Futaba Transmitter Modification - How do I do this?

[tennesseejim]

I have a 4 channel Futaba transmitter I would like to modify, but I'm not sure how to accomplish this. The transmitter is a T4VF. I wanted to change the left stick so that it is throttle only (channel 2 only). I wanted to add a three position switch for channel 4 and use the switch to control the ballast tank pump via an electronic reversing switch.

Have any of you done this? Can I use a simple switch to accomplish this? Anyone know now I would wire the switch to make this work?

Any help would be appreciated - Jim

[JWLaRue]

Jim,

I've done this for my

[color=#000000]Jim,

I've done this for my r/c tanks.....

The left stick can be made throttle-only by either]

[tennesseejim]

Jeff]

[color=#000000]Jeff]

[tennesseejim]

I went to Radio Shack

I went to Radio Shack and bought a Toggle Switch SPDT. Center position is off. Anyway, I wired everything up, but it does not work as expected. When the switch is in the center position, the servo stays "homed" as expected. But, no matter which of the other two positions I put the switch in, the servo rotates all the way in a counter-clockwise direction.

I had expected the servo to rotate clockwise also.

I was playing with the wire leads in the radio and noticed the same thing - no matter which one I touched to the ground, the servo rotated counter-clockwise only - no clockwise movement.

Any suggestions? Do I need to use a pot instead of a switch?

Thanks - Jim

[JWLaRue]

I can't tell for certain

I can't tell for certain from the description, but it could be that you have the wires connected 'backwards'...as in the throwing the switch to either 'on' position is producing the same signal to the receiver.

Can you post or e-mail a photo of your wiring?

-Jeff

[subdude]

You need to have resisters

You need to have resisters in the other two wires. No time to explain now, more later.

Jim

[JWLaRue]

Jim,

I'd like to hear more

Jim,

I'd like to hear more about the resistors......I am not using any with my Futaba SkySport and it works just fine!

-Jeff

[skip asay]

Transmitter sticks move potientometers which

[color=#000000]Transmitter sticks move potientometers which are configured as variable voltage devices, as opposed to variable current. Positive (+) is connected to one side of the pot and ground (-) is connected to the other side. Moving the transmitter stick causes an increase (or decrease) in voltage out of the center pin of the pot. This varying voltage is fed to the encoder which then tells the servo which direction to move as well as how far to move.

The best way to enable a 3 position switch is actually to use 3 pots]

[dietzer]

See SCBG Articles for an

See SCBG Articles for an article titled "Firing Buttons for the Futaba Transmitter". This article provides a description of adding two pushbuttons to a Futaba xmitter. You should be able to replace the two pushbuttons with a three way switch provided its of the on-off-on type. It requires only two potentiometers, and includes a brief writeup (including circuit diagram) of how to make the modification.

For those who would like to add a rotary knob to their Futaba, this webpage also has an article dealing with that. A rotary knob would replace one of the gymbals, and would be good if you wanting to vary something like speed or depth and have it stay there without having to worry about the self-centering action of the joystick gymbals. This same circuit would work with a slide type potentiometer if you'd rather use that in place of the rotary knob...

Hope this helps,

Carl

[tennesseejim]

Hey Subdude]

[color=#000000]Hey Subdude]

[subdude]

Jim,
Sorry for the delay.

Jim,
Sorry for the delay. The easiest thing to do is to see the article Carl has referenced above. You can substitute 2.5k resistors for the pots. The pots make it a nicer conversion though, as you have adjustable end points.

Jim

[tennesseejim]

Thanks -

I'll be stopping

Thanks -

I'll be stopping by Radio Shack on the way home....

[JWLaRue]

Hmmmm.....we need to do some

Hmmmm.....we need to do some testing!

I have a SkySport transmitter that is modified with two push buttons (and no resistors) and it works fine.......

This is a common modification that the r/c tank crowd uses...and I found the web page that describes it]http://www.fragarmor.org/Advanced%20Hints%203.htm[/url]

-Jeff

[skip asay]

While I've done this and

While I've done this and similar modifications in the past, I'll admit that they were older transmitters. Caution must be used since not all encoders are capable of accepting high input current which is what happens when using a switch without at least having resistors in the circuit. It obviously works for the SkySport radio but will it work with ALL radios? I don't know so I'll stick with pots. I like the ability to limit end travel, as well.

Skip Asay

[JWLaRue]

Good advice, Skip!

Good advice, Skip!