The CD4001 quad 2-input NOR gate is a very versatile IC that can be used in an almost infinite variation. Here we will use it in the application of a simple alarm system. The power supply suggested for the CD4001 is 5 to 15Vdc Max. The CD4001 has a typical transition voltage value of 50% of its supply voltage with a possible spread of 30% to 70% d
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epending on its production. The delay is set by R1/C1) for exemple, R1=680k and C1=10uf give a time delay of approx 8 secs. Thus time can adjusted by the choice of R/C values. This delayed trigger allows time to set the module in the "Standby" and exit within the time delay period before the alarm is triggered. Again on re-entering the alarm must be reset within that delay period. Gate A forms the trigger circuit and gates B&C form a tone generator of 800hz to the speaker activated by the transistor. In the next circuit in addition to the delay ON circuit we added an extra gate to provide for an auto/delayed turn off function. C2 & R2 are used to automatically turn off the alarm. Like C1 & R1, C2 & R2 can be selected for the duration the alarm will stay on then automatically turned off. It must be reset to be reactivated. Two outputs are available as shown. But, the delay period may not be long enought to manually reset the unit. We can eliminate the guess work by integrating an auto-exit /entry delay that will not require a manual reset as shown in the next circuit. R1/C1 and R2/C2 forms the exit /entry delay ciruits. When the power is first applied (standby) all sensor switches (S3, S4) are enabled except S1a/b which is disabled for a pre-set period via time-delay network C1/R1. At the end of this period S1 is automatically enabled. When S1 is activated the output of gate-A goes high and is locked by the action of D1...
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The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
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This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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