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    • #9131

        Hi all,

        Has anyone build experiment 57 of the Lagacy manual ?
        It is an experiment with a Schmitt-trigger as time measuring device.

        Well, it doesnt seem to work !
        After building you’ll notice that after the capacitor is charged to a certain level, the Schmitt-trigger turns on the light bulb.
        That seems fine, but after a second or so, the light goes out !
        That’s not how this is suppose to work !
        The troubled part is the 120 Ohm resistor which should be replaced into 220 Ohm.
        Now the circuit acts as it should.
        To improve the circuit’s performance, I also changed some more components.

        I’ll make a small series with more experiments around this with surprising reults !

        Here’s the corrected diagram of V1, check it out !

        Schmitt trigger V1

        • This topic was modified 3 years, 3 months ago by LectronFan.
      • #9133

          Excellent work as always Frank!  Thanks very much.

          Perhaps I should send this to Mr. Max Guerth who worked with Mr. Greger back in the day as his circuit ‘troubleshooter’.  Mr. Guerth told me that he had to refine many circuits because they did not work as they should.  For example, a flip flop block in the Ausbausystem 3 model did not ‘flop’!

          Your contributions are so valued, thank you.  I wish more of our fellow Lectroneers would weigh in here and add to the great information that you are providing the forum.


        • #9134

            Hi Michael,

            That’s the big advantage of the Lectron system.
            Once a circuit isn’t working as suspected, it’s so easy and fast to adapt without the need of desoldering or chang the wiring !

            The problem with the original design was that the current flowing through the 120 Ω resistor was too large.
            Once the capacitor was charged, the Schmitt trigger activates and made the capacitor discharge through the B-E junction of T1 and the 120 Ω resistor.

            Now by choosing a 220 Ω value for R7, this doesn’t occur anymore !

            In the next experiment, we will make use of this phenomenon to make a cool circuit !

            Many greetings,


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