e circuit appears to
operate as it was designed=2C except that it appears to cut out at 1=2C may
be 2 amps.
I have to run off to Minneapolis for a few days=2C but when I get back=2C
I'll hook up a
highly accurate ammeter in the present arrangement=2C and see exactly how m
uch current
shuts it off.
Any ideas=2C or suggestions are highly appreciated.
Thanks=2C Mike Welch
Message 4
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| Subject: | Re: IvoProp current limiter -revisit |
At 02:56 PM 6/21/2011, you wrote:
>Bob N,
>
> Quite a while back I built and installed the IvoProp current
> limiter circuit you desgned.
>By all account, it appears to work, with one significant exception;
>it cuts out very quickly
>when cycling in either direction. In other words, the blades barely
>move at all.
Okay, just so folks know what we're talking about here's a recap
of the circuit and design goals for the system Mike has crafted:
-----------------------
http://aeroelectric.com/Pictures/Schematics/IVO-Prop_Pitch_Controller.pdf
Design goals:
Provide absolute current limit on the order of 9A:
Q114 is a power FET that saturates with bias
through R104, R105 and D109 when power is applied
through "M" connections that sense motor power.
Voltage drop across R117/R118 is monitored through
R116 causing Q115 to turn on when drop across the
R117/118 exceeds Vbe of Q115. This is approx .6
volts. When Q115 turns on, it starves Q114 of gate
drive and causes it to become a constant current
generator with calibration set by the combination
of R117/R118.
Any time the constant current loop is active,
LED D109 will be illuminated. D109 will flash
each time the prop pitch motor is energized
and the system becomes an active inrush current
limiter.
Limit the duration of the current limit mode to
100-200 mS whereupon the system goes open circuit
and removes power from the motor:
At any time the current limiter is active,
Q115 collector current through R105 will turn
on Q103 causing the collector to pull up to
the supply rail. This causes C112 to charge
through R106 until zener D110 conducts at about
8V. This event will occur approximately 120 mS
after onset of current limit.
When D110 conducts, it pulls the base of Q115
more positive causing the Q115/Q103 pair to
"latch up" not unlike an SCR. When the latching
event occurs, the collector of Q115 pulls to
a few millivolts above ground depriving Q114
of all gate drive.
Normal operation:
D109 will flash each time the motor control switch
is closed due to motor inrush current being
electronically limited. D109 will also flash a
bit longer (about 120 mS) when the prop pitch motor
reaches the mechanical stop and the current limit is
invoked.
As long as the prop pitch motor is powered
D108 will be illuminated. When the prop
pitch system reaches a mechanical limit and
the control switch is NOT relaxed, D019 flashes
for about 120 mS and D108 goes dark.
Releasing the motor control switch removes
power from the latching loop and discharges
C112 through R119, R104, BC junction Q103,
and R106.
The system spends so little time in I-limit
mode that Q114 does not require a heat-sink.
D109 and D108 staying on together indicates
a malfunction and the motor control switch
needs to be released within a second or so
to avoid over-heat damage to Q114.
--------------------
> Yes, the LEDs light up, and all other aspects of the circuit
> appear to function properly.
>The only weakness is the extreme shortage of blade movement. I know
>the obvious, question
>is; do we know if the blades are free to mover properly? As far as
>I know, yes, they
>used to work just fine, prior to the installation of the current
>limiter circuit.
The green LED should be illuminated when the
pitch motor is being commanded and the system
is NOT in a current limited mode. If the
motor hits the stop and current spikes, the current
limit mode kicks in. The green LED should dim or
go dark . . . the amber LED should illuminate
saying that current limiting operation is in
effect. One should release the switch quickly
after the amber LED comes on.
> By watching the entire system (circuit, prop blades/motor, etc),
> the circuit appears to
>operate as it was designed, except that it appears to cut out at 1,
>maybe 2 amps.
