Adding an Audible Alarm to my EDM900

[CMMPilot]

I do a lot of Cross Country flying which includes a fair amount of Auto Pilot. My trip from Florida (KINF) to DC (KVKX) takes approximately 4 hours, if the wind is right.  I love my EDM 900 and it gives me a level of comfort I didn't have in my previous aircraft without an Engine Monitor. It has saved my on at least 2 occasions where engine trouble caused me to declare an emergency. On a recent flight I was reading a magazine and when I put it down to change frequencies, I noticed the yellow warning light was blinking. A quick scan of the EDM 900 indicated "Low Fuel" which was not a big deal as the alarm is set for 10 gallons (almost an hour of gas) and I still had 20 in the other tank. Although this situation was not a big deal, I started to think about how long the light could've been flashing without me knowing.  I'm sure I was reading for over 5 minutes...

 

I contacted JPI to see if they had a terminal connection for an audible output. NOPE. Just the LED light alarm output.  I asked about adding an audible alarm and he agreed that it wouldn't make any difference if I wired it into the light circuit. The EDM 900 has a 3 wire alarm circuit where the Black wire provides power and the Red (Red Light) and Green (Yellow Light) wires provide ground to complete the appropriate circuit. So if I wired a small speaker with the hot side from the circuit breaker and the ground tied into the red or green wire, I would get an audible alarm when the light was lit. That became my plan, so I wanted to share how I did it. 

 

 

First, I installed the audible alarm by connecting it to the Red Alarm Light. Unfortunately I chose a beeper that was the same sound as my gear alarm, but at least the gear alarm is intermittent and the EDM alarm is continuous, so I know the difference. 

 

Second, I added a second alarm for the Warning (Yellow) circuit. I could have used the same but found a "buzzer" rather than a "beeper" that I liked and it would give me an audible difference for Red (Beeper) and Yellow (Buzzer) alarms.

 

Third, I considered my last Emergency situation where I lost a cylinder at 15,500' and had a 20 minute descent to the closest airport. I think the continuous audible alarm for 20 minutes might ADD to my STRESS rather than help the situation. After all, I am mainly concerned about not noticing an alarm on a long cross country, when I might be reading or watching a movie and only glancing at the panel from time to time. I don't want a "YELLOW" to go unnoticed until it becomes a "RED" or worse. The audible alert solves this issue, but creates another one with extended situations where it may add to the stress. I realize I can "clear" warnings but they do come back after a few minutes and it's one more thing to worry about.
For this I decided to simply install a switch that I can use to silence the audible alarm, but will have no effect on the visual LED alarm.  This was an easy add-on and took me longer to label the panel than it did to install the switch.

Ultimately, it works like a charm and as I designed it so I'm super happy with the results. I feel I have added an additional layer of safety that makes me feel more comfortable on long XC trips.

Piezo Beeper      Buzzer 12V-85dB    VONVOFF Toggle Switch 12V

 

 

I will go over the simple steps I used to complete the task and try to reference the photos.

 

Step 1:  Remove the Glare Shield

Step 2:  Locate the Circuit Breaker for the Engine Monitor and Disconnect

Step 3   Connect a wire to the "cold" side of the circuit breaker

Step 4:  Run the wire to the center of the console, behind the Remote Engine Alarm Light

Step 5:  From the Beeper, Connect the Red Wire to the wire coming from the Circuit Breaker and connect the Black Wire to the Red Wire on the Remote Engine Alarm Light. (The circuit is completed by the EDM 900 connecting the light to ground, therefore, the wire from the circuit breaker represents a "hot" lead and is connected to the Red Wire on the Audible Alarm Beeper. The Black Wire from the Beeper is connected to the Red Wire from the EDM 900 (which drives the Red Warning Light). This is done with an in-line connection, so when the EDM 900 completes the circuit to illuminate the Red Light on the Remote Engine Alarm Light, it also completes the circuit for the Audible Alarm Beeper.)

Step 6:  Repeat Step 5 for the Buzzer on the Green Wire (Yellow Light Circuit)

Step 7:  Wire the switch between the circuit breaker and the hot wire used for both speakers. In this case I used a white wire from the Circuit Breaker and it connected to the Red Wire for each speaker. Opening the switch will disconnect the power to each speaker, so it will not sound when the LED light circuit is grounded. 

