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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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