Need to turn off Pull up Voltage on Pin 22 in EMS

Swaflyer737

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I have scoured book, setup in Skyview, and forums. I cannot figure out where I turn off pull up voltage. Please either reference the exact page of manual or just tell me.

This is for my HYD 12v sense line. ie, ON it will send 12v (see 5v) to EMS. Right now it in data debug it shows 4.98v-----I need it to show zero

Thanks in advance
 

Rhino

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I'm not sure I understand what you need. Pull up voltages from hydraulic ECUs/ECMs aren't full power by design. They draw an indicator voltage off of system power using a pull up resistor that provides an output lower than system power. So, assuming you have 12 volt system power, you should never be getting 12 volts input to the Skyview from an ECU/ECM pull up resistor. If you're getting 4.98 (or 5) volts from the ECU/ECM, then the Skyview is probably displaying it just as the ECU/ECM is sending it. Are you trying to get a voltage readout on the Skyview or an ON/OFF indication? ON/OFF indicators are contacts, not voltage displays, and must be routed to a general purpose pin (page 7-73 of install manual version AI v16). You set the limits in the setup. The cut over level for an on/off indication is 2 volts. 0 to 2 volts will indicate off, and anything higher than 2 volts will indicate on. If you want the Skyview to indicate ON when the ECU/ECM outputs 5 volts, you should be able to do that by inputting to a general purpose pin and configuring it that way in setup. If you want the Skyview to indicate OFF when the ECU/ECM outputs 5 volts, it gets more complicated.
 

Swaflyer737

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Rhino, I was hoping you comment. This has been frustrating and I am either completely off or a simple step away. I have been able to program 2 Alternators warning lights, Canopy, Gear, Trims, etc. and all our working, but this one has left me baffled.

First here is what I have done for context. I removed a HYD actuator light that consisted of the 12v sense line and a gnd. PUMP on, 12volts sent to the light. All I did is remove the light, cap the gnd wire and wire the 12V sense line (with 1.2 ohn resistor) to PIN 22 on the D37 of the EMS. I mapped it as a CONTACT and then set the RANGE exactly like the book said and as you indicated above. In the skyview I created a HYD widget that is ON or OFF.

No matter what is happening (PUMP ON or OFF) PIN is reading 4.98 volts and Widget doesnt change.
I have put the voltage meter to the PIN to see what I am getting and it is 12v. I have changed from PIN 22 to PIN7 (I had pigtailed for later)
just make sure it wasn't an issue between a TYPE A or TYPE C. I also bypassed resistor.

Bottom line, PIN 22 or PIN 7 when set up as a contact reads 4.98 volts and if I could get it to read zero, then when I apply the 12v sense line it would make obviously trigger my widget. I know this because if I just GND pin 22 the widget changes and I see Zero on the debug screen.

I thought I read/heard that you can disable the 5v pullup on Enhanced PINS (type C) and this would solve my problem

Hope this helps you understand where I'm at. Probably simple and I'm ready for some schooling.

Thank you
 

Rhino

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My guess is there's something else in that circuit. The first step is to isolate the source of the problem by disconnecting the wire. You need to confirm the voltage out of the pump (ECU/ECM) pull up resistor, and determine exactly where the 4.98 volts is coming from. Disconnect the wire from the pump to the Skyview and measure the voltage from the source (with a voltmeter, not the Dynon). If you get 4.98 volts from the source, regardless of the hydraulic pump condition (on or off), the problem is with the signal from the pump actuator. If that line voltage changes when you cycle the pump as designed, check the voltage on pin 22 on the Dynon. If it's 4.98 volts on the Dynon even with the wire from the pump disconnected, you have a problem with the Dynon. Any voltage difference along that line, not attributable to the resistor, is a wiring issue. If all you have in the line is the resistor, disconnect at both ends and measure the continuity. If you get anything other than 1.2 ohms, there's something else in that line. If all else fails, run an entirely new wire. Basically there's a progression.
1. Verify voltage from the pump changes at the source with the pull up sense wire disconnected at the pump.
2. Verify the voltage at pin 22 on the Dynon is zero with the wire disconnected at the Dynon (powered on).
3. If steps 1 and 2 pass, check the continuity and resistance on the wire with it disconnected at both ends, or replace with a new wire.
4. You can run a new wire temporarily outside the aircraft, without routing through the firewall, just as a troubleshooting step. That will tell you for sure if a new wire will solve the problem.
5. If you run a new wire, confirm you get less than 2 volts with pump off, and more than 2 with it on (never more than 15 volts to pin 22). Adjust resistance in the line as necessary, or add a voltage divider.
 

