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Mike Welch
Joined: 13 Feb 2011
Posts: 272
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 Posted: Tue May 31, 2011 4:19 pm Post subject: Dynon alarm circuit revisited |
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List members,
I've got a perplexing situation, and for the life of me, I can't seem to figure this one out.
I built the Dynon alarm circuit that Bob N. designed last year. I also combined it with a strobing
LED circuit later. On the bench (kitchen table),the whole thing works PERFECT. No flaws...no
hiccups, hook up all the right wires, and the LED comes on when it's supposed to! (see the
enclosed circuit diagram & photos)
(Note: Bob sent me a slight revision that added a 10K resistor and test wire not shown in
his original design. It branched off the node between the two 10K resistors and base of the 2N3904)
(Second note: the photo of the completed circuit I built didn't have the green wire & 10K resistor
for the test function, yet. You will also notice in this photo I added a 555 timer/4017 cascading LED
circuit which is tied in together with the alarm circuit LED. Works perfect on the test bench as designed,
no problems!!)
But, here's the weird part. Somehow, when I hook the circuit up in my plane, it does NOT work right.
A little background on the circuit, first; The alarm circuit has an "always" hot lead, which is hooked
to my +12volt instrument bus bar (purple wire). Next, it has the "alarm" wire hooked up to the
Dynon alarm signal wire (light blue wire). Next, I have a "push to test" green wire, hooked up to
my pistol grip on the yoke handle. Lastly, is the white ground wire.
I've installed the circuit, which is enclosed in a little 'project box', about 20 times in my plane.
I can NOT seem to get the entire circuit to operate properly. With all (4) wires hooked up
properly, and you turn on power to the instrument +12volt bus bar, the circuit's LED always
flashes once to show the thing is working. But if I apply power from the pistol grip button, it does not
turn on the LED & accompanying strobing LEDs (like it should!!)
and, YES!!! I have checked that the pistol grip button is sending power to the green wire!!
If I manually hook up a pigtail from the +12volt bus bar, and apply power to the light blue (alarm wire)
wire, everything works fine!! But, then, when I try the power to the "test wire" I get nothing!!!
Now, here's the pisser!! When I unhook everything, take it back to the house(again!), and hook it up
to my Radio Shack 12 Volt transformer, the silly thing works perfect again!!! I've done this about
15 times, at least. Works perfect on the 12 volt transformer power supply, but not in the plane!
Okay, here's some things I've managed to find out; when checking the power at the +12volt
instrument bus bar, the reading is about 11.95 volts. But when checking the voltage coming from
the pistol grip wire, it's usually about a quarter volt LESS!! I attribute this to slight wiring differences,
and routings. Is THIS why it won't work???
One more thing. On one of my many R&R's I found that the 10K resistor in the test wire leg had
burned out. I don't know why. I replaced it, so I figured it must have been the whole problem all along.
Nope! With a new resistor, the circuit works great on the kitchen table, but not in the plane.
To the best of my knowledge, the only distinguishable difference between my kitchen table tests
and the installed tests are the super minor voltage differences between the 'always hot' power supply
and the pistol grip button voltage supply, which is only a fraction of a volt. I have noticed, though,
if I run a test wire from the +12volt terminal connector/'always hot' wire and connect it to the Dynon
larm signal wire....everything acts correct!!! But, if I try to get the test wire to do the same think...
..I get nothing! Take it apart...go into the house, and if I try the test wire, it works great!!
I'm really lost on this one!! Is it possible that the circuit is so sensitive that only precise, matching power
inputs will work?
Opinions welcome!
Mike Welch
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sprocket(at)vx-aviation.c
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| Posted: Tue May 31, 2011 5:44 pm Post subject: Dynon alarm circuit revisited |
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Here’s a possibility:
When idle, it’s possible that the Dynon alarm tone output is high. This turns on the 2N3904, which discharges the capacitor and turns the LED on briefly. When the capacitor charges up, the lamp goes off. At this point, your test input will have no effect because the 2N3904 is already on.
The fix for this would be to put a capacitor in series with the Dynon output. That way, if the the Dynon tone is left high, it will allow the 2N3904 to go off and let the test lead operate.
Vern Little
Vx Aviation
www.vx-aviation.com
From: Mike Welch (mdnanwelch7(at)hotmail.com)
Sent: Tuesday, May 31, 2011 5:15 PM
To: aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com)
Subject: Dynon alarm circuit revisited
List members,
I've got a perplexing situation, and for the life of me, I can't seem to figure this one out.
