Part 14 (1/2)

As the bolts were no longer magnets, F sprang right back to I, the current pa.s.sed long enough to re-magnetize the bolts. This operation was rapidly repeated.

218. Use. If you wish to use the buzzer simply to call some one occasionally, a dry battery or Leclanche cell is best. This apparatus is good to work a gravity cell when it needs regulating.

APPARATUS 126.

[Ill.u.s.tration: Fig. 101.]

_219. Electric Bell._ Fig. 101. Before making this bell, carefully read the directions and explanations given for the electric buzzer, App. 125.

The parts are very much alike in the two instruments, and most of the lettering of them has been made the same in the ill.u.s.trations. If you look at Fig. 101 from the side, with the letters M and Q at the bottom, you will see that this bell is merely a modified form of App. 125.

The Base is 7 5 1/2 in. To the upper end of this is nailed the cross piece, D. To D are fastened the binding-posts.

The Parts, F, G, H, I, J, K, L, M, N, P, Q, are the same as explained in App. 121 and 125.

The Magnet is fastened to the base by a tin strip, C, which is screwed down at both ends. By nailing a strip, like D, along the left side of the base, the magnet may be fastened to this. This strip would take the place of the base of App. 125.

The piece, F, of two thicknesses of tin, is made longer than it was in App. 125; in fact, it projects through L and forms the part N. To the lower end of N is fastened a large bullet. Hold the cutting-edge of a strong knife-blade upon the bullet, and with a few taps of a hammer drive the blade into it to make a gash.

Put the end of N into the cut, then hammer the bullet so that N will be pinched. If you have no bullet, cut a long strip of tin, about 3/8 in.

wide, and wind this about the end of N to serve as a ball.

The Bell, E, may be taken from an old alarm-clock. This is not screwed directly to the base, as it would not ring well. After you have the ball, O, properly fixed, hold E, so that O will strike it near its rim; then cut a piece of wood about 5/8 5/8, and long enough to put under E, to raise its rim to the right place. This piece must be screwed to the base from the underside, and on to its top is placed the screw which pa.s.ses through the bell. In other words, E is mounted upon a rod which is fastened to the base.

The Adjustments are made as in App. 125. By bending N a little, O can be made to tap E properly.

The Battery for a bell that is to be used much should be an open circuit one, such as the Leclanche, or the ordinary dry batteries. It is cheaper to buy a dry battery than it is to make one suitable for bells. A and B show wires that lead to the bell from the battery. One of the wires should be pa.s.sed through a push-b.u.t.ton.

APPARATUS 127.

_220. Electric Bell._ By arranging the buzzer of App. 125 with a bell, you can use the same for an electric bell. The part, F, should be made long enough to extend entirely through L, and project beyond L for about 2 in. To the end of this is fastened a large bullet, or a band of tin.

(See App. 126.)

[Ill.u.s.tration: Fig. 102.]

APPARATUS 128.

_221. Combination Buzzer and Telegraph Sounder._ Fig. 102. This apparatus is good for experimental purposes, where you do not wish to go to the trouble to make two separate pieces. For the dimensions and explanations see App. 121 and 125. There is but a slight change in App.

125 to make this.

222. Connections. The inside ends (-- 123) of the magnet wires are fastened together at S. The outside ends are joined to the two binding-posts, Y and Z, made like App. 46. A wire, P, joins Y with the screw in T, which is a piece of stiff tin or copper, which presses down upon the top of I. In this way a connection may always be had between I and T. A wire, R, joins F electrically with X; it is held under the head of the screw, G. (See App. 125 about adjustments.)

223. Operation. When you wish to use the apparatus as a buzzer, join your battery wires to X and Z. If the current enters Z, it will pa.s.s through the magnet coils out to Y, through P, T, I, F, and R to X. If you use it as a telegraph sounder, join the battery wires to Y and Z.

The current will then pa.s.s simply through the coils; it will not bother to go into P, F, etc., as it has no place it can escape. If used simply for experimental purposes almost any cell of sufficient strength will do. If for telegraph, use App. 9; if for buzzer, use an open circuit cell, as, for example, a dry cell.