Читать книгу Harper's Electricity Book for Boys - Joseph H. Adams - Страница 13

Push-buttons and switches are a necessity in every home where electric bells, lights, or fans are used, for with them connections are made or broken. The telegraph-key and the commutators on a motor and dynamo are only improved forms of the push-button, and this simple little device is really an indispensable part of any electrical equipment.

The simplest form of push-button is a bent piece of tin or thin sheet-metal screwed fast to a small block of wood, as shown in Fig. 1. Under the screw-head one end of a wire is caught, and the other wire end is secured by a washer and a screw driven into the block directly under the projecting end of the strip of metal. By pressing a finger on the tin it is brought into contact with the screw-head under it, and the circuit is closed; on releasing it, the tin flies up and the circuit is opened again.

An enclosed push-button is shown in Fig. 2. It is made of the cover or body of a wooden box, a spool-end, and several other small parts. A round piece of thin wood is cut to fit inside the box and so form the base for the button. On this the spring strip is attached with screws, and the wire ends are made fast, as shown in Fig. 3. The wires are carried through the bottom of the base and along grooves to the edge, and thence to their final destination. The end of a spool is cut off and glued to the top of the box, as shown in Fig. 2, and a hole is made in the box to correspond in size with that in the spool. Through this aperture the button (cut from a wooden dowel or shaped out with a knife) passes, so that the end projects about a quarter of an inch beyond the spool. To prevent the button from falling out, a small steel nail should be driven across the inner end, or a washer may be tacked to the end of the stick, as shown in Fig. 4.

The button is mounted by screwing the base fast to the door or window casing, it being understood that the wires have been first arranged in place. The button is then set in the hole and the cap is placed over the base, covering it completely. By means of small screws, passed through the rim of the box and into the edge of the base, the cap is held in place. A coat of paint or varnish will finish the wood-work nicely, and this home-made button should then answer every requirement.