Stall Warner now in RV's?

[dlomheim]

I guess I have been concentrating on my rotary installation a bit too much over the past few years since I didn't know the new kits were coming out with a stall warning system option. What is the theory of operation? Reed valve with plumbing to the cockpit like a Cessna, or some sort of angle of attack device with an electrical noise maker / light? Also how hard would this be to add on after the fact once the wings were already closed up?

Thanks for any info.

Doug Lomheim
90116; Mazda 13B, FWF

[TSwezey]

It is just a metal tab hooked up to a switch. Fairly simple. Doable to retrofit but it will take a little work. Probably will have to take the fuel tank off. It works.

[Jeff R]

I have just been installing mine and the little circuit board doesn't seem to be working properly. The board has a voltage regulator IC that is rated at 12 volts, which powers a classic 555 timer set in the astable mode to generate a rectanuglar waveform for the audio. That signal is passed to the output port through a DPDT relay. The relay also has the 12 volts applied to one side of the coil, and the other side connects to the microswitch located out in the wing. During a stall, the microswitch connents to ground, completing the circuit through the coil and thus energizing the relay, which then passes the audio signal to the output port.

In trying to trace the ckt out, I found that the Ground port of the ckt board is unconnected. The ckt boardd ground is actually made through one of the 4 mounting holes, so be sure the mounting screws made a good ground connection with the airframe.

The ckt, to me, is a little strange. Why use a 12 volt regulator, when the input voltage is only a bit more than that? And, with 12 volts, you get a very high audio output voltage with a lot of dc content. I was measuring about 5 VAC, which would be deafining. Using a 5 volt regulator and trim pot so the output voltage could be adjusted, plus using an ac coupling capacitor to filter out the dc and some of the high frequency content present in square waves would be the way I would go if I were designing this thing.

If others have theirs working I would sure like to get some feedback on how the volume was and how they actually connected the audio. Did you connect to the headset speakers or go into an intercome, ect?

[az_gila]

Originally Posted by Jeff R

...
The ckt, to me, is a little strange. Why use a 12 volt regulator, when the input voltage is only a bit more than that? And, with 12 volts, you get a very high audio output voltage with a lot of dc content. I was measuring about 5 VAC, which would be deafining. Using a 5 volt regulator and trim pot so the output voltage could be adjusted, plus using an ac coupling capacitor to filter out the dc and some of the high frequency content present in square waves would be the way I would go if I were designing this thing.

...

It sounds like the device was designed to drive a sonalert or buzzer directly rather than an audio input.

[jthocker]

I just finished an installation in an RV8. The circuit board actually needs to be isolated from the airframe contrary to the directions, to make it function correctly. I did this with nylon mounting screws. It still requires some adjustment, as it comes on a little early. The big problem is, it's absolutely deafening!

[DaAV8R]

Originally Posted by TSwezey

It is just a metal tab hooked up to a switch. Fairly simple. Doable to retrofit but it will take a little work. Probably will have to take the fuel tank off. It works.

I recently installed the warner during the wing build. The warner kit provided with the wing kit is basically a retro fit kit. It includes the template for an already built wing. I don't think the tank would need to come off. The wire routes thru the spar in the warner bay. It should be a fairly simple install. Sounds like we might need to wear earplugs under our headset though

[airguy]

The 12-volt voltage regulator is probably there to handle a 28-volt aircraft power setup, to prevent cooking the rest of the circuit on first powerup. I agree with the audio filtering comments earlier in the thread, that would be the way to go. An alternative would be just to pass the microswitch discrete on/off signal directly into the panel and have it trigger an aural warning in the headset rather than having the warner generate it's own signal.

[Finley Atherton]

Originally Posted by Jeff R

If others have theirs working I would sure like to get some feedback on how the volume was and how they actually connected the audio. Did you connect to the headset speakers or go into an intercome, ect?

Hi Jeff,

Firstly, my knowlege of electronics is pretty basic.

I wired the audio directly to the headset jacks and the warning tone was too loud. I temporarily installed a resistance substitution wheel in the audio line and found that 2.2k resistance got the volume about right. I then permanently installed a 2.2k resistor.

Fin
9A

[Av8torTom]

The kit is actually designed as a retrofit with a template to help you locate the access hatch, rivet holes and wing hole for the vane. The kit includes a buzzer circuit, but could also be used to turn on a light if you wanted.

T.

[dlomheim]

Thanks for all the replies...does anyone know off hand how much Van's wants for it?

If not no biggie...I'll get around to looking it up when not so busy...

Doug