Rhino

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After thinking about this, if it were me, I'd:
1. Disconnect the existing circuit at both ends, and ignore it.
2. Verify the voltage is good out of the ECU/ECM (2 to 15 volts) with the pump on, and zero volts with the pump off.
3. Confirm there is not always 4.98 volts on pin 22 of the Dynon when it's powered on, even with the wire disconnected. Otherwise contact Dynon.
4. Run a new test wire from the ECU/ECM outside the aircraft into the cockpit to pin 22 (confirm good voltages before connecting to Dynon).
5. Install a new wire permanently if step 4 passes. Contact Dynon if it doesn't.
I'd do it this way because it identifies the source and eliminates the need to test the existing wiring. But that's just me.
 

Swaflyer737

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After thinking about this, if it were me, I'd:
1. Disconnect the existing circuit at both ends, and ignore it.
2. Verify the voltage is good out of the ECU/ECM (2 to 15 volts) with the pump on, and zero volts with the pump off.
3. Confirm there is not always 4.98 volts on pin 22 of the Dynon when it's powered on, even with the wire disconnected. Otherwise contact Dynon.
4. Run a new test wire from the ECU/ECM outside the aircraft into the cockpit to pin 22 (confirm good voltages before connecting to Dynon).
5. Install a new wire permanently if step 4 passes. Contact Dynon if it doesn't.
I'd do it this way because it identifies the source and eliminates the need to test the existing wiring. But that's just me.
What you said in question 3 has been the culprit. I have 4.98 volts on pin 22 or pin 7 with nothing attached to it, but configured as a contact.
question 2 is the first thing I did measuring it pump, then the actual pin in the Sub D connector.....and to be clear that pin reads 12v.

One thing of note is I have only used PIN 3 as the ground. I have not grounded the other possible GND pins (5,16,17) 13 I used with canopy.

Again thanks for your help.
 

Rhino

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Okay, I think I see the problem. General purpose contacts don't work on simply the absence or presence of voltage. When in the OFF state, the input can't just be open. It has to be connected to ground. So when you remove the voltage being supplied in the ON state, the pin must be grounded in order for the EFIS to read zero, and give you an OFF indication. That's why you see OFF when you manually ground the pin. It appears the sensor in your ECU/ECM is simply disconnecting voltage and creating an open circuit when it's turned off, rather than switching from voltage to ground, which is what the Skyview is looking for. If there isn't a way to reconfigure the ECU/ECM to supply ground when it's turned off, you probably need to install a relay that supplies ground in the OFF state. I'm assuming the other sensors you're using are already supplying ground when they're in an OFF state, and that's why they work. A simple automotive SPDT relay should work fine.
 

Rhino

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This should be the relay configuration you need.

1659945408838.png

This is what you see in a typical automotive SPDT relay. The typical (not necessarily guaranteed) pinout is:

85 - ground
86 - sensor input trigger voltage to key the relay (from your ECU/ECM in this case)
87 - switched input (either 12 volts system power, or the trigger voltage from your ECU/ECM in this case)
30 - switched output (to pin 22 on Skyview in this case)
87a - normally open in cars, but this is where you need to connect ground for the Skyview to see when the relay is off

EDIT: Some may notice I've switched the input and output connections. In automotive applications, pin 30 is the input and 87 is the output. But since we need to supply ground in the OFF condition, I made pin 30 the output, and pins 87 and 87a the inputs. Electrically speaking, it makes no difference anyway, as long as the required connection is made.

Automotive relays are designed to trigger with 12 volts, but will typically trigger with much less than that, so your ECU/ECM should have no trouble activating it. If the voltage from your ECU/ECM is 2 to 15 volts, you can tie pins 86 and 87 together. Then it will trigger both the relay and the Skyview widget. This install can be done with a solid state circuit too, but this is simpler, and it allows you to install the relay in a pigtail on the wiring harness behind the panel to make relay replacement a plug and play operation, should it ever be needed.

The general purpose contacts on the Skyview don't act like a typical voltage sensor. They don't really care about voltage at all, because they aren't really looking for voltage to tell them something is turned on. They're really looking for ground to tell them something is turned off. By the way, Dynon also recommends a 10k ohm resistor inline to to any general purpose contact that ever gets 12 volts, or thereabouts, sent to it.

