Page:Popular Science Monthly Volume 92.djvu/778

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��Popular Science Monthly

���flying, undoubtedly to spy out the land and to see that no enemies are in the vicinity. This characteristic of all birds is taken advantage of in this device. A sprig, top of a fence post, brick or stone is fastened to a short movable arm which is in control of the electric con- tacts. These con- tacts are adjusted so that the feath- ery, light body of a bird readily presses the movable arm downward thus closing the cir- cuit which releases the shutter of the camera and the picture of the shy creature is secured. The construction of this apparatus is very simple indeed, as can readily be seen from the diagram. An empty cigar box was used for the house. This was securely fastened to a comparatively thick base. Long strips of iron, 3^ in. wide and 1 16 in. thick, were used. Out of this the support A was made as shown in the illustration. This projects about 1 in. above the cigar box, a hole B was therefore bored. Two holes, C and D, situated about }4 in. above the top of the box, were drilled into the iron A. The arm E was- then made. This projects 2 or 3 in. beyond the box. This arm also has two holes cor- responding to C and D. A nail is loosely passed through these holes. This forms the axle or pivot for the arm E. The arm flaps are bent together and fastened with a U-shaped clip at F. The arm carries a block of wood G which is fastened just be- yond the edge of the box so that it does not come into contact with it. To this block a wire // is attached which holds a piece of metal (copper preferable) cut as shown. The loop / lets the metal ./ touch both poles, K and L, which con- sists of two brass wires 5 in. long. The branch M upon which the bird hops, is

��Box enclosing ail the mechanism which con- trols the electric switch for making contact

���Diagram showing connections for the elec- tric circuit and metal connector in the switch

��pressed down. Another piece of metal, -V, attached at extends to within a few inches of the bottom of the box. This is the balancer or lever arm and may be ad- justed by the movable weight P so that the slightest pressure at M at once con- nects the metai J with the two poles K and L, thus closing the electric circuit. F The camera is

placed upon a board which car- ries the electro- magnets. One pole of the electro-mag- net is connected with pole Q of the box, while the other is connected with one pole of the battery. The other pole of the battery is connected with pole R of the box. When the twig M is pressed down, the metal strip J makes a contact with both poles. The electro - magnet becomes magnetized, draws the iron core and releases the shutter. Since the graflex has a push button to release the shutter, an angle iron is taken; a knob is placed at one ex- tremity and adjusted so as to come into contact with the button. The other ex- tremity carries a weight which alm.ost counterbalances the resistance ol the shutter. A slight downward pressure will now release the shutter. This pres- sure is supplied by the magnet. For operation of a shutter situated in back of the lens see Popular Science Month- ly, June 1917.

The camera is focused upon atwig or other object placed upon the arm E. The instant a bird hops upon the twig, current flows, the magnet is charged, and draws the angle iron downward, releasing the shut- ter. Thus the picture is taken. It will be found of great advantage to introduce a bell into the circuit so that it \\ ill in- stantly ring when a contact is made and a picture secured, thus enabling the camera to be immediately brought in.

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