System Integration Guidelines to Minimize
EMI cont’d
• Use holes and avoid the use of slots for cooling openings
• Use chokes on power leads and or twist power leads to
eliminate noise issues
• Make sure all power terminals are clean and tight
• Do not run wires parallel to each other, which could cause
crosstalk issues
• Avoid tying or locating signal leads (DC) close to power leads (AC)
• Keep ballast module approximately two feet away from a
CRT, computer or other magnetic field-sensitive devices.
Use thicker shielding if close proximity is unavoidable
• Ferrite cores can normally be used to eliminate a resonance
problem or control interference
System Integration Hints
Physically locate the ballast away from circuitry that is
noise sensitive or circuitry that is routed outside of the
system housing. This will help control EMI/RFI emissions
and help enable the ballast to be compatible with the system.
Don’t bundle sensitive signal leads with the ballast input
and output power leads. Intentional spacing or shielding
may be required to enable the ballast to be compatible
with adjacent circuitry. A common symptom is interference
with adjacent circuits during ignition.
Operating Voltage
Maintaining the proper input voltage is extremely important.
Do not exceed the absolute maximum voltage listed for
your particular ballast. It may cause a nonrecoverable
failure of the lamp, ballast or both.
When operating with batteries, it’s important to research
the batteries’ characteristics when fully charged and how
they discharge to ensure compatibility with your ballast.
If a lamp fails to start, the ballast will shut down and will
only draw a low amount of power. The power must be
cycled off and back on in order to re-light the lamp.
Input Power Supply Selection
The power ratings of the ballasts refer to the output
power to the lamp. The ballast input power will always
be greater than its output power because of its efficiency
limitations. The ballast has a capacitive input, which will
demand a short-duration inrush current from the power
supply. This is usually not a cause for concern.
Input Wiring for Printed Circuit Board (PC)
Version Ballast
Welch Allyn recommends complying with IPC-A610D
solder process standard or equivalent. Construct an input
power connector assembly compatible with the input
connector (Molex 41791 connector 2-pin series or equivalent)
located on the ballast circuit board assembly. The input
connector can be found at the bottom edge of the ballast
assembly shown in Figures 1 & 2, location J101. Pin 1
is the positive input voltage and Pin 2 is the negative
input voltage. Slide the connector housing portion of the
assembly onto the input power connector, location J101,
until the mating halves lock in place. Observe the wiring
voltage polarity as specified in the pinouts section in the
performance specifications table. Failure to observe input
power wiring polarity could result in failure of the product.
Wiring for Printed Circuit Board (PC) Version Ballast
Figures 1 & 2: Ballast Assemblies
18, 21 & 24 W Ballast
50 W Ballast
All measurements are mm [in.]
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