27906 Parallax Inc, 27906 Datasheet - Page 10

• Manufacturer Part Number: 27906
• Description: BASIC STAMP ACT BOARD NO PWR
• Manufacturer: Parallax Inc

Specifications of 27906

• Module/board Type: Activity Board
• For Use With/related Products: BASIC Stamp®
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

SMAX – Set Speed Maximum
Description: Sets the maximum desired rate of travel in units of positions/0.5 second (same units as
SSRR – Set Speed Ramp Rate
Description: This command sets the rate of acceleration/deceleration for the beginning/end of travel.
Copyright © Parallax Inc.
Command #:
Command #:
[Command:Address],[SpeedH],[SpeedL]
8
9
[Command:Address],[Rate]
Transmit Data Format
Transmit Data Format
the QSPD command). The speed value is an unsigned 16-bit value sent high byte first
(SpeedH) then low byte (SpeedL). The default value is 36 positions/0.5 sec which equates
to 120 rotations/minute.
immediately. It is recommended that the maximum speed value only be modified during a
stopped state; however, the SMAX command technically allows for a new maximum speed
to be set at any time.
The maximum speed value is considered a “true” speed because the Position Controller will
maintain a constant overall average speed regardless of terrain, slope, or motor loading
(as long as the driving motor has sufficient power to do so).
Controller can constantly monitor the wheel’s actual speed, it can dynamically increase or
decrease power to the motor in order to maintain the desired speed value. For example, if
the motor is driving up a hill, the Position Controller will throttle up power to the motor to
maintain constant speed; and will throttle down or even apply an opposite torque if
necessary when traveling down hill.
Note that at very low speeds (around 1 position/0.5 second) motion may not be as
smooth. The user may notice the individual advancements of the set point every 0.5
second; however, the overall rate of travel will still exactly match the user-specified
maximum.
*While not recommended, it is possible to change the maximum speed value in mid-travel.
Keep in mind that this value is the maximum speed that the position controller is allowed
to travel. During motion, if the Position Controller receives a new speed maximum which
is greater than the current speed maximum, it will begin accelerating at the speed ramp
rate up to the new speed maximum. If the Position Controller receives a new speed
maximum which is lower than the current speed maximum, the speed will instantly be
clipped to the new value which will generally be abrupt and undesirable.
The speed ramp rate is an 8-bit unsigned value with units of positions/0.25 sec
value is the rate of change of speed (in positions/0.5 sec) per 0.5 second. The default
value on power up is 15 positions/0.25 sec
{0 ≤ Speed ≤ 65535}
{1 ≤ Rate ≤ 255}
Hex Value:
Hex Value:
0x40
0x48
Position Controller Kit (#27906)
Changes in the maximum speed limit become effective
Binary Value:
Binary Value:
01000 000
01001 000
2
.
Configuration
Configuration
Receive Data Format
Receive Data Format
Command Category/Type:
Command Category/Type:
N/A
N/A
v1.1 3/22/2010 Page 10 of 13
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Single, All
Single, All
2
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