[WingsOnWheels]

Maybe I am doing something I'm not supposed to, but I am having an issue with the contact inputs on the dynon.

I have some LED annunciator legend lights on my panel. These lights have a common power source and the ground is connected to a contact input. On a couple of these I also connected the contact input to the Dynon EMS.

While testing the lights if one of the two contacts tied to the EMS was connected to ground, both of the lights would illuminate. If I unplugged the EMS, all the lights would work correctly.

Right now, power and ground are not connected to the EMS. I was testing the lights using a battery so there is no common ground between the EMS and contact input.

Has anyone else seen this? Is it just a result of testing part of the system without having everything hooked up?

Thanks,

 

[vlittle]

Maybe I am doing something I'm not supposed to, but I am having an issue with the contact inputs on the dynon.

I have some LED annunciator legend lights on my panel. These lights have a common power source and the ground is connected to a contact input. On a couple of these I also connected the contact input to the Dynon EMS.

While testing the lights if one of the two contacts tied to the EMS was connected to ground, both of the lights would illuminate. If I unplugged the EMS, all the lights would work correctly.

Right now, power and ground are not connected to the EMS. I was testing the lights using a battery so there is no common ground between the EMS and contact input.

Has anyone else seen this? Is it just a result of testing part of the system without having everything hooked up?

Thanks,

Hi Colin. A similar issue was actually covered in the SkyView forum on the Dynon site.

First of all, you shouldn't be putting signals into the EMS without it powered on. If you do, it may 'self power' from one or both of the inputs.

The inputs to the EMS are 5 volt tolerant, but your LEDs are pulled up to 12 volts. This means that the input protection in the EMS is being turned on, and current is flowing from the 12 volts, through the LED and into the EMS clamped at 5 volts.

The solution is to put diodes in series with the EMS inputs. Almost any type will work, just "point it" away from the EMS. This blocks the current from flowing into the EMS input, but still allows it to be pulled low when the contact is activated. It also means that you don't have to have the EMS on for the annunciators to work.... which is the whole point, I think.

I think this is the root of the problem.

Cheers, Vern

 

[WingsOnWheels]

Vern,

Thank you for the input I'll add the diodes as you suggested.

I don't see how (during this test) the EMS could pull current through the LED. The EMS and the contact input aren't currently connected to any common ground or power source. It looks more like the EMS is grounding the two contact inputs together so Light #2 is being grounded through Light #1 contact input within the EMS. This may be part of the issue with test with the EMS unpowered.

Either way, the diodes should fix the issue. I'll find out for sure when I finish the wiring and do fuctional testing with everything connected (soon hopefully).

Thanks,

 

[WingsOnWheels]

Fyi for anyone else with this issue, the diode did the trick. Installed with the stripe away from the ems. Thanks again for the help.

 

[n82rb]

another issue I came up against installing the ems. the contact inputs are 5V and can tolerate up to 15V. for monitoring a on off function ie a fuel pump or pitot heat many people are just feeding 12v off the switch to the contact. If your alternator goes a little high, over 15v, you risk frying the ems. My solution was to take the 12v input from the switch (fuel pump on, pitot on ect) and run it through 2 10k resistors in series with the other end tied to ground. take the contact input from between the resistors. the voltage will be 1/2 the input , 6v so even with a slightly high alternator output the voltage will never be high enough to hurt the EMS. current is less than 1/2 millamp so no problem there. cheap insurance for the EMS.

bob burns
RV-4 N82RB

 

[Dynon]

Bob,
If we spec something at 15V, you can feel comfortable that it meets the DO-160 spec for 12V airplanes, which requires tolerance up to 30V. So while what you did works, it isn't totally needed. You won't kill the EMS if your alternator dies and you get 18V.