I built the Dynon alarm circuit that Bob N. designed last year. I also combined it with a strobing
LED circuit later. On the bench (kitchen table),the whole thing works PERFECT. No flaws...no
hiccups, hook up all the right wires, and the LED comes on when it's supposed to! (see the
enclosed circuit diagram & photos)
(Note: Bob sent me a slight revision that added a 10K resistor and test wire not shown in
his original design. It branched off the node between the two 10K resistors and base of the 2N3904)
(Second note: the photo of the completed circuit I built didn't have the green wire & 10K resistor
for the test function, yet. You will also notice in this photo I added a 555 timer/4017 cascading LED
circuit which is tied in together with the alarm circuit LED. Works perfect on the test bench as designed,
no problems!!)
But, here's the weird part. Somehow, when I hook the circuit up in my plane, it does NOT work right.
A little background on the circuit, first; The alarm circuit has an "always" hot lead, which is hooked
to my +12volt instrument bus bar (purple wire). Next, it has the "alarm" wire hooked up to the
Dynon alarm signal wire (light blue wire). Next, I have a "push to test" green wire, hooked up to
my pistol grip on the yoke handle. Lastly, is the white ground wire.
I've installed the circuit, which is enclosed in a little 'project box', about 20 times in my plane.
I can NOT seem to get the entire circuit to operate properly. With all (4) wires hooked up
properly, and you turn on power to the instrument +12volt bus bar, the circuit's LED always
flashes once to show the thing is working. But if I apply power from the pistol grip button, it does not
turn on the LED & accompanying strobing LEDs (like it should!!)
and, YES!!! I have checked that the pistol grip button is sending power to the green wire!!
If I manually hook up a pigtail from the +12volt bus bar, and apply power to the light blue (alarm wire)
wire, everything works fine!! But, then, when I try the power to the "test wire" I get nothing!!!
Now, here's the pisser!! When I unhook everything, take it back to the house(again!), and hook it up
to my Radio Shack 12 Volt transformer, the silly thing works perfect again!!! I've done this about
15 times, at least. Works perfect on the 12 volt transformer power supply, but not in the plane!
Okay, here's some things I've managed to find out; when checking the power at the +12volt
instrument bus bar, the reading is about 11.95 volts. But when checking the voltage coming from
the pistol grip wire, it's usually about a quarter volt LESS!! I attribute this to slight wiring differences,
and routings. Is THIS why it won't work???
One more thing. On one of my many R&R's I found that the 10K resistor in the test wire leg had
burned out. I don't know why. I replaced it, so I figured it must have been the whole problem all along.
Nope! With a new resistor, the circuit works great on the kitchen table, but not in the plane.
To the best of my knowledge, the only distinguishable difference between my kitchen table tests
and the installed tests are the super minor voltage differences between the 'always hot' power supply
and the pistol grip button voltage supply, which is only a fraction of a volt. I have noticed, though,
if I run a test wire from the +12volt terminal connector/'always hot' wire and connect it to the Dynon
larm signal wire....everything acts correct!!! But, if I try to get the test wire to do the same think...
...I get nothing! Take it apart...go into the house, and if I try the test wire, it works great!!
I'm really lost on this one!! Is it possible that the circuit is so sensitive that only precise, matching power
inputs will work?
Opinions welcome!
Mike Welch
No virus found in this message.
Checked by AVG - www.avg.com
Version: 10.0.1375 / Virus Database: 1509/3672 - Release Date: 05/31/11
[quote][b]
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Mike Welch
Joined: 13 Feb 2011
Posts: 272
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| Posted: Tue May 31, 2011 6:36 pm Post subject: Dynon alarm circuit revisited |
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Vern,
Thanks for the reply. No, the Dynon alarm tone is not always 'high', since it's true and original
function is to hook up to your intercom, and alert you if there is an AOA alarm. A constant high tone would
give a continuous loud screaming alarm in your headphones. Besides, if it were on (high), as
soon as I hooked it up, the circuit would activate. THAT part of the thing seems to work ok.
Bob simply tapped off the intercom alarm signal wire and designed this circuit, which will then allow
for a visual alarm, in addition to the audio alarm.
It's a darndest thing!!! You only have four wires....it's not like there's much to go wrong!!! Purple wire gets constant +12v,
white goes to GND bus bar, green wire is the 'test' wire, & lastly, the light blue wire is the Dynon. Whether I hook up the
circuit in the house, or hook it up in the plane, it's awful simple. In the house....it works, in the plane...it doesn't. The ONLY
difference is that the power and grounds are different, but the hookups are pretty much the same.
BTW, regarding your suggestion; if the circuit is in the plane, and I unhook the Dynon wire from the Dynon, I CAN hook up
a simple alligator clip wire from the +12v instrument bus to the light blue Dynon wire, and everything is great. Works like champ!!
But, when I try to do the same exact thing (+12v to the green test wire)....nothing. Take it into the house, hook it up.......and it works!!
