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Here is a VLF receiver tuned to 300 kHz designed to detect the crackle of approaching lightning. A bright lamp flashes in sychrony with the lightning ...

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Sometimes a zener diode of the required voltage is not available. Here are a number of components that produce a characteristic voltage across them. S...

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This circuit is called Type-1 SE. Low current from a solar cell is stored in a large capacitor and when a preset voltage-level is reached, the energy ...

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t has a clever 2- transistor self-latching arrangement to keep the circuit ON until the voltage drops to 1.5v. The circuit turns on at 2.8v. This give...

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This circuit is an improvement on the Sun Eater I shown above. It works exactly the same except the slight re-arrangement of the components allows an ...

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Type-3 circuits are current controlled or current- triggered. This is another very clever way of detecting when the electrolytic has reached its maxim...

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The green LEDs cause the Solar Engine on the opposite side to fire and the Solar Photovore turns toward the light source. The motors are two pager "vi...

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It is a Photopopper using low-cost components. It uses two red or green flashing LEDs to turn the circuit on when the voltage across the electrolytic ...

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A Schmitt Trigger is any circuit that has a fast change-over from one state to the other. In our case we have used 2 transistors to produce this effec...

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This circuit will test crystals from 1MHz to 30MHz. When the crystal oscillates, the output will pass through the 1n capacitor to the two diodes. Thes...

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Both inputs need to be on to switch the output off, if both inputs are high then the output is low. Both Diodes are needed to prevent feedback, The in...

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Both inputs need to be high to switch the output on....

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NOT Gate The result is the opposite of the input, if the input is high then the output is low, somtimes called an inverting buffer, although buffers g...

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Output is high until one or more of the inputs are used. More inputs can easily be included, as you can see the inputs share the same transistor base,...

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This circuit can be used to escape from the nuisance of mobile phone rings when you are at home. This circuit will give a visual indication if placed ...

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