Dynon and Voltage

I am going to ask here because do many of you fly with the Dynon products.

I am testing and getting to know my panel today and noticed something odd. I have a D180 and D10A. When I bring up the EMS info on the D10A the voltage on it is different from what I see on the D180 by about .6V higher.

I found this odd since I thought the EMS info on the D10A was just a repeat of the info on the D180. Anyone seen this before? the big question is what is the real voltage, I am using a power supply putting out 13.8 volts. The D180 reads 12.6 and the D10A reads 13.4.

The only thing I can think of is that the D180 is on my E-bus and the power to it goes through a diode to prevent back flow of power when feed via an alternate feed path. The diode does cause a voltage drop, but I thought the D10A when on the EMS page is just repeating what is on the D180.

Multiple possibilities here.

1. Bad Grounding
2. Dynons are configurable. Do either of the units have an internal backup battery? If so, you may be reading internal voltage on one of the units. Check your configuration.
3. Bad Grounding.
4. Did I mention Bad Grounding?

The 10A has three different inputs for voltage plus an internal battery:
Primary Power
Keep Alive Power
External Backup Power

The display can be enabled to show Master Voltage (M), External Backup Voltage (E), and Internal Battery Voltage (I).

Measure the first two voltages at the D10A connector pins. Mine are within 0.1V of what is displayed. If you happen to have an old RS-232 type of break-out box, you can attach it in-line with the Dynon unit and measure the voltages while the unit is powered on.

If the power to the two different Dynon units comes from two different sources, then you must determine (measure) each voltage at its source.

It sounds like the voltage drop across the E-bus diode. I noticed a similar voltage drop on my e-bus system. Try turning your e-bus switch on to connect the e-bus direct to the main battery line (effectively bypassing the diode) & see if the voltmeters read the same then.

I ended up fitting a Schottkey diode from perihelion Design as it has a much lower voltage drop & so keeps my EMS & EFIS voltmeters more-or-less in line.

Dave

I thought it repeated

I know why there is a voltage difference between what the busses supply and it is due to the drop through the diode.

My surprise was when I put the D10A to display EMS information my understanding was that this is repeated from the D180, it is obvious now that it uses local voltage information from the screen it is displayed, at least for voltage information. I will try the alternate feed path just to confirm this for myself.

Run with E-Buss Always On?

Just discovered the same thing. the voltage on the E-buss is about a 1 lower than battery, and main busses. They're the same when the E-buss switch is closed. Probably going to normally operate by closing both the main buss and E-buss switches (basically the Nuckolls Z-11 circuits), then all Skyview operation, back up battery charging and system sensing will be actual battery voltage.

Not how I anticipated it, but, if an electrical problem requires operation on the E-buss only, I would now only have to open the main buss switch as the E-buss would already be hot.

What do you think? I don't really want to spend an other $100 for a shotsky and I don't want the EFIS running on the main buss.

Mike,

I have a D-100 and a D-120, which are both on my Ebuss. I am experiencing the same as you.

This is a head scratcher since my understanding is that the EFIS is retrieving the voltage reading from the EMS and just displaying the resultant value.

Obviously this is not the case and the EFIS is either performing some operation on the data retrieved or using a source other than the source used by the EMS.

Good question for the Dynon folks.

MD

It does repeat stuff that is not native to the screen that is available on the other screen if they are networked together.

In this case that screen has it's own voltage monitoring circuit and that is what you are seeing.

Brantel is exactly correct. All of the EMS data is repeated from the D180 to the EFIS-10A, except for the voltages which are available locally. On the EFIS-D10A display, if you switch to the primary flight page and have voltage data turned on, it should match what it shows on the EMS page.

-Robert
Dynon