Digital IC
Chandelier Dimmer
Many of the chandeliers have a pull chord switch. Now add a novelty to your chandelier and surprise the guests. Place a small wire down the lamps from this circuit and touch it once, they will come on dimly. Touch again they glow with medium brightness. Another touch drives them full. One more touch the [...]
Morning Alarm for babies
Here is a pleasant wake up alarm for the babies. As the morning light breaks in, the alarm gently wakes up the baby with a soothing musical note. What a pleasing way to make the baby rise to the day!
As already described, LDR has a very high resistance in darkness, which falls low as the [...]
Telephone Light
Telephone rings in the dead of the night and you grope in darkness for the light switch or may be for the cordless handset. Here is ingenious circuit which makes a light bulb glow whenever the telephone rings.
This is a good application where mains are triggered by triac by the action of an opto-coupler. The [...]
Stitching Machine Motor Speed Control
Motor operated stitching machines have a series of carbon buttons in an enclosure operated by foot pedal. As the pressure on the foot pedal is increased or decreased by the foot, these buttons come close or move farther away, their resistance changes and hence the speed of the motor. Even though crude, it seemed to [...]
Electronic Lock
Here is an electronic code lock, which can be used as a door latch or key for ignition, etc. Operation is fairly tricky and there lies the beauty of the circuit. There are a number of switches, actually nine, which should be operated in a particular and owner – configured -sequence, or else the circuit [...]
Four Station Quiz
Here we have another Quiz circuit using a number of CMOS ICs. Now the number of contestants can be easily increased even though the present circuit shows only four. It uses a two input Quad AND gate (74HCT08), a four input Dual AND gate (74HCT21), a dual D flip flop (CD4013), and a 555. Truth [...]
Simple Quiz Circuit with SCR
Here is a small and simple circuit to catch the first to punch the button in a quiz game. It is basically designed for two but can be expanded to accommodate more contestants. Present circuit works straightaway on mains but can be modified for use at low and less risky AC voltages also.
Silicon Controlled Rectifier [...]
Door Knob alarm
Here is circuit if you want an alarm to be sounded when somebody touches some thing. If any body touches say, the door handle, buzzer inside rings. But if want to keep the intruder away, keep the circuit on in the night or when you are away. It can be configured for use in a [...]
Light Sensitive Staircase Switch with Triac
Operation of the third circuit is much similar except that it has photo sensitivity. The circuit is shown in Schematic
When there is no sufficient light/the reset pin is held low by R14 (4.7K resistor) and the circuit works as it is described in the earlier paragraph. But if there is sufficient light, resistance of LDR [...]
Staircase switch with CD4013
If you really want to have classical staircase switch with push to switch on from one place and off from another place, here you have more circuits. Now you have two options to build the circuit here, one with light sensitive and another without it. Time delay is not incorporated here. We can use both [...]
