Today's Message Index:
----------------------
1. 05:36 AM - Re: Runaway trim (Greg Campbell)
2. 06:33 AM - Re: Runaway trim ()
3. 07:41 AM - Re: Annunciator HELP! (Robert L. Nuckolls, III)
4. 07:49 AM - Re: Annunciator HELP! (Robert L. Nuckolls, III)
5. 09:54 AM - Re: Annunciator HELP! (Richard Tasker)
6. 10:07 AM - Re: Annunciator HELP! (john@ballofshame.com)
7. 11:28 AM - Re: Annunciator HELP! (Ron Quillin)
8. 12:12 PM - Re: Annunciator HELP! (Robert L. Nuckolls, III)
9. 12:40 PM - Re: Annunciator HELP! (Fiveonepw@aol.com)
10. 01:04 PM - Re: Annunciator HELP! (Fiveonepw@aol.com)
11. 01:17 PM - Re: Annunciator HELP! (Fiveonepw@aol.com)
12. 01:38 PM - Re: Annunciator HELP! (Richard Tasker)
13. 02:03 PM - Re: Annunciator HELP! (john@ballofshame.com)
14. 02:50 PM - Re: Annunciator HELP! (The Kuffels)
15. 04:19 PM - Re: Annunciator HELP! (Richard Tasker)
16. 04:19 PM - Re: Runaway trim (marcausman)
17. 06:10 PM - Re: Annunciator HELP! (Fiveonepw@aol.com)
18. 06:28 PM - FET vs. NPN (was HELP!) (Fiveonepw@aol.com)
19. 08:59 PM - Re: FET vs. NPN (was HELP!) (Richard E. Tasker)
20. 09:35 PM - Re: FET vs. NPN (was HELP!) (Fiveonepw@aol.com)
Message 1
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Subject: | Re: Runaway trim |
I still advocate a simple DPDT switch of the ON-OFF-(ON) variety
as the best "last resort" trim disconnect and reverser.
Most trim systems boil down to this:
Power -> Trim Controls -> 2 wires -> Trim Motor
The fancier the controls - the more likely the problems.
Especially if the fancy controls involve a lot of relays, etc..
Disconnecting a runaway trim system "quickly" is essential if
all you can do is "stop" the runaway condition.
But... if it's likely that you could "reverse" the runaway condition
and then stop it it at a neutral trim setting - then even speed is of less
concern.
My contention is that you can do both: 1)quickly STOP, and 2) optionally
REVERSE
the runaway trim condition. All you have to do is add a DPDT ON-OFF-(ON)
switch
between the "Controls" and the Trim Motor.
Power -> Controls -> Trim Disconnect & Reverser Switch -> 2 wires -> Trim
Motor.
With the handle in the:
ON position - your normal trim controls command the trim motor
OFF position - nothing goes to the trim motor
(ON) position - the reverse signal gets sent to the trim motor.
It's simple, it's testable, it's reversible. About the only thing it can't
fix is a jammed trim motor.
It borders on foolproof - but you don't want to underestimate the ability of
fools.
Yes - it adds to the "parts count", but it's only 1 part - and it's failure
modes are pretty benign.
If anybody sees any problems with my logic - I'd appreciate hearing about
it. I've been flying it
happily for 2+ years now.
Greg
Message 2
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Subject: | Re: Runaway trim |
That was my solution as well Greg. Agree with you 100%.
Bob McC
>From: "Greg Campbell" <gregcampbellusa@gmail.com>
>To: "aeroelectric-list@matronics.com" <AeroElectric-List@matronics.com>
>Subject: Re: AeroElectric-List: Runaway trim
>Date: Fri, 8 Jun 2007 08:33:21 -0400
>
>I still advocate a simple DPDT switch of the ON-OFF-(ON) variety
>as the best "last resort" trim disconnect and reverser.
>
>Most trim systems boil down to this:
>Power -> Trim Controls -> 2 wires -> Trim Motor
>
>The fancier the controls - the more likely the problems.
>Especially if the fancy controls involve a lot of relays, etc..
>
>Disconnecting a runaway trim system "quickly" is essential if
>all you can do is "stop" the runaway condition.