--Ian Jordan
Dynon Avionics

 

[n82rb]

ian, thanks for the reply. you need to make sure that everybody in tech support is on the same page. I went that route because I called support to ask about the contacts internal pull up when monitoring a voltage with and inductive load. who ever I talked with put the fear of god into me that I could destroy the EMS above 15v period and said that was not a good way use the contact input, it should only be used with 5v only. that surprised me because your support forum mentioned monitoring the voltage that way, and as robust as your products are, i assumed that the design had protections for that situation.

bob burns
RV-4 N82RB

 

[Taildrgr]

I was wondering if you could use the EMS contact input to monitor something like a pump by using a DPDT switch with one throw to turn the pump on and one throw to just close a contact to ground through the EMS?

 

[n82rb]

that would work. you can also monitor the voltage going to the pump. the only problem is that the internal pull up will try to pull the line high when the power is off because of the inductance of the motor. there is not a true path to ground through the motor to pull the line down. you could use the voltage divider i used, or an external pull down resistor on the monitor line to pull it down.

bob burns
RV-4 N82RB

 

[Dynon]

Bob Butley,
You generally can just hook to the + wire from your pump to the EMS input. Our experience has not been generally the same as Mr. Burns'. A DC motor has a very low impedance to ground, and thus when off you see about 0V, and when on you see 12V. The EMS can deal with this just fine. If it really was able to pull the voltage of the motor up, the motor would run!

The method of a DPST or DPDT switch also works fine, but is some extra complexity.

Bob Burns,
I'll make sure our phone tech support is more aware of the EMS contact voltage restrictions.

 

[WingsOnWheels]

I was wondering if you could use the EMS contact input to monitor something like a pump by using a DPDT switch with one throw to turn the pump on and one throw to just close a contact to ground through the EMS?

For some of the overvoltage reason Bob mentioned, I used a DP switch for the boost pump and connected one side to ground. Looks like I could have saved myself the trouble now. Not a big deal though, does the job as-is.

 

[KRviator]

I was wondering if you could use the EMS contact input to monitor something like a pump by using a DPDT switch with one throw to turn the pump on and one throw to just close a contact to ground through the EMS?

That is exactly what I did for my P-Mag kill switches. DPDT, one side switches the P-Mag, the other side grounds the EMS contact input.

In the same manner, I had several unused pins on the EMS and connected a pair of them to the 12V input at the Pmag itself, so I can also assure they're powered up by the aircraft. Four green dots = both ignitions alive and on.

 

[GalinHdz]

In the same manner, I had several unused pins on the EMS and connected a pair of them to the 12V input at the Pmag itself, so I can also assure they're powered up by the aircraft. Four green dots = both ignitions alive and on.

I am about to convert from SLICK mags to dual P-Mags so I have a few questions.

1 - Why four green dots instead of just two (one green dot for each mag)?
2 - Which pins did you use in your harness?
3 - Did you just wire the +12v directly to the unused pins?
4 - What is your pin configuration?
5 - How did you wire up the P-Mags to provide tach input to the EMS?

 

[KRviator]

I'm away from the plane for a couple of weeks for work so can't give you the pin detail, but from memory, they were simply four unused GP pins. The manual says that if you stick 5V+ into a standard pin, it'll accept 12VDC, but max out at 5. Thats all I did, and make my On/Off cutoff at 2 Volts from memory.

The Ignition On switches are DPDT, and switch the EMS contact to ground. The PMag power source is taken from the Ships Power wire at the Pmag itself as a guarantee that the mag is actually powered, not just 'should be' powered.

The 4 dots are made up of 2 x Ignition on & 2 x Ignition powered.

The Dynon Left & Right tach input is designed for a standard 12VDC tach source, so all I did was wire straight from each P-Mag into the respective pins, 32/33 from memory.

 

[GalinHdz]

I'm away from the plane for a couple of weeks for work so can't give you the pin detail, but from memory, they were simply four unused GP pins. The manual says that if you stick 5V+ into a standard pin, it'll accept 12VDC, but max out at 5. Thats all I did, and make my On/Off cutoff at 2 Volts from memory.

The Ignition On switches are DPDT, and switch the EMS contact to ground. The PMag power source is taken from the Ships Power wire at the Pmag itself as a guarantee that the mag is actually powered, not just 'should be' powered.

