This circuit is suitable for musical bell in doors, home security alarm systems, burglar alarms etc. The main part of this alarm circuit is an UM66, which is a melody generator IC. It is a very small IC that almost looks like a transistor, it has an inbuilt tone and a beat generator. This IC is programmed to generate certain frequencies.When power is turned on, the melody generator is reset and melody begins from the first note. Many versions of UM66T are available which generate tones of different songs. The power (Vcc) for this circuit should not exceed 3V or else it may lead to the damage of our UM66 IC. If you want to join this circuit to other circuits, sharing a common Vcc which is greater than 3V then a zener diode voltage regulator can be employed. This is a very simple battery powered melody generator circuit. Feel free to leave a comment in the comment box below for any doubts. When power is switched On, UM66 starts to generate the melody current. The output from the UM66 IC has no sufficient power in order to drive a speaker.
So we are using an NPN transistor as an amplifier. The operating voltage of UM66 is 1.5V to 3V. The supply voltage should not exceed 3V, If is happens, the IC will damage. Here is the assembled form of above circuit in i-St@r Lab. The Zener diode is used for protecting UM66 from high voltage I would think this was a combination of sun and some have a small light inside so it is visable at night . I expect if it was line voltage some one would have felt this before . Please Visit the InterNACHI Awards page Stronger Light could do this .. If someone at some point replaced the original chime button with a lighted version (which are 16 volt max) on an old system operating at 24 or 36 volt, But the good news is the home needs no further outside illumination Good call Marc, I bet your correct, I'd never have twigged that one "To realize our true destiny, we must be guided not by a myth from our past, but by a vision of our future." NACHI Education & Training Consultant Commercial property Inspection Tampa, Orlando, Sarasota, Jacksonville, Ft Launderdale, Miami, Florida.NACHI cell 484-429-5466Home inspection Clearwater, St Petersburg, Tampa.
Simple - too hot is too hot And the problem is ??? Voltage is too high if it is a lighted bulb -- (It will not last long and should be bright) A simple meter from radio shack will find the problem - This is out of the SOP of the HI However, could you provide the address of this house - I have a few realtors I'd like to send by to try out this hot button... You�re Your Own Job Security.Background: How a Typical Wireless Doorbell's Power Supply and Sound Player WorkNextPrevThere are a lot of parts that make up a wireless doorbell. But for this project, you only need to be concerned with the power supply and the speaker.An AC powered wireless doorbell is going to have an AC-to-DC converter to turn the 120 volts AC into a small DC signal (usually about 12 volts). To bring the voltage down, it may use a transformer or just a power resistor. Then to convert the AC sine wave signal to a series of DC pulses, it will typically use four diodes arranged as a square bridge rectifier.
Lastly, a capacitor smoothes out the DC pulses into more constant DC signal.We need to identify the positive and negative DC lines at the output of the AC to DC converter. The easiest way to do this is to observe the orientation of the capacitor: One side of the capacitor will be marked with a large negative sign. This is connected to the negative output of the power supply. The other side is connected to the positive output of the power supply.Next you need to check how the speaker is connected to the rest of the circuit. In most cases, the positive terminal of the speaker will be connected to the positive supply voltage from the power supply. The negative terminal of the speaker will be connected to the collector of an NPN transistor. The emitter of the transistor will be connected to the negative terminal of the power supply. The base of the transistor will be connected to processor chip. There may be a resistor between them. To play the tone, the chip sends a series of pulses to the transistor, which rapidly connects and disconnects the negative terminal of the speaker to the negative terminal of the power supply.
This causes the speaker to play a tone.In this project we will be connecting to the positive and negative terminals of the power supply and to the output transistor at the negative terminal of the speaker. Cut the Speaker Wires and Attach Extension WiresNextPrevThe first thing that you need to do is cut the speaker wires near the center. Then strip the insulation off of the ends. Solder another six-inch piece of wire to each one. (It helps if you keep them color coded.) Insulate each connection with either heat shrink tubing or electrical tape. Solder an Extension Wire to the Negative Terminal of the Power SupplyNextPrevNext, we need to connect a wire to the negative terminal of the doorbell's power supply. As mentioned earlier, the easiest way to identify the negative output of the power supply is to check the terminals of the capacitor. The side of the capacitor that is labeled with a large negative sign "-" is connected to the negative terminal of the power supply. Find any terminals that are connected to this and solder on a piece of wire that is about eight inches long.
