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How to actuate an annunciator light?

claycookiemonster

Well Known Member
On some Boeings, there is quite a deal made of annunciator lights which indicate switch position versus lights which indicate system operation. For example, suppose you wanted a switch to indicate that your landing lights were on; if the annunciator was wired to the switch, but the lights were burned out, you would get a positive indication even if the lights were dark.
I want to have three annunciators; Canopy open will be red, boost pump on will be blue, and pitot heat on will be yellow.
I figure I can rig a canopy switch to back up the one that lives within Dynon. How can I rig up switches to indicate that the boost pump is actually operating, rather than just switch position? I believe the Dynon pitot tube operates in a sort of "Auto" mode, where it comes on as it sees fit? I want my light to indicate that the pitot is actually being powered, and not just that the system is operating and will turn it on and off when it wants.
 
I think that it would be easy to go overboard in this.

For example, on the boost pump, no matter where you hook the light into the circuit it’s ultimately only going to show power on/off to that point. To really show pump operation, you need to activate that light with a pressure switch.

You should already have a fuel pressure gauge that shows the same thing, so in my mind, having a light that show me the same pressure rise is overly complicated.

I do however, want a light/cas message to show me that I forgot to turn the switch off.

I have 4 available discreet inputs available with my Garmin stuff and I’m prioritizing CAS messages for; parking brake on, pitot on, remote start arm, carbon monoxide warn.

The first 3 of those are based on switch/cable position, because in my case, I feel like anything else adds complexity and potentially causes more problems than it solves
 
A simple method to accomplish your goal is to use a reed switch.
Wrap several turns of the wire going to the device around the reed switch body, as the current flows it will produce a magnetic field activating the switch.
This method was widely used in industrial machines prior to the implementation of PLC’s.
 
I hvave an AG6 annunciator. I’ve found it to be very flexible and very helpful, and sounds like it would accomplish your goals. It’s $170 at Spruce. Here are the many screens possible… I note that canopy open or closed are possible warning displays. It sounds an aural warning, which can be silenced by pressing the display.

Fuel pump….the AG6 gives me an annunciation warning only after it’s been running for a few minutes (can’t remember what it’s set for, but it is adjustable). It would be pretty easy to configure it to monitor fuel pressure.

https://www.aircraftextras.com/AG6.htm

https://www.aircraftspruce.com/catalog/inpages/aeag6.php
 
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You mentioned landing lights. With LED lights, the current drain is small. Please leave those lights on all the time - on a hazy day, it will definitely make your plane more visible.

I had two acquaintances in separate mid-air collisions, two decades apart. One got killed. The other survived but her plane was totaled. In both cases, the other airplanes had no survivors.

Dave
 
overcomplicating things

Desert Rat raised a valid issue in pointing out the "going overboard" tendency.

First let's be clear, you are dealing with an RV where you as the pilot can visually see and hear things in the cockpit unlike Boeing jet liners.

I have a boost pump light next to the boost pump switch.
You can hear the boost pump when you turn it on and you will see a rise in pressure. The light merely tells me that I should turn it off when I choose to do so.

The canopy... Well, you can see the canopy handle better than any light in the sea of modern touchscreen overloaded information screens.

Landing lights, again if you fly at night you can absolutely visually verify that the lights are on. It would also be highly unlikely that both sides of the wing tip light go out at the same time.

Pitot tube may be the exception here no matter how sophisticated your wiring may be there is no way to visually verify operation except on the ground before an IFR flight.
 
Current not Voltage

That’s still just showing current in the wire, i.e. switch operation

So it shows the circuit is drawing current. If the wire fell off the pump, there's still voltage after the light, but no current. So detecting current is a step up towards knowing the pump is actually working.

If the pump fails open, voltage will be present, but no current.
If the pump shorts out, you should blow a breaker, and show no voltage or current.
If the pump is running but failing to make pressure (ex: a vane pump with broken vanes) then it will show voltage and current draw.
 
The tough one is the thermostatically controlled pitot tube heater, since if it’s warm out the thermostat will keep it off. In flight in cold wx, the ‘current sensor’ noted earlier would work, but possibly not continuously, as the thermostat cycled.
 
You are probably over thinking this. When I turn on the boost pump on my RV10 I see two things happen. The fuel pressure goes up and the alternator load goes up. Seeing both of those things happen assures me the pump is actually working. My shunt is between the alternator and the rest of the system so it is a load meter. It does not tell you if the battery is charging or discharging.
 
If you are using the Dynon pitot tube you can tell that the pitot tube is getting power on your EMS monitor. You can’t prove it is getting hot while in the cockpit with absolute certainty, but the indicator is supposed to turn red if it does not heat up properly.
All of the indicators on the jets I flew only told you that there was power going to the pitot tube. They did not tell you if they were getting hot or not. We turned them on for 30 seconds during preflight and made sure they were warm.
 
Well, looking back, I misinterpreted what was written in the Dynon installation manual.

"Dynon Avionics Heated AOA/Pitot Probe utilizes a heating element whose temperature is accurately measured and regulated by a microprocessor-based controller. The controller monitors a temperature sensor embedded within the pitot body to regulate the heat for the front half of the Probe to a constant temperature."

So, the probe, ONCE TURNED ON, varies the current flow to the heating element in an attempt to maintain a constant temperature of about 158F. That's all the "auto" there is. But, it's only ON if I switch it ON.
 
I suppose if you’re truly concerned about the pitot actually heating up you could attached/bond a thermal coupler / temperature prob to it and a display to read it on in the cockpit.
 
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