SEPAR 409
SERIES OR PARALLEL OPERATION
OF LAMPS AND IMPEDANCES

Simple Light Bulb Circuit

The following circuit is a simple circuit that can be used for low voltage uses, and with care, line voltage uses. The page author built a version for photoflood lighting purposes. It does not keep the screw shells of lamps on the neutral side for safety in case bulbs are removed. The requirement of polarized plugs with the screw shell connected to the neutral blade makes this circuit technically illegal to use today for permanently-wired line-voltage circuits. But a simple provision makes it safer. And since it is built as a portable device, not building wiring, the National Electrical Code does not really apply.

The SEPAR circuit numbers used here have been used by the page author for years to catalog the various circuits.

The same circuit can be used for switching impedances and nonpolarized heating elements.

SEPAR 409
  • SEPAR 409

    SEPAR 409

    Wanting more functions, the page author first thought of modifying SEPAR 401 with a 4-position switch to give F, G, H, and open. The original position H was relabeled I to allow H to be used with F and G. The result was SEPAR 401A.

    Then he wanted to actually switch photoflood lamps with it, since this change provided a function needed for this (not available in SEPAR 401). So he redesigned the circuit to use groups of wall switches that are commercially available.

    He also moved switch C to the other terminal of lamp 2. This connects two screw shells to switch B (the other two screw shells already were connected to switch J). The result is SEPAR 409.

    SEPAR 409 provides all series combinations and all parallel combinations.

    SEPAR 409 provides two series of two lamps each, a setting needed by photographers.

    All 56 possible output displays are shown, out of 4096 switch settings.*

    Note that if only one switch in a group can be set to its letter position at any one time (setting more than one letter in a group is redundant), there are only 864 switch settings.

    The four groups include:
          switches D & E
          switches F, G, & H
          switches I & J
          switches K & L

    SWITCHLAMPS
    SWITCHLAMPS
    Settings1234 Settings1234
    o †offoffoffoff ACH †DIMDIMoffoff
    ABONoffoffoff AEJDIMoffDIMoff
    BCFoffONoffoff AILDIMoffoffDIM
    DFJoffoffONoff CEFJoffDIMDIMoff
    JKoffoffoffON BCGKoffDIMoffDIM
    ABCF †ONONoffoff DFLoffoffDIMDIM
    ABDFJONoffONoff ACDJ †DIMDIMDIMoff
    ABJKONoffoffON ACGLDIMDIMoffDIM
    BCDFJoffONONoff AELDIMoffDIMDIM
    BCFJKoffONoffON BCDKoffDIMDIMDIM
    DFJKoffoffONON ACDL †GlimGlimGlimGlim
    ABCDFJ †ONONONoff (P-S)----
    ABCFJKONONoffON ACHJKDIMDIMoffON
    ABDFJKONoffONON AEJKDIMoffDIMON
    BCDFJKoffONONON ABCGKONDIMoffDIM
    ABCDFJK †ONONONON ABEKONoffDIMDIM
    (S-P)---- BCDFLoffONDIMDIM
    ACEHJDIMGlimGlimoff CEFJKoffDIMDIMON
    ACHILDIMGlimoffGlim ABCDFLONONDIMDIM
    ADHILDIMoffGlimGlim ACDJKDIMDIMDIMON
    ACHIKGlimDIMoffGlim ABCDKONDIMDIMDIM
    ACEFJGlimGlimDIMoff ACDHK †DIMDIMDIMDIM
    ADHIKGlimGlimoffDIM (P-S-P)----
    ACFILGlimoffDIMGlim ACEFJKGlimGlimDIMON
    ADFILGlimoffGlimDIM ACEHJKDIMGlimGlimON
    CDFILoffGlimGlimDIM ABCEGKONGlimGlimDIM
    ACDHILDIMGlimGlimGlim (S-P-S)----
    ACEFLGlimGlimDIMDIM ACEHLDIMGlimglimglim
    ACEGLDIMGlimGlimDIM ACEHKGlimDIMglimglim
    ACDFILGlimGlimGlimDIM Special----
    ACDHIK †DIMDIMDIMDIM BJ †safety bulb change
    SEPAR 409 built by page author

    SEPAR 409 constructed by the page author
     

    P A
     
    1 23 4K L
    B CF G
    H  
    D EI J

    SEPAR 409 panel

    A safety feature is included for changing light bulbs without disconnecting the cords. Turning ON switches B and J connects all of the screw shells and/or neutral polarized outlet slots to the neutral.