Step 8:  Drill a 1/4" hole in the panel to mount the switch and label properly.

Step 9:  Install the Switch into the panel.

Step 10:  Make sure all connections are soldered and protected with shrink wrap tubing.

Step 11:  Zip Tie all loose wires and the Buzzers to the wire loom to avoid entanglement in the controls.

Step 12:  Turn on the Circuit Breaker and Test

Step 13:  Replace the Circuit Breaker in the Panel

Step 14: Replace the Glare Shield

 

***Alarms sound during the initial boot up for the EDM 900, along with the warning lights.

 

Well that's it!  It took less than an hour to complete. Of course, everything was overseen and inspected by my A&P IA.   Ultimately, it works like a charm and as I designed it so I'm super happy with the results. I feel I have added an additional layer of safety that makes me feel more comfortable on long XC trips.   I'll include a couple of images for you to see.

 

Let me know your thoughts and if you would do anything different.

 

Thanks,

Chris  

N231JY

 

 

 

 

 

[slowflyin]

I've always thought an audible alarm would be a nice addition.  

[EricJ]

That's not a bad idea at all.

Mine is connected to my AV-17, so she says, "Engine Monitor", when the alarm goes off.   That's been very useful a number of times.   Similarly anybody that has a PMA450 or similar PSE audio panel that allows discrete inputs, you can program it to say whatever you want when the input triggers.  

Short of installing any of that stuff, adding a buzzer/alarm sounds like a good thing.    The LED by itself is very easy to miss.

[tmo]

I believe discrete inputs start with the 450A; would the 'unswitched' inputs on a plain 450 that I have also work? From the IM it looks like they are different pins, J2-17,-19, -30 and J1-24 for discrete, J1-29, -31, -44 and J2-15 for unswitched, so not just a name change. Also the discrete messages are set up via flightmate which I think is a feature starting with the 450A.

[LANCECASPER]

On 8/25/2023 at 2:56 PM, CMMPilot said:

I do a lot of Cross Country flying which includes a fair amount of Auto Pilot. My trip from Florida (KINF) to DC (KVKX) takes approximately 4 hours, if the wind is right.  I love my EDM 900 and it gives me a level of comfort I didn't have in my previous aircraft without an Engine Monitor. It has saved my on at least 2 occasions where engine trouble caused me to declare an emergency. On a recent flight I was reading a magazine and when I put it down to change frequencies, I noticed the yellow warning light was blinking. A quick scan of the EDM 900 indicated "Low Fuel" which was not a big deal as the alarm is set for 10 gallons (almost an hour of gas) and I still had 20 in the other tank. Although this situation was not a big deal, I started to think about how long the light could've been flashing without me knowing.  I'm sure I was reading for over 5 minutes...

 

I contacted JPI to see if they had a terminal connection for an audible output. NOPE. Just the LED light alarm output.  I asked about adding an audible alarm and he agreed that it wouldn't make any difference if I wired it into the light circuit. The EDM 900 has a 3 wire alarm circuit where the Black wire provides power and the Red (Red Light) and Green (Yellow Light) wires provide ground to complete the appropriate circuit. So if I wired a small speaker with the hot side from the circuit breaker and the ground tied into the red or green wire, I would get an audible alarm when the light was lit. That became my plan, so I wanted to share how I did it. 

 

 

First, I installed the audible alarm by connecting it to the Red Alarm Light. Unfortunately I chose a beeper that was the same sound as my gear alarm, but at least the gear alarm is intermittent and the EDM alarm is continuous, so I know the difference. 

 

Second, I added a second alarm for the Warning (Yellow) circuit. I could have used the same but found a "buzzer" rather than a "beeper" that I liked and it would give me an audible difference for Red (Beeper) and Yellow (Buzzer) alarms.

 

Third, I considered my last Emergency situation where I lost a cylinder at 15,500' and had a 20 minute descent to the closest airport. I think the continuous audible alarm for 20 minutes might ADD to my STRESS rather than help the situation. After all, I am mainly concerned about not noticing an alarm on a long cross country, when I might be reading or watching a movie and only glancing at the panel from time to time. I don't want a "YELLOW" to go unnoticed until it becomes a "RED" or worse. The audible alert solves this issue, but creates another one with extended situations where it may add to the stress. I realize I can "clear" warnings but they do come back after a few minutes and it's one more thing to worry about.
For this I decided to simply install a switch that I can use to silence the audible alarm, but will have no effect on the visual LED alarm.  This was an easy add-on and took me longer to label the panel than it did to install the switch.