Drill Holes to Route the Wires Outside of the Doorbell HousingNextPrevFind a drill bit that is the same size as the extension wires and drill five holes in the housing of the doorbell. Then feed the wires through them and close up the housing. Be sure to keep track of which wires are connected to what. It may help to label the wires with a small piece of tape. Attach Two Switches to the Output TransistorNextPrevNow we need to connect to the output transistor. This is the wire on the board that used to be connected to the negative terminal of the speaker. First, take this wire and connect two more extension wires to the end of it. Then solder a sliding switch onto the end of each one. These switches will let us turn the tone and the light on and off.One switch will be used to control the audible tone of the doorbell. To set this up, take the wire that is connected to the negative terminal of the speaker and solder it to one of the switches. When the switch is turned on, it will connect the speaker and the tone will play.
The other switch will be used to control the light. On this switch, solder another extension wire. This wire will be connected to an external circuit that will turn the light on and off. The Control CircuitNextPrevThe control circuit is a basic 555 timer circuit. This configuration is called "Monostable" mode. Vcc and GND for this circuit are connected directly to positive and negative terminals of the doorbell's power supply. Pin 2 (the trigger pin) is connected to the free wire on the second switch. When the doorbell is activated, pin 2 is connected to ground through the output transistor. This causes the output at pin 3 will turn on for a length of time that is determined by the values of the capacitor and the resistor. You can determine this time using the formula: Time(in seconds) = 1.1 x R(in ohms) x C(in Farads). Prototype and Troubleshoot the Circuit on a BreadboardNextPrevAs with any electronics project, you should first test the circuit out on a breadboard. I attached an LED to the output for testing.
In the final version, the output would be connected to the solid state relay.Here are some common problems that you may encounter and how to deal with them:If the output of the power supply is not stable enough, it can cause the timer circuit to malfunction. To fix this, add an additional capacitor between the doorbells. I used a 330 microfarad capacitor.If pin 2 is connected directly to the output of the doorbell and nothing else, it can experience some interference from static electricity. This can cause false triggering. To solve this, add a 1kohm resistor between pin 2 and pin 4 (the positive supply voltage). This acts as a pull-up resistor and keeps the pin HIGH until it is pulled LOW by the signal from the doorbell. Solder the Circuit Onto a Printed Circuit BoardNextPrevOnce you are happy with how your circuit is performing, solder all the components onto a printed circuit board. Connect the Output of the Circuit to the Solid State RelayNextPrevNow we need to connect the control circuit to the solid state relay.
Connect one wire from pin 1 (ground) on the control circuit to the negative input terminal on the solid state relay. Then connect pin 3 (the output) on the control circuit to the positive terminal on the solid state relay. I recommend insulating the connections with heat shrink tubing. Cut the Extension CordNextPrevThe extension cord needs to be cut into several sections in order to provide power to the various parts of the system. Start by cutting the cord 6" from the female end. Then cut another section that is about 1' long. Separate the two wires of this 1' section. Cut one of these separated pieces in half. Lastly, strip the insulation off the ends of each piece. Connect the Wires With Twist-on Connector CapsNextPrevThere are two sets of wires that need to be connected. First take one wire from the male end of the power cord, one wire from the female end of the power cord, and one of the short separated wires. Connect these three with a twist-on connector cap. Then take the other wire from the male end of the power cord, the other wire from the female end of the power cord and the long separated wire.
Connect these with a twist-on connector cap. Connect the Power Cords to the Solid State Relay NextPrevNow take the two short separated wires from the power cord and crimp on a pair of quick disconnect connectors. Fit these onto the load terminals of the solid state relay. Connect the LightNextPrevI chose to use a small CFL fluorescent light as the light for this project. To connect the light, I mounted it inside a small light socket, then attached the two remaining wires from the power cord assembly to the screws on the light socket. Cut Holes in the Housing for the Power Cord and the SwitchesNextPrevAt this point, all the electrical components are connected. Now we need to prepare the housing. Cut one slot for the power cord and two slots for the switches. You can do this with either a knife or a rotary cutting tool. Mount All the Parts Inside the HousingNextPrevAll that is left is to mount all the parts to the inside of the housing. Start by mounting the light socket to the center of the housing.