Had you tested this before? With the values selected
for R117 and R118, current limit should be on the
order of 10 amps. If your 'stalled' current is
2A, then the current limit is kicking in MUCH to
low.
> I have to run off to Minneapolis for a few days, but when I get
> back, I'll hook up a
>highly accurate ammeter in the present arrangement, and see exactly
>how much current
>shuts it off.
Good lick. But be cautious about this measurement.
The TIME that the Q114 can stand to run at 10A
(140 watts) is limited by the size of heat-sink it
enjoys. Normal operations will have you releasing
the switch within a second or so of having the amber
light come on so when things are working right, a
large heat-sink is not needed. Experimental measurements
are another matter. Be quick.
> Bob, is it possible to "vary" the circuit's current
> limitation. Example....if the present resistors
>that control the circuit's current to "top out" at such and such
>amps, would it be reasonable to
>redesign the circuit to allow for 'differing" overloads. Do you get
>what I'm trying to say?
Yes but . . . this does not appear to be the
root cause of symptoms you're observing.
Bob . . .
Message 5
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I think I found the ghost...When I first heard it it sounded like AC cycling (the
noise was very consistant). AFter going thru this symptom with a few folks...Garmin
techs saying they never heard of it b-4...
I was scratching my head and looked up. The antenna was hovering between two floursent
lights in the garage...it WAS AC!
Dan
--- On Tue, 6/21/11, Dan Billingsley <dan@azshowersolutions.com> wrote:
> From: Dan Billingsley <dan@azshowersolutions.com>
> Subject: AeroElectric-List: PTT buzz
> To: aeroelectric-list@matronics.com
> Date: Tuesday, June 21, 2011, 10:40 AM
> --> AeroElectric-List message
> posted by: Dan Billingsley <dan@azshowersolutions.com>
>
> I just finished wiring the Ray Allen G205 stick in
> conjunction w/ Garmin SL40 radio and the intercom PM1000 (PS
> Engineering). Turning it all on and headphone jacks
> connected...I talk into mic and hear loud and clear. When I
> key the PTT, I immediately get a pulsating buzz. I release,
> it goes away.
> Could this be a ground loop? don't know...never heard this
> b-4.
> Thanks,
> Dan B
>
> AeroElectric-List Email Forum -
> FAQ,
> - MATRONICS WEB FORUMS -
> List Contribution Web Site -
> -Matt
> Dralle, List Admin.
>
>
>
>
Message 6
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At 04:18 PM 6/21/2011, you wrote:
><dan@azshowersolutions.com>
>
>I think I found the ghost...When I first heard it it sounded like AC
>cycling (the noise was very consistant). AFter going thru this
>symptom with a few folks...Garmin techs saying they never heard of it b-4...
>I was scratching my head and looked up. The antenna was
>hovering between two floursent lights in the garage...it WAS AC!
>Dan
Hmmmm . . . good hypothesis. If you turn off the lights
does the buzz go away?
Bob . . .
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| Subject: | push to test circuit for differing loads |
I posted on VAF yesterday and got a partial answer to my question there, which
caused me to have more questions so I thought I better get to the right place!
I have seven annunciator LEDs on my panel; as it turns out all but one switch the
positive side of the LED but one switches the ground. I understand how to
arrange diodes in a push to test circuit if all the LEDs are switched the same
way but cannot find an example of a circuit where there is a mixture of ground
and positive switching with a single push to test button. The response to my
post on VAF suggested a double pole push button but I have not found a suitably
small DPST (ON) device. I'd really like to make the circuit with a small
SPST (ON) pushbutton but am short on the circuit knowledge.
Does anyone have a reference diagram of such a circuit that I could 'borrow'?
Thanks! Phil
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=343682#343682
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| Subject: | push to test circuit for differing loads |
Phil,
Just off the top of my head (and without having seen a schematic of your
particular setup) I'd say that what you're asking for is not possible. In a
single pole you could handle the ground legs of the test circuit (with
proper isolation diodes as you mentioned) or the high-side circuit, but not
both.