>
>But... if it's likely that you could "reverse" the runaway condition
>and then stop it it at a neutral trim setting - then even speed is of less
>concern.
>
>
>My contention is that you can do both: 1)quickly STOP, and 2) optionally
>REVERSE
>the runaway trim condition. All you have to do is add a DPDT ON-OFF-(ON)
>switch
>between the "Controls" and the Trim Motor.
>Power -> Controls -> Trim Disconnect & Reverser Switch -> 2 wires -> Trim
>Motor.
>
>With the handle in the:
>ON position - your normal trim controls command the trim motor
>OFF position - nothing goes to the trim motor
>(ON) position - the reverse signal gets sent to the trim motor.
>
>It's simple, it's testable, it's reversible. About the only thing it can't
>fix is a jammed trim motor.
>It borders on foolproof - but you don't want to underestimate the ability
>of
>fools.
>
>Yes - it adds to the "parts count", but it's only 1 part - and it's failure
>modes are pretty benign.
>If anybody sees any problems with my logic - I'd appreciate hearing about
>it. I've been flying it
>happily for 2+ years now.
>
>Greg
Message 3
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Subject: | Re: Annunciator HELP! |
At 12:10 AM 6/8/2007 -0400, you wrote:
>This post is for the techno-weenies- all others delete NOW!
>
>Goal: Illuminate an annunciator light when TruTrak servos are OFF using
>NKK LB series illuminated pushbutton:
>
><http://rocky.digikey.com/scripts/ProductInfo.dll?Site=US&V=360&M=LB25RKW01-5C-JC-RO>http://rocky.digikey.com/scripts/ProductInfo.dll?Site=US&V=360&M=LB25RKW01-5C-JC-RO
>
>This device is a DPDT PB with LED lamp, built-in resistor for the
>LED. (Reason for using PB instead of simple lamp is provide built-in PTT
>function with N.O. contacts. LED has its own +&- contacts on back of switch)
>
>Consultation with TruTrak reveals that the torque line (pin6) to either
>servo can be used to sense when power is applied to the servo, thereby
>providing the necessary input. They sent a drawing showing a 10K resistor
>tied to this pin gating on a darlington transistor to provide the switch
>(ground path) for a lamp. Good, but I need the light OFF when power is on
>this pin. Please don't ask why, this is what I want to happen.
>
>I begged the list for guidance some time ago and Bob very generously
>supplied sketches (THANKS!) for how to achieve this using a IRF510 MOSFET
>to either (1) turn the lamp ON as TruTrak indicated, or (2) turn the lamp
>OFF by connecting the MOSFET between a 470 ohm resistor supplying the LED
>and ground, which I understand would essentially remove voltage from the
>LED by shorting its supply voltage to ground. With 13 volts supplied,
>this would be about 30mA through the MOSFET when it is gated on, probably
>not resulting in a new-clee-ur event. Problem is, I assume Bob is
>referring to the resistor normally used to control LED current and since
>in the LB series switches this resistor is built into the LED, connecting
>the MOSFET to the LED supply voltage would essentially result in a dead
>short (minus MOSFET internal resistance) to ground. I'd surmise Mr.
>MOSFET would melt?
See if this helps:
http://www.aeroelectric.com/Pictures/Schematics/FiveOnOnePW.jpg
Bob . . .
Message 4
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Subject: | Re: Annunciator HELP! |
At 12:10 AM 6/8/2007 -0400, you wrote:
>This post is for the techno-weenies- all others delete NOW!
>
>Goal: Illuminate an annunciator light when TruTrak servos are OFF using
>NKK LB series illuminated pushbutton:
>
><http://rocky.digikey.com/scripts/ProductInfo.dll?Site=US&V=360&M=LB25RKW01-5C-JC-RO>http://rocky.digikey.com/scripts/ProductInfo.dll?Site=US&V=360&M=LB25RKW01-5C-JC-RO
>
>This device is a DPDT PB with LED lamp, built-in resistor for the
>LED. (Reason for using PB instead of simple lamp is provide built-in PTT
>function with N.O. contacts. LED has its own +&- contacts on back of switch)
>
>Consultation with TruTrak reveals that the torque line (pin6) to either
>servo can be used to sense when power is applied to the servo, thereby
>providing the necessary input. They sent a drawing showing a 10K resistor
>tied to this pin gating on a darlington transistor to provide the switch
>(ground path) for a lamp. Good, but I need the light OFF when power is on
>this pin. Please don't ask why, this is what I want to happen.
