The Experimenter for April, 1925
402
Electric Alarm
BELL IN BED ROOM
By Glen McWilliams
An alarm clock located in a warm room was connected to a bell in an upstairs bedroom through a storage battery and through the spring contacts illustrated above. When the alarm started the winding key completed the bell circuit, thus ringing the bedroom bell.
WHEN the cold air in an unheated ipstairs bedroom seemed to interfere tvith the alarm clock twice one week, causing a mechanic to lose several hours' work, it was decided to place the clock in a warm room and run wires to an electric bell in the bedroom. As none of the known methods of connecting an alarm clock and electric bell were satisfactory, the attachment showH was made in a few minutes from a piece of spring brass and a scrap of hard rubber, fastened to the clock with two screws, and connected in the circuit as shown. As the device closes the bell circuit periodically as the winding key revolves, the method has never yet failed to arouse the sleeper. We received a very neat model of this apparatus from which our photo was made by our artist. A well made apparatus is the best exponent of the quality of the instrument.
When an ingenious 'mechanic found that the operation of his alarm clock was retarded by the excessively low temperatures of his bedroom he devised the "remote control electric alarm" illustrated above. The diagram of connections Is shown ut left.
Elecirormagneiic Hammer and Screwdriver By Walter C. Healy ONE often finds nails, brads or ceedingly hard press them into the
in hammering small tacks, that it is exand tiresome to first material and then to
apply the hammer. One also finds while using small screws or while trying to start larger ones in awkward places that it is very trying to have them slip from his grasp and either fall upon the floor and get lost or else drop into some inconvenient place.
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Much trouble can be saved in hammering small nails or tacks, by converting the ordinary hammer into the electro -magnetic type shown above. A switch mounted on the handle enables the operator to attract or drop the nails conveniently.
To correct these difficulties I have constructed an electromagnetic hammer and a screwdriver of the same sort. They are superior to the permanent magnetic tools of this type because in a permanent magnetic hammer if you should happen to get too many tacks or other small nails on it they have to be removed one by one, which is not in the least desirable. The same applies to a permanent magnetic screwdriver. When a certain screw has to be dropped into some specific place the magnetism cannot be shut off, whereas in the electromagnetic instruments the magnetism can be applied or withdrawn at will simply
by the pressure Of the user's thumb.
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good qualities of these handy tools are numerous, but I will not take the time nor space to tabulate them, but get to the construction of the tools themselves. Anyone with even a slight knowledge of electricity will be able to produce a very efficient finished article with the commonest tools at a nominal stun. The following materials will he needed for the hammer: Any ordinary hammer that has a wooden handle (a rivet hammer is best) ; a piece of springy metal (a corset rib serves the purpose well) ;; inch wide and about 15 feet of annunciator wire; 12 inches of insulating adhesive tape; 3 very small brass or copper screws, and 10 feet of thin double -stranded lamp cord. Drill a ยกy -inch hole 4 inches long through the handle of the hammer, as shown in Fin. 1, also making a 4 -inch outlet for the lamp cord at (0). Place the piece of springy metal in a vise and file into shape as shown in Fig. 2, so as to make a comfortable thumb-:witch. Drill two holes the size of your screws in the base. Place strips of tape the length of the hammer -head with their sticky side tip, on the top and sides of the head, Fig. 3. Wind annunciator wire over taped hammer -head, leaving about one -quarter of the head protruding on either side. Draw and stick the ends of the tape together to hold the wire firmly in place, Fig. 3. Screw thumb -switch on handle of hammer in a place convenient for your thumb to reach, also place contact screw directly beneath the thumb -switch. Hook up as shown in Fig. 4. Attach to one or two dry cells and the hammer is ready for use. I would advise taping the handle from the top at least as far as the thumb -screw in order to conceal the lead wires and at the same time hold them in position. The materials necessary for the screwdriver are the same as those for the hammer, with the exception that a common wooden -handled screwdriver is used in place of the hammer listed. To make the magnetic screwdriver: Drill a /-inch hole through about twothirds of the handle, making a 4 -inch outlet at (0), Fig. 1. File the springy metal to shape shown in Fig. 2, then bend it as shown in Fig. 3 and slot it, Fig. 2. The slots can best be made by first drilling two small holes the size of your screws and then using a
hack -saw or a file to lengthen them. (B using several hack -saw blades on one frame a very accurate slot can be made.) Tape and wind the same as for the hammer, fastening the whole coil to the handle by means of either another piece of tape or by jamming the free ends of the tape already used inside the ferrule of the screwdriver, Fig. 4. A combination of both these methods will prove very satisfactory. Screw thumb -switch in a convenient place for use and screw contact point, i.e., one
a
small coil mounted on a screwdriver as shown above will greatly facilitate the work by holding the screws to the screwdriver until the former is in place and well centered in the aperture.
of your brass or copper screws, so that it will touch the thumb -switch when the switch is moved forward, Fig. 5. Hook up in the same manner as you did the hammer, Fig. 4. Tape the handle, from the coil, at least as far as the thumb-switch. To use the screwdriver simply attach it to one or two dry cells. The current can be turned on and left on by pushing the thumb -switch forward and turned off by reversing the motion. This switch cart also be used on the hammer if wanted, although I do not think you will find it preferable to the other.