Show To Heat Filament of Vacuum Tubes Batteries Only Practical Method of Supplying Re Re- Current Batteries have proven the only practical practical practical method of ot supplying the current to heat the filaments of vacuum tubes tube's for radio receiving sets Various attempts attempts at nt- I tempts have been made from time to time to utilize ordinary commercial electric current for this purpose but complicated and expensive apparatus was necessary necessary to smooth out the fluctuations fluctuatIons fluctuations and pulsations an essential requirement for quiet reception Some method must be used to replace replace replace re re- reI re- I place the energy taken from the battery bat bat- I tery Dry cell batteries are ore replaced by fresh ones In storage batteries I the energy y can be replaced by sending sending sendIng send send- ing n a current through the battery In Inthe Inthe inthe the opposite direction The rhe ordinary source of household current available for this purpose Is alternating current which consists of Impulses alternately In one direction and then In the other reversing In direction direction di di- direction di- di sixty times each ench second To use this current to charge n a battery the Impulses that flow In the opposite direction direction direction di- di di di- must be checked or converted so that the current flowing through the battery Is In one direction only L i A f fl 60 Cycle Current V v 8 I To r e aa w I Diagram Showing How Cur Current ent Is IB Rectified A common method Is a n vibrating device device device de de- de- de vice built to make contact that allows the current to pass sixty times n a second second sec sec- second ond In one direction and to break contact contact con con- tact while the current flows In the opposite direction The timing In chargers of ot this kind must be synchronized synchronized s' s absolutely with the alternations or reversals In direction of current flow This type of ot charger requires attention attention attention atten atten- tion from time to time Ume to adjust the contacts and occasionally replace ce them when worn out Many Mony times trouble Is experienced with sticking contacts which will cause the battery to discharge discharge discharge dis dis- dis- dis charge during the charging process Another method methO 1 Is the use of an evacuated d bulb containing two ele ele- ments A filament Is kept heated and and the other element Is not heated Current will flow from the hot element element element ele ele- ele- ele ment to the cold electrode but not In inthe the reverse direction This type tune of charger needs no attention save for forthe forthe forthe the replacement of ot the bulb If the filament filament filament fila fila- ment becomes worn out or broken Both the vibrating type charger and the time bulb t type pe make a certain amount of ot noise due to the vibrator In the first case and to the movement of the transformer laminations In the second type of charger which makes a hum while the charger Is In operation The electrolytic t type pe of charger makes use of ot the fact when certain pairs of ot dissimilar metals are Immersed Immersed Im Im- immersed im- im mersed In electrolyte te they allow current cur curs rent to flow In one direction only Common Common Com Com- Common mon examples use a n lead and an nn aluminum alum olum- rod Immersed In a solution of borax and water for charging storage I B batteries The diagram shows how the current Is rectified In the case of the time vibrating vibratIng ing and bulb t type pe of chargers the lower half of ot the cycle GO-cycle wave is cut cutoff cutoff off otT thus allowing only the upper half to go through the battery Obviously these chargers are ore only working half of the time B By using the electrolytic t type pe of charger both sides of the wave are changed Into pulsations that will produce a n unidirectional current suitable suitable suitable suit suit- able for charging As there are no moving parts the charger Is noiseless In operation and requires no adjustments adjustments adjust adjust- ments or replacements |