HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Aug 08, 2012, 09:59 AM
Agressive driver
United States, CA, Santa Barbara
Joined Jun 2011
1,202 Posts
Discussion
Changing radio pots for two position switches

Hello

I was wondering if I could take an old radio, remove the pots on steering and throttle and solder in two way toggle switches, and then have the functionality of a two way switch on that channel, as if the switch had been there all along, like the gear switch? Would this also work vise versa, putting pots on what used to be toggle switches?

Thanks, Zane
zanek is offline Find More Posts by zanek
Reply With Quote
Sign up now
to remove ads between posts
Old Aug 08, 2012, 12:48 PM
Registered User
Romania, Dolj, Craiova
Joined Sep 2007
14,264 Posts
Switch instead pot works, requires two resistors, viceversa not, you can't replace a switch with a pot without making this thing known to radio firmware.
renatoa is offline Find More Posts by renatoa
Reply With Quote
Old Aug 08, 2012, 02:05 PM
Agressive driver
United States, CA, Santa Barbara
Joined Jun 2011
1,202 Posts
Okay. What size resistors do I need and where do i put them?
zanek is offline Find More Posts by zanek
Reply With Quote
Old Aug 08, 2012, 02:20 PM
59 years of RC flying
Daedalus66's Avatar
Canada, ON, Ottawa
Joined Feb 2006
16,001 Posts
Quote:
Originally Posted by zanek View Post
Okay. What size resistors do I need and where do i put them?
Do you want it to work like gear switch with servo going full travel?
Daedalus66 is online now Find More Posts by Daedalus66
Reply With Quote
Old Aug 08, 2012, 02:24 PM
Agressive driver
United States, CA, Santa Barbara
Joined Jun 2011
1,202 Posts
Yes. So if I understand correctly, pots are essentially variable resistors? So to go full travel I would use a resistor that is equal to the max. ohm value of my pot? and less for less travel?
And I just put the resistor between the switch and each of the wires going to the TX?

Thanks, Zane
zanek is offline Find More Posts by zanek
Reply With Quote
Old Aug 08, 2012, 02:36 PM
Registered User
Romania, Dolj, Craiova
Joined Sep 2007
14,264 Posts
if you want full travel, then you must replace the pot with a single resistor of same value, usually 5-10k, and the switch will be connected as follows: the two fixed contacts at the resistor ends, and the bouncing contact instead pot cursor.
If you want adjustable range, it's a more complicate play of values.
renatoa is offline Find More Posts by renatoa
Reply With Quote
Old Aug 08, 2012, 02:45 PM
Agressive driver
United States, CA, Santa Barbara
Joined Jun 2011
1,202 Posts
Okay. Thanks for your help.
zanek is offline Find More Posts by zanek
Reply With Quote
Old Aug 08, 2012, 03:02 PM
59 years of RC flying
Daedalus66's Avatar
Canada, ON, Ottawa
Joined Feb 2006
16,001 Posts
The pot acts as a voltage divider. The setup varies from one transmitter to another, but lets assume the pot is 5K ohms and has 6 volts across it (one end is grounded, the other connected to +6v regulated). With the wiper in the middle it will see 3v. At one end of travel it might see 2v and at the other end 4v (since the pot is often 270 degree travel but the stick assembly limits it to perhaps 30 degrees each way).

In this case, one could replace the variable resistor with three fixed 1.6K resistors in series (adding up to roughly 5K). With 6v across the resistors, you will get 2v at one junction and 4v at the other. That would give full servo travel in each direction, depending on which you picked. You set up the switch accordingly.

That's the general principle. If you give specifics about the transmitter, someone can probably give you some guidance on actual values and the best way to do it. The numbers above are just for illustration.

