Long Interval RC Timer Using Op-Amp

With the help of high gain high impedance operational amplifier, we can build a long time delay with resistor-capacitor (RC) circuit since it allow high resistance resistors to be used. We can calculate the time (t) using the following formula; Time (t) = R4.C.ln(Vr/(Vr-Vi)). For design example is a 100 second timer, where this circuit uses this following components: Vr=10V, […]

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LM139 One-Shot Multivibrator

The circuit below is a one-shot multivibrator. One shot multivibrator is also known as monostable multivibrator, or timer. The main function of such circuit is producing a fixed width pulse. The width of this pulse is determined by the component value selection at the time of designing the circuit. The main component of this circuit is the LM139, and this […]

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Delayed Car Door Alarm

Opening car’s door is very simple activity, and off course it’s just a daily activity which require no special skill. Almost nothing can go wrong, but forgetting to close the door when we doing or thinking on many tasks is a common thing. This can lead to many consequences, from as simple as air conditioner inefficiency to as dangerous as […]

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LM139 One Shot Multivibrator/Timer

One shot multivibrator circuit is also known as monostable multivibrator or timer. The function of such circuit is simply produce a pulse strobe with a fixed width, regardless of the pulse width of the triggering input.  Below is the circuit’s schematic diagram of simple one shot multivibrator uses one section of an LM139 comparator. The width of the output pulse […]

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