Remote controlled vehicles.

Discussion in 'The Projects Forum' started by 36jemini, May 2, 2010.

  1. 36jemini

    Thread Starter New Member

    Apr 30, 2010

    For some time I have wished to build a remote control for, RC tanks, cars, etc. using a radio frequence. I have thought of one with around 3-8 channels. I have looked at several web pages, but haven't found a schematic yet. Not even for 3 or 4 channels.

    Well, one schematic, using DTMF caught my attention, but I don't know if it can send more than one signal at a time, and it annoys me that it is either on or off output on the receiver. (An engine only running on full speed or standing still wouldn’t be fun). The steering would also just be straight, left or right, nothing in between. A servo steering would be much better.

    What I’m looking for, is a system that is able to:
    • Vary the voltage on one or two engines (electric) for speed control.
    • Have some way of turning e.g. front wheels or a gun tower
    • Have a few relays switching on/off at the same time as a switch on the transmitter.
    If you know of something near my idea, please post it. Also if you need me to specify something please tell me.

    In advance thank you.
    Jesper, Denmark
  2. retched

    AAC Fanatic!

    Dec 5, 2009
    Hobby servos and a RF receiver will accept the transmission from your remote control and use it to operate the servos. The servos can be set up to steer, throttle, rotate turrets and just about anything.

    Building the transmitters and receiver is not cost effective of size efficient.

    You can buy SMALL receivers and such that will be in a smaller package than you could put together for the same price.

    Even if you wanted to use DTMF for the control, why do you feel you wouldn't have a range of steering?

    You could set the steering servo to steer 3 degrees at a time, rather than FULL left and FULL right. So, you would be going straight, and every time you press the LEFT button, the vehicle steers +3 more degrees left. If you press twice, it would steer 6 degrees and 10 times would steer 30 degrees.. Get it?

    I would recommend using spring return servos for your steering, because when you let off the stick, you want the vehicle to continue on the new path. You dont want to have to steer right to straighten the wheel after a left turn. Much easier.

    So for servos, 1 spring return servo for steering, 1 speed controller per motor. If the speed controller has a forward and reverse function, thats all you need to start.

    Then a receiver that matches the frequency to your transmitter.
  3. bertus


    Apr 5, 2008
  4. hgmjr

    Retired Moderator

    Jan 28, 2005
  5. 36jemini

    Thread Starter New Member

    Apr 30, 2010
    First of, thank you all very much for the quick response. :)

    @ Retched:
    I don't really care how big the final circuit will be, because it is more the building process of it that matters to me. :D
    One question to your answer: If I want to set a steering servo to adjust 3 degrees per button press, would that need a extra circuit or can a servo be programed? :confused:

    @ Bertus:
    Thanks for the links, but I want to build the whole system myself. I a quite familiar with the RC forum, but they only deal with commercial RC equipment.

    @ Hgmjr:
    Thank you very much for your links too. The has some interesting schematics. I think I will change from the DTMF circuit, to the 8-bit system on that site instead, since a single IC will be decoding the signal, instead of 4.
    Link: 8. bit system

    The next (Or kind of same) question is, where will I find a schematic for a transmitter and receiver module?
  6. rjenkins

    AAC Fanatic!

    Nov 6, 2005
    Have a look towards the bottom of this page, there are example schematics for multi-channel encoder & decoder compatible with off-the-shelf model servos.

    There are also TX & RX circuits.
  7. 36jemini

    Thread Starter New Member

    Apr 30, 2010
    If I understand what the text to the Basic Radio Control Encoder and Decoder reads, it will be a servo steering encoder/decoder module, for only one servo?
    The angle of the servo will then be determined by a normal computer joystick?
    Thanks for the attention, but I think I have to start with something a little more simple.
  8. rjenkins

    AAC Fanatic!

    Nov 6, 2005
    It's the last two circuits on the page.

    They are shown set up for six channels, but can be used for anything from 2 - 8 channels.

    With one encoder + transmitter / one receiver + decoder, you have a setup comparable to a commercial multi-channel RC system.

    The servo positions are controlled by potentiometers (or switched resistors). You could use commercial RC joysticks, the mechanics from computer joysticks or just pots with control knobs.

    You can make a basic functional joystick with two volume control type pots and a couple of bits of bent metal & threaded rod.
  9. 36jemini

    Thread Starter New Member

    Apr 30, 2010
    @ rjenkins:
    Thanks for the explanation of the servosteering. I think I will make 2 joysticks with 2 pots each, like the ones in a commercial RC transmitter.

    Now I only have one question back: Do i have to chose a specific type of transmitter and reciver curcit? Should it be AM or FM?
    Do you know of a curcit or where to find one?
    Last edited: May 9, 2010
  10. 36jemini

    Thread Starter New Member

    Apr 30, 2010
    Hey again
    I have done some more searching on the transmitter subject.

    I wonder, would it be possible to take a simple voice transmitting curcit, and replace the mic with the pulsing signal im getting from the Johnson counter.
    Like this one:
    or do i need a curcit with a crystal to have enough reliabillity?