But I have another suggestion: You could add a small 2-pole relay to manage
the LED test circuitry and control its coil w/ your SPST pushbutton. There
are all kinds of cheap, circuit board mountable, smaller-than-a-sugar-cube
relays that could do the job (I don't have part numbers available to me at
the moment).
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of pmnewlon
Sent: Tuesday, June 21, 2011 15:02
Subject: AeroElectric-List: push to test circuit for differing loads
I posted on VAF yesterday and got a partial answer to my question there,
which caused me to have more questions so I thought I better get to the
right place!
I have seven annunciator LEDs on my panel; as it turns out all but one
switch the positive side of the LED but one switches the ground. I
understand how to arrange diodes in a push to test circuit if all the LEDs
are switched the same way but cannot find an example of a circuit where
there is a mixture of ground and positive switching with a single push to
test button. The response to my post on VAF suggested a double pole push
button but I have not found a suitably small DPST (ON) device. I'd really
like to make the circuit with a small SPST (ON) pushbutton but am short on
the circuit knowledge.
Does anyone have a reference diagram of such a circuit that I could
'borrow'?
Thanks! Phil
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=343682#343682
Message 9
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I didn't turn the lights off but I was able to roll the plane out from under the
lights a ways. When I did that, the noise became less prominent. I will need
to wait until I have an extra hand to roll the plane all the way out of the garage
(The slope + gravity= plane in street). One of the guys I talked to today
had a good point about when I key the mic inside the closed space I have quite
a bit RF dancing back and forth in there. Would it be reasonable to say it
could be some feedback interference as well?
Dan
--- On Tue, 6/21/11, Robert L. Nuckolls, III <nuckolls.bob@aeroelectric.com> wrote:
> From: Robert L. Nuckolls, III <nuckolls.bob@aeroelectric.com>
> Subject: Re: AeroElectric-List: PTT buzz
> To: aeroelectric-list@matronics.com
> Date: Tuesday, June 21, 2011, 2:45 PM
> --> AeroElectric-List message
> posted by: "Robert L. Nuckolls, III" <nuckolls.bob@aeroelectric.com>
>
> At 04:18 PM 6/21/2011, you wrote:
> Billingsley <dan@azshowersolutions.com>
> >
> > I think I found the ghost...When I first heard it it
> sounded like AC cycling (the noise was very consistant).
> AFter going thru this symptom with a few folks...Garmin
> techs saying they never heard of it b-4...
> > I was scratching my head and looked up. The antenna
> was hovering between two floursent lights in the
> garage...it WAS AC!
> > Dan
>
> Hmmmm . . . good hypothesis. If you turn
> off the lights
> does the buzz go away?
>
>
> Bob . . .
>
> AeroElectric-List Email Forum -
> FAQ,
> - MATRONICS WEB FORUMS -
> List Contribution Web Site -
> -Matt
> Dralle, List Admin.
>
>
>
>
Message 10
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| Subject: | IvoProp current limiter -revisit |
Bob and Mike,
I have been using Bob's circuit on my IVO and it works flawlessly. It's a
simple and foolproof way to protect the gear train that drives the blade
pitch mechanism.
When I finished the circuit, Bob asked if I had access to an oscilloscope in
order to verify it's operation. One of my EAA chapter members has one and
we captured the traces per Bob's specs. Perhaps Mike could do the same
thing and that might provide a clue as to what is (or isn't) happening.
Bob's description says that when the current limit is reached, D108 (amber
LED) flashed for 120 ms and D109 (green LED) goes dark. In my
implementation, the amber LED stays lit as long as I hold the switch (the
motor stops) - the green LED does go dark. I don't know if that is
significant, but thought I'd mention it. When the motor is running, the
green LED is on, but the amber LED is off (except for the flash at startup).
