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DigiSpeed-GX™
- Users Guide
Page 9
4 Board Description
4.1
Introduction
The DigiSpeed-GX™ controller provides the capability to
control a device such as the the spindle speed of a DC or AC
motor via computer control
May of the devices that the DigiSpeed-GX™ is designed to
work with such as the KBIC-120 controller supplied by KB
Electronics, use a "Hot Ground" circuitry. That is, the
reference voltages for setting the speed are at MAINS
POTENTIAL voltage. This voltage is dangerous and can be
lethal.
This style of controller uses a control voltage, usually in the
0 –10Vdc range to control the motor speed from 0 – max
speed. In reality, this voltage can be anywhere in the range
of 5Vdc to 15vdc. The maximum output voltage of the
DigiSpeed-GX™ and thus the speed of the motor can be
limited by an attenuation trim-pot that reduces this control
voltage supply.
AC motor controllers are usually Variable Frequency Drives (VFD) and have terminals for
the connection of an external manual control potentiometer, or a 0-5Vdc, 0-10Vdc control
voltage.
The DigiSpeed-GX™ circuitry is essentially in two parts. One part contains low voltage
logic level circuitry that includes a micro controller and interfaces to the PC or controlling
device. It is supplied by 5Vdc that is referenced to the controlling devices ground. The
other part of the DigiSpeed-GX™ circuitry is connected to the DC Speed controller
control circuitry. This part is at MAINS POTENTIAL.
The two parts of the circuitry are separated by opto-isolation. This ensures that the
dangerous MAINS POTENTIAL voltages are kept away from the low level logic
circuitry. The two parts of circuitry must never be connected together. If it happens, a
catastrophic failure of the DigiSpeed-GX™ circuit and your PC will occur.
Copyright 2006 ©
Homann Designs
Revision 0.1
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