The 4 dots are made up of 2 x Ignition on & 2 x Ignition powered.

The Dynon Left & Right tach input is designed for a standard 12VDC tach source, so all I did was wire straight from each P-Mag into the respective pins, 32/33 from memory.

THANKS! This really helps!

Did you wire the EMS tach input to the P-Mag tach output (pin 6) or to the "P" Lead pin like with other magnetos?
But I still don't understand why 4 dots. Why didn't you use just 2 dots. Green if there is +12v to that mag, Red if there is no voltage to the mag?

 

[KRviator]

THANKS! This really helps!

Did you wire the EMS tach input to the P-Mag tach output (pin 6) or to the "P" Lead pin like with other magnetos?
But I still don't understand why 4 dots. Why didn't you use just 2 dots. Green if there is +12v to that mag, Red if there is no voltage to the mag?

I used the P-Mag Tach output. It will provide a Tach signal even if that P-Mag is not providing a spark. The Dynon EMS is setupFTP accept 2 RPM inputs so that makes things easy.

Two - one left & one right - contact input dots tell me if the ignition is hot/providing spark (green) or disabled (Red). This is sourced from one side of the DPDT ignition switch, so the switch could be "ON" but a failure of the P-Mag would inhibit the spark. Unlikely but a possibility. It is more for my peace of mind in that I can have the 20% EMS page up for takeoff, and look down a series of green dots to satisfy myself everything is as it should be.

And the other two tell me if I have 12V power (IIRC I've actually set up as >3V) at each P-Mag ships power input. Green if ships power is available, red if it isn't.

 

[GalinHdz]

I used the P-Mag Tach output. It will provide a Tach signal even if that P-Mag is not providing a spark. The Dynon EMS is setupFTP accept 2 RPM inputs so that makes things easy.

Two - one left & one right - contact input dots tell me if the ignition is hot/providing spark (green) or disabled (Red). This is sourced from one side of the DPDT ignition switch, so the switch could be "ON" but a failure of the P-Mag would inhibit the spark. Unlikely but a possibility. It is more for my peace of mind in that I can have the 20% EMS page up for takeoff, and look down a series of green dots to satisfy myself everything is as it should be.

And the other two tell me if I have 12V power (IIRC I've actually set up as >3V) at each P-Mag ships power input. Green if ships power is available, red if it isn't.

OK, that makes sense. I start on my P-Mag install next week. Wish me luck.

 

[GalinHdz]

And the other two tell me if I have 12V power (IIRC I've actually set up as >3V) at each P-Mag ships power input. Green if ships power is available, red if it isn't.

How did you wire, set up and configure the 12V dots? I really want to do this.

 

[KRviator]

Wiring was dead simple, as I've got the Dynon harness. Run wires 4 & 23 through the firewall, strip & twist the end of wire 4 to the power wire for the right P-Mag and install it in the P-Mag's 6-pin connector, then do the same for wire 23 and the left P-Mag.

Why these wires in particular? Because I'm not the sharpest tool in the shed, and these wires colours correspond with the Tach-input wires, that is, white/blue for the right tach, and purple/blue for sensing the power supply to the right P-Mag, white/green for the tach input on the left, with purple/green for the power sense wire.

Once you've done that, configure these two input pins as contact pins, with the ranges 0-2.5 Volts as Red, and 2.5-5.0V as Green. Ranges 3-5 "Enable" option should be set to "No". You are in fact putting 12V into the EMS, however, it is rated to accept this, even though the sensor range maxes out at 5.0V, so even though you're putting in 12V, the most you can detect is 5.0 volts, hence the 2.5V changeover point.

I can't remember if it was the 12V P-mag power input or the ignition switch contact input, but during testing I do remember one of them stayed high a second or two after selecting the switch "Off", so I changed the 2.5V changeover point to 3 or 4 volts - might have even made it 4.5 volts - in order to bring the alarm closer to the trigger point. This is something you'll have to test in the setup diagnostics - monitor the actual input to the pins as you shutoff ships power to the P-Mags and see how long it takes.