If there is anything I can do to help, just let me know.
Dennis Glaeser
Message 11
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| Subject: | IvoProp current limiter -revisit |
Bob=2C
Thank you for the highly informative description of the circuit. I know
to keep the
toggle switch testing very brief=2C however=2C I did mount the FET on a 1 1
/2" X 2" piece
of aluminum for a heat sink. The heat sink=2C and complete circuit is cont
ained in a
neat plastic box.
After I get back from my mini-vacation=2C I'll do my best to test the cir
cuit...carefully.
I also verify the correct LEDs are lighting as you described.
Thanks a bunch=2C I'll get back ya early next week.
Mike Welch
PS. Do they have fish in Minnesota?
Message 12
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At 08:29 PM 6/21/2011, you wrote:
><dan@azshowersolutions.com>
>
>I didn't turn the lights off but I was able to roll the plane out
>from under the lights a ways. When I did that, the noise became less
>prominent. I will need to wait until I have an extra hand to roll
>the plane all the way out of the garage (The slope + gravity= plane
>in street). One of the guys I talked to today had a good point about
>when I key the mic inside the closed space I have quite a bit RF
>dancing back and forth in there. Would it be reasonable to say it
>could be some feedback interference as well?
Possible . . . but low risk. The lighting
interference hypothesis is much stronger
given that the noise changed when you moved.
Modern fluorescent lamps not only generate
noise from the cacophony of molecular
noise in the gas filled tube, they feature
electronic ballasts also renowned for their
ability to 'sing' at a constellation of
frequencies.
I'm betting on the lights.
Bob . . .
Message 13
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| Subject: | Re: IvoProp current limiter -revisit |
At 09:12 PM 6/21/2011, you wrote:
>Bob and Mike,
>
>I have been using Bob=92s circuit on my IVO and it
>works flawlessly. It=92s a simple and foolproof
>way to protect the gear train that drives the blade pitch mechanism.
>
>When I finished the circuit, Bob asked if I had
>access to an oscilloscope in order to verify
>it=92s operation. One of my EAA chapter members
>has one and we captured the traces per Bob=92s
>specs. Perhaps Mike could do the same thing and
>that might provide a clue as to what is (or isn=92t) happening.
>
>Bob=92s description says that when the current
>limit is reached, D108 (amber LED) flashed for
>120 ms and D109 (green LED) goes dark. In my
>implementation, the amber LED stays lit as long
>as I hold the switch (the motor stops) ' the
>green LED does go dark. I don=92t know if that is
>significant, but thought I=92d mention it.
You bet. I'd forgotten how that thing was supposed to work.
Q103/Q115 form a time-delayed latching switch that switches
ON as soon as C112 charges up enough to cause D110 to
go into conduction. Once the latch triggers, Q115 is held
on 'saturated' until power is removed.
> When the motor is running, the green LED is
> on, but the amber LED is off (except for the flash at startup).
So the amber LED flashes at start up indicating that
the current limiter did its job while the motor spins
up. When the system hits mechanical stops, the led
will light again when current limit becomes active.
A few milliseconds later, the latch trips and the
motor current goes to zero. Green led goes dark.
Amber LED stays lit.
So my earlier admonition about being quick on the switch
to avoid overheating Q114 is all wet. The time-delayed
shut-down latch protects Q114.
>
>If there is anything I can do to help, just let me know.
You just did. Thanks!
If there's enough interest in this device, it could
be packaged up nicely in a box like this:
Emacs!
Since you guys did all the development and proof of concept
work, it would only take a couple hours to package it up
and add it to the product line. We could also make this
a DIY project and sell the ECB, case and connector hardware.
Bob . . .
Message 14
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| Subject: | IvoProp current limiter -revisit |
I will take 2
Deems
If there's enough interest in this device=2C it could
be packaged up nicely in a box like this:
Since you guys did all the development and proof of concept
work=2C it would only take a couple hours to package it up
and add it to the product line. We could also make this
a DIY project and sell the ECB=2C case and connector
hardware.
