HOUSE  BELL
 
There are wireless house bell which are a small radio emitter and a receiver with a bell. We have found a cheap one, which frequency is   433,92 MHZ, which works on coded signal, and which range is given 100m. .Such specification makes it a possible tool to trigger the shutter release of a camera.
The modification is simple, and only needs a relay SIL REED, available in the electronic components.
 On the cradle, I have confirmed the effective release at 100m, and irregular release up to 150m.
A round model with 150m range has a 170mm antenna in the receiver. The shape is not practical, and the crescent electronic board is not easy to replace in another box.

 
 
The maker of this wireless house bell is Kangtai. It is distributed in France under the trade mark Kangtai and by the company GEFOM www.gefom.com under the trade mark Gefolec. But there is also a round shape receiver under the trade mark PT with a given range of 150m.

 DISMOUNTING

  • On the back take away the plastic handle.
  • Remove the two screws
  • Open the battery compartment
  • Take out the cover
  • On the speaker, unsolder the wire connected to the circuit board, and the led.
  • Remove the speaker, and the battery connector linked to it.
  • Remove the screw on the circuit board
  • Take out the circuit board

 

 

 

 

 

 

REMOVE THE BELL CIRCUIT

  • Unsolder the small bell circuit from the main circuit board

SETTING THE RELAY

The relay is referenced SIL REED 1T
  • At the place of the former bell circuit, drill 4 holes Ø0.5mm lined up, 2,5mm step (start drilling on the circuit side of the board)
  • By grinding, cut the circuit tracks near the drilled holes 1, 3 and 4.
  • Set and solder the relay ( there is no direction)
  • With a thin electric wire, link the eye 3 to the minus
  • Solder two wires on the eyes 1 and 4 and connect them on the release connector. See Connexion

 

 

 

 RE-CONNECT THE LED

The led is re-used as "on" indicator

  • Link the two last pins of the switch (red line)
  • Add a ground wire and solder it at M
  • Grind the circuit track at the place shown with blue arrow.
  • Connect the led to this wire and to the wire linked to P (if the led would not light, invert the connections)
  • Put the led on the cover, and maintain it with adhesive tape or with a drop of glue.

 MODIFY the BATTERIES

  • Cut the small wall holding the batteries (leave the second one which will be used to press the battery against the springs)
  • Replace the flat connector by the short one with a spring
  • Unsolder the ground (minus) wire on this connector (this wire is linked to GND on the circuit) and solder it on the long connector. Remove some plastic wall to pass the wire.
  • Remove the long connector on the opposite side
  • Unsolder from this connector the "plus" wire (linked to VCC on the circuit) and solder it on the short spring connector.
  • Install an unmistaking boss
  • Set a battery CR-P2 and adjust the springs to make good connexion with the battery.

 
For a good work of the relay, the circuit must be fed with 6Volts. A lithium battery CR-P2 is used.  
This unmistaking boss has been done with 2 components compound, and moulding the battery shape.

 

The end A is active; the B end can be let free.

 

 CHANGE THE ANTENNA

It's not  mandatory, but it increases the range to 150m.
  • Prepare a wire Ø1mm or more, 170mm long
  • Remove the existing antenna wire AB
  • solder the new wire at place shown A

 RE-ASSEMBLY

  • Run the release chord until the battery compartment
  • Close the hole let by the handle.
  • Put back the circuit board and screw it
  • Mount the cover and screw it
  • Place the battery 6V
  • Test it
   Note arrangement of release chord during transportation.