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NEWSLETTER

 2ND ISSUE 1999 EDITION

Pneumatic Robots - Click to enlarge

CONTENTS:

- What's New
- On the net
- EA says OK
- Focus Kits
- Software
- Robocup News
- Hints & Tips

WHAT'S NEW
I normally don’t review a product until we have received stock. However, since there’s been an unusual amount of interest in the Pneumatic Robots kit that I’m going to tell you about it!

Controlling things by pneumatics or air pressure has many advantages over electrical control which is evident by the fact that this is generally the way things are done in industry. Pneumatic cylinders are used to provide linear movement whilst the ‘machine intelligence’ is performed by electrical or rather electronic circuits (usually programmable controllers or computers).

The control of the air is performed by solenoid valves (i.e. an electromagnet that opens an air valve). Because the solenoid can be connected to the computer interface, the pneumatic functions of the model can be controlled by computer.

Of course, to provide the air supply one must have a compressor. Fischertechnik provides a low-cost solution by including in the Pneumatic Robots kit a reliable miniature compressor and a compressed air reservoir to ensure a constant air supply.

The Pneumatic Robots kit (p/n 34948) also includes; 4 pneumatic cylinders, 3 solenoid valves, 2 motors, 1 light barrier, 1 emergency stop switch and an instruction manual with details of 4 models; pneumatic door opener, sorting unit, processing centre and pneumatic gripper (you’ll soon discover the benefit of the pneumatic gripper as it can pick up objects of varying size with none of the problems associated with using an electric motor gripper).

As with the Industry Robots kit, this kit may be purchased for use with your own Control Unit (PLC or computer interface) or it may be purchased as an add-on to other fischertechnik kits. A complete package with construction set, interface, power supply and software is also available.

ON THE NET
Significant price reductions have occurred on most computer controlled kits, check this out through our new website address:

http://www.procontechnology.com.au

Don’t forget to take a peek at the low-cost DIY I/O board. This kit would provide an ideal project for school electronic courses. Also posted on the net is information regarding the new IR control set.

EA SAYS OK
A three page review of the industry robots kit (30408) appeared in September issue of Electronics Australia magazine - Australia’s most popular electronics and technology mag!

Here’s what they said: ‘Good points: Exceptional manuals, High quality and professional design. Lots of programming options too. Bad points: You’ll need patience.’

Our comment: If you don’t have the patience then we’ll construct the model for you for a nominal fee when you purchase any COMPLETE kit!

Mr Peter Oskam of NZ says: 'I received the Industry Robot more than 2 weeks ago, and like the author in EA assembled the kink-arm robot version. With the help of the Check interface I soon had it running the sample program (from the software supplied - LLWIN). The manual and software are both excellent, thank you and fischertechnik.'

Check out their website at: http://www.electronicsaustralia.com.au

FOCUS KITS
A new series of kits have been developed to replace the UT series. Designed for upper-primary and lower secondary levels these kits provide detailed instruction in Structures, Mechanisms and Electrical Control.

The kits and detailed instruction manual (with assignments, teacher’s notes, suggested solutions and extension ideas) was developed by Economatics in the UK.

The ‘Mechanisms’ kit provides experience with: rotary motion, power transmission, gear systems, levers and linkages. The ‘Electrical Control’ kit covers: simple circuits, circuit diagrams, control logic, motorised gearing systems, torque, ratios and the effect of load on an electric motor. The ‘Structures’ kit covers: structures terminology, rigidity, load failure, struts and ties, triangular frames, stability and centre of mass.

Mr Steve Rich, Head of Design and Technology - Weatherhead High School Wallasey UK, says: 'Fischertechnik is a good material to use for teaching about structures. You can apply real forces to it, and see the resulting deformations without damaging or destroying the structure. It is one of the few kits that allow you to build up a relatively large structure quickly and simply.'

SOFTWARE
32 bit software for the Mobile and Industry Robots kits has been released and an upgrade of the Turtle/Profi kit software is also available. More examples are provided in Delphi and VisualC++ than before and examples of ‘real-time’ operation are also given. i.e. ‘real-time’ means that control programs continue to run even when the computer is running other applications! Upgrades are half normal price to all customers who have returned their licence agreements.

The drivers for the serial port interface has had minor changes. In particular, you can now detect if the computer is communicating with the interface. Available free-of-charge to registered users.

ROBOCUP NEWS
Melbourne has won the right to host the world’s robot soccer competition - RoboCup - in the year 2000. This event will be staged during the PC-IT exhibition in August. The game is played on a miniature indoor field. Two teams of 3 or 4 robots attempt to score goals. The robots are completely computer controlled with no human intervention allowed.

Schools can become involved in the excitement of this sort of contest by running their own competitions. Schools in Germany, for example, use the fischertechnik ‘Mobile Robots’ kit to construct vehicles that pick up and hold as many ping-pong balls as they can - the vehicle that picks up the most ping-pong balls is the winner! See our website for more information.

Both primary and secondary schools can now be involved with the Robocup junior challenge - check out the website at: www.robocupjunior.org.au

Fischertechnik can now supply a suitable mobile robot kit for the robocup junior challenge. Click here for details.

HINTS & TIPS
Tip 1. Normally motors run only at full speed. However, some degree of speed control can be obtained by switching the motor on and off rapidly (or more technically called Pulse Width Modulation PWM). The Power Controller unit from fischertechnik uses this method to control the motors speed with a variable potentiometer used to adjust the ‘Pulse Width’ and hence speed of the motor. However, the same technique can be used when controlling motors from the computer. The following BASIC example provides a 50% duty cycle - that’s 50% on and 50% off - slowing down the motor accordingly.

By changing this duty cycle the motors speed changes. This can be done by adding more ‘if’ statements in the program after ‘Motor M1, MCW’ to speed it up or after ‘Motor M1, MOFF’ to slow it down!

Tip 2. The humble diode - the device that conducts current in one direction but not the other - may be used to stop motors driving past their end points when using the new IR remote control or simply to save inputs on the computer interface.

A simple test can be performed by using a diode such as the IN4004 (costs 10 cents at any electronics store) placed in series with a motor and then connected to the power source. As you change the polarity of the source you’ll find that the motor runs in one direction but not the other!

The following circuit makes use of this characteristic of diodes to allow the motor to run in the reverse direction when the switch is activated. The switch stops the motor but the diode allows the motor to still run in the reverse direction, away from the switch, as required.

Limit switch circuit

This switch and diode arrangement could be used to replace the home position switches on the Industry Robot models. By doing this you would save up to 4 inputs on the computer interface which can be used for other things. How does the computer know when it has reached the home position? Simply by checking the pulse switch, when the motor stops so does the pulses! With a minor modification to the QBASIC or VB programs, which we supply with the Industry Robots kit, you’ll be in business - simply replace all references to the switches with zero. You can then use the spare inputs for other things - like detecting when a block is in place and ready to be picked up.

Tip 3. Did you know that the fischertechnik interface can drive up to two stepper motors? The fischertechnik plotter is now available as a training model and the stepper motors and mounting hardware are available as spare parts! The recommended stepper motor is a four wire, 2 coil bi-polar unit. One coil connects to M1 whilst the other coil connects to M2. The stepper sequence must be performed by the computer program as in the following BASIC program:

To operate in the reverse direction execute:

The 'Delay 5' above is a subroutine that has been defined in previous newsletters. In VB or QBASIC the minimum time interval is 55ms so the speed of the stepper motor will be rather slow. The good news however, is that under VisualC++ intervals of 1ms resolution can be obtained! If using the 30402 interface unit, these delays may be removed. Because of the RS232 transmission times of about 5ms.