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Friday, April 11, 2008

Working Of Remote Control System

Wireless control has always seemed to fascinate people, and Questor’s remote control system is the heart of his appeal. While the technical aspects of remote control may be
a little hard for the novice to grasp, Questor’s remote control system is rather simple in construction. Before I go into detail on how the system is comprised, a brief explanation of remote control is in order.

A remote control system consists of three basic components.The first is the transmitter or “encoder.” Moving controls on thetransmitter causes it to send or encode signals to the second part of the remote control system, the receiver, or decoder. Thereceiver gets the signals from the transmitter and then decodesthem. Depending on what signal the receiver decoded, it willactivate a servo, the third part of the system. Servos are the
mechanical part of a remote control system.

A wheel or sometimes bar on the servo will turn in proportion with the movement
of the transmitter’s control. This movement can then be used to directly control the function of a robot, or in Questor’s case to trip switches that control his movements.
Questor’s remote control system is a standard off-the-shelf type like that pictured in Fig. 4-1. Notice the three main parts of the system. The robot requires a system with a minimum of two channels.

A two-channel system has two servos; each of the servos is used to control one of the robot’s motorized wheels. The system used in my version of Questor has three
channels; the third channel is used to trip two switches that can turn other items on the robot on or off.

The switches that the servos trip are called leaf switches (Fig below). A leaf switch is a very small on/off switch that is triggered by depressing a small metal strip or “leaf” on the switch. By using four leaf switches, it is possible to recreate the function of the DPDT switches used in the temporary control box.

A total of eight switches is needed to duplicate the function of the DPDT switches used to control the robot’s motorized wheels. One servo is then used to trip four switches in
such a way to drive the wheel either forward or reverse. You use the control sticks on the remote control transmitter in the same way as you flipped the DPDT switches on the temporary control box; up is forward, center is off, and down is reverse.

If you chose a remote control system with more than two channels, you can use the other servos to trip leaf switches for turning other devices on or off, or control motors (forward,
stop, and reverse) within the robot. The third servo of my remote control system is used to turn a horn on and off.

You need only one leaf switch per function if that function is to be turned only on or off. Figure above shows how the leaf switches are positioned and triggered for either on/off or forward/reverse control. By now you’re probably wondering
where all this fits inside of Questor. The remote control system (servos and receiver), leaf switches, and other components are mounted on a motherboard that is then installed inside Questor’s framework.

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