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    • #6862

      Hi all,

      What’s missing in the Lectron manual for the base and expansion set is a toggle flip flop.

      This flip flop has only 1 input and when activated, the output switches state.

      This is a real nice circuit to be used in different circuits where a certain state has to be “remembered”.

      It can also be used as a divider. It divides the input in 2. We will demonstrate this later.

      Here’s the circuit :

      Toggle flip flop

      A little remark here : for diode D1, use only the high current type (not the Ge diode) !

      By the way, this diode is only used here to substitute for a wire block 😛

      Everybody knows a flip flop but this circuit has a few changes. We have 2 capacitors C2 & C3 across the base resistors R4 & R8. These help switching the transistors faster than normal.

      Will the circuit still work without these ? Try it out !

      R6 & R7 are connected in series to match the value of R5.

      The circuit around S1, C1 and R2 create a short pulse to trigger the flip flop.

      T3 is is used as an emitter follower (high input resistance) so T2 is not affected.

      You can change the circuit into a stage with grounded emitter and the lamp connected to the collector.

      Will the circuit still work you think ?



    • #8297

      Hi all,

      Since I got myself a Legacy Lectron set, time to covert this nice circuit to Ge transistors.

      I was browsing through the Braun student manual and found this exercise n° 11.53.

      But since it uses many duplicated blocks, not included in a standard Legacy set, I made small modifications to the circuit.

      And this circuit rocks ! After each press of the switch, the light bulb switches state from on to off etc.

      Legacy toggle flipflop

      Now some questions for the true Lectroneers !

      • Each time we connect the battery. Will the lamp be on or off ?
      • What is the function of the 2 diodes ?
      • Will the circuit still work if we use 0,1 µF capacitors instead of the 10 µF ?
      • If we replaced R1 with a light bulb in series with a 47 Ohm resistor. Will the circuit still work ?

      The answers can easily be found after building the circuit.

      Good luck !

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