Q Amateur ■ 

 Electrician 



-ksA Wii-eless Operator 



Making an Electrically Heated 



Soldering Iron 



AN electric soldering iron is not a 



x\. tool for the inexperienced person 



to build; however, with extreme care and 



the proper materials, a very good tool can 



The necessary parts for the construction 

 of an electrically heated soldering iron 



be made. An improperly designed and 

 constructed electric soldering iron may 

 often result in fireworks of a dangerous 

 variety. The home-made kind will be 

 somewhat cheaper than one of a similar 

 size and like heating element and just as 

 good results can be had from its use. 



The handle is turned in a lathe from 

 maple stock to the dimensions given in 

 the diagram. A hole is bored axially 

 through the handle and a 6-in. length 

 of ^-in. gas-pipe forced into it. Two 

 feet of asbestos-covered copper wire 

 should be led through the pipe and han- 

 dle and to an attachment plug. The 

 other terminals of the wire are attached 

 to the resistance winding. The winding, 

 whose resistance causes the copper head 

 to be heated, consists of i8 ft. of No. 

 30 nichrome wire, which is wound in 

 six layers on the copper spool. Each 

 layer should be well insulated with leaf 

 mica, and the outer la\er well covered. 

 A protective copper tube is pressed over 



the winding, covering it completely. 

 The dimensions of this tube and of the 

 copper are given in the drawing. Care 

 should be taken that the wire does not 

 come in contact at any place with the 

 metal parts. Without a rheostat the 

 iron will consume about 100 watts. 



An Electric Burglar Alarm Attached 

 to a Door-Lock 



A BURGLAR alarm which is oper- 

 ated when a door is opened can be 

 constructed by screwing a spring A in 

 the back wall of the mortise of the door 

 jamb, bending it so that it makes a 

 contact with the lock-bolt, as indicated 

 in the sketch. The spring forms one 

 contact and the iron covering the door, 

 tlie other. The two contacts thus 

 formed are connected to bell magnets 

 B through a closed circuit battery. 

 The other connections are shown in the 

 diagram. 



When the door is locked the bell C 

 will not ring; but when the bolt is 



DOOR 

 CLOSED CIRCUIT B4TTERV 



B/^TTERY 



Spring contact in a door-lock for sounding 

 a burglar alarm when the door is opened 



disengaged from the spring the circuit is 

 broken, allowing the armature of the 

 bell magnets to spring back, closing the 

 circuit. — Charles W. Christman. 



947 



