P-Mag capability demo

[larrynew]

Έλληνας για μένα.

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[Brantel]

I had a few flights this weekend with the Pmag display and the results are very promising.

The Pmag display is plug and play, plug in the Pmag serial line, add power and it just works. The Pmag display automatically negotiates with the Pmag and puts it into data stream mode.

Most of the data points are working very well. I have sent the following to Tom and Brad at EmagAir. There are a couple more questions about their data format I need in order to finish this up 100%...I put ???? in place of the command codes since I am not at liberty to disclose those.

"Hey Tom,

I am close to finishing the code to parse the data streaming from the PMag..

RPM - Works 100%, EICAD seems to display in multiples of 10 but the data has good resolution so I combine the two bytes and display them as is.

ADV ? Works 100%, Found out there is a multiplier required and some rounding errors in the display on EICAD so I just decided to multiply the HEX number by 1.4 and display the value as a float instead of rounding. This gives me an output in this format ##.#? Seems the EICAD rounds the output, the multiplier was tough to reverse engineer but I used EICAD to help figure it out. Seems EICAD will never display 23,26,30,33,37,40 or 44 due to the rounding errors...

MAP - Still not sure if this is manifold pressure or not. Seems at low power it always reads 0 and goes up to 31 as the power comes up but it does not match my MAP gauge in the plane so I am not sure. Can you shed some light on what this data is and how to correctly display it? This one has been the most challenging one to figure out what is going on since I do not have anything to reference it to?.

MODE - I am just displaying whatever it shows. Currently I have noticed it is a 01 when in setup mode and 00 when in running mode. Is this correct? Are there any more modes other than 00 and 01?

VOLTS ? Works 100% after I figured out the voltage always reads 1 volt below ships power and that the resolution of the data is down to a tenth. I am displaying this as a float in this format ##.#

TEMP ? Works 100%

C1 ? Works 100% from 0 to 99, but I do see that my Pmag always runs low on the scale even though I know everything is ok, the max I see is around 22-24, but at high power it drops to 0-5.

C2 ? Works 100% from 0 to 99, but I do see that my Pmag always runs low on the scale even though I know everything is ok, the max I see is around 22-24, but at high power it drops to 0-5.

My goal was to have my display mirror the readings I get when I connect EICAD in parallel with the data stream. So far I have reached this goal but I did away with the rounding error on the ADV variable, display RPM with a resolution of 1 instead of 10 and display VOLTS down to the tenth.

Since EICAD does not display MAP or MODE, I do not have anything to compare to in order to ensure my data display is correct, your help would be appreciated on these?

This device I am creating is intended to replace the need for carrying a laptop on the airplane to monitor the P-Mag. Most laptops are almost impossible to read out in the daylight. This device will be about the size of a pack of cigarettes and is plug and play. Plug it into the Pmag data line, power it up and it starts working?no buttons to press at all. It does not send any commands for safety reasons other than ?????? and ?????? to start the streaming mode. I am about 95% there with it and just need a few more bits of info as requested above to finish it. At this point I do not intend to sell these, for now it is for my own personal use.

Best regards and thanks for your help in advance?The ignition is working great!

Brian C."

This is where this is at at the moment. I will shoot some in flight video once I get answers to the above questions....

[elippse]

I can see eventually being able to send text messages to your ignition from your i-phone and asking it how the engine seems to be running. At an advanced stage, if the ignition thinks something doesn't seem right, it could send you a priority text advising of what it thinks is wrong. Finally you can go the full AirBus route and have it fly the plane from takeoff to landing; all that you'd have to do is text it before takeoff with where you want to go. Just don't send it any text that might not agree with what it's doing, as it just might totally takeover and eject you. HAL! HAL, do you hear me?

[TCONROY]

Not sure where you are picking up RPM out of, but be aware that the RPM out of the RS-232 data stream is not 100% accurate. We ran into this with several customers that had their laptops connected to the Pmag and the RPM indicated was different than what our EFIS was showing. Talked to Pmag and they said the indication out of RS-232 doesn't have a very fast sample rate and is subject to error.

[Brantel]

I flew with it the other day and it is accurate enough for monitoring purposes. In a steady state, the P-mag output always matched my Dynon 100%. The RPM out of the P-mag is displayed in their EICAD program with a resolution of 10 rpm. The serial data has it in a resolution of 1 rpm and I am displaying it that way. The EICAD RPM display can be wrong by a significant amount due to rounding errors. I do not round the RPM display....

The rate at which the P-mag sends data is about once a second so if you are rapidly changing RPM it will not keep up.

Again this is for monitoring purposes and is not intended to replace a normal RPM readout. I display it just because it is there in the data stream.

[RVG8tor]

Brantel,

What are you using to get RPM data to the Dynon? I will have a dual P-Mag setup and I thought I could hook up the wire from the Dynon to the P-Mag to get RPM sent to the Dynon 180 (I assume you just use one of the P-Mags for this). Are you saying this is not accurate, or is there an RPM connection and also RPM data sent via the serial signal? Thanks for any help?

Also curious if there is a need for a Hobbs meter with the Dynon products.

Originally Posted by Brantel

I flew with it the other day and it is accurate enough for monitoring purposes. In a steady state, the P-mag output always matched my Dynon 100%. The RPM out of the P-mag is displayed in their EICAD program with a resolution of 10 rpm. The serial data has it in a resolution of 1 rpm and I am displaying it that way. The EICAD RPM display can be wrong by a significant amount due to rounding errors. I do not round the RPM display....

The rate at which the P-mag sends data is about once a second so if you are rapidly changing RPM it will not keep up.

Again this is for monitoring purposes and is not intended to replace a normal RPM readout. I display it just because it is there in the data stream.

[Brantel]

My RPM display on the Dynon is fed from the Tach signal of the P-Mag on the right side and the P-Lead thru a resistor of the regular mag on the left side. Has nothing to do with the serial output from the P-mag...

If you have dual P-mags, you can hook up both sides to the Tach signal on each P-mag and be Golden.

With a dual P-mag system, you really only need to hook up one side since the tach signal is there even when the P-mag P-lead is grounded. Nothing wrong with hooking em both up though...

The RPM is also output over the serial output in the serial stream.

I have found the tach signal very accurate and the serial RPM accurate enough.

The Dynon has a built in Hobbs meter. No need for an external one.

[PaulR]

I have on P-Mag and one Slick. Is there any reason to pick up the tach signal anywhere EXCEPT the P-Mag. My understanding is the only time it doesn't put out a signal is when it's not powered. Seems like the only time that will happen is very low RPM's and the master is off or the breaker pulled.

[Brantel]

No reason that I can tell.. I did both just because I was too lazy to remove the other one that was already connected to the left mag....

[Jim Wright]

I am not interested in programming electronic mags, I just want to know that BOTH are working and if one fails I am advised. I don't want to unknowingly be flying around on one mag.
Is there a simple monitoring system available?
Jim Wright