>
>I begged the list for guidance some time ago and Bob very generously
>supplied sketches (THANKS!) for how to achieve this using a IRF510 MOSFET
>to either (1) turn the lamp ON as TruTrak indicated, or (2) turn the lamp
>OFF by connecting the MOSFET between a 470 ohm resistor supplying the LED
>and ground, which I understand would essentially remove voltage from the
>LED by shorting its supply voltage to ground. With 13 volts supplied,
>this would be about 30mA through the MOSFET when it is gated on, probably
>not resulting in a new-clee-ur event. Problem is, I assume Bob is
>referring to the resistor normally used to control LED current and since
>in the LB series switches this resistor is built into the LED, connecting
>the MOSFET to the LED supply voltage would essentially result in a dead
>short (minus MOSFET internal resistance) to ground. I'd surmise Mr.
>MOSFET would melt?
See if this helps:
http://www.aeroelectric.com/Pictures/Schematics/FiveOnOnePW.jpg
Try the same technique as suggested before except the external
resistor needs to be fairly low resistance and handle a bit of
power . . . like just under 1 watt. The added resistance will
make the internal LED a tad dimmer but I suspect not so much that
it would be unsatisfactory. This is simpler than a relay and
easier to fabricate. You can put all the stuff on a "perf board"
from Radio Shack. They probably have all the parts too.
Bob . . .
Message 5
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Subject: | Re: Annunciator HELP! |
No offense to Bob or his design, but using a 1W resistor to dissipate 1W
is not a recipe for a long and reliable life for the resistor. When we
design electronics circuits we always de-rate components significantly,
which Bob also normally does.
I would suggest the attached circuit (I hope it attaches), all
components of which are readily available at Radio Shack or a number of
other component houses. While it uses a couple additional parts, they
are cheap and easy to use. This circuit will do what you want and not
dissipate much of anything in either state.
Respectfully,
Dick Tasker
Robert L. Nuckolls, III wrote:
> <nuckollsr@cox.net>
>
> At 12:10 AM 6/8/2007 -0400, you wrote:
>
>> This post is for the techno-weenies- all others delete NOW!
>>
>> Goal: Illuminate an annunciator light when TruTrak servos are OFF
>> using NKK LB series illuminated pushbutton:
>>
>> <http://rocky.digikey.com/scripts/ProductInfo.dll?Site=US&V=360&M=LB25RKW01-5C-JC-RO>http://rocky.digikey.com/scripts/ProductInfo.dll?Site=US&V=360&M=LB25RKW01-5C-JC-RO
>>
>>
>> This device is a DPDT PB with LED lamp, built-in resistor for the
>> LED. (Reason for using PB instead of simple lamp is provide built-in
>> PTT function with N.O. contacts. LED has its own +&- contacts on
>> back of switch)
>>
>> Consultation with TruTrak reveals that the torque line (pin6) to
>> either servo can be used to sense when power is applied to the servo,
>> thereby providing the necessary input. They sent a drawing showing a
>> 10K resistor tied to this pin gating on a darlington transistor to
>> provide the switch (ground path) for a lamp. Good, but I need the
>> light OFF when power is on this pin. Please don't ask why, this is
>> what I want to happen.
>>
>> I begged the list for guidance some time ago and Bob very generously
>> supplied sketches (THANKS!) for how to achieve this using a IRF510
>> MOSFET to either (1) turn the lamp ON as TruTrak indicated, or (2)
>> turn the lamp OFF by connecting the MOSFET between a 470 ohm resistor
>> supplying the LED and ground, which I understand would essentially
>> remove voltage from the LED by shorting its supply voltage to
>> ground. With 13 volts supplied, this would be about 30mA through the
>> MOSFET when it is gated on, probably not resulting in a new-clee-ur
>> event. Problem is, I assume Bob is referring to the resistor
>> normally used to control LED current and since in the LB series
>> switches this resistor is built into the LED, connecting the MOSFET
>> to the LED supply voltage would essentially result in a dead short
>> (minus MOSFET internal resistance) to ground. I'd surmise Mr. MOSFET
>> would melt?
