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    • #6808

      Hi everyone,

      Sometimes we need a circuit which can count events like days of bright sunlight, temperatures above a certain level etc.

      We call these circuits integrators. We normally use operational amplifiers to accomplish this task, but today we are going to build a discrete components.

      The circuit is operated as follows.

      Which each press on S1, we add an event. The progress of these events is displayed on the meter.

      Instead of S1, we could also use a circuit around the LDR or NTC. Who will come up with a circuit design ?

      With S2, we reset the meter back to zero.

      Here’s the circuit setup :


      We will recognize the Darlington circuit which drives the meter.

      It’s used here because it puts no load on the previous stage (2,2M Ohm resistor).

      Who will explain the first stage around T1 ?

      As experiment tip : replace C1 with 0,1µF or even 47nF. What do you notice when operating the circuit ?

      Replace C2 with 100µF. What happens now ?

      For the true Lectroneers, redesign this circuit with a LDR as trigger and a variable sensitivity and integrator slope.


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