    Turning P off, B on, and J on makes the system safe for changing bulbs.

    If it is possible that the controls could be tampered while the user is changing a bulb, a key-operated switch could be put on switch P for added safety.

KEY TO TABLE ENTRIES

ON
  - Connected directly to power

DIM
  - 2 or 3 lamps in series
  - series in a series-parallel
  - series in a parallel-series

Glim
  - 4 or more lamps in series
  - parallel in a series-parallel

glim
  - Inner series in an (S - P - S)
    (even dimmer than Glim)

off
  - No current through lamp


  - Switch position unimportant

(A)     (letter in parentheses)
  - Switch must be ON

(o)     (o in parentheses)
  - Switch must be off

*
  - All possible displays shown.
  - Redundant combos not shown.


  - Former settings for photofloods

Letters indicate closed switches.

No letter for a switch, or an o for a switch, means the switch is open, or is in the unlabeled position.

Redundant combinations include connections to only one side of the line, shorted out lamps, and extra connections that no current flows through.

Magenta shading shows new combinations not possible with SEPAR 401.

Yellow shading shows better switch combinations than those on SEPAR 401.

In SEPAR 409, any time a lamp is at full brightness, the screw shell is always connected to neutral.

(S - P) is a series-parallel circuit (parallel inside series).

(P - S) is a parallel-series circuit (series inside parallel).

(S - P - S) is series-parallel-series.

(P - S - P) is parallel-series-parallel.

 
Panel Illustrations

' A
 
3 21 -o o
B 'C o
o  
'  
 -D
o '

Symbols for panel illustrations:

' Switch must be on.
o Switch must be off.
- (alone) not used.
1 (number) lamp on original unit.
A (letter) switch on original unit.
-A (letter) invert original switch.

  • Percentages and Voltages for Identical Loads

    Series-Parallel
    Combinations
    Constant Resistance Loads Variable Filament Resistance
    Voltage Percent 120 V Supply Label Filament Color Voltage Percent 120 V Supply Filament Color
    Lev 1Lev 2Lev 3 Lev 1Lev 2Lev 3 Lev 1Lev 2Lev 3 Lev 1Lev 2Lev 3 Lev 1Lev 2Lev 3 Lev 1Lev 2Lev 3 Lev 1Lev 2Lev 3
    Any Parallel 100%-- 120V-- ON--     100%-- 120V--    
    2 in Series 50-- 60-- DIM--     50-- 60--    
    3 in Series 33.3-- 40-- DIM--     33.3-- 40--    
    4 in Series 25-- 30-- Glim--     25-- 30--    
    Any in Parallel with 2 in Series 10050- 12060- ONDIM-     10050- 12060-    
    2 Parallel sets of 2 in Series 50-- 60-- DIM--     50-- 60--    
    2 Series sets of 2 in Parallel 50-- 60-- DIM--     50-- 60--    
    1 in Series with 2 in Parallel 66.733.3- 8040- DIMGlim-     8614- 10416-    
    1 in Series with 3 in Parallel 7525- 9030- DIMGlim-     964- 1155-    
    2 in Series with 2 in Parallel 4020- 4824- DIMGlim-     47.55- 576-    
    1 in Ser w/ 1 in Par w/ 2 in Ser 604020 724824 DIMGlimglim     83.316.78.33 1002010    

    The nonlinearity of filament resistance with current (heat) causes some of the series-parallel combinations to not display the expected filament brightness. This is because the lamps drawing lower current have a resistance as low as 1/10 of the resistances of the lamps drawing high current. The right three columns of the table show this effect.

OTHER CIRCUITS SEPAR 409 CAN EMULATE
  • SEPAR 301

    As on SEPAR 301

    SWITCHLAMP
    AB CD123
    ooooffoffoff
    ooDONoffoff
    oBoDIMDIMoff
    oBDONoffoff
    oCooffoffoff
    oCDONONoff
    AooDIMDIMDIM
    AoDONoffoff
    ABoDIMDIMoff
    ABDONoffoff
    ACooffoffON
    ACDONONON
    SEPAR 301

    12 switch positions.

    Note that hot and neutral are reversed in this emulation.