EDIT: Those numbers will obviously give too much servo travel if the pots are 270 degrees.
Daedalus66 is online now Find More Posts by Daedalus66
Last edited by Daedalus66; Aug 08, 2012 at 03:17 PM.
Reply With Quote
Old Aug 08, 2012, 03:24 PM
59 years of RC flying
Daedalus66's Avatar
Canada, ON, Ottawa
Joined Feb 2006
16,001 Posts
Quote:
Originally Posted by RENATOA View Post
if you want full travel, then you must replace the pot with a single resistor of same value, usually 5-10k, and the switch will be connected as follows: the two fixed contacts at the resistor ends, and the bouncing contact instead pot cursor.
If you want adjustable range, it's a more complicate play of values.
Could you explain a bit further and reconcile with (or correct) the explanation I gave, please.
Daedalus66 is online now Find More Posts by Daedalus66
Reply With Quote
Old Aug 08, 2012, 03:28 PM
Agressive driver
United States, CA, Santa Barbara
Joined Jun 2011
1,202 Posts
Quote:
Originally Posted by Daedalus66 View Post
The pot acts as a voltage divider. The setup varies from one transmitter to another, but lets assume the pot is 5K ohms and has 6 volts across it (one end is grounded, the other connected to +6v regulated). With the wiper in the middle it will see 3v. At one end of travel it might see 2v and at the other end 4v (since the pot is often 270 degree travel but the stick assembly limits it to perhaps 30 degrees each way).

In this case, one could replace the variable resistor with three fixed 1.6K resistors in series (adding up to roughly 5K). With 6v across the resistors, you will get 2v at one junction and 4v at the other. That would give full servo travel in each direction, depending on which you picked. You set up the switch accordingly.

That's the general principle. If you give specifics about the transmitter, someone can probably give you some guidance on actual values and the best way to do it. The numbers above are just for illustration.

EDIT: Those numbers will obviously give too much servo travel if the pots are 270 degrees.
I totally understand now. Thanks for the explanation
zanek is offline Find More Posts by zanek
Reply With Quote
Old Aug 08, 2012, 04:09 PM
Registered User
United Kingdom, Slough
Joined Aug 2003
1,952 Posts
With JR sets, a 2 position switch will go from 0V to 5V as they use 5V for most of the electronics. You can use a 3 position switch to replace a pot to give minimum, centre and maximum.
theaton56 is offline Find More Posts by theaton56
Reply With Quote
Old Aug 09, 2012, 12:22 AM
Registered User
Romania, Dolj, Craiova
Joined Sep 2007
14,264 Posts
Quote:
Originally Posted by Daedalus66 View Post
Could you explain a bit further and reconcile with (or correct) the explanation I gave, please.
There is nothing wrong in your post, nothing to correct.
What I proposed is in the first schematic below, and is based on fact that usually, RC (stick) pots are not 270 degrees, they are special build with even less than 90 degrees movement.
What you proposed is in the second schematic and is correct as well, depends on pot type, if it rotates the full resistor range or only partial.

LE: and in the 3rd, the three position switch version, described by theaton
renatoa is offline Find More Posts by renatoa
Last edited by renatoa; Aug 09, 2012 at 12:28 AM.
Reply With Quote
Old Aug 09, 2012, 05:48 AM
59 years of RC flying
Daedalus66's Avatar
Canada, ON, Ottawa
Joined Feb 2006
16,001 Posts
Thanks. In the end, of course, there's going to be some trial and error if one cares about the precise output values (as opposed to having just high and low output to trigger a switch in the model, say). So one would probably use a couple of variable resistors to fine tune the setup.
Daedalus66 is online now Find More Posts by Daedalus66
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Changing radio pots for two position switches zanek DIY Electronics 3 Sep 04, 2012 03:27 AM
Mini-HowTo Turnigy 9x v2 standard firmware, mode switch 3 position switch for dji naza gps :) stein3247 Multirotor Electronics 3 Jul 20, 2012 04:23 AM
Discussion Changing Two Position Switch to Turnable Dial Grips Radios 5 Mar 28, 2012 10:11 AM
Question Changing a rotary pot for a switch Frank Hurd Radios 2 Mar 13, 2012 08:16 AM
Discussion Changing toggle switches to Pots on radio? ziomatrixacs DIY Electronics 5 May 16, 2010 10:12 AM