I did something similar to this some time ago, for an entirely different purpose. The parts I used SHOULD be the same for you, so you can try them if you want. These are ten packs though, and you only need one, so find a smaller quantity if you can to save money. You also don't need 30 amp if you can find smaller, but that's a typical rating in automotive relays.

Here's a reference on relays:

Sorry I didn't see this sooner (I should have). I started reacting to what I was reading first, without thoroughly reading all the rest, both here and in the manual.
 
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Swaflyer737

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I understand that and it make sense. Two questions.
1. 87a, I am grounding that on one of open grounds on my Sub D (5,16 or 17) or just aircraft ground.
2. Just split 86 and 87 from my single source 12v wire from pump?

Thanks again for the help. Went to Autozone to find a relay, they don't have any. I leave town in morning for 10days so wont get to see if fix works. I'll keep you posted.
 

Rhino

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1. You can hook it to the same ground the Skyview uses, or one of the ground pins.
2. Yes, split or jumper them together to the pull up voltage from the pump. But if you're using a relay socket, it's easier just to tie the wires together there instead of directly on the relay or the pump. Plus the socket makes changing the relay much easier.

Here's a 5 pack of relays plus sockets on Amazon. Apparently they don't sell them singly.

This is the socket this one uses:
1659994225107.png


Remember to confirm your pinouts before connecting. I believe they're all standard, but that isn't guaranteed. And the folks that sell them are notorious for creating confusing diagrams.

I attached the first draft of a diagram I drew, which might help. Let me know if something's missing or if you discover any mistakes, and I'll post an updated version.
 

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Rhino

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I can provide info for a solid state switch if you want. It may be considered a more elegant solution, but it's more expensive. Alternatively, if you're the adventurous craftsman type, I could give you sources to help you build your own. it would take a bit of time, but would likely cost less than the relay.
 

Swaflyer737

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We are done!!!! Was able to find one at NAPA that would work and was able to wire in this afternoon. Works now as advertised and was able to make a clean install of relay as if I knew what I was doing:).

Cant thank you enough for taking time out to get me squared away. I will have to wait 10 days to fly it, but at least everything in the new system is working as I intended.

All the best,
Bryan
 

Rhino

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This is my first draft of a diagram for using a socket for the relay. Input is welcomed.

8/22/22: Draft 2 posted.
 

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djones

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Didn't see this until now, easiest way to solve it would have been to install a 10K pull down resistor in the line to the EMS to ground. This would effectively ground the pull up voltage when the switch was not supplying 12 volts. Current through the resistor would only be a little over 1 mA with 12 volts supplied.
 

Rhino

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Thanks, Don. Engineer to the rescue. Now Bryan can decide if he wants to change it. Would the pull down resistor go in before or after the 10k inline resistor?

EDIT: I should ask that more specifically. Should the pull down resistor shunt to ground between a 10k inline resistor and the EMS, or between the switch/sensor and the 10k inline resistor?
 
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Rhino

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Like maybe this?

9/14/22: Image removed. See post #22.
 
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vlittle

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Some of the EMS inputs don’t allow the internal pullups to be disabled. In this case, for example, I use 20K series resistors with a 10K shunt resistor. Use the raw sensor data to determine the ON and OFF voltages and set the threshold in the middle.

I used this technique to measure my fuel pump switch and EMAG power switch. I have more details, but I am travelling right now.
 

Rhino

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Yes. What I posted is applicable to the enhanced type C general purpose inputs (pins 8, 22, 23, and 31).
 

djones

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Like maybe this?
View attachment 5146
8/20/22: Changed the configuration to put the pull down resistor before the inline resistor because I think I got it wrong the first time. Still hoping Don will confirm.
Actually, I would put the pull down between the series resistor and EMS. It would probably still work the way you have it, but it isn't ideal.
 

vlittle

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Here's more detail on what I did (for the EMS inputs that have programmable pullups). The first diagram is a bit hard to read, but the 10K resistors are all connected to ground. With the internal pullups set to 10K, the voltage thresholds are as listed. By putting the shunt resistors nearest to the EMS, the input voltage is scaled down so as not to exceed 5 Volts, rather than the up to 15 Volts that would normally be applied.

The second diagram shows how I soldered the resistors onto a DSub solder-cup connector. The photo that looks like a robot saying "Resistor Pack" shows the Dsub connected. Note: for the special inputs that can disable pullups, the voltage thresholds will be different.

Vern
 

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