    Items in parentheses must have the setting given.
     

    SEPAR 301 on
    SEPAR 409 panel

    ' '
     
    1 23 -o o
    D 'C o
    B  
    ' oo A
    SEPARswitch
    301409ONoff
    -A(A)-
    DBbrtdim
    -C(C)-
    -D(D)-
    -E-(o)
    CFbrt3
    -G-(o)
    BH23
    -I-(o)
    AJ32
    -K-(o)
    -L-(o)
    11  
    22  
    33  
    -4  

    As on SEPAR 409

    SWITCHLAMP
    BF HJ123
    ooooffoffoff
    ooJONoffoff
    oFoDIMDIMoff
    oFJONoffoff
    oHooffoffoff
    oHJONONoff
    BooDIMDIMDIM
    BoJONoffoff
    BFoDIMDIMoff
    BFJONoffoff
    BHooffoffON
    BHJONONON
  • SEPAR 302

    As on SEPAR 302

    SWITCHLAMP
    ABCD123
    oooffoffoff
    ooCoDIMDIMoff
    ooCDONoffoff
    oBCooffONoff
    oBCDONONoff
    AoooDIMoffDIM
    AooDDIMDIMDIM
    ABoooffoffON
    ABoDoffoffON
    AoCoDIMglimglim
    AoCDONoffoff
    ABCooffONON
    ABCDONONON
    SEPAR 302

    16 switch positions.

    Lamps 1 and 3 traded.

    Switch E works backwards.
     

    SEPAR 302 on
    SEPAR 409 panel

    ' A
     
    3 21 -o o
    B 'C o
    o  
    '  
     -D
    o '
    SEPARswitch
    302409ONoff
    AA32
    BBbrtdim
    -C(C)-
    -D(D)-
    -DE2brt
    CFbrt3
    -G-(o)
    -H-(o)
    -I-(o)
    -J(J)-
    -K-(o)
    -L-(o)
    31  
    22  
    13  
    -4  

    As on SEPAR 409

    SWITCHLAMP
    ABF-E321
    oooffoffoff
    ooFEDIMDIMoff
    ooFoONoffoff
    oBFEoffONoff
    oBFoONONoff
    AooEDIMoffDIM
    AoooDIMDIMDIM
    ABoEoffoffON
    ABoooffoffON
    AoFEDIMglimglim
    AoFoONoffoff
    ABFEoffONON
    ABFoONONON
  • SEPAR 305

    As on SEPAR 305

    SWITCHLAMP
    ABCD123
    oooffoffoff
    oooDoffoffoff
    ooCDONoffoff
    oBooDIMDIMoff
    oBoDoffoffoff
    oBCooffONoff
    oBCDONONoff
    AooDDIMDIMDIM
    AoCDONoffoff
    ABooDIMDIMON
    ABoDoffoffON
    ABCooffONON
    ABCDONONON
    SEPAR 305

    16 switch settings.

    Lamps 1 - 4 reversed.

    Switch L works backwards.
     

    SEPAR 305 on
    SEPAR 409 panel

    ' o
     
    - 32 1 '  
     -D
    A 'B o
    o  
    ' oo C
    SEPARswitch
    305409ONoff
    -A-(o)
    AB32
    -C(C)-
    -D(D)-
    -E-(o)
    BFbrt3
    -G-(o)
    -H-(o)
    -I-(o)
    CJbrtdim
    -K(K)-
    -DL2brt
    -1  
    32  
    23  
    14  

    As on SEPAR 409

    SWITCHLAMP
    BFJ-L432
    oLoffoffoff
    oooLoffoffoff
    ooJoONoffoff
    oFoLDIMDIMoff
    oFoooffoffoff
    oFJLoffONoff
    oFJoONONoff
    BoooDIMDIMDIM
    BoJoONoffoff
    BFoLDIMDIMON
    BFoooffoffON
    BFJLoffONON
    BFJoONONON
  • SEPAR 401

