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How to -Using switches to control speed

Now here is a real challenge. The switch icon can only produce a 0 and 1 output so the motor can only be set to these two values. However, it would be useful to set two speeds, say between 50 and 100%.

This is done with the offset option in the amplifier.

The output is 50% when the switch is OFF and 100 when the switch is ON ( 1X50.0 + 50.0 = 100).

Motor speed ramping

In this stategy you want the motor to ramp up, proceed at top speed for several seconds and then ramp down in speed. Obvious need fo worksheets.

1. Put down the three work sheets. Make sure the icon labels convey useful information. In this case we show that the run time of two icons is 999 seconds because we will exit the sheets with an internal sheet stop.

2. Enter strategy for speed up icon

Set-Point:

This is set to generate a forward output and is applied to motor 1.

Decision ON to REVERSE

This changes the ON to REVERSE and is a simpler way than using another set point. ( Can you see the easy way to set the buggy motion to reverse?)

Generator 1/s

This creates a pulse every second

Pulse Counter

This counts the pulses and this produces an increasing number.

Amplifier X10

This multiplies the count by 10.

Comparator

This generates an ON value when the input reaches 11.

3. Enter strategy for top speed worksheet

This worksheet uses the same motor control icons as the previous sheet but the speed control has been removed. This means the motors are set to the 100% default value.

4. Enter strategy for ramp down worksheet

This worksheet is the same as the ramp up worksheet except that now the motor speed should start at 100 and come down in steps of 10.

This is achieved changes to the Amplifier icon.

The incrementing counter value is multiplied by -10.0 and added to 100.0.

The values decrease as required.