SaA

Analogue Interface Boards for Robots and Joysticks

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What is a Joystick?

Joysticks have been around longer than Robots, so these interfaces were originally intended for use with Joysticks! However the term 'Robot-Wars Interfaces' could be more appropriate!

A joystick (aka wig-wag control in US) is essentially a 'potentiometer' with a lever attached. It doesn't matter (to the controller) whether the pot has a lever attached or not, most robots simply use a pot operated by the standard radio control Servo.

The controller is arranged so that you move the lever forward from the centre position and the motor starts to rotate in one direction. Moving the lever backwards causes the motor to rotate in the opposite direction.

So any interface for a joystick must give a speed and a direction signal to the controller. That is exactly what out interfaces do.

A dual axis joystick is commonly used on wheelchairs where forwards-backwards movement (first pot) controls both motors together and transverse movement (second pot) speeds one motor and slows the other, allowing steering. So one movement is speed and the other, difference. There is a list on site of some manufacturers.

In some other applications (e.g. a remote controlled pan and tilt head for a camera) separate motors can be used, one for each axis, one controlled by front to back movement and the other only by transverse movement. This is in effect two separate single-axis controls rather than a true 'dual-axis' control.

4QD's 'flagship' range of controllers (the 4QD series) incorporate circuitry so they may operate in single-axis 'joystick' mode. The NCC series are single-ended only: reversing cannot be controlled by a single joystick type pot so 4QD have designed interfaces for the NCC series. The Pro uses the same interface.

Use for Robots and Radio Control.

4QD now produce a range of Microcontroller (Digital) interfaces for Radio Control applications. See Radio Control Interfaces.

A standard model radio control unit consists of two joysticks. One of these is usually used for speed, by moving it front and back: forward for forward speed and backwards for reverse, while the second stick may be for steering. Of course, these two movements may be combined in a single 'dual axis' stick.

The second stick may alternatively be a speed control similar to the first, e.g. for a tank where one stick would control the right track and the other would control the left. In this case the two channels are independent and you would use either two single axis interfaces or one Dual Channel interface, in 'Independent' mode.

Or the second stick may be used for steering, by moving it left and right. In this case it may (as in a model car) control a separate steering motor, or it may control the steering by 'differential' control, i.e. by causing one motor to go faster and the other to go slower.

The Dual Channel interface can also operate in this 'Differential' mode. Be aware that as various radio control systems have different facilities (including mixing) there is a possibility of confusion. The DCI does mixing - but if you have a r/c transmitter that mixes - you don't want the DCI to mix as well. The simplest (and cheapest) radio controls have two totally separate channels - one will operate one of the DCI's input pots and the other channel will operate the second DCI pot. This is the commonest system, which is described here.

The joystick interfaces described here are designed to work from a potentiometer (or pot) - usually worked by a lever - the 'stick' of the joystick. However, the potentiometer may just as easily be moved by the mechanical movement of the standard radio control servo. This is, to an electronic engineer, crude, but has the great advantage of being very simple to implement and to understand as you can see exactly what is happening.

It also has the great benefit of isolating the receiver's electronics from the potentially noisy high current stages, greatly reducing the chances of any noise (e.g. from arcing at the motor's commutator and brush gear) travelling along earth wires and being radiated from (read interfering with) the receiving aerial.

The input pot is actually supplying a varying voltage (4.5v ±1.5v) to the interface and you can just as well use a variable voltage, if that happens to suit you.

  • Controllers with 'Joystick' input

    Some of our controllers can be set up to accept joystick (or wig-wag) input. These include

    Boards available.

    Several boards are available: a single axis interface (available in two styles), and a Dual channel Interface.

    Single-axis 'Joystick' interface, pot mounted version.

    To convert a single VTX, NCC or Pro series controller to joystick input.

    Picture: jsi.gif
    Size: 47mm x 51mm
    Output: 3.5v for full deflection of 50° pot
    Pot deflection (JSA-002):±25° electrical about centre. (±150° mechanical travel)
    Centring: electrical centring adjustment on board.
    Operating voltage:12v to 48v systems.

    6 way connector for pin-to-pin connection with Pro, VTX or NCC controller.
    3 way connection for ignition switch and battery condition meter.

    The interface is available:

    1. JSB-001: board only, without potentiometer and mounting bracket.
    2. JSB-002: an assembly, with standard potentiometer and mounting bracket to give ± 45° for full output (suits use from standard radio control servo).
    3. JSB-003: an assembly, with special 50° potentiometer and mounting bracket.

    The following potentiometers are available:

    1. Special 50° pot suitable for this board - to give ±25° for full speed.
    2. Standard pot. (±120°)

    Price List
    DescriptionOrder CodePrice ListAdd to cart
    board onlyJSB-001Add
    Assembly, with standard potJSA-003Add
    Assembly, with special 50° potJSA-002Add
    Potentiometers
    Special 50° potPOT-050Add
    Standard 10K pot POT-103Add

    For quantity orders, the board can be manufactured with altered performance or tailored to individual requirements.

    Single-axis Joystick interface, Daughter version.

    Electrically the same as the single axis interface, this version plugs into the 6 pin input connector on the NCC. It has three 3 pin connectors: the first is the ignition, the second connects to the (remote) potentiometer and the third gives travel end stop facilities which reverse the motor direction when activated. These may be used for a collision detection system. Note: although this will fit the later VTX board, the cover for the boxed version of the VTX wil not then fit in place.

    Picture: jsid.gif

    Price List
    DescriptionOrder CodePrice ListAdd to cart
    Single axis, daughter boardJSD-001Add

    Dual Channel Interface

    This interface is designed to operate with either two potentiometers or a standard joystick. For radio control applications our Digital Radio Control Interfaces may me of more interest! It has two modes (selectable by on-board links): Independent (or 'tank style') and Differential (or 'Speed and Steer' mode). It can also be used in other applications of course.
    Size: 81mm x 80mm
    Output: 3.5v for 45 degree movement with standard pots (to suit r/c servos)
    Input: suitable for 10K pot.
    4.55±1v for full speed to VTX (approx 3.8v)
    Adjustments: centring (2 adjustments)
    Ramping: two adjustments
    Mix: one adjustment
    Operating voltage:12v to 36v systems.
    For 48v, add 820R 1W in positive supply
    Supply current 30mA

    Dci

    Price List
    DescriptionOrder CodePrice ListAdd to cart
    Dual Channel InterfaceDCI-111Add
    Standard 10K pot POT-103Add
    Spare jumper links (pk 10)JLK-001Add

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    Document URI: www.4qd.co.uk/accs/jsi.html
    Last modified: Thursday, 27-Mar-2008 11:19:35 GMT
    Page's Author: Richard Torrens
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