Signs of the Times - March 2013 - (Page 30)
LIGHTING TECHNIQUES
By Marcus Thielen
Marcus Thielen is a physicist and lighting-industry
consultant from Duisburg, Germany.
Sign Power Supplies and Interference
Accounting for invisible and undesirable impacts
This month’smost likely undesirable,
column will deal with
invisible, and
radio-frequency radiation from our
signs. This radiation may cause interference, known as radio frequency
interference (RFI), in nearby wirebound or wireless communication
systems, including all of the related
trouble.
In the last few years, our voice
and data-communication networks
have become exponentially more
dense. Additionally, however, another
major change in power-supply technology causes interference to become
severe for sensitive applications
like air-traffic control, long-distance
radio, etc.
In the US, FCC (Federal Communications Commission) governmental
regulations (www.fcc.gov/cgb)
regarding interference and enforcement may vary locally, so review
regulations before the sheriff turns
off your customer’s sign on behalf
of the FCC.
To understand technological
differences in power supplies from
Ballast (inductance)
This “jewel of enlightenment” plasma sphere by Bill Parker operates by radiating
radio frequency into space. Devices of this size cause interference and are potentially
dangerous for people with electro-medical implants.
past to present, let’s first examine
“classic” technology, which very
rarely causes interference problems.
For fluorescents, HID and neon
Starter
signs, the “classic” ballast comprises
a core-and-coil, transformer assembly
to generate enough voltage to start
the lamp; the lamp current is regDC smoothing
Transformer
DC voltage
regulator
PFC capacitor
RFI blocking
AC to DC
converter
DC smoothing
AC to DC
converter
RF to DC
converter
RFI blocking
Fast switch
AC to DC converter
Ballast (inductance)
Photo 1: T8, 36W fluorescent-lamp control gear: (Top) A classic
core-and-coil ballast; (Bottom) A modern switched power supply.
30 SIGNS OF THE TIMES / MARCH 2013 / www.signweb.com
RFI blocking
Fast switch
Transformer
DC voltage
regulator
Photo 2: A “Walldog”-type, LED, posterboard power supply:
(Top) Classic core-and-coil technology; (Bottom) New switching
type, three times more powerful than the classic one, but it
creates interference.
http://www.fcc.gov/cgb
http://www.signweb.com
Table of Contents for the Digital Edition of Signs of the Times - March 2013
Signs of the Times - March 2013
Contents
ST Update
Smart Inking
Technology Update
Vinyl Apps
Strictly Electric
Lighting Techniques
The Moving Message
Technology Review
Technology Review
Design Matters
New Products
ADA: One Year Later
The Supergraphic Connection
ISA Sign Expo 2013 Preview
Compensability and Valuation of Billboards in Condemnation
Industry News
Advertising Index
Editorially Speaking
Signs of the Times - March 2013
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