>
>
> See if this helps:
>
> http://www.aeroelectric.com/Pictures/Schematics/FiveOnOnePW.jpg
>
> Try the same technique as suggested before except the external
> resistor needs to be fairly low resistance and handle a bit of
> power . . . like just under 1 watt. The added resistance will
> make the internal LED a tad dimmer but I suspect not so much that
> it would be unsatisfactory. This is simpler than a relay and
> easier to fabricate. You can put all the stuff on a "perf board"
> from Radio Shack. They probably have all the parts too.
>
> Bob . . .
>
>
Message 6
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Subject: | Re: Annunciator HELP! |
Why not use 2 transistors to invert the signal instead?
-John
www.ballofshame.com
> <nuckollsr@cox.net>
>
> At 12:10 AM 6/8/2007 -0400, you wrote:
>
>>This post is for the techno-weenies- all others delete NOW!
>>
>>Goal: Illuminate an annunciator light when TruTrak servos are OFF using
>>NKK LB series illuminated pushbutton:
>>
>><http://rocky.digikey.com/scripts/ProductInfo.dll?Site=US&V=360&M=LB25RKW01-5C-JC-RO>http://rocky.digikey.com/scripts/ProductInfo.dll?Site=US&V=360&M=LB25RKW01-5C-JC-RO
>>
>>This device is a DPDT PB with LED lamp, built-in resistor for the
>>LED. (Reason for using PB instead of simple lamp is provide built-in PTT
>>function with N.O. contacts. LED has its own +&- contacts on back of
>> switch)
>>
>>Consultation with TruTrak reveals that the torque line (pin6) to either
>>servo can be used to sense when power is applied to the servo, thereby
>>providing the necessary input. They sent a drawing showing a 10K
>> resistor
>>tied to this pin gating on a darlington transistor to provide the switch
>>(ground path) for a lamp. Good, but I need the light OFF when power is
>> on
>>this pin. Please don't ask why, this is what I want to happen.
>>
>>I begged the list for guidance some time ago and Bob very generously
>>supplied sketches (THANKS!) for how to achieve this using a IRF510 MOSFET
>>to either (1) turn the lamp ON as TruTrak indicated, or (2) turn the lamp
>>OFF by connecting the MOSFET between a 470 ohm resistor supplying the LED
>>and ground, which I understand would essentially remove voltage from the
>>LED by shorting its supply voltage to ground. With 13 volts supplied,
>>this would be about 30mA through the MOSFET when it is gated on, probably
>>not resulting in a new-clee-ur event. Problem is, I assume Bob is
>>referring to the resistor normally used to control LED current and since
>>in the LB series switches this resistor is built into the LED, connecting
>>the MOSFET to the LED supply voltage would essentially result in a dead
>>short (minus MOSFET internal resistance) to ground. I'd surmise Mr.
>>MOSFET would melt?
>
> See if this helps:
>
> http://www.aeroelectric.com/Pictures/Schematics/FiveOnOnePW.jpg
>
> Try the same technique as suggested before except the external
> resistor needs to be fairly low resistance and handle a bit of
> power . . . like just under 1 watt. The added resistance will
> make the internal LED a tad dimmer but I suspect not so much that
> it would be unsatisfactory. This is simpler than a relay and
> easier to fabricate. You can put all the stuff on a "perf board"
> from Radio Shack. They probably have all the parts too.
>
> Bob . . .
>
>
Message 7
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Subject: | Re: Annunciator HELP! |
At 09:51 6/8/2007, you wrote:
>No offense to Bob or his design, but using a 1W resistor to
>dissipate 1W is not a recipe for a long and reliable life for the
>resistor. When we design electronics circuits we always de-rate
>components significantly, which Bob also normally does.