Beats the heck of me what's going on!!!
Thanks for your thoughts, Vern.
Mike W
When idle, it’s possible that the Dynon alarm tone output is high. This turns on the 2N3904, which discharges the capacitor and turns the LED on briefly. When the capacitor charges up, the lamp goes off. At this point, your test input will have no effect because the 2N3904 is already on
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sprocket(at)vx-aviation.c
Guest
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| Posted: Tue May 31, 2011 9:19 pm Post subject: Dynon alarm circuit revisited |
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Hi Mike.
Then I think that the output of the Dynon is bipolar (+ to – voltage) so that when the tone is off, it’s biasing the 2N3904 base voltage so low that your test voltage is not quite enough to overcome this bias. This may be why it’s sensitive to the voltage on the test input. Simply changing the test resistor to a lower value will fix that (4.7K).
V
From: Mike Welch (mdnanwelch7(at)hotmail.com)
Sent: Tuesday, May 31, 2011 7:33 PM
To: aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com)
Subject: RE: Dynon alarm circuit revisited
Vern,
Thanks for the reply. No, the Dynon alarm tone is not always 'high', since it's true and original
function is to hook up to your intercom, and alert you if there is an AOA alarm. A constant high tone would
give a continuous loud screaming alarm in your headphones. Besides, if it were on (high), as
soon as I hooked it up, the circuit would activate. THAT part of the thing seems to work ok.
Bob simply tapped off the intercom alarm signal wire and designed this circuit, which will then allow
for a visual alarm, in addition to the audio alarm.
It's a darndest thing!!! You only have four wires....it's not like there's much to go wrong!!! Purple wire gets constant +12v,
white goes to GND bus bar, green wire is the 'test' wire, & lastly, the light blue wire is the Dynon. Whether I hook up the
circuit in the house, or hook it up in the plane, it's awful simple. In the house....it works, in the plane...it doesn't. The ONLY
difference is that the power and grounds are different, but the hookups are pretty much the same.
BTW, regarding your suggestion; if the circuit is in the plane, and I unhook the Dynon wire from the Dynon, I CAN hook up
a simple alligator clip wire from the +12v instrument bus to the light blue Dynon wire, and everything is great. Works like champ!!
But, when I try to do the same exact thing (+12v to the green test wire)......nothing. Take it into the house, hook it up.......and it works!!
Beats the heck of me what's going on!!!
Thanks for your thoughts, Vern.
Mike W
When idle, it’s possible that the Dynon alarm tone output is high. This turns on the 2N3904, which discharges the capacitor and turns the LED on briefly. When the capacitor charges up, the lamp goes off. At this point, your test input will have no effect because the 2N3904 is already on.
The fix for this would be to put a capacitor in series with the Dynon output. That way, if the the Dynon tone is left high, it will allow the 2N3904 to go off and let the test lead operate.
Vern Little
Vx Aviation
www.vx-aviation.com
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No virus found in this message.
Checked by AVG - www.avg.com
Version: 10.0.1375 / Virus Database: 1509/3672 - Release Date: 05/31/11
[quote][b]
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mikerv6a(at)ao-cs.com
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| Posted: Wed Jun 01, 2011 12:11 am Post subject: Dynon alarm circuit revisited |
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Hi Mike
Regarding your Dynon alarm indicator:
How about showing us the whole schematic as-built?
Also, one of your observations invites a second look.
If a 10K resistor burned out in a 12V system, then EITHER:
It wasn't really a 10K resistor, since 12V and 10K makes
about 14 milliwatt power dissipation, which means no burnout by
any kind of failure in a 12V system. OR somehow you got
quite a bit more than 12V into your test.
Mike Linse
Corvallis, OR
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Mike Welch
Joined: 13 Feb 2011
Posts: 272
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| Posted: Wed Jun 01, 2011 4:39 am Post subject: Dynon alarm circuit revisited |
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Hi Mike,
Regarding the burned out resistor, a while back when I was first installing the
whole circuit, somehow I got a 24" long jumper wire hooked up wrong!!!
When I turned on the ignition switch, it started burning and melting & losing
lots of magic smoke. I quickly yanked it out of the plane!!
Thinking I really screwed up big time, I took the box out of the plane, took
it back inside the house and hooked it up. Everything works great!!
Where, or how that 10K resistor got burned out, I don't know. Yes, it was a
10K, I still have it. Yes, I replaced it with a 10K. I've even checked both of the
resistors for their accuracy (for the light blue wire & green wire). 9.84K for the
green, and 9.84K for the light blue. One works perfect, one doesn't.
I'll see what i can do about posing the whole schematic. It may have to come
as two complete circuits. (The one I just posted is the alarm part of it)
Mike
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