Set the alarm option to self-clearing, as you don't want to do your run-up and power test and then have to clear 4 alarms afterwards.

 

[GalinHdz]

Wiring was dead simple, as I've got the Dynon harness. Run wires 4 & 23 through the firewall, strip & twist the end of wire 4 to the power wire for the right P-Mag and install it in the P-Mag's 6-pin connector, then do the same for wire 23 and the left P-Mag.

Why these wires in particular? Because I'm not the sharpest tool in the shed, and these wires colours correspond with the Tach-input wires, that is, white/blue for the right tach, and purple/blue for sensing the power supply to the right P-Mag, white/green for the tach input on the left, with purple/green for the power sense wire.

Once you've done that, configure these two input pins as contact pins, with the ranges 0-2.5 Volts as Red, and 2.5-5.0V as Green. Ranges 3-5 "Enable" option should be set to "No". You are in fact putting 12V into the EMS, however, it is rated to accept this, even though the sensor range maxes out at 5.0V, so even though you're putting in 12V, the most you can detect is 5.0 volts, hence the 2.5V changeover point.

I can't remember if it was the 12V P-mag power input or the ignition switch contact input, but during testing I do remember one of them stayed high a second or two after selecting the switch "Off", so I changed the 2.5V changeover point to 3 or 4 volts - might have even made it 4.5 volts - in order to bring the alarm closer to the trigger point. This is something you'll have to test in the setup diagnostics - monitor the actual input to the pins as you shutoff ships power to the P-Mags and see how long it takes.

Set the alarm option to self-clearing, as you don't want to do your run-up and power test and then have to clear 4 alarms afterwards.

THANKS! I will be doing the wiring connections today so this information came at the perfect time.

 

[GalinHdz]

Wiring was dead simple, as I've got the Dynon harness. Run wires 4 & 23 through the firewall, strip & twist the end of wire 4 to the power wire for the right P-Mag and install it in the P-Mag's 6-pin connector, then do the same for wire 23 and the left P-Mag.

Why these wires in particular? Because I'm not the sharpest tool in the shed, and these wires colours correspond with the Tach-input wires, that is, white/blue for the right tach, and purple/blue for sensing the power supply to the right P-Mag, white/green for the tach input on the left, with purple/green for the power sense wire.

Once you've done that, configure these two input pins as contact pins, with the ranges 0-2.5 Volts as Red, and 2.5-5.0V as Green. Ranges 3-5 "Enable" option should be set to "No". You are in fact putting 12V into the EMS, however, it is rated to accept this, even though the sensor range maxes out at 5.0V, so even though you're putting in 12V, the most you can detect is 5.0 volts, hence the 2.5V changeover point.

I can't remember if it was the 12V P-mag power input or the ignition switch contact input, but during testing I do remember one of them stayed high a second or two after selecting the switch "Off", so I changed the 2.5V changeover point to 3 or 4 volts - might have even made it 4.5 volts - in order to bring the alarm closer to the trigger point. This is something you'll have to test in the setup diagnostics - monitor the actual input to the pins as you shutoff ships power to the P-Mags and see how long it takes.

Set the alarm option to self-clearing, as you don't want to do your run-up and power test and then have to clear 4 alarms afterwards.

I completed the P-Mag installation today and it was exactly as you stated. With the engine off it takes about 1 second for the GREEN dots on the EMS page to turn RED when I cut the +12V power to each P-Mag.

The engine turned on within 1 propeller rotation when it used to spin 2-3 times before it turned on. This was a nice surprise. My Lycoming O-360-A4M has always run very sooth but it is even smoother now, all the way down to below 800RPMs.

During the test flight I noticed the peak EGT on all 4 cylinders is now about 30-40F lower than before. I suppose this is due to a more complete fuel burn within the cylinders. I also notice that if I cut the +12V to the P-Mags with the engine running, the GREEN dots on the EMS page don't turn RED. I suppose this is because at that point the EMS senses the +12V provided by the internal generator so the GREEN dots stays GREEN.

Needless to say I am very satisfied with the results. THANKS for all your help.