Adding second voltage widget to HDX.

cbretana

Member
Joined
Jul 10, 2019
Messages
274
I am trying to add a second voltage widget to my HDX screen, to monitor the voltage output of my alternator, using pin 2 (yellow wire), on the EMS-220 DB-37. I hooked up the yellow wire from the EMS-220 DB-37 wire harness (pin 2), to the point where I wanted to monitor the voltage, (alternator output lead).

I was able to successfully set up the widget on pin 2, and position it in the screen, using the configuration screen, but it does not display any data. In the sensor debug screen, the row for pin 2 shows no data, not even in the "raw data" column. Is there something else I'm missing?
 

djones

Administrator
Staff member
Joined
Jul 19, 2010
Messages
267
Did you configure pin 2 in sensor input mapping? EMS SETUP > SENSOR INPUT MAPPING
 

cbretana

Member
Joined
Jul 10, 2019
Messages
274
I think so. That's the screen that lists all the pins in sequence, and has columns FUNCTION, SENSOR, and NAME?, right? I configured it exactly like it shows on page 7-83 of the install doc, FUNCTION = VOLTS, SENSOR = VOLTAGE MEASURE, except I named it "ALT", not "MAIN".

There was no SAVE button on this screen though, you just exit from it. The values were still there when I went back in though. And when I set up the screens to show a new widget on pin 2, it correctly labeled it as "ALT Volts".

Is there somewhere else where you have to "enable" the pin?

My only hypothesis is that the wire attached to the alternator output is broken or not properly making contact. That's my next thing to check....
 
Last edited:

cbretana

Member
Joined
Jul 10, 2019
Messages
274
Is there any way to check the continuity of the yellow wire that should be connected to pin 2? The wire is definitely connected to the place I want to measure the voltage, (the P-lead of the alternator), but in the SV config screen, where you can monitor the RAW DATA for each pin, it shows zero....

I know the P-lead is putting out voltage. I have measured the voltage there independently.

So either the wire is not connected to pin2, (it might be the wire for pin 12), or something else needs to be done to enable pin2 in the SENSOR INPUT MAPPING WIZARD.
 
Last edited:

cbretana

Member
Joined
Jul 10, 2019
Messages
274
When I installed my HDX and SV-EMS-220, I used the pre-built EMS DB-37 harness designed for Lycoming 4 cylindar carbureted engines. When I look at the pinout chart for this version of the harness on page 7-19 of the install doc, for pins, it says "no connection". Does that mean that pin2 is not even installed in this harness?

I notice from the pinout descriptions that there are three pins annotated that they are connected to a yellow wire, pin 2, pin 12, and pin 14. I only seem to have two yellow wires on my wire bundle. One of them is already in use for my Kavlico fuel flow sensor so that must be pin 14. Which pin is the other yellow wire connected to?

Unfortunately, (my bad), I installed the SV-EMS-220 just in front of the firewall, (long EZ pusher), with the DB-37 pointed at the firewall, and all the wires going through the firewall, in such a way that it would be a major job to take it all apart to check pin connections, or to add another pin into the connector.
 
Last edited:

Rhino

Well-Known Member
Joined
Jul 20, 2009
Messages
1,244
There may not be a wire. Page 12 of the HDX wiring digram (https://www.dynonavionics.com/inclu...- WIRING DIAGRAM TYPICAL HDX DUAL DISPLAY.pdf) shows no splice on that pin. So there would presumably be a wire coming out of the connector, but it only goes a certain distance before coming to the point where there's no splice taking it any further. If you have access to the pin, checking continuity would be easy with an ohmeter. Then, assuming it goes nowhere, the question becomes whether or not you can access the splice location to add your own wire.
 

cbretana

Member
Joined
Jul 10, 2019
Messages
274
Didn't know about that document. And in the legend on page , it says that the X means an "unterminated wire". That certainly means I must be hooked up to pin 12. I need to check the wires coming out of the DB37 for another, shorter, unused, yellow wire.
 

cbretana

Member
Joined
Jul 10, 2019
Messages
274
Disassembled the DB37 connector to my EMS-220. Found that indeed, there was no wire attached to pin 2 on the connector. Had to add an additional wire to get the second voltage widget to work.

Might I suggest that ALL pins on the DB37 on this wire harness be wired up. At a minimum, where there are only a small number of pins that have a specific functional capability, (like the voltage sensor logic on pins 1 & 2), that they should both have a wire attached?
 

Rhino

Well-Known Member
Joined
Jul 20, 2009
Messages
1,244
Then people would be coming here posting, "Where does this wire go?!?" You can please some of the people some of the time.....
 
Top