Here's a link to an Ohmite pdf used for selecting and derating resistors.
http://ohmite.com/cgi-bin/showpage.cgi?product=appnotes_res_select.pdf&kw=resistor_selection__pdf_version_only_
The chart suggests no altitude derating below 5000 ft, increasing to
~.84 at FL250.
Other derating factors and a good old-fashioned nomograph is even included.
That one watt device really won't be happy with ~14 volts across it.
Ron Q.
Message 8
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Subject: | Re: Annunciator HELP! |
At 12:51 PM 6/8/2007 -0400, you wrote:
>No offense to Bob or his design, but using a 1W resistor to dissipate 1W
>is not a recipe for a long and reliable life for the resistor. When we
>design electronics circuits we always de-rate components significantly,
>which Bob also normally does.
>
>I would suggest the attached circuit (I hope it attaches), all components
>of which are readily available at Radio Shack or a number of other
>component houses. While it uses a couple additional parts, they are cheap
>and easy to use. This circuit will do what you want and not dissipate
>much of anything in either state.
>
>Respectfully,
>
>Dick Tasker
That works too. The 220 ohm was running a bit warm. 270 would be better.
Bob . . .
Message 9
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Subject: | Re: Annunciator HELP! |
In a message dated 6/8/2007 9:44:21 AM Central Daylight Time,
nuckollsr@cox.net writes:
See if this helps:
http://www.aeroelectric.com/Pictures/Schematics/FiveOnOnePW.jpg
>>>
Helps?! Now I have no excuse to not get this puppy done- Bless yore punkin'
heart, Bob- once again the muddy waters become crystaline!
VERY much appreciate the assist!
Mark do not archive
************************************** See what's free at http://www.aol.com.
Message 10
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Subject: | Re: Annunciator HELP! |
In a message dated 6/8/2007 9:52:21 AM Central Daylight Time,
nuckollsr@cox.net writes:
The added resistance will
make the internal LED a tad dimmer
Probably not a problem, but if necessary NKK offers internal LEDs w/o the
resistor, but was hoping to keep all annunciator PBs the same.
Power to these lamps is via a PWM dimmer...
_http://fdatasystems.com/LC_40.htm_ (http://fdatasystems.com/LC_40.htm)
...which they claim is "low frequency" without giving actual freq. My
reading indicates MOSFETs operate well even at high freqs, so I suspect not a
problem. Would this affect operation in any way i.e. extra heat?
With MOSFET on and dimmer at full power, current should be about 64 mA or
about .9watts (if my bad math is close)- should I heatsink this thing or can I
just screw it to a support rib behind the panel (with a dab of h/s compound)
with short wires (pigtail) soldered to legs, covered in heatshrink to insulate
them?
Thanks again!
Mark
************************************** See what's free at http://www.aol.com.
Message 11
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Subject: | Re: Annunciator HELP! |
In a message dated 6/8/2007 12:10:40 PM Central Daylight Time,
john@ballofshame.com writes:
Why not use 2 transistors to invert the signal instead?
Hi John- As you likely noticed I can't even get my mind around ONE of the
stupid things- could you elaborate? Better yet, send me a schematic, part#s etc.
- I'm in full learn mode...
Appreciate the interest-
Mark do not archive
************************************** See what's free at http://www.aol.com.
Message 12
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Subject: | Re: Annunciator HELP! |
It runs at approximately 170-180 Hz.
Dick Tasker
Fiveonepw@aol.com wrote:
> In a message dated 6/8/2007 9:52:21 AM Central Daylight Time,
> nuckollsr@cox.net writes:
>
> The added resistance will
> make the internal LED a tad dimmer
>
> Probably not a problem, but if necessary NKK offers internal LEDs w/o
> the resistor, but was hoping to keep all annunciator PBs the same.
>
> Power to these lamps is via a PWM dimmer...
>
> http://fdatasystems.com/LC_40.htm
>
> ...which they claim is "low frequency" without giving actual freq. My
> reading indicates MOSFETs operate well even at high freqs, so I
> suspect not a problem. Would this affect operation in any way i.e.
> extra heat?
