28824 Parallax Inc, 28824 Datasheet - Page 2

• Manufacturer Part Number: 28824
• Description: SERVOPAL SERVO PULSER TIMER
• Manufacturer: Parallax Inc

Specifications of 28824

• Accessory Type: Servo Motor Control
• Product: Microcontroller Accessories
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: BASIC Stamp®
• For Use With: 28803 - KIT BOARD OF EDU W/O PWR SUPP
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Hardware Interface and Initialization
Interface to the ServoPAL is realized through its /Inp input and Alarm “output”. When the ServoPAL
powers up, both lines are configured as normally-high inputs, pulled up to a nominal +5V through
internal 20K to 50K resistances. Commands to the ServoPAL are sent as negative pulses to the /Inp pin.
If the alarm feature is not used, the BASIC Stamp can use the Alarm pin for any other purpose. If this is
done, however, you must be careful not to trigger an alarm inadvertently, or else a bus conflict may
occur.
The ServoPAL runs autonomously on power obtained from the servo headers. Therefore, it does not reset
when the BASIC Stamp resets, and continues to send out pulses during and after reset if it was sending
them out before. But it can be reset, nonetheless, by sending a pulse of 100mS duration to the /Inp pin.
Here’s the recommended initialization sequence for the ServoPAL in PBASIC:
© Parallax, Inc. • ServoPAL (2007.10.30)
Servo 1
Below is a photo of the ServoPAL installed on a BOE-Bot’s P12/P13 servo header. The wheel servo
motor cables are plugged into the ServoPAL. In this case, the /Inp input pin is P12, the Alarm
output pin is P13, the right servo is Servo 0, and the left servo is Servo 1.
Gnd
Vdd
Top View
Servo 0
Vdd
Gnd
Alarm
Gnd
Vdd
Servo Header
Vdd
Gnd
/Inp
To Servo 1
Alarm
Gnd
Vdd
Everything Connected
To Servo 0
Vdd
Gnd
/Inp
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