Show Systems - Support Equipment
Box for low power 220 VAC lasers
Many smaller air-cooled lasers, and even some lasers up to 5
watts output, need 220-230 VAC for operation but at only 10-15 amps or less. This
paper describes a simple "spider box" that can be used to make 220
VAC power from two 110-115 VAC outlets without the use of a heavy step-up
An example of a spider box
This paper discusses medium and high voltage AC power wiring. The
voltages discussed are dangerous and can be lethal - the reader is
advised to use caution and standard electrical safety practices when working
with AC power. Connection of this device to the AC lines in your area may be
subject to approval/certification of the device - check with local
authorities before connecting to your power grid.
Most lasers that output more than a few milliwatts require
220-230 VAC for operation. In most cases, this means using heavy cables and
locating a stove plug or three phase power source for the laser. There are
many air-cooled and even a few small water cooled lasers that require fairly
low amperages at 220-230 VAC -some less than 15 A for operation.
These can be powered quite simply using a spider box rather then a heavy
step-up transformer. A step-up transformer will typically only deliver a
little less than half the input amperage [E.G. if a step-up transformer is
plugged into a 16 A 115 VAC outlet, it will deliver about 7.5 A at 220-230
VAC]. The spider box overcomes this and allows up to a 15 A laser or laser
system to be powered from two U-ground outlets [provided they have 15A or
A spider box combines the phases from two 15 A U-ground plugs into 220-230
VAC. Depending on the amperage requirements of your laser, there may be some
power left over to run low-load devices such as a projector, controller or
laser graphics computer.
The circuit shown below was designed to operate a
Spectronika 5 watt CV laser system [which requires about 8 A at 220-230 VAC]
as well as providing two 110-115 VAC outlets, one to power the projector and
one for the controller and graphics computer. It can be used [with
modifications] to power any small laser that draws up to 15 A at 220-230 VAC.
Spider Box schematic diagram
To build the spider box, we used a readily available small
220 V breaker panel capable of holding a maximum of eight single pole
breakers. Smaller boxes are available however, this one was an "off the
shelf" unit available at Home Depot [and many other hardware/electrical
stores]. In the schematic above, the two ground lines are tied together and
also attached to the case of the box by means of the grounding
strip/terminal. The two neutral lines are also tied together and connected
to the neutral terminal strip in the electrical box. The live lines are
connected one to each of the live input terminals of the single phase box.
NOTE: The wires in the 14 gauge input cables follow the standard North
American colour scheme of green, white and black - the lines are shown as
red and black in the schematic for clarity.
A 10 A dual pole breaker was installed in the box and the output side was
routed to a 220 V U-ground socket which has two horizontal prongs rather
then the vertical prongs typically seen on U-ground sockets. If your laser
requires more then 10 A, then a 15A dual pole breaker can be used. A
receptacle for this type of plug was mounted into a water resistant, outdoor
type, molded plastic receptacle box with spring loaded cover flaps. These
are readily available at most electrical and hardware stores and are light
weight and durable. A ground connection was made from the U-shaped pin to
the grounding strip attached to the interior of the case.
On the opposite side of the breaker box (see photo above) another similar
water resistant, outdoor type, molded plastic receptacle box with spring
loaded cover flaps was mounted and fitted with two standard U-ground
receptacles. Each of these was connected to it's own 5 A breaker to provide
protection for the connected equipment. If your laser requires more then 10A
of power, these additional receptacles should be eliminated.
NOTE: Some dual 115 VAC receptacle assemblies come with a small metal strip
that ties the two neutral and hot lines of the receptacles together. If this
is present, it should be removed on the live side so that the outlets
function with common ground, common neutral and separate hot lines.
Two 115 VAC neon indicators were mounted to the top of the front of the
breaker box and each was wired from one phase to ground (N1 and N2 in the
schematic). In the event that the load on the spider box exceeds the
capacity of the building socket and a breaker blows, these lights help to
determine which of the 115 VAC outlets is at fault so that power can be
In order for the box to deliver the 220-230 VAC, the two
110-115 VAC U-ground connectors must be plugged into outlets on separate
phases, and the building wiring needs to be correct. If the hot and neutral
are swapped on one of the wall receptacles, there will be a short. We use a
small AC line tester which looks like a large U-ground plug with 3 lights on
the back to verify that the building socket is correctly wired before
plugging in the box.
By inserting the probes from a multimeter into the 220 VAC socket on the
breaker box, we can quickly determine if the outlets are on different
phases. When the wall outlets are on the same phase, the voltage reads well
below 220. When the wall outlets are on different phases, the meter will
read between 208 and 230 VAC depending on the local power supply.
The box has about 3 meters (12 ft) of 14-3 cable for each of the U-ground
plugs. In areas well supplied with circuits such as a professional theatre
or auditorium, this is often enough to connect to wall receptacles that are
on different phases. In some locations, we simply use an additional 10 meter
(30 ft) 14-3 U-ground extension cord to extend one of the plugs to a
receptacle on another phase that may be at some distance from the spider
box. We also carry a couple of 10 Meter (30 ft) 14-3 extension cords with
the horizontal prong 220 V plugs and sockets so that we can locate the
spider box out of the way at the bottom of the scaffold and run the 220-230
VAC power up to the laser.
NOTE: You should find out what other items are connected to the circuits you
intend to use for the spider box so that the total load of your laser system
plus other items do not exceed the rated load for the outlets.
The spider box allows us to power up our 5 watt, air-cooled
Copper Vapour laser, the X-Y beam projector, the control console and a
graphics computer without the need of a step-up transformer, bulky cables or
finding a 220 V connection. It is simple to assemble, weighs less and cost
less than a step-up transformer. It can be used to quickly and easily
provide 220-230 VAC power for any laser that draws less than 10-15 amps.
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companies named on the relevant page(s). Laser F/X does NOT endorse or
recommend any products/services and is NOT responsible for the technical
accuracy of the information provided. We provide this information as a
service to laserists using the Backstage area.
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