modifying Dynon AOA audio alert

[Sam Buchanan]

I am interested in connecting the AOA audio alarm on my D-10A to a device that would be audible or visible in the cabin of the RV-6. I assume the audio output is a modulated signal since it is intended to be connected to an aux input of the intercom or audio panel. Is there an easy way to convert this output to DC voltage that would drive a beeper/buzzer/warning light/whatever?

[Sam Buchanan]

Originally Posted by Sam Buchanan

I am interested in connecting the AOA audio alarm on my D-10A to a device that would be audible or visible in the cabin of the RV-6. I assume the audio output is a modulated signal since it is intended to be connected to an aux input of the intercom or audio panel. Is there an easy way to convert this output to DC voltage that would drive a beeper/buzzer/warning light/whatever?

Here is a reply I received from Dynon:

"The output of the audio line is 16.8V peak-peak, at 1k ohm of impedance, and between 200 and 1KHz. It will drive into an audio panel and put noise in your headset. We generate different noises for different alarms (general alarm, AoA, autopilot, altitude alerter...)

If you're looking to put it into a external buzzer or drive an external light, we can't be much help, as we didn't design it for that nor have we ever attempted it. With a small op-amp and some thought it could be done for sure though."

Ok....you electrical engineer types.....how do we make this happen?

The AOA alert is the only one my EFIS will spit out. I just need a way
to have the alert trigger a 12vdc light or beeper. I can tweak the Dynon
AOA calibration to make it hit at the AOA I want.

[uk_figs]

I have the dual dynons (100 and 120) and the 120 has the ability to ground a line if any alerts occur, I have this wired into the Vans oil pressure warning light circuit such that the big red light lights up on any alarm as well as low oil pressure (acts like a master caution light) but the AoA alarm appears to be the only one that does not trigger this circuit. This would actually be very useful as it would flash the light right in front of me at whatever AoA alarm onset setting I chose.
In your case it sounds as if you would have to get a small amplifier to drive the speaker, found this project on the web http://www.arrl.org/tis/info/pdf/9606041.pdf as an example. One question would be whether you could hear it in the RV cockpit.

[rzbill]

I have built a few simple circuits with the help of my dad (now passed unfortunately).

If I were to try this, I would first rectify the output (diode bridge and a capacitor) and send it to an OP amp like a 741 set up as a voltage comparitor to trigger at some voltage between zero and the minimum rectified output voltage. The output of the 741 would go to a power transistor to drive the buzzer.

This is simplistic logic. There are other items needed (power supply such as a 7805, voltage dividers in the right spots, ect)

So, this is an AeroMechanicals idea. You EEs can flame away.

EDIT **
As expected, I have been "schooled" by the more experienced electrophiles
See Vern's posts further down the thread. Simple..

[Brantel]

Sam,

Might be easier to sniff the serial stream for the AOA data and act on that.

Similar to this device:

http://www.vx-aviation.com/documents/VSpeed_ADS.pdf

I think "vlittle" is the maker of that thing so he would have some significant info for you on this method.

The problem with a simple comparator is that Dynon uses the same output for many different alerts at different freq's and patterns so identifying and isolating just the AOA alarm will be difficult at best.

[Leland]

Sam, I emailed you a JPEG of the schematic that I used that was made with Radio Shack parts, as I could not post it here. I sent it to the "hiwaay" address on your website. My LED is mounted on the panel under the glareshield. The LED is very bright and cannot be ignored, not even in bright sunlight. I cannot discern the individual pulses but it certainly serves as a good stall indicator. Even though the LED emits a narrow beam of light, the right side passenger can easily see it. I set the Dynon so that the warning comes on about 5 knots above a stall.
Leland
RV9A
N137LC

[Sam Buchanan]

Originally Posted by Leland

Sam, I emailed you a JPEG of the schematic that I used that was made with Radio Shack parts, as I could not post it here. I sent it to the "hiwaay" address on your website. My LED is mounted on the panel under the glareshield. The LED is very bright and cannot be ignored, not even in bright sunlight. I cannot discern the individual pulses but it certainly serves as a good stall indicator. Even though the LED emits a narrow beam of light, the right side passenger can easily see it. I set the Dynon so that the warning comes on about 5 knots above a stall.
Leland
RV9A
N137LC

Thanks for the replies, fellas!

Leland, I haven't seen the schematic in my inbox, it may have been snagged by a spam filter. The address is "sam-at-hiwaay.net". I would like to see your schematic.

A transducer I already have in the plane and is available for an audible alarm is the Mallory SC628. I like having an audible alarm since the eyes can remain outside the cockpit. My old uEncoder would "beep-beep, beep-beep" whenever a low airspeed threshold was hit and I really liked that feature. One reason I haven't just tied the Dynon audio feed into the intercom is because of how the intercome mutes the aux input when someone opens a mic. I prefer to not have a situation where mic audio could cover up the AOA alert. I also customarily bypass the intercom when flying solo so an aux input would not be available.

The Dynon AOA alert, as far as I can tell, is variable, increasing in amplitude and maybe frequency as the AOA increases. I prefer a simpler alert that goes to full volume at a predetermined value. The D-10A only provides an audible alarm for AOA so there is no problem with differentiating between AOA and some other alarm.

I'll take all the ideas submitted under consideration along with any more to come. Sounds like there are several pilots who would like to have a simple Dynon AOA alarm output instead of the one provided in the firmware.

Dynon...are you listening?

[rzbill]

Originally Posted by Brantel

The problem with a simple comparator is that Dynon uses the same output for many different alerts at different freq's and patterns so identifying and isolating just the AOA alarm will be difficult at best.

Quite right. I realized it while in the car coming back from dinner tonight.
Since I have never done it, I do not know the complexity of picking a single frequency (assuming different tones for different alarms) out of the range of possibilities. The question has my curiosity now. I will look in my books when I get home from this work travel up in COLD COLD SNOWY CANADA.

[Sam Buchanan]

Originally Posted by rzbill

Quite right. I realized it while in the car coming back from dinner tonight.
Since I have never done it, I do not know the complexity of picking a single frequency (assuming different tones for different alarms) out of the range of possibilities. The question has my curiosity now. I will look in my books when I get home from this work travel up in COLD COLD SNOWY CANADA.

To repeat...the only audio alert my D-10A spits out is for AOA.

The problem of picking out a particular alarm applies only to those with the larger EFIS units or engine monitors.

[Brantel]

Well in that case, rzbill's idea would work like a charm....Cheap too!