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Remote Door Chimes in Australia

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Remote Door Chimes in Australia
« on: 13 / June / 2010, 03:29:23 »
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I have tried a number of remote door chimes available in Australian hardware stores and shopping centres.

The Kambrook and Arlec brand receiver section of the chime use two AA cells.

The receiver and chime are an all in one chip. There is no available technical information on the net for the chip. I managed to trace the circuit board and find the output driver transistor. The speaker positive is connected to battery positive. The speaker negative is connected to a surface mount transistor collector, the emitter to ground and the output of the chime chip drives the transistor base.

Disconnecting the speaker and connecting the output to the camera USB will not work. There is no positive voltage drive. Leaving the speaker in circuit produces about one volt output at the transistor collector connection. Too low to drive the camera USB.

I have observed the chime signal on a oscilloscope. Regardless of the chime note, the chime duration is close to five seconds.

Altronics and Jaycar are now the only electronics suppliers in Australia. Even they only have a limited electronics range.

Jaycar have a Burp machine CAT. NO. GH1081 listed on their web site for $5.00. I have not seen one except from the web picture. Judging by the description it seems the operation is the same as a wireless doorbell chime.

For the price of the unit it is worthwhile gutting one in the name of experimentation. 

The following is a general guide to modifying a remote door bell chime.

Open the unit and place a digital voltmeter across the speaker terminals.
Press the remote.
If the voltage is around 1.5 volts the transistor may drive a 4N28 opto coupler Jaycar CAT. NO. ZD1928.
If the voltage is below 1.5 volts look carefully on the printed circuit board.
You will find a miniature transistor soldered flat on the printed circuit board.
One side is connected to ground. A large thick trace which may have many connections and wires connected.
You will find one trace that seems to have nothing connected to it.
Look carefully; that track will join onto a black blob; that is the onboard chime chip. On older chimes it may be a 16 pin soldered IC.
That track will be the chime output.
Place a meter probe on that track and ground.
Press the remote.
The voltage may go as high as 2 volts.
If that is the case, use that point to drive an opto coupler.
I recommend using a 500 ohm series resistor.
 

The output of the opto coupler can be used as a transistor switch using an external 5 volt supply to drive the camera USB.

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Offline colinbm

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Re: Remote Door Chimes in Australia
« Reply #1 on: 13 / June / 2010, 04:16:59 »
Hi thepanoguy
I have the Burp machine apart.
It has 4 AAA batteries = 6 volts.
With the speaker disconnected, I am getting 5 volts & up to 6 volts at the speaker wires ends, on the press of the transmitter.
The circuit seems pretty simple, as door bells can be.
This one has 2 "black blobs", one is mounted vertical, has 6 pins, VO, GND, OSC, TG & VCC.
The other is on a second PCB just raised off the main board (looking a bit like an IC), it has 8 pins & is marked Rx. The pins are on thr RH side A1, A0, VDD & VT, on the LH side A2, unreadable, V something & DI, there is a resistor SMD ? on the botton of this Rx board on a track that leaves & re-enters the "black blob" marked 274.
There is also an IC as well.
Just near where the speakers wires leave the board is a transister (UTC M28SL SFA).
Would a photo be of a help, if I can just paste one here ?
Cheers
Col

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Offline colinbm

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Re: Remote Door Chimes in Australia
« Reply #2 on: 13 / June / 2010, 04:29:39 »
Hi the panoguy
I just reconnected the speaker & the voltage only rises to 1.5 volts.
The IC I mentioned has 8 pins & is marked as 49Z11HA LM358P.
Col

Re: Remote Door Chimes in Australia
« Reply #3 on: 14 / June / 2010, 05:47:48 »
For anyone contemplating building a wireless remote in Australia.
Jaycar part number GH1081

I purchased one of the Burp Gadgets from Jaycar.
I looked at the waveform on an oscilloscope.
The Burp sound output (speaker wires) is of no use for a USB camera remote.
The waveform varies with each press and the voltage generated is too low.

On the PC board there is an IC marked U2.
Bottom right hand side of the U2 sub board is a pin marketed VT. (small o bottom right on the PC board)
When the remote is pressed a 5 volt pulse appears.
If you hold down the remote button the 5 volts stays until released.
Solder a red wire (positive) to U2 VT terminal and a black wire (negative) to B-.

For short circuit purposes it may be advisable to solder a 500 ohm resistor in series with the red wire before connecting to a USB cable.

I have managed to trace part of the circuit board.
 
The black IC LM 358 looks like it functions as an oscillator generator for IC U2.
The pulse output is on IC U2 pin VT.
My oscilloscope measures a 5 volt positive output pulse.
IC U2 pin VT connects to U3 pin TG.
U3 pin VO connects to the base of a transistor which drives the speaker.
Therefore; U3 is the sound generator chip and redundant for USB camera remote functionality.
The sound may be useful as a feedback to inform that the photo has been taken.
Otherwise, you can disconnect the speaker wires, after a while the sound generated is annoying.

UPDATE: 15 June 2010

I have de-soldered U3. The sound drove me mad.
I have tested the unit on a Canon S3IS.
The first press turns on the camera.
The second press zooms the lens.
If the remote is continuously pressed, then ouput stays high.

I am not a programmer; the continuous output may be useful in a script.
ie one press shoot photo; hold down remote zoom lens and take a second photo.

For the cost $5.00AUD, the unit is far superior to the other remote doorbells on the Australian market and easier to set up.

UPDATE: 18 June 2010

IC U3 causes random erratic behaviour when observed on an oscilloscope.
De-solder IC U3 with de-soldering wick.
The voltage on IC U2 Pin VT using a digital multimeter measures 4.8 volts.
You may have to press the transmitter for one second.
IC U2 Pin VT stays high for as long as the transmitter is pressed.
« Last Edit: 18 / June / 2010, 04:22:28 by thepanoguy »


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Offline colinbm

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Re: Remote Door Chimes in Australia
« Reply #4 on: 14 / June / 2010, 05:59:48 »
Hey that is great thepanoguy
Thanks very much for doing all this for us, it is great.
I will get the resistor & get it up & working.
Yes the burps are a bit revolting as opposed to the farts machine !
I have a cheap Arlec that has the dog bark that I was hoping to use to put some smiles on the subjects faces. The Burp Machine is a nicer unit. Just need to find a nice box for the batteries & board.
Thanks again, much appreciated.
Col

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Offline colinbm

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Re: Remote Door Chimes in Australia
« Reply #5 on: 15 / June / 2010, 01:08:17 »
Hi thepanoguy
I am happily getting the Burp into a neat size box & making a camera bracket to mount it on.
You mentioned "For short circuit purposes it may be advisable to solder a 500 ohm resistor in series with the red wire before connecting to a USB cable."
Is this the correct size, the physical size is larger then anything on the board ?
Cheers
Col

Re: Remote Door Chimes in Australia
« Reply #6 on: 15 / June / 2010, 04:57:30 »
The resistor is only a safety measure to stop blowing up the IC. The resistors on the PC board are quarter watt. Jaycar sell half watt. Good enough for your purpose.
 

 

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