Ultimately, it works like a charm and as I designed it so I'm super happy with the results. I feel I have added an additional layer of safety that makes me feel more comfortable on long XC trips.

Piezo Beeper      Buzzer 12V-85dB    VONVOFF Toggle Switch 12V

 

 

I will go over the simple steps I used to complete the task and try to reference the photos.

 

Step 1:  Remove the Glare Shield

Step 2:  Locate the Circuit Breaker for the Engine Monitor and Disconnect

Step 3   Connect a wire to the "cold" side of the circuit breaker

Step 4:  Run the wire to the center of the console, behind the Remote Engine Alarm Light

Step 5:  From the Beeper, Connect the Red Wire to the wire coming from the Circuit Breaker and connect the Black Wire to the Red Wire on the Remote Engine Alarm Light. (The circuit is completed by the EDM 900 connecting the light to ground, therefore, the wire from the circuit breaker represents a "hot" lead and is connected to the Red Wire on the Audible Alarm Beeper. The Black Wire from the Beeper is connected to the Red Wire from the EDM 900 (which drives the Red Warning Light). This is done with an in-line connection, so when the EDM 900 completes the circuit to illuminate the Red Light on the Remote Engine Alarm Light, it also completes the circuit for the Audible Alarm Beeper.)

Step 6:  Repeat Step 5 for the Buzzer on the Green Wire (Yellow Light Circuit)

Step 7:  Wire the switch between the circuit breaker and the hot wire used for both speakers. In this case I used a white wire from the Circuit Breaker and it connected to the Red Wire for each speaker. Opening the switch will disconnect the power to each speaker, so it will not sound when the LED light circuit is grounded. 

Step 8:  Drill a 1/4" hole in the panel to mount the switch and label properly.

Step 9:  Install the Switch into the panel.

Step 10:  Make sure all connections are soldered and protected with shrink wrap tubing.

Step 11:  Zip Tie all loose wires and the Buzzers to the wire loom to avoid entanglement in the controls.

Step 12:  Turn on the Circuit Breaker and Test

Step 13:  Replace the Circuit Breaker in the Panel

Step 14: Replace the Glare Shield

 

***Alarms sound during the initial boot up for the EDM 900, along with the warning lights.

 

Well that's it!  It took less than an hour to complete. Of course, everything was overseen and inspected by my A&P IA.   Ultimately, it works like a charm and as I designed it so I'm super happy with the results. I feel I have added an additional layer of safety that makes me feel more comfortable on long XC trips.   I'll include a couple of images for you to see.

 

Let me know your thoughts and if you would do anything different.

 

Thanks,

Chris  

N231JY

 

 

I thi

 

 

 

Nice schematic and not that an audible warning is a bad idea, but I think I would skip all of those steps and just leave the magazine at home so you can scan the panel to notice the warning light you already have plus keep an eye out for traffic and a spot to land when you lose an engine.

I might listen to XM or music on my phone but on low. Whether on autopilot or not it's my responsibility as pilot in command to stay engaged. Magazines and movies are great when you're a passenger.

[CMMPilot]

I just completed a cross country trip from Florida to Colorado, over the Mountains to tour the Grand Canyon, and back home via Indiana. I spent a lot of this trip at altitude running LOP. If you have a Turbo Mooney, you know that the TIT can start to runaway as the pressure changes or if relative wind changes dramatically. 
 

My point is that the audible alarm was great for alerting me when the TIT started to climb without me touching a single control other than the yoke. Especially in the mountains when I was busy outside the airplane a lot of the time.  Now letting the TIT get above 1620 never lasted more than a few seconds. I’m very happy with this added layer of safety. 
 

there are other obvious advantages for all types of notifications, but this one was most poignant during my recent (30 hours of flying in 4 days) Cross Country trip.

[RoundTwo]

5 hours ago, CMMPilot said:

If you have a Turbo Mooney, you know that the TIT can start to runaway as the pressure changes or if relative wind changes dramatically. 

I can understand how a change in pressure can be felt by the engine, but I’m totally confused how a change in wind can affect an engine. 

