VansAirForceForums  
Home > VansAirForceForums

-POSTING RULES
-Advertise in here!
- Today's Posts | Insert Pics

Keep VAF Going
Donate methods

Point your
camera app here
to donate fast.

  #11  
Old 11-24-2021, 04:22 AM
storkeye storkeye is offline
 
Join Date: May 2015
Location: Aylesbury, UK
Posts: 28
Post Resistor

Ray/Avanza - If I'm reading the diagram correctly Discrete In 1 - 4 won't need a pull up resistor but GP1 to 7 would. I suspect that's because the GP inputs can be high or low whereas the Discrete Ins can only be low. Is that right?

Paul - I like the redundancy of a seperate pressure switch. It would be a bad day to see the glass go off and the oil pressure light come on!

Rodrigo - I think that's what the design has come to, wiring the Discrete In to the negative output is in parallel so an LED failure shouldn't affect the EFIS.

The LED's have arrived so I'll be testing this all out in the shop later today.

Thanks everyone for all your advice.
__________________
Abe
Bucks, England
https://g-rvaa.uk/
RV-7 tailwheel
Empennage & Wings done. Fuselage in progress.
2021 Dues Paid
Reply With Quote
  #12  
Old 11-24-2021, 12:32 PM
Draker's Avatar
Draker Draker is offline
 
Join Date: Jun 2016
Location: Livermore, CA
Posts: 576
Default

Just another way to skin this cat: I went and built a small circuit board to drive my 12V annunciator LED lights from G3X (and other) active low signals:



This board accepts four low-current active-low discrete signals, and uses those signals to drive four independent LEDs (diode/resistor method described above). It also includes a 556 timer that will momentarily test-flash the LEDs when a button is pushed.

Schematic:


Board layout:


The board attaches to the back of my panel, where the LEDs and switch are mounted:



Front view:



I can make the Eagle files available if anyone wants to use this as the basis for their design. Disclaimer: Experimental, amateur built, not flying yet, may not work for your application.
__________________
Ryan Drake
Livermore, CA
https://stiletto.smugmug.com/RV7
Donated 12/31/2020
RV-7A (N12VD): Finishing final tasks for engine-start and airworthiness!
Reply With Quote
  #13  
Old 11-24-2021, 01:46 PM
Walt's Avatar
Walt Walt is offline
 
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 6,358
Default

Quote:
Originally Posted by Draker View Post
Just another way to skin this cat: I went and built a small circuit board to drive my 12V annunciator LED lights from G3X (and other) active low signals:
Just to be clear, the G3X discrete signals are inputs, not outputs, so I assume you are just paralleling the G3X inputs with your module to drive external LED's rather than have an EICAS message displayed on the PFD?

The G3X does have a master caution and warning output that will drive some LED's.
__________________
Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 2000+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
Reply With Quote
  #14  
Old 11-24-2021, 02:00 PM
vlittle's Avatar
vlittle vlittle is offline
 
Join Date: Jan 2005
Location: Victoria, Canada
Posts: 2,374
Default

This might help. Although it is Dynon (so the required pullups can be configured inside the EMS), the 1n4007 diodes provide the isolation from the 12V'ish levels that the LEDs have.

Dynon will say that you can connect 12V signals directly to their EMS inputs, but if there is an LED, the current will leak through the internal resistors and make the lamps glow, hence the diodes.

Garmin looks like a more conventional input, but the pullups need to be provided externally. You still need the diodes.

http://www.vx-aviation.com/sprocket/...tics-2/EMS.pdf

VV
__________________
===========
V e r n. ====
=======
RV-9A complete
Harmon Rocket complete
Part of EAA award-winning OnSpeed team
The VV in huVVer.tech
Victoria, BC (Summer)
Chandler, Az (Winter)
Reply With Quote
  #15  
Old 11-24-2021, 03:08 PM
Draker's Avatar
Draker Draker is offline
 
Join Date: Jun 2016
Location: Livermore, CA
Posts: 576
Default

Quote:
Originally Posted by Walt View Post
Just to be clear, the G3X discrete signals are inputs, not outputs, so I assume you are just paralleling the G3X inputs with your module to drive external LED's rather than have an EICAS message displayed on the PFD?

The G3X does have a master caution and warning output that will drive some LED's.
That's right, I wasn't clear: I'm using this for two signals from the G3X (master warning and caution), and two from other devices which should also be able to parallel into G3X discrete inputs. I'm not relying on any of those signals to drive LEDs directly, even though they may be able to. The board was designed before I decided what signals to connect.
__________________
Ryan Drake
Livermore, CA
https://stiletto.smugmug.com/RV7
Donated 12/31/2020
RV-7A (N12VD): Finishing final tasks for engine-start and airworthiness!
Reply With Quote
  #16  
Old 11-25-2021, 01:36 PM
rapid_ascent rapid_ascent is online now
 
Join Date: Mar 2008
Location: Dublin, CA
Posts: 1,638
Default

Abe,

Sorry I was traveling yesterday.

I should have taken a little more time to understand the information that you posted from the install manual. It's not totally obvious from the way that it is written, but I think I now understand what they mean. I inserted the information that is important here for the discretes.

When configured as Active Low, the inputs conform to the following specification:
Active: Vin < 3.5 VDC, or Rin < 375 Ω
Inactive: Vin > 8 VDC, or Rin > 100 kΩ


So for the active condition you have your switch to ground so that is no problem you meet the requirements. The inactive statement is more murky.
If we let the supply voltage = 12V for our example then if Rin = 100K and Vin = 8V that works out to 80uA. That also means that there is an internal pullup of 12V-8V/80uA or 50K ohms. Its a strange way to write this spec, but I think I get what they are saying now.

Now it doesn't hurt to have an external pullup but when you are in the active state you will be consuming more current 12V/4.7K = 2.5mA approximately, but give it a try without the pullup.

There was mention by others of needing an external diode. I don't think you will need one. Some experimentation may be needed to confirm all of this. I hope this helps.
__________________
Ray Tonks
2022 Donation Paid
Titan IOX-370, Dual PMAGs, 9.6:1 Pistons, FM-150
RV-7 Fuselage in progress
* Cabin Interior - In progress
RV-7 SB Wings
* Both Wings fully skinned
* Fuel Tanks Complete - No leaks finally
* Ailerons Complete
* Flaps Complete
RV-7 Empennage - Complete (a little fiberglass work left)
Vans Training Kit # 2 - Complete
RV-7 Preview Plans
Vans Training Kit #1 - Complete
EAA Sheet Metal Class - Complete
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 10:02 PM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.