>
> With MOSFET on and dimmer at full power, current should be about 64 mA
> or about .9watts (if my bad math is close)- should I heatsink this
> thing or can I just screw it to a support rib behind the panel (with a
> dab of h/s compound) with short wires (pigtail) soldered to legs,
> covered in heatshrink to insulate them?
>
> Thanks again!
> Mark
>
>
> ------------------------------------------------------------------------
> See what's free at AOL.com
> <http://www.aol.com?ncid=AOLAOF00020000000503>.
>
>*
>
>
>*
>
Message 13
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Subject: | Re: Annunciator HELP! |
Actually, there was an e-mail that went out around the same time as mine
that actually had a schematic for such thing. I don't have all my e-mail
in front of me so I can't point you to it unfortunately but now that I
mentioned it you probably know exactly what I'm talking about (my
apologies for not being able to credit whoever drew the schematic).
The schematic showed regular transitors, I think. Bob had suggested a
FET, albeit in a slightly different application. I don't know enough
about the problem to really have an educated opinion on which is "better".
Maybe those two can duke it out and converge to the optimal solution.
-John
www.ballofshame.com
>
> In a message dated 6/8/2007 12:10:40 PM Central Daylight Time,
> john@ballofshame.com writes:
>
> Why not use 2 transistors to invert the signal instead?
>
> Hi John- As you likely noticed I can't even get my mind around ONE of the
> stupid things- could you elaborate? Better yet, send me a schematic,
> part#s etc.
> - I'm in full learn mode...
>
> Appreciate the interest-
> Mark do not archive
>
>
> ************************************** See what's free at
> http://www.aol.com.
>
Message 14
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Subject: | Re: Annunciator HELP! |
Also <<No offense to Bob or his design>> or the several components of
Dick Tasker < can't even get my mind around ONE of the stupid things-
could you elaborate? Better yet, send me a schematic, part#s etc>> but
wouldn't the following work?
Change Bob's 220 (or 270) ohm resistor to 5k or maybe even 10k. Insert
one identical FET between the resistor and the switch. The junction of
the 1st Drain and the replaced resistor goes to the gate of the 2nd
FET. The drain of the 2nd FET is connected to lamp power (as is the
high end of the replaced resistor), the source goes to the high input of
the switch LED. The other end of the switch LED goes to ground as in
the original circuit.
So when the TruTrak pin 6 is high the 1st FET conducts. The current
through the new resistor lowers the voltage to the 2nd FET's gate and
turns it off, turning off the lamp. When the pin 6 is low the 1st FET
is off. Lamp power high goes through the 5k resistor to the 2nd FET
gate and turns it on, turning on the switch LED. This eliminates the
dimming of the lamp by running its power through a high wattage resistor.
Don't have the facilities to draw and attach a schematic but the change
to Bob's drawing is hopefully simple enough to be clear.
Tom Kuffel
AL7AU
Message 15
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Subject: | Re: Annunciator HELP! |
Kinda like this if you like FETs better... Both schematics attached.
Dick Tasker
The Kuffels wrote:
> <kuffel@cyberport.net>
>
> Also <<No offense to Bob or his design>> or the several components of
> Dick Tasker < can't even get my mind around ONE of the stupid things-
> could you elaborate? Better yet, send me a schematic, part#s etc>>
> but wouldn't the following work?
>
> Change Bob's 220 (or 270) ohm resistor to 5k or maybe even 10k.
> Insert one identical FET between the resistor and the switch. The
> junction of the 1st Drain and the replaced resistor goes to the gate
> of the 2nd FET. The drain of the 2nd FET is connected to lamp power
> (as is the high end of the replaced resistor), the source goes to the
> high input of the switch LED. The other end of the switch LED goes to
> ground as in the original circuit.
>
> So when the TruTrak pin 6 is high the 1st FET conducts. The current
> through the new resistor lowers the voltage to the 2nd FET's gate and
> turns it off, turning off the lamp. When the pin 6 is low the 1st FET
> is off. Lamp power high goes through the 5k resistor to the 2nd FET
> gate and turns it on, turning on the switch LED. This eliminates the
> dimming of the lamp by running its power through a high wattage resistor.