Bob . . .
Message 15
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| Subject: | Re: push to test circuit for differing loads |
At 06:01 PM 6/21/2011, you wrote:
>
>I posted on VAF yesterday and got a partial answer to my question
>there, which caused me to have more questions so I thought I better
>get to the right place!
>
>I have seven annunciator LEDs on my panel; as it turns out all but
>one switch the positive side of the LED but one switches the
>ground. I understand how to arrange diodes in a push to test
>circuit if all the LEDs are switched the same way but cannot find an
>example of a circuit where there is a mixture of ground and positive
>switching with a single push to test button. The response to my
>post on VAF suggested a double pole push button but I have not found
>a suitably small DPST (ON) device. I'd really like to make the
>circuit with a small SPST (ON) pushbutton but am short on the
>circuit knowledge.
>
>Does anyone have a reference diagram of such a circuit that I could 'borrow'?
You betcha. Did this in some airplane wayyyyyyy back when.
The annunciators were light bulbs instead of leds but
the principal is the same.
You can get the parts at Radio Shack . . .
http://tinyurl.com/3lu334y
The transistors operate saturated so given
the intermittent duty service, will not require
heat-sinks. Wire 'em up and truck on. You could
probably get it to work fine with physically
smaller transistors but these TO-200 devices are
robust and easy to mount to a piece of perf-board.
Bob . . .
Message 16
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| Subject: | IvoProp current limiter -revisit |
Thanks for the responses=2C guys. I really wish I had more time to try and
figure it out
right now=2C but I'll have to wait until next Monday or so=2C after I get b
ack.
I went out and did a quick cycle or two of the circuit=2C and the LEDs appe
ar to turn on and off
as Dennis describes. The pitch motor obviously is twisting the prop blades
=2C but the whole
thing still seems to be working exactly as it should=2C except it only has
a one second range=2C
from switch on to circuit off=2C maybe at most=2C two seconds!
I did see that if I keep switching in the same direction=2C over and over
=2C I can get the opposite
direction to stay "lit" longer=2C getting it to twist for 3-4 seconds. I e
ven kept "pressuring it"=2C
and the 10A circuit breaker popped. I reset it=2C and everything still wor
ked fine...just briefly.
I'll know more after I get back.
Thanks=2C Mike W
Message 17
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| Subject: | Re: push to test circuit for differing loads |
Check out the IL-4A or IL-12A on this site:
http://vx-aviation.com/page_2.html
The datasheet has the schematic for what you want if you feel like
building your own.
Thx,
Vern Little
Vx Aviation
From: Robert L. Nuckolls, III
Sent: Tuesday, June 21, 2011 7:52 PM
Subject: Re: AeroElectric-List: push to test circuit for differing loads
At 06:01 PM 6/21/2011, you wrote:
I posted on VAF yesterday and got a partial answer to my question
there, which caused me to have more questions so I thought I better get
to the right place!
I have seven annunciator LEDs on my panel; as it turns out all but one
switch the positive side of the LED but one switches the ground. I
understand how to arrange diodes in a push to test circuit if all the
LEDs are switched the same way but cannot find an example of a circuit
where there is a mixture of ground and positive switching with a single
push to test button. The response to my post on VAF suggested a double
pole push button but I have not found a suitably small DPST (ON) device.
I'd really like to make the circuit with a small SPST (ON) pushbutton
but am short on the circuit knowledge.
Does anyone have a reference diagram of such a circuit that I could
'borrow'?
You betcha. Did this in some airplane wayyyyyyy back when.
The annunciators were light bulbs instead of leds but
the principal is the same.
You can get the parts at Radio Shack . . .
http://tinyurl.com/3lu334y
The transistors operate saturated so given
the intermittent duty service, will not require
heat-sinks. Wire 'em up and truck on. You could
probably get it to work fine with physically
smaller transistors but these TO-200 devices are
robust and easy to mount to a piece of perf-board.
