Wireless Telephone/Doorbell Mod Guestbook
Using this simple circuit pressing the doorbell switch causes all the phones on your base system to ring.
I got fed up with waiting around the house for deliveries and found wireless doorbell systems had limited range so I decided to link the doorbell into my existing wireless
There is however a problem with this basic system. If someone presses the doorbell twice (not uncommon) the 2nd press turns the ringing off and all you get is a quick ring. Also if the doorbell is pressed again any time the doorbell is ringing the phones will stop ringing.
What is needed is a circuit to do the following
sense the bell switch being pressed
send a signal to make the phones ring
electrically isolate the circuit from the telephone base
flash an LED on the bell push when the door bell is ringing
ignore any further presses on the bell push while bells are ringing
allow resetting of the bells when the front door when answered
allow conventional door bell to be used if required
in a noisy environment give a visual ring indication
I have used a 556 timer IC this is in fact 2 x 555 timers in a single chip. The 2 timers are both wired as monostables i.e. they only have 1 stable state and when activated revert back to their original state in a preset time.
The 1st monostable has an adjustable time from seconds to a few mins and this triggers the 2nd monostable that is configured to have an adjustable time of a fraction of a second to a few seconds and this provides the trigger for a relay that makes the phones ring. The 1st monostable also ignores all further presses of the bell push until it returns to it's normal state.
I have also added a reset button mounted on the inside of the front door. Pressing this stops all telephones ringing and can also be used when pairing phones to the base station. There is also a changeover switch so I can use the conventional doorbell if required.
Basic Circuit diagram
Circuit diagram showing connections to external components.
Vero board layout
Vero board layout front and rear.
Components list for Door Bell Mod
- Vero board
D2 1N4148 100V/0,2A/4nS, 1N4148 100V/0,2A/4nS
D3 Si-diode, 1N4148
- Solder pin, 1 mm
IC1 DIL14, 556 Timer
C6 Electrolytic cap. 8,5 x 15,5mm, 220 uF/63V
C4 Ceramic 5mm, 0.1mF
C3 Electrolytic cap. 6,5 x 15,5 mm, 10 uF/ 25 V
C3 ceramic 2,5mm, 0.1mF
C3 Electrolytic cap. 6,5 x 15,5 mm, 47 uF/ 25 V
R1 Resistor 0207, 10K
R5+R8 Resistor 0207, 770
R3 Resistor 0207, 1K
R9 Resistor 0207, 10K
R4 Resistor 0207, 10K
R7 Resistor 0411, 1K
C2 Capacitor, 0.0047mF
D2 SI-diode 1A, 1N4001
R6 Resistor 0411, 1K
R2 Resistor 0207, 10K
P2 Trimmer PT6S, 100K
P1 Trimmer PT6S, 1M
T1 TO-92, BC548
SC1 Socket DIL14 (low cost)
D4 Flashing LED
D1 Flashing LED
(19/4) (19/5) wire: hole distance 1; L = 2.54 mm
(24/6) (24/5) wire: hole distance 1; L = 2.54 mm
(29/4) (29/5) wire: hole distance 1; L = 2.54 mm
(14/10) (14/14) wire: hole distance 4; L = 10.16 mm
(24/4) (24/1) wire: hole distance 3; L = 7.62 mm
(27/8) (25/4) wire; L = 12.58 mm
(34/13) (34/14) wire: hole distance 1; L = 2.54 mm
(22/1) (22/0) wire: hole distance 1; L = 2.54 mm
(40/6) (40/7) wire: hole distance 1; L = 2.54 mm
In it's normal state the "bell push" switch and "bell silence" switches are open and the relay is not operated.
IC1a and IC1b are both wired as monostables.
On pressing the "bell push" switch the trigger of IC1a is taken low. The output of IC1a therefore goes high switching on transistor Q1. This causes LED D6 (flashing LED) to light and sends a pulse through capacitor C2.
This pulse takes the trigger of IC1b low and therefore the output of IC1b goes high operating relay RL1. Relay RL1 operating shorts the telephone base "find handset" or "paging" terminals causing all the phones on that base to ring.
IC1a monostable time period is set by C1,VR1 and R6. VR1 is adjusted so that the monostable time period is a few seconds longer than the phones ring for eg 30secs for a Diverse 6410 or 60sec for a Diverse 7410. This ensures that multiple pressing of the "bell push" switch do not retrigger IC1a and b causing the bells to stop ringing.
IC1b monostable time period is set by C3,VR2 and R7. VR2 is adjusted to give a short period (usually less than a second) just enough to trigger the telephone base.
The "bell silence" switch when pressed resets IC1a by taking it's reset pin low. IC1a output then goes low stopping the LED from lighting. IC1b trigger is also taken low so the output then goes high for the set period of the monostable operating RL1 and stopping the phones from ringing. Note if the "bell silence" switch is held down the monostable time period of IC1b is overridden and RL1 remains operated while the "bell silence" switch is held down. This can be used to set up the phones to the base station as they often require the "find handset" or "paging" button held down for a number of seconds to activate a handset search.
Note the optional "ring repeater" LED can be used to give a visual indication that the doorbell is ringing in a noisy room.
You will need to take a 6 wire cable to the door or use 3 x 1pr bell wire. I had a 1pr bell wire going to my door for my original bell so just ran in 2 more 1pr bell wire. 1pr connects to the normal door bell push switch, 1pr to the flashing LED and 1pr to the bell silence switch. Note I just used another standard door bell push for the bell silence switch. I mounted it on the door frame on the opposite side to the bell push. Mount the "bell ringing" LED in the door bell push in a suitable holder and label if required.
If the optional ring repeater LED is required then 1 pr cable is required as well.
You will need to run a 1pr cable to you telephone base. This will need to be connected across the "find handset" or "paging" terminals on the PCB of your base.
Note this involves taking your base apart and soldering directly to the PCB. This of course will invalidate your warrantee and may also destroy your phone. Only carry this out if you are competent to do so and always disconnect the power and phone line connection to the base first. If you cause a fault on your phone or line your service provider may well charge you to sort it out.
If you are adding/keeping your old door bell you will need to add a 2 way switch. I have used a small toggle switch for this and it can be mounted in any convenient out of the way place even in the old doorbell case. See schematic for connection to external components for wiring details.
This circuit uses around 30mA so use a suitable 12v regulated power supply.
A visitor arrives and presses the "bell push". The "Bell Ringing" led on the "bell push" starts flashing and all the phones in the house start ringing anywhere in the house or garden within range of the base station. You can either go to the front door press the "bell silence" switch on the inside of the front door to stop the phones ringing and then open the door or if you have a phone nearby press any button on the phone to stop the bells ringing then go to the front door and open it.
You are on the phone having a conversation when a visitor arrives and presses the "bell push". Depending on the phone base the phone you are talking on will not ring but all the other phones will start ringing. This is something to bear in mind if you have taken a call on a handset for example in the garden and are not in earshot of the other phones.
You get an incoming call and the phone start ringing at the same time as a visitor arrives and presses the "bell push". As soon as you answer the call the other handsets will start ringing (I set the "find handset" or "paging" ring to a different ring) to indicate someone is at the door. Note some bases eg Diverse 7410 have a preset "find handset" ring.
Power cut. During a power cut wireless phones and their bases will go off so the phones will not ring. I still have my old battery doorbell so I have wired in a 2way switch to enable it when needed. When power is restored the phones will ring for the timeout period. This may be annoying in the middle of the night but at least it may serve as a reminder to reset your electric alarm clock.