>
> Don't have the facilities to draw and attach a schematic but the
> change to Bob's drawing is hopefully simple enough to be clear.
>
> Tom Kuffel
> AL7AU
>
>
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Subject: | Re: Runaway trim |
john(at)ballofshame.com wrote:
>
> Another thing to consider which I haven't seen anyone do is a warning tone whenever
the trim or flaps are energized. -John
> www.ballofshame.com
John, you haven't looked hard enough. :o The Vertical Power system shows on
the pilot display when either trim or flaps is running, and will have audio tones
as well. There are no mechanical relays - each flap and trim control circuit
uses two solid state switches in series, so that if one fails you don't have
a runaway condition. We also stop the motor if opposite trim or flap is commanded
- so if the down trim wire shorts for example, you press the up trim button
and the motor stops. Hold this for 3 seconds and the trim switch is disconnected.
You can then run the trim & flaps from the display (using the soft keys)
as a backup. We also suggest putting a mechanical switch in line with the
trim motor as an additional disconnect if you so choose.
Runaway trim is a very bad condition, and we really wanted to design a system that
makes electric trim safe yet easy to wire. Come by and take a look at OSH.
--------
Marc Ausman
http://www.verticalpower.com
RV-7 IO-390 Flying
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=117391#117391
Message 17
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Subject: | Re: Annunciator HELP! |
In a message dated 6/8/2007 4:07:04 PM Central Daylight Time,
john@ballofshame.com writes:
Actually, there was an e-mail that went out around the same time as mine
that actually had a schematic for such thing.
>>>
Yeah, it was that Dick Tasker guy- if I understand it correctly, looks like a
neat arrangement...
Thanks for the interest!
Mark do not archive
************************************** See what's free at http://www.aol.com.
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Subject: | FET vs. NPN (was HELP!) |
>>>>Kinda like this if you like FETs better... Both schematics attached.
Since we are now knee-deep in this, pros-cons on MOSFET called out in Bob's
original design (IRF510- assume this is component compatible to Kuffel
suggestion?) and 2N2222 transistor- cost, mounting considerations, efficiency etc?
Or not really a big deal as either are good choices?
Great stuff- you guys are the best! (xoxoxoxo 8-))
Mark do not archive
************************************** See what's free at http://www.aol.com.
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Subject: | Re: FET vs. NPN (was HELP!) |
The two transistor (bipolar or FET) approach is slightly better (in my
opinion) than the single transistor approach in that it doesn't draw
significant currents except when the LED is on. The single transistor
approach is somewhat of a compromise since it has to draw a relatively
significant current to keep the LED off. If you had the LED with no
built-in series resistor it would be better, but would still be somewhat
less desirable.
As far as using a bipolar transistor vs a FET, that is pretty much up to
user preference. I suppose a slight case could be made for the bipolar
transistor being less susceptible to static electricity handling
problems, but with a tiny bit of care, that is moot.
This is not to say that there are not cases when one or the other is
definitely preferable, but for the circuit in question it really makes
no practical difference.
Dick Tasker
Fiveonepw@aol.com wrote:
> >>>>Kinda like this if you like FETs better... Both schematics attached.
>
> Since we are now knee-deep in this, pros-cons on MOSFET called out in
> Bob's original design (IRF510- assume this is component compatible to
> Kuffel suggestion?) and 2N2222 transistor- cost, mounting
> considerations, efficiency etc?
>
> Or not really a big deal as either are good choices?
>
> Great stuff- you guys are the best! (xoxoxoxo 8-))
>
> Mark do not archive
>
>
> ------------------------------------------------------------------------
> See what's free at AOL.com
> <http://www.aol.com?ncid=AOLAOF00020000000503>.
>
>*
>
>
>*
>
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Subject: | Re: FET vs. NPN (was HELP!) |
In a message dated 6/8/2007 11:02:57 PM Central Daylight Time,
retasker@optonline.net writes:
for the circuit in question it really makes
no practical difference.
>>>
Thanks again as always, sir!
Mark do not archive
************************************** See what's free at http://www.aol.com.
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