Testing initial installation - trim sensing

[dnelson]

Hi TT,

I'm in the 'wiring phase' and I've just completed the AFS-Pilot w/ V2.34 (I think), Pitch servo, and AFS-ARINC wiring. I've yet to purchase the 430W so I don't have a good GPS/serial source. Also, I've yet to attach the wings and wire up the Roll servo.

I've confirmed that ARINC is working to/from the AFS-Pilot from/to the AFS-4500.

A rigged up a simple GPS serial source (NMEA-0183 output) to the AFS-Pilot and got that working:
- Flashing asterisk - Ok
- I selected Alt-Hold, adjusted the vertical speed (+1000, -1000, and 0) and noted that the pitch servo responded appropriately - Ok

So far so good. With 'Alt-Hold' engaged and VS set to '0', I applied a little force to the pitch servo to simulate an 'out of pitch' condition. I did not see the 'rolling wheel' display on the AP to indicate 'Out of Trim'. Is this expected?

I also noted that the pitch servo had a very pitch whine as soon as the A/P was powered on and the servo got quite warm (not hot) after about 5 mins. Are these normal indications?

Thank you,
/\/elson

[TrutrakTech]

So far so good. The servo will get warm during operation, that's normal. The whining noise is also normal, but we can take care of that if it ends up getting transmitted into your audio system.

Where did you apply the force? Either grab the stepper motor itself, or put force on the elevator itself. You can also check the voltage out of pin number 7 of the pitch servo. It should be 2.5 at neutral and swing toward 0 or 5 when "out of trim". Thanks!

[dnelson]

Hi Lucas,

I was gently pushing on the servo arm itself as none of the rigging is in place. I believe this was yoga position "stretch arm rearward and look forward while curled over bulkhead". ;)

Thanks for confirming the noise and heat.

2.5V on pin 7 of servo in neutral position - Excellent!

Thanks Lucas!

/\/elson

[dnelson]

Hi Lucas,

I disconnected the 'trim sense' wire from the A/P and measured 0.29V with the A/P on, valid GPS signal, and 0 Vertical Speed. Just to make sure it wasn't silly wiring, I also measured it at the servo w/ the same results.

When I apply pressure to the servo's arm with VS=0, it has a range of 0-5V.

For completeness, I also tried different "neutral" positions of the servo arm by rotating it around be setting the VS to 2000 then setting VS to 0. Same results.

Sounds like an RMA is in order unless you can think of anything else.

Thanks,
/\/elson

[TrutrakTech]

You'll need to leave the wire connected as the circuit loading changes when disconnected.

If it was really showing 0.29V connected, you'd be seeing the scrolling bars. Try testing it again with all the connectors in place. Just remove the backshells for access to the wires/pins. Thanks!

[dnelson]

Hi Lucas,

Ok, I'll repeat the test and measure in-line.

Thank you,
/\/elson

[dnelson]

Hi Lucas,

I made up an in-line harness and did as you suggested. Success!

What I learned (in case somebody else goes down this road):

- You have to put quite a bit of force on the servo's arm (my guess is a couple of pounds). Just doing it with my hand was not enough. I ended up positioning the servo's arm vertically and pushing on it with a wooden dowel while watching the VOM.

- The "rolling wheel" display is not immediate. It seemed to take about a second before it would display.

Thank you,
/\/elson

[TrutrakTech]

Hi Lucas,

I made up an in-line harness and did as you suggested. Success!

What I learned (in case somebody else goes down this road):

- You have to put quite a bit of force on the servo's arm (my guess is a couple of pounds). Just doing it with my hand was not enough. I ended up positioning the servo's arm vertically and pushing on it with a wooden dowel while watching the VOM.

- The "rolling wheel" display is not immediate. It seemed to take about a second before it would display.

Thank you,
/\/elson

Good to hear! Yes, there is a slight delay so it isn't overactive. Thanks!

[stevebucknor1]

I am in the 'wiring phase' and I've just completed the AFS-Pilot w/ V2.34 (I think), Pitch servo, and AFS-ARINC wiring. I've yet to purchase the 430W so I don't have a good GPS/serial source. Also, I have yet to attach the wings and wire up the Roll servo. It is really fantastic.