[CMMPilot]

No science here, just experience. I was traveling east with a 30kt quartering tailwind that changed to a 35kt direct headwind in less than 30 miles and although I made no power or mixture adjustments the TIT started dropping another 30° LOP.   My guess is the change in wind resulted in a change in pressure. But maybe you’re right, it was probably the other way around…

[LANCECASPER]

On 11/11/2023 at 9:53 AM, CMMPilot said:

I just completed a cross country trip from Florida to Colorado, over the Mountains to tour the Grand Canyon, and back home via Indiana. I spent a lot of this trip at altitude running LOP. If you have a Turbo Mooney, you know that the TIT can start to runaway as the pressure changes or if relative wind changes dramatically. 

 

17 hours ago, CMMPilot said:

No science here, just experience. I was traveling east with a 30kt quartering tailwind that changed to a 35kt direct headwind in less than 30 miles and although I made no power or mixture adjustments the TIT started dropping another 30° LOP.   My guess is the change in wind resulted in a change in pressure. But maybe you’re right, it was probably the other way around…

In 30 years of flying turbo airplanes I've never seen that happen. The engine has no idea whether you have a headwind or tailwind.

The first three of those thirty years were in a Mooney 231  (without a Merlyn Automayic Wastegate Controller). It was a little finicky and small power adjustments had to be made in cruise but not much, I see that you have the Merlyn in 231JY. If it's working properly you shouldn't have to make many adjustments. 

[RoundTwo]

23 hours ago, CMMPilot said:

No science here, just experience. I was traveling east with a 30kt quartering tailwind that changed to a 35kt direct headwind in less than 30 miles and although I made no power or mixture adjustments the TIT started dropping another 30° LOP.   My guess is the change in wind resulted in a change in pressure. But maybe you’re right, it was probably the other way around…

You’re in good company because there are a lot of pilots and boaters that believe their vessel is somehow aware of how the media they’re operating in is moving relative to the earth.

[CMMPilot]

Okay guys…I’m the first to admit I’m naïve about many aspects of Flying, still relatively new and wanting/willing to learn so constructive feedback is always humbly appreciated. 

[CMMPilot]

On 11/12/2023 at 5:54 AM, LANCECASPER said:

 

In 30 years of flying turbo airplanes I've never seen that happen. The engine has no idea whether you have a headwind or tailwind.

The first three of those thirty years were in a Mooney 231  (without a Merlyn Automayic Wastegate Controller). It was a little finicky and small power adjustments had to be made in cruise but not much, I see that you have the Merlyn in 231JY. If it's working properly you shouldn't have to make many adjustments. 

I wish I had 30 years behind the yoke!  I do have a Merlyn so you’re telling me it may not be working correctly?  On the recent XC trip, I had to make minor adjustments to the mixture at least every 20-30 minutes on a 3 hour flight. I would set the TIT at 1590 (about 50° LOP) ,with a smooth running engine. It would remain relatively stable for a while, but then would start either climbing (richer) or descending (leaner) in Temp on its own, and I would have to make a small adjustment back. 
it was definitely not as stable as when I run ROP. Should I have someone look at the Merlyn?

[LANCECASPER]

49 minutes ago, CMMPilot said:

I wish I had 30 years behind the yoke!  I do have a Merlyn so you’re telling me it may not be working correctly?  On the recent XC trip, I had to make minor adjustments to the mixture at least every 20-30 minutes on a 3 hour flight. I would set the TIT at 1590 (about 50° LOP) ,with a smooth running engine. It would remain relatively stable for a while, but then would start either climbing (richer) or descending (leaner) in Temp on its own, and I would have to make a small adjustment back. 
it was definitely not as stable as when I run ROP. Should I have someone look at the Merlyn?

