How to Mount an Electronic Coin-Toss Circuit in a Box - dummies

How to Mount an Electronic Coin-Toss Circuit in a Box

By Doug Lowe

When you have successfully built a coin-toss circuit on a printed circuit board (PCB), you’ll want to give the project a finished presentation by mounting it in a project box.

All the parts for this project can be purchased at RadioShack— with the exception of the standoffs, which you can get at a local hardware store.

Part Number Quantity Description
270-1803 1 Project enclosure 5″ x 2.5″ x 2″
270-326 1 9 V battery holder
n/a 8 1/2″ 6-32 standoff male-to-female
n/a 6 6-32 nuts (to fit standoffs)
n/a 4 6-32 1/4″ bolts (to fit standoffs)

Here’s the procedure for putting the project together:

  1. Drill the required mounting holes in the lid.

    Drill a total of eight holes in the lid. Four are for mounting the circuit board, two are for the LEDs, and two are for the metal finger contacts.

    The smaller holes are 1/8″ while the two larger holes are 3/16″. Note: The distance between the four holes at the top of the lid must be exactly 13/8″ so that they line up with the mounting holes in the circuit board. The measurements for the other holes don’t need to be as precise.

    Template for drilling holes in the lid of the project box.
    Template for drilling holes in the lid of the project box.
  2. Drill a 5/16″ hole for the pushbutton near the top of the left side of the box.

    Hold the box in the palm of your left hand and drill the hole at a location where your thumb will be able to easily reach the button.

  3. Mount the pushbutton.

    Remove the nut from the neck of the pushbutton, pass the neck through the hole from the inside of the box, and thread the nut onto the neck from the outside of the box. Tighten with pliers.

  4. Epoxy or hot glue the 9 V battery holder to the base of the box.

    Position the holder near the top of the box, adjacent to the hole you drilled for the switch.

  5. Mount the circuit board standoffs.

    Mount four of the 1/2″ standoffs on the underside of the lid by inserting the threaded end of the standoff through the appropriate hole and attaching a 6-32 nut on the other side.


  6. Mount the finger-touch contacts on the lid.

    To make the metal contacts that the user can touch to toss the coin, first insert the threaded end of one of the standoffs through the hole from the top side of the lid. Then screw a second standoff into it from the bottom of the lid. Then attach a 6-32 nut to the threaded end of the standoff that’s beneath the lid.


  7. Mount the circuit board to the standoffs.

    First bend the LEDs around so that they wrap over the edge of the circuit card and then face straight down. Be careful not to break the leads or damage any solder joints.


    Position the circuit board over the four standoffs. The LEDs should slide right into the two 3/16″ holes you drilled for them in Step 1. If they don’t, just nudge them a bit to make them fit. Secure the circuit board to the standoffs using the 6-32 bolts.

  8. Connect the finger contacts.

    Attach the free ends of the two jumper wires connected to the circuit board to the two finger contacts. To connect each wire, wrap the stripped end of the wire tightly around the threaded part of the standoff. Then, attach a 6-32 nut to the standoff and tighten with pliers.


  9. Install the battery.

    Insert the battery into the holder, and connect the snap adapter.

  10. Attach the lid to the box.

    Use the screws that came with the box.

  11. Toss a coin!

    Depress the pushbutton with your thumb. Then, touch your index finger to the two finger contacts, and watch the LEDs alternate. Let go and see whether the red or green light stays lit.