Make A Switch Board

*Make Switch Boards

Constructing these boards takes some time so you need to plan ahead.

The board is constructed with a 1′ x 1′ square of pegboard with a 1×2 frame around the bottom. All the connections for switches and motors are connected on the bottom to #6 x 3/4″ bolts run through the peg board holes. The bolts allow teams to connect the switches using alligator test leads. Make sure you buy these bolts from a commercial bolt supplier. You can spend 10 times as much for these if you purchase them at a retail store like Lowes or Home Depot.

The board includes (adapt this for your own supplies):

  • Double “C” battery holder
  • small electric motor with a plastic gear (get a bag of motors and a bag of gears from Edmund scientific and it costs less than $1 per setup). The motor is mounted on a small block of wood to elevate the gear so the motor will turn.
  • Incandescent light holder and lamp
  • LED light holder and LED
  • Double Pole Double Throw Knife Switch
  • Momentary Normally Open Pushbutton
  • Momentary Normally Closed Pushbutton
  • Magnetic Switch
  • Double Pole Double Throw Lever switch

A local surplus electronics shop is the best place to find switches. You can also go to Radio Shack or some other consumer electronics store but you will pay too much for the switches. If there is not a surplus electronics shop in your area then you can probably find these switches at a web based surplus electronics shop such as www.allelectronics.com. Many of the switches shown in the sample picture on the first page are switches designed to go in a metal panel. They are very difficult to install into a piece of pegboard.

Steps (You can click thumbnails for larger pictures)

The first step is to cut out 12″ x 12″ pieces of pegboard and attach them to 1×2 wood frames    
Next, layout your switches. The picture of the board on the first page has a large number of switches. The picture on the right is a simpler version of the board. This minimum configuration provides everything needed to teach teams the basics on switches. There is extra space on the board so that additional devices (relays or solenoids for instance) can be added in the future  
If you use a gear on the motor shaft then installing the motor takes an extra step. A 1 x 1 x 1-1/2″ block of wood has to be screwed to the pegboard to allow the gear room to turn. The motor is attached to the block with a wire tie (to make replacement easy). Drill holes through the block and the pegboard to run the wires to the bolts. The wires should be soldered to the solder terminals on the motor.  While we did not try this an alternate might be to use a slightly larger block and a conduit clamp to hold the motor in place.  
Some devices may require that you drill additional holes for installation. For this board we had to drill holes to bolt down the magnetic switch, the knife switch and the battery holder. We also had to drill holes for the toggle switch, the LED lights and the Momentary pushbutton switches.
Click thumbnails for close-ups of some of the switches installed on the boards.
     
On the underside you can use bare wires to connect switch terminals to the #6 bolts. It is best to solder the connections to the switch terminals.  
Label the switches: If you use a magnetic switch typically used for home security you will need to label the normally open and normally closed switches. More than likely the NO and NC connection points will not be labeled as you expect. The normally closed connection is open when there is no magnet near and the normally open connection is closed when there is no magnet near. This may be because when the switch is used for security on a window the magnet is normally next to the switch so in its application as a security switch it is normally closed.  
Put together kits with alligator clips and a magnet for the magnetic switch. Store them in inexpensive disposal storage containers.  

Create worksheets to match your boards configuration.

Tips on construction of the boards

  • Adapt the layout for your board according to the the switches that you have available.
  • We constructed these boards with a double C battery holder because they were convenient in size and “C” batteries are used in the other electrical projects. You can certainly use other sizes.
  • The LED on the board is OK to use at the 3 V output by the battery pack. If you elect to use a higher voltage power source you will have to install a resistor inline with the LED to keep from burning it up. Go to http://led.linear1.org/1led.wiz for an on-line calculator to help you determine resistor size. You can get the voltage and mA specifications for your LEDs from the packaging.
  • The LEDs are mounted in sockets we purchased from Radio Shack. It requires soldering wires to the leads of the LED to make the connection to the bolts. We looked for a socket that we could plug the LED’s into to make replacement easier but were not successful in finding one.
  • It is important to have a DPDT knife switch because it helps to visually explain the concept of poles and throws
  • The boards in the example used push buttons from Radio Shack. These do not work that well in the pegboard. Try to find some pushbuttons from a surplus dealer
  • Verify that switches, leds and motors work before you install them. Its better to find out they don’t work before you install them.
  • Check that the switches work as you expect them to. The DPDT switch that is installed on the simple version of the board must have been a factory second. The solder terminals on the back were reversed from what would be typical. We had to remove the wiring and re-wire it when we tested the board.

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Creative Commons Attribution-Noncommercial-Share Alike 3.0 United States License

©2009 Heather Compton

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