    As on SEPAR 401

    SWITCHLAMPS
    SWITCHLAMPS
    Settings1234 Settings1234
    o †offoffoffoff ACGJ †DIMDIMoffoff
    ABONoffoffoff AEJDIMoffDIMoff
    BCFoffONoffoff AHLDIMoffoffDIM
    DFJoffoffONoff CEFJoffDIMDIMoff
    JKoffoffoffON CFHLoffDIMoffDIM
    ABCF †ONONoffoff DFLoffoffDIMDIM
    ABDFJONoffONoff ACDJ †DIMDIMDIMoff
    ABJKONoffoffON ACGLDIMDIMoffDIM
    BCDFJoffONONoff AELDIMoffDIMDIM
    BCFJKoffONoffON BCDKoffDIMDIMDIM
    DFJKoffoffONON ACDL †GlimGlimGlimGlim
    ABCDFJ †ONONONoff (P-S)----
    ABCFJKONONoffON ACGJKDIMDIMoffON
    ABDFJKONoffONON AEJKDIMoffDIMON
    BCDFJKoffONONON ABCGKONDIMoffDIM
    ABCDFJK †ONONONON ABEKONoffDIMDIM
    (S-P)---- BCDFLoffONDIMDIM
    ACEGJDIMGlimGlimoff CEFJKoffDIMDIMON
    ACEFJGlimGlimDIMoff ABCDFLONONDIMDIM
    ACFHLGlimGlimoffDIM ACDJKDIMDIMDIMON
    ADFHLGlimoffGlimDIM ABCDKONDIMDIMDIM
    CDFHLoffGlimGlimDIM (P-S-P)----
    ACEFLGlimGlimDIMDIM ACEFJKGlimGlimDIMON
    ACEGLDIMGlimGlimDIM ACEGJKDIMGlimGlimON
    ACDFHLGlimGlimGlimDIM ABCEGKONGlimGlimDIM

     

    SEPAR 401

    648 switch combinations.

    47 useful nonredundant positions listed at left.

     

    Ignore switch H.

    Use switch I for 401 switch H.

    Items in parentheses must have the setting given.

    As on SEPAR 409

    SWITCHLAMPS
    SWITCHLAMPS
    Settings1234 Settings1234
    o †offoffoffoff ACGJ †DIMDIMoffoff
    ABONoffoffoff AEJDIMoffDIMoff
    BCFoffONoffoff AILDIMoffoffDIM
    DFJoffoffONoff CEFJoffDIMDIMoff
    JKoffoffoffON CFILoffDIMoffDIM
    ABCF †ONONoffoff DFLoffoffDIMDIM
    ABDFJONoffONoff ACDJ †DIMDIMDIMoff
    ABJKONoffoffON ACGLDIMDIMoffDIM
    BCDFJoffONONoff AELDIMoffDIMDIM
    BCFJKoffONoffON BCDKoffDIMDIMDIM
    DFJKoffoffONON ACDL †GlimGlimGlimGlim
    ABCDFJ †ONONONoff (P-S)----
    ABCFJKONONoffON ACGJKDIMDIMoffON
    ABDFJKONoffONON AEJKDIMoffDIMON
    BCDFJKoffONONON ABCGKONDIMoffDIM
    ABCDFJK †ONONONON ABEKONoffDIMDIM
    (S-P)---- BCDFLoffONDIMDIM
    ACEGJDIMGlimGlimoff CEFJKoffDIMDIMON
    ACEFJGlimGlimDIMoff ABCDFLONONDIMDIM
    ACFILGlimGlimoffDIM ACDJKDIMDIMDIMON
    ADFILGlimoffGlimDIM ABCDKONDIMDIMDIM
    CDFILoffGlimGlimDIM (P-S-P)----
    ACEFLGlimGlimDIMDIM ACEFJKGlimGlimDIMON
    ACEGLDIMGlimGlimDIM ACEGJKDIMGlimGlimON
    ACDFILGlimGlimGlimDIM ABCEGKONGlimGlimDIM

     

    SEPARswitch
    401409ONoff
    AAAo
    BBBo
    CCCo
    DDDo
    EEEo
    FFFo
    GGGo
    -H-(o)
    HIHo
    JJJo
    KKKo
    LLLo
    11  
    22  
    33  
    44  

    SEPAR 401 on
    SEPAR 409 panel

    ' A
     
    1 23 4K L
    B CF G
    o  
    D EH J
SEPAR 409 IN DEPTH

Complete table of SEPAR 409 switch positions

Simple switching selection between series and parallel


LINKS:

  1. SELECTING SERIES OR PARALLEL OPERATION (Main Page)
  2. LIGHT BULBS, SPECTRA, and HUMAN VISION
  3. Computers, Science, and Measurement