Replace dial with 3 pos switch

[jaybob]

Hi guys. I've got a radiopost ts401 and was wondering if anyone would know if its possible to replace one of the dials with a 3 position switch. Help would be much appreciated. Thank you

[Mikeinsocal]

I have the same question about the same radio... the only problem with this that I see is that for me I want to use it for a dig servo and I don't believe we would be able to set the end points for that channel so the servo would just want to go to full lock and burn itself up.

[jaybob]

I currently have the third channel for 2 speed. The transmitter does allow for end point adjustments so that we don't kill the servo. i have no use for all three of the dial adjustments. i hope someone has experience in changing sliders/dials to 3 pos switch. i've read somewhere that you can use resistors to divide the voltage between three pos (0v, 2.5v,5v - providing the input is 5v)
also curious if i have to do anything to the transmitter to recognize any change from dial to switch.

[heyok]

It isn't extremely difficult to change a pot to a toggle switch.
You will need a SPDT Center Off toggle switch and two resistors. Use 10K (or 4.7K) for both resistors.



Both the existing pot in the transmitter and the toggle switch will have three terminals. Move the three wires from the pot to the toggle switch. Make sure the middle wire from the pot goes to the middle wire of the toggle switch!
Join one end of each resistor to the center terminal of the toggle switch. The other end of each resistor goes to an outer terminal of the toggle switch.
Like this: O--resistor--O--Resistor--O
The "O" is shown to represent the switch terminals.

That's it. Now you have a three position channel instead of a linear channel.
You mentioned that the end points are adjustable in the transmitter. That will continue to work. There is no center trim for this new switch. If that is needed, let me know and I can describe how to do that too.

[jaybob]

Thank you very much. My switch order came in yesterday. I will try that asap. While I have it open, what do I need to do to be able to adjust centre trim?

I appreciate your help very much.

[heyok]

To be able to set the trim, you will need another pot. Probably a "trim pot" which is one that you would adjust with a screw driver, or use a pot with a shaft if that is better for you.
Try a 1K pot. The center of the pot goes to the center of the toggle switch.
The two remaining legs each get a resistor. The other end of the resistors each go to the outer terminals of the toggle. Try 10K resistors. If that doesn't give enough range for the trim control, try 4.7K

O--10K--C--10K--O
The C is the center terminal of the trim pot.
O is an outer terminal of the toggle switch. Note that C is wired to the center terminal of the toggle switch.

Hope that is clear

You're welcome.

Al

[Hydrocarbon92]

The other way is to use a single 20k 20-turn trim pot w/o the 10k's.

It's really not needed unless your radio has no trims, most allow +/- 10%. Get ten 5% resistors and pick the closest 2. When it's turn on you simply adjust the trim on til the output is neutral.

[heyok]

Sure, that will work, and it uses fewer parts!
My way just limits the amount of throw the trim can produce.