Bob . . .
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Message 18
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| Subject: | IvoProp current limiter -revisit |
At 11:17 PM 6/21/2011, you wrote:
>Thanks for the responses, guys. I really wish I had more time to
>try and figure it out
>right now, but I'll have to wait until next Monday or so, after I get back.
>
>I went out and did a quick cycle or two of the circuit, and the LEDs
>appear to turn on and off
>as Dennis describes. The pitch motor obviously is twisting the prop
>blades, but the whole
>thing still seems to be working exactly as it should, except it only
>has a one second range,
>from switch on to circuit off, maybe at most, two seconds!
>
>I did see that if I keep switching in the same direction, over and
>over, I can get the opposite
>direction to stay "lit" longer, getting it to twist for 3-4
>seconds. I even kept "pressuring it",
>and the 10A circuit breaker popped. I reset it, and everything
>still worked fine...just briefly.
Okay, if your 10A breaker popped, the motor/gearbox
combo is drawing way too much current . . . for reasons
as yet unknown. The limiter may well be doing what
it was designed to do. Try taking it out of the circuit
as described earlier and then measure the current.
Bob . . .
Message 19
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| Subject: | IvoProp current limiter -revisit |
At 10:42 PM 6/21/2011, you wrote:
>I will take 2
>
>Deems
noted. thanks.
Bob . . .
Message 20
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| Subject: | push to test circuit for differing loads |
Ok - devil's advocate here.
Bob's schematic parts count: 2 transistors, 4 resistors = 6 components - or
-- ONE small, 2-amp, DIP DPDT relay.
Which way is stronger/better/faster/easier?
_____
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Vern
Little
Sent: Tuesday, June 21, 2011 20:29
Subject: Re: AeroElectric-List: push to test circuit for differing loads
Check out the IL-4A or IL-12A on this site:
http://vx-aviation.com/page_2.html
The datasheet has the schematic for what you want if you feel like building
your own.
Thx,
Vern Little
Vx Aviation
From: Robert L. Nuckolls, III <mailto:nuckolls.bob@aeroelectric.com>
Sent: Tuesday, June 21, 2011 7:52 PM
Subject: Re: AeroElectric-List: push to test circuit for differing loads
At 06:01 PM 6/21/2011, you wrote:
I posted on VAF yesterday and got a partial answer to my question there,
which caused me to have more questions so I thought I better get to the
right place!
I have seven annunciator LEDs on my panel; as it turns out all but one
switch the positive side of the LED but one switches the ground. I
understand how to arrange diodes in a push to test circuit if all the LEDs
are switched the same way but cannot find an example of a circuit where
there is a mixture of ground and positive switching with a single push to
test button. The response to my post on VAF suggested a double pole push
button but I have not found a suitably small DPST (ON) device. I'd really
like to make the circuit with a small SPST (ON) pushbutton but am short on
the circuit knowledge.
Does anyone have a reference diagram of such a circuit that I could
'borrow'?
You betcha. Did this in some airplane wayyyyyyy back when.
The annunciators were light bulbs instead of leds but
the principal is the same.
You can get the parts at Radio Shack . . .
http://tinyurl.com/3lu334y
The transistors operate saturated so given
the intermittent duty service, will not require
heat-sinks. Wire 'em up and truck on. You could
probably get it to work fine with physically
smaller transistors but these TO-200 devices are
robust and easy to mount to a piece of perf-board.
Bob . . .
href="http://www.matronics.com/Navigator?AeroElectric-List">http://www.matro
nics.com/Navigator?AeroElectric-List
href="http://forums.matronics.com">http://forums.matronics.com
href="http://www.matronics.com/contribution">http://www.matronics.com/c
_____
No virus found in this message.
Checked by AVG - www.avg.com
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