Help with EMS pinouts - custom sensors, SDS EFI

[lgabriel]

Hello!

I have an EMS-220 with an EMSKIT-L4F probe set that's going on a Lancair 360.  I'm sketching out what pins to use for everything, and I'm out of ideas.

In addition to everything in the probe kit, I want to install the following:
[list bull-blackball][*]Left Fuel Quant: VM probe with Princeton converter, 0-5V
[*]Right Fuel Quant: VM probe with Princeton converter, 0-5V
[*]PLX AFR: 0-5V
[*]High side hydraulic pressure.  I can't post links yet, but search Mouser.com for M7139-03KPN-500000, 0.5-4.5V
[*]Low side hydraulic pressure.  Same sensor, 0.5-4.5V
[*]Three landing gear indicators, contact type
[*]Two ECU fault indicators...this one is a bit tricky (see below)
[/list]
It's my understanding that there are only four pins (type C) that support 0-5V sensors: 8, 22, 23, and 31. Here are my questions regarding this:
[olist][*]The probe kit uses pin 8 for fuel px, which is similar in type to the oil px sensor which uses pin 6 (type B).  Can I move the fuel px sensor to pin 4 (type A), and therefore clear up a type C pin?
[*] Is there some secret way of not using type C inputs for the princeton type fuel probes?
[*] Can I use a non-type C contact (with a pull-up resistor) for the hydraulic px sensors, and somehow calibrate out any bias the resistor would add?
[*] Does anyone have any bright ideas for monitoring all this stuff?
[/olist]
As for the ECU fault indications...when the ECU wants to notify you of a fault, it sends one of its pins to ground.  The traditional way of dealing with this is to supply a lamp with 12V, then connect the ground side of the lamp to the pin.  Here's what I'm wondering:
[list bull-blackball][*]Can I just connect the ECU fault pin to the EMS, and have it alarm when the pin is shorted to ground?  Or do I have to build a pull-up circuit outside of the EMS first?
[/list]
Thanks for your time!

Louis

 

[dynonsupport]

Louis,
Sounds like you have done your research and know our product pretty well. Good job on that!

1) You can move Fuel Pressure to pin 4 no problem.

2) There is no secret way to move the Princeton off the type C's. The non-secret way would be to build a buffer that could sink current not just source it.

3) Yes, and in fact we do this with our own Kavlico sensors. They are nominally 0.5-4.5V as well, but when faced with a 10K pull-up to 5V, they become a little bit non-linear. For our 3 PSI sensor, the table looks like this:

c_x4=0
c_x3=0.0019134861181372
c_x2=-0.0123881586776756
c_x1=0.778681361977834
c_x0=-0.417515868206885

So in that example, if it was linear, 0.5V would be 0 PSI and 4.5V would be 3PSI. But the pull-up distorts it and requires the above. Pretty sure if you multiply everything by 1,000 you will get a 0-3,000 PSI sensor.

Now, the above is for Kavlico sensors. You may want to see if you can find one so that you can just use our equations and history with them instead of needing to verify a new brand yourself.

4) Yes, see above

You can just hook the ECU outputs to the EMS contact inputs. The EMS has a 10K pull-up for contact inputs, so it should just work, assuming the ECU is an open collector output.

I think your only real issue here is if you will run out of the 13 general purpose inputs we support, and you probably will. Above you list 10 inputs, and you don't have fuel pressure, oil pressure, or oil temp in there. Well, maybe you will juuuuuust make it... MAP, RPM, Amps, Batt volts all have their own pins so maybe you are OK.

If you are willing to hack up the sensor file, I believe it is possible to use Pin 2, the volts 2 input for whatever you want as well, but it has a lot lower resolution since it's a 0-36V input instead of 0-5V.

Sounds like a fun airplane. Can we get a ride?

 

[lgabriel]

Wow, thanks for the immediate and detailed response.  You guys are awesome!

It looks like Kavlico makes an appropriate sensor (PTA5000-3000-2-B).  Now if I could just find someone who sells it...

For anyone who's curious, here's what my pin table looks like:

1. Left Bus Voltage
2. Right Bus Voltage
4. Fuel Px
6. Oil Px
7. Oil Temp
8. AFR
9. NLG
10. LMG
11. RMG
12. CHECK ENG L
14. Fuel Flow 1 (out)
15. Power for FF1, FF2
18. Power for Fuel PX, Oil PX, MAP sender, Hyd 1, Hyd 2
19. Fuel Flow 2 (return)
20. CHECK ENG R
21. Hyd Hi
22. Hyd Lo
23. L Fuel Quant
24. Amps +
25. Amps -
26. MAP
31. R Fuel Quant
34. L ECU RPM
35. R ECU RPM

I'll use a VP-X for flap and trim position inputs.

You betcha!  Just as soon as I crawl out from under this mountain of engine sensors I'm amassing. 

Louis

 

[mmarien]

Louis - I see you have SDS EFI. Is that the EFII system or did you build it yourself? How did you handle switching from one ECU to the other or do they work in parallel?

 

[lgabriel]

Hi mmarien!  Your posts on this forum have been a great help and inspiration for my system--thanks for blazing the trail!

It's an EFII dual ECU kit with some modifications.

The airplane's mission involves flying over hostile terrain, so I've tried to design in as much redundancy as possible.  There are two independent buses (two alternators, two batteries, VP-X on the left, circuit breakers on the right).

I've attached a schematic of my ECU switching plan--here's the explanation:

Both ECUs are running during normal operation, because each ECU controls its own set of plugs.

I've designed a switching system that avoids any single point of failure (like a 3PDT switch) to select which bus powers the injectors, which ECU has control of them, and which fuel pump is active.

Operationally, there are three switches on the panel: Left ECU, Right ECU, and ECU Select (which normally resides in the Left position unless I'm checking things or having an emergency). 

Hopefully...this lets me keep the engine running if I lose a bus, if I lose an ECU, or if any one of the relays or switches in the system fails.

I've been working on this for a while, so let me know if I casually glanced over something that needs further explanation.

Thanks!

Louis

 

[mmarien]

Thanks Louis. I picked a lot of my ideas from this forum also.

The two ECU's and two power sources at once make the wiring a bit complicated. I prefer the one OR the other scenario. Appendix F in the VP-X manual make a good case for dual batteries with EFI. Since your ECU's are not monitoring each other and don't depend on each other, you could make it simpler by just switching entirely from one to the other. Just a thought .

 

[lgabriel]

Ha! Sounds like I'm in for a bit of a redesign. I was using the kit harness as a starting point and it never crossed my mind to completely isolate the ECUs. Time to get smart on how SDS deals with ignition coils!

Although I have considered the aux battery plan, I'm drawn more to having two separate and relatively equal systems. Any battery plan I can come up with solves things for about 45 minutes, which doesn't cut it for the mission.

Thanks for the help--I may be pestering you again shortly!

Louis