That sounds about right from back when i flew my 231 without the Merlyn, but @jlunseth has a lot of time in a 231 and maybe we can get him to chime in

[jlunseth]

I am in the process of getting a new engine. The old engine would require a few minor adjustments when LOP but would eventually settle down after a couple of adjustments. We will see what the new engine does. I can't say that the adjustment issue was any different ROP than LOP though. The real difference is that when LOP and you are trying to stay right at or under 1600 TIT, a few tenths of a GPH makes a difference. So my typical fuel flow is 11.1-.3. If it goes to say 11.6 or .7, especially in warm conditions, that can push the TIT over 1600 and I might intervene and do something about it. The same kind of variation when ROP has an insignificant effect on TIT because TIT is already about 100 dF cooler ROP than LOP, that is the nature of LOP ops. Being in the vicinity of 20-60 dF lean of peak is equivalent to being in the vicinity of 125 dF or more ROP, so a small variation is not significant (I am talking about our TSIO360LB in real life now, the GAMI people would suggest a significantly greater ROP number, like 160 dF, which doesn't work well in our engine). We will see what the new engine does.

I should also say that those variations, say from 11.1 to 11.6 or .7, eventually go the other way in my experience and the fuel flow goes back down. I just consider making the adjustments to be a part of flying LOP with the 231 engine and systems, which are somewhat primitive compared to the later turbo'd Mooneys. Remember that the 231 does not have an automatic wastegate controller, so if the output of the turbo drifts up because of some condition, it is up to the pilot and not the wastegate controller to adjust for it. There are a couple of general categories of things that affect this. One, in my experience the slick Mooney airframe will keep accelerating at a slow pace for some time once at cruise, and that acceleration increases ram air, which increases MP, which increases FF in the 231 system. Two, you will run into atmospheric variations that speed up or slow down the aircraft or change the pressure, and again, if you want to adjust for it to keep your FF on the nut, that is up to you and not the wastegate controller. Three, the system is just not as smooth as later Mooneys, but it still works great.

[CMMPilot]

6 hours ago, jlunseth said:

I am in the process of getting a new engine. The old engine would require a few minor adjustments when LOP but would eventually settle down after a couple of adjustments. We will see what the new engine does. I can't say that the adjustment issue was any different ROP than LOP though. The real difference is that when LOP and you are trying to stay right at or under 1600 TIT, a few tenths of a GPH makes a difference. So my typical fuel flow is 11.1-.3. If it goes to say 11.6 or .7, especially in warm conditions, that can push the TIT over 1600 and I might intervene and do something about it. The same kind of variation when ROP has an insignificant effect on TIT because TIT is already about 100 dF cooler ROP than LOP, that is the nature of LOP ops. Being in the vicinity of 20-60 dF lean of peak is equivalent to being in the vicinity of 125 dF or more ROP, so a small variation is not significant (I am talking about our TSIO360LB in real life now, the GAMI people would suggest a significantly greater ROP number, like 160 dF, which doesn't work well in our engine). We will see what the new engine does.

I should also say that those variations, say from 11.1 to 11.6 or .7, eventually go the other way in my experience and the fuel flow goes back down. I just consider making the adjustments to be a part of flying LOP with the 231 engine and systems, which are somewhat primitive compared to the later turbo'd Mooneys. Remember that the 231 does not have an automatic wastegate controller, so if the output of the turbo drifts up because of some condition, it is up to the pilot and not the wastegate controller to adjust for it. There are a couple of general categories of things that affect this. One, in my experience the slick Mooney airframe will keep accelerating at a slow pace for some time once at cruise, and that acceleration increases ram air, which increases MP, which increases FF in the 231 system. Two, you will run into atmospheric variations that speed up or slow down the aircraft or change the pressure, and again, if you want to adjust for it to keep your FF on the nut, that is up to you and not the wastegate controller. Three, the system is just not as smooth as later Mooneys, but it still works great.

This is great information!  I already noticed the relationship between FF and TIT when LOP. All of this makes sense, especially when considering how old this tech really is.  I stress a lot about running the turbo too hard or causing some sort of failure because I let the TIT or MP get too high. Thats why (and the original reason for my post) the Audible alarm was a nifty addition (I thought) to help me prevent those situations. 
Hope the new engine treats you right!

[jlunseth]

I use 1600 as my personal limit. I try to keep the TIT under that and will make adjustments as necessary, but I am not manic about it. If the TIT goes a little over 1600 and is stable it does not worry me. The experts tell us that the turbo is ok as long as you stay under the redline (1650 for ours). The turbo in my old engine was somewhere around 1500 hours or more since overhaul, I would regularly have my A&P check it for wear and it was fine. I did notice that if the temps started to rise above 1600 and were difficult to control that they would just keep rising. That might happen if I was in the higher altitudes where cooling is poor. I would just fly ROP in that event.