Trim Selector Switch & Indicator

[cajunwings]

Setting up your plane the way you want it is one of the best parts of EAB world. My solution is to have trim switches on the pilots stick only and redundant back ups on the panel where either seat can use.

Don Broussard
RV9 Rebuild in Progress
57 Pacer

[GalinHdz]

Originally Posted by Carl Froehlich

I used Infinity grips for pilot and co-pilot. I put a DPDT toggle switch on the panel that provides the common ground path for the stick trim hat and flap switch. The switch positions places control with the pilot or co-pilot, never both.

Reasons:
- Did not want to have a co-pilot (especially a non-pilot) messing with trim or flaps unless I specifically allowed it.
- Wanted to have a way to make the co-pilot seat kid safe.
- Wanted a backup if I broke off the pilot trim or flap switches (in this case the pilot reaches over to the co-pilot stick).

Simple and effective.
Carl

If you notice that is exactly what the panel switch does and for the same reasons. It connects the ground to the pilot flying while disconnecting the ground for the pilot not flying. The only thing I added now was a switch position indicator. Like you say, simple and effective.

Originally Posted by n82rb

seems a bit of overkill when a couple of 2 cent resistors would have worked fine. but to each his own. great looking panel by the way.

bob burns

I am curious. How would you do it with a couple of resistors?

[bret]

Originally Posted by Carl Froehlich

I used Infinity grips for pilot and co-pilot. I put a DPDT toggle switch on the panel that provides the common ground path for the stick trim hat and flap switch. The switch positions places control with the pilot or co-pilot, never both.

Reasons:
- Did not want to have a co-pilot (especially a non-pilot) messing with trim or flaps unless I specifically allowed it.
- Wanted to have a way to make the co-pilot seat kid safe.
- Wanted a backup if I broke off the pilot trim or flap switches (in this case the pilot reaches over to the co-pilot stick).

Simple and effective.
Carl

I did the exact same thing with my infinity grips. P or CP

[BobTurner]

Originally Posted by GalinHdz

I am curious. How would you do it with a couple of resistors?

I think this was in reference to powering the LEDs off 12 volts.

[GalinHdz]

Originally Posted by BobTurner

I think this was in reference to powering the LEDs off 12 volts.

That is the only thing I could imagine but I could be wrong.

The reason I used this DC - DC converter is that, unlike regular LED's, Bi Color LED's are very sensitive to voltage variations. Trying to provide 2.2v with no more than about a 0.2v difference is almost impossible with resistors and a typical aviation alternator. So this device is not only works as a voltage converter but a very accurate voltage regulator. And it cost less than $8.00.

[lr172]

I would wire it with the pilot always active and the co-pilot switched. While you could have the first scenario again, you could never have the second. This seems like a better solution with reduced consequences for forgetting to place the switch in the proper position. The pilot will always be able to deal with an untrimmed condition and only the co-pilot could experience a problem.

I am sure you know, but relays should be used so that only one switch can be active and controlling at any time (wired so Pilot switch can interupt the co-pilot curcuit. This eliminates that risk of a short.

Larry

[SmilingJack]

Originally Posted by rapid_ascent

I have a switch similar to Carl's where I can disable the co-pilot stick functions by opening up the ground to the co-pilot stick. This stops the passenger from hiting something by mistake. I'm not too worried about the 2 pilot case.

I did what you did Ray.

Installed (in my case 2) switch(s) that enable or disable the GIB stick buttons.

I installed 2 so I can enable the small stuff - pitch and roll trim with one switch for the novice pax and another switch for those who fly - Starter, Fuel pump, A/P Disc and Flaps.

I wasn’t “thinking” whilst building and in the beginning wired the rear MIC trigger button to those switches... Well....once I started getting ready for first flight I had a nice ground loop I induced

I removed that wiring and just figured that MIC button was safe to stay hot. I mean, if someone is playing MAV back there and going to guns....I’ll hear them clicking away and then stop them!

[rapid_ascent]

Yeah I figured the PTT was ok for the passenger to be able to use.

[rapid_ascent]

Galin,

I think the reference to a couple of resistors has to do with how LEDs are driven. LEDs are driven normally by current and are current limited. The LED voltage that you are referring to is at a specific current. So... You can run LEDs off of 12V you just need to add a resistor in series. That resistor have a voltage drop across it, 12V - Vled. The resistor is selected by setting the desired current. R = (12V - Vled) / I(led drive current).

[GalinHdz]

Originally Posted by rapid_ascent

Galin,

I think the reference to a couple of resistors has to do with how LEDs are driven. LEDs are driven normally by current and are current limited. The LED voltage that you are referring to is at a specific current. So... You can run LEDs off of 12V you just need to add a resistor in series. That resistor have a voltage drop across it, 12V - Vled. The resistor is selected by setting the desired current. R = (12V - Vled) / I(led drive current).

In the typical airplane circuit you can't expect to control voltage within the tolerances of these kinds of LED's with just a resistor. Since the airplane electrical circuitry can't remain within tolerances, then you have to design for this. In all cases, if you exceed the maximum breakdown voltage your current goes into runaway and you fry the semiconductor. Bi Color LED's are much more sensitive to voltage variations than typical LED's so resistors are not a good choice for this particular application.

You can see how current is affected by voltage variations to this LED on this Bi Color LED Spec Sheet. You need about 2.0v to get them both to work but once you get beyond about 2.3v, your current goes into runaway and your LED goes "POOF". Interesting enough in this particular case the RED LED goes "POOF" way before the GREEN one does.

Remember a resistor will let current go through based on the voltage it sees. Less current will flow through a resistor at 12.0v than will pass trough the same resistor at 14.4v. In this particular application, the voltage difference(s) in typical airplane circuits are outside this LED's tolerance of about 0.3v. Think of the converter/regulator as a very accurate and fast variable resistor and you will get what I mean.

We can do heavy discussion about this but it is irrelevant to this situation. Just keep the voltage within tolerance and everything else falls into place. That is why I opted for the $8.00 converter/regulator in this particular application not a resistor.

And yes "POOF" is a highly technical term.