Doorbell Circuit

Tone Doorbell circuit

When the door is pushed, you hear a whisper that "slide up" to a higher frequency. The oscillator frequency is determined by AF coupling capacitance, C 1 and the value of the resistor connected between the base of IQ and the earth. This resistance, RBG is equal to (Ri + R2) RJ. First, suppose that 51 is closed and R2 have been adjusted to produce a pleasant, low frequency tone. The capacitor C3 charges through R6 until it reaches such a tension that will cause diode Dl to conduct. ..

Bell circuit with two 555 timers

This simple Bell circuit uses two 555 timers. The frequency is controlled by the capacitors that must be preserved almost identical in value to each other for best results. Fine tuning is done with R1 and R2. ..

Wireless doorbell 300MHz

The operation of a 303MHz circuit has been covered in our project WIRELESS DOORBELL. We are not going over how the circuit works but explain the importance of some of the components and how they effect the range. The most critical component is the transistor. A quality transistor is important in the RF section and Japanese transistors are by far the best for this purpose. The transistor used in the 303MHz oscillator has a maximum frequency of operation of 1,000MHz and this is where its gain is equal to "1," so we want a transistor to have a good gain at 300MHz. A BC 547 transistor will not operate at this frequency so we have used a 2N 3563 which is low cost and will operate up to 1,000MHz. ..

Announcer DoorBell

M1 is a clamp connected to the 24V (dc or ac) power from the gate opener. The diode bridge rectifies the alternate voltage (should the opener use dc current, it merely adjust the positive and negative rail to match circuit polarity), in order to get the power required by the 24 V relay. The same potential, limited in current by the series resistor R1, feeds the 5V regulator IC1. The 5V stabilized voltage from IC1 powers the Nutchip; the R3-C5 network ensures proper RESET to the chip. The input stage consists of a double switch relay, RELAY1. The original photocell's output connects to M2, therefore it powers the relay. ..

Melody Doorbell circuit

In all the houses exist the bells in the door. All want, they have the possibility of being possible to change the intensity, the tone of sound. With this circuit we have this possibility. With the materials round the gates, we can change the sound. For the materials that exist in the circuit the frequencies are roughly 5 KHZ and 2 KHZ. The circuit functions only for small time interval afterwards the pressure of switch. Simultaneously with the sound we have also optical clue from LED D2. Changing the capacitors C2-C3, with different price of capacity, we create new sounds. ..

Door Chime with ATtiny12

The device described here does just that. The circuit connects to the doorbell circuit - taking power from the 18 VAC from the doorbell transformer and switching power to the doorbell circuit most of the day. The user interface is a pushbutton, a toggle switch, and two LEDs. One LED - the green one -blinks at 1 Hz, just to give me some comfort that the circuit is working. The amber LED glows whenever the doorbell is disabled. To set the timer, you just push the button momentarily, and when its released, the amber LED will come on and the doorbell circuit is disabled (the door bell button doesn't work) for a 10 hour period. At the end of the 10 hour period, the amber LED goes off and the doorbell is enabled. ..

This circuit is a modified hartley oscillator with a couple of extra components included. The transformer is a small audio transformer, type LT700. The primary is center tapped with an impedance of 1Kohms at 1KHz . The secondary has an impedance of 8 ohms. The inclusion of R1 and C1 give this oscillator its characteristic "chirp". As the 100u capacitor charges via the 4.7K resistor, R1 the bias for the transistor is cut off...

This circuit provides a delayed visual indication when a door bell switch is pressed. In addition, a DPDT switch can be moved from within the house which will light a lamp in the door bell switch. The lamp can illuminate the words "Please Wait" for anyone with walking difficulties...

The transmitter circuit is made up of two building blocks - the 303MHz RF oscillator and the 32kHz crystal controlled oscillator. The 303MHz oscillator consists of a self-oscillating circuit made up of the coil on the PC board and a 9p (9 puff) capacitor (actually 4p and 5p in parallel). The circuit starts-up by the transistor producing noise. This rising-and-falling signal on the collector is passed to the parallel tuned circuit (the tank circuit) and the base sees a very smooth sinewave at a frequency of 303MHz...

Reverse engineered circuit diagram of a commercial Electronic Bird. This one was built into a plastic christmas ornament and runs off a 9V battery. Note that L1 is actually just an audio transformer with an unused secondary winding...

The circuit is built around the popular and less expensive quad D-latch CD4042B (IC1). There are four switches fitted at four different doors/gates outside the home and a monitoring panel (as shown in Fig. 2) in the common room of the home...

This very simple and self-powered device was conceived to allow a person to monitor if someone has rung his home door-bell when he was out. As most door-bells use 12Vac supply, the circuit must be simply connected to the two door-bell-coil leads...

This schematic will activate a beeper in the basement, whenever the front doorbell is pressed...

If you can`t hear your doorbell when you are in your basement try this circuit. This circuit takes advantage of the 24vac power source located near the furnace. Using a simple current transformer technique, the circuit sounds a beeper whenever the main door chime is activated...

The circuit in Figure 1 prevents damage to the chime and improves the chime`s effectiveness by repeating the chime strike for as long as the pushbutton remains depressed. The circuit controls both front and rear chimes...