require some kind of manual or automatic switching device to enable
to switch on and off. Originally, streetlights
were turned on and off manually by a 'Lamplighter', but over time,
all sorts of automated methods of switching have been
invented and used.
mounted some 8ft-10ft from ground level, these
electric switch boxes were simple but rugged switch
devices that had to be operated manually by a 'Lamplighter'.
The switch would be activeted by the 'lamplighter' reaching
up with a wooden pole with a hook or loop fixed onto
the end of it. The external rocker-switch would them
be pulled down into either the on or off position to
operated the lamp above. Click
here for images.
and 'Calendar' Time-switches
25-30 years ago, 'time-switches' were the accepted
method of switching streetlighting on and off. Early
examples were clockwork and needed to be regularly wound,
as well as being manually re-set every couple of weeks to allow for
the variances in lighting up times during the year. Over the years automatic
electro-mechanical clocks were
developed that were designed to
allow for the variance in lighting-up times, these
were known as 'calendar-time-switches'. However, over the last quarter of a century,
calendar-time-switches have all but disappeared from use in streetlighting.
Today, the vast majority of streetlights in the UK,
and elsewhere around the world, are controlled by light-sensitive photocell controlled switches; a far more cost
effective and reliable method of controlling streetlights.
or 'Ripple' control was an automated
switching system used in the post-war period and during the 1950's by some local
Britian. It enabled the 'switching' of street lighting over
large areas, to be controlled from a single unit at an electric sub-station.
Individual street lights, or groups of street lights were fitted with a
frequency sensitive tuned relay. When it was time to switch the streetlights
on, a burst of high frequency signal was sent down the mains supply from the
sub-station, and these relays detected the signal and closed the circuit to the
lamp. When it was time to switch off the streetlights another burst was sent.
Sometimes the HF signal generator at the sub-station was controlled by a master
time-switch, or sometimes was even operated manually. This switching system was
probably the forerunner of the telephone control switching systems used today.
My sincere thanks to Mike Docherty for providing the technical information.
known as PECU's (photoelectric control units), Photocells
are electronic light-sensitive devices usually mounted
on the top of the lantern or sometimes on the column
top. These devices measure the light level, and as daylight
begins to fail and light level drops, the photocell
will sense this and activate the switch/controller,
turning the lamp on. Likewise, when the light level
increases again, the photocell will sense the increasing
levels of light and will extinguish the lamp.
are available that react differently to differing light
conditions, so that the optimum performance and economy
can be obtained from streetlighting during lighting-up times. The photocells are also designed to have a
delayed reaction to rapidly changing light levels (such
as rain storms in daylight hours), so
that they don't repeatedly switch the lighting on and
off under those conditions.
Like most components,
photocells will eventually fail during their service
life, but when they do, they are designed to fail 'on'.
You may have seen streetlights lit during the
day (day-burning); quite often the problem is caused by a failed photocell.
There are two
basic types of photocell: one-part photocells and two-part
In a one-part
photocell switch, the photocell and control switch are integral to
one another. The photocell unit fits directly into
the control switch, known as a NEMA
socket (National Electrical Manufacturers Association),
normally mounted on top of the lantern.
The photocell is fixes into the NEMA socket by means of a bayonet type
fixing, so if it fails or needs replacing
it's as easy to change as a light bulb. The advantage
of these types of photocell controlled switches
is that they are compact and can be easily accommodated
within the structure of the lantern.
differ in that the photocell and switch are not as one;
normally the photocell is situated in the top of the
lantern, but the control switch may be located some distance
away, in the base of the lamppost column for instance.
here for image.
Intelligent Management (IM) control systems.
IM is a control system that relies on radio waves to
communicate from a base station via a radio transmitter to a transmitter/receiver
node mounted on
the top of each individual lantern. The software in the system not only allows
the on/off switching when required, but also has the capability of dimming
lanterns by activating a dimming circuit within the lantern's electronic
ballast, e.g. dimming of streetlighting in the early hours of the morning when the
roads are empty. This has the potential of considerable cost savings on current
energy consumption levels.
IM also enables information on the lamp life of individual
lanterns to be relayed back to the control centre, informing the operator
whether or not any given lantern is operational. Therefore unnecessary
dayburning of lamps can be prevented, and costly nighttime inspections of
installations can be avoided.
major advantage of the system is that it can be implemented into an existing
installation and does not require additional ground works. However, if a dimming
capability is required from the installation, suitable
replacement lanterns with a built-in dimming capability
need to be used.
IM installations require a radio transmitter base station
(and possibly sub-stations) to be installed at suitable locations,
which means that the initial cost of installing an IM
system could prove prohibitive.
I understand that Mayflower Intelligent Management Systems
(MIMS) have recently developed an IM control system that has
the capability of dimming conventionally ballasted lanterns
with the use of a special adapted transmitter/receiver node.
My thanks to Dave Bisby of Sheffield
City Council for this information.
Here are some
examples of the switches and photocells held in the collection:
No243HS manually operated '2-pole fused' switch mounted
in a 'Bombay' watertight cast iron box for either
pole or wall mounting. The car keys give a sense of scale.
With the box open; from top to bottom, the porcelain spring
loaded contact discs, the
two porcelain fuse holders, and the cast iron sealing chamber. Note the asbestos
'REVO' manually operated 'rocker' switch for conduit
mounting. These types of swiches were usually mounted
between the column
top and the bracket supporting the lantern.
The switch is in acquired condition, and aside from
the bent arm on the rocker switch, it's complete and
is an excellent candidate for a complete rebuild and
refit to a suitable REVO bracket from the collection.
(early non-Calender types)
wound 'clockwork' Venner BF/43 250v, 5amp
time-switch (minus its outer case), Circa 1920's. These
early devices were for 24-hour switching, but had
no automatic adjustment for seasonal variances in lighting
up times, so had to be manually reset every couple of
weeks. The square ended spindle sticking out from the
centre of the clockwork mechanism is where the key would
engage to windup the spring powered motor. The car keys
show how small these early devices were.
its outer case, a Venner MPX 'electric' 200-250v,
50Hz, 10 amp time-switch (24hour, non-calander).
Saved from Oldham M.B.C's Uppermill Council Depot in
1974 by Dorron Harper. This early electric time-switch
had orignally been new to Saddleworth U.D.C. in about
Y-MK2 200v-250v 50Hz 30(12)A Calendar Time-switch
TJSSP Timeswitch, enclosed
TJSSP Timeswitch, case cover removed revealing the electric clock
and switching device
TJSSP Timeswitch dismantled, showing contact pins
that locate into the back of the casing
S251 20Amp 240v 50Hz Calendar Time-switch
Zodion SS5 Photocell (minus its NEMA socket)
Zodion SS6 Photocell (minus its NEMA socket)
and light detector. The 'S' on the photocell detector
indicates South, and is the direction that the 'S' needs
to face when the detector is mounted on top of the lantern,
so correctly aligning itl for sunrise and sunset. The spike on
top of the detector is to prevent birds from perching
on top of the dectector and covering it in
droppings, which would eventually block out the light
and stop the photocell from operating correctly. The
control switich would be mounted inside the column.
or Rythmatic control switching
An ATE (Automatic Telephone and Electric Co Ltd,
of Liverpool), 250v AC 1450 Hz Rythmatic Control
Switch (Rhythm 0.66 on / 1.00 off). This Bakelite encased
unit dates from the late 1940's and came from Lytham
St Annes. Car keys used
to give an idea of scale.