On Thu, 01 Jan 2015 05:39:50 +0000, Johny B Good
wrote:

On Wed, 31 Dec 2014 17:02:07 +0000 (UTC),
(Andrew Gabriel) wrote:

In article ,
jkn writes:
Hi all
has anyone done any exploratory/repair work on these sort of things? You
know the ones, they operate in the 433MHz band I think, and you set some
DIP switches on both bell push and receiver so that the codes match.

I know they are cheap rubbish, and the attrition rate is high; nevertheless I
am thinking of taking a closer look at one that has stopped working. My first
guess was imply that the press switch had failed; but it's a PCB mounted switch
with an ON resistance of 50Ohms, which seems at least hopefull.

There is some failry shonky soldering, some of which I will probably redo. There
is also a little rust on a 3-wire metal cased part with '433.920' marked on it;
a SAW filter I assume? I guess this may have failed, but the LED on the bell push
doesn't go on when you press the switch, and I think this is independant of the
oscillator/transmitter. Oh, and yes I checked the batteries...

As I say, not a big deal, but I'd be interested if anyone knows of any common
failure modes before I get in too deep...

Check for (and clean) battery contacts - corrosion on the permanently
live parts of outdoor electronics is quite common. Corrosion products
caused by battery leakage can be amazingly good insulators too.

That probably explains why my cheap wireless door chime is still
fully functional even after 5 or more years. The only battery I've had
to replace is the 3 x AA cell battery in the sounder unit I keep in my
upstairs office (about 4 or 5 battery changes in total afaicr).

I'm using the wireless door bell as a repeater to our existing
trembler bell mounted on the front door frame which is currently
powered from a pack of 3 PP3s wired in series. I've wired the wireless
sender to the trembler bell via a 12v zenner and small silicon diode
so that when the outside bell push is operated it also powers the
wireless sender.

The tiny 12v battery in the wireless bell push is only ever used if
its own button is pressed to attract my attention, usually by the XYL
when coming back home with a lot of shopping or, occasionally, to
announce her departure if I'm in the office with the door closed.

Operating the wireless sender's own push button doesn't operate the
front door trembler bell (which is handy for testing the wireless door
bell since I can hear it if I leave the office door open for such
testing).

The wireless bell push is never exposed to any extreme weather
conditions that would normally apply in most installations and this
seems to demonstrate the benefit of avoiding such environmental
stresses.

If the problem turns out to be the push button switch (500 ohms on
resistance?), a better solution might be to purchase an ordinary bell
push as a replacement and wire it across the original switch contacts
and relocate the wireless sender on the inside of the door frame where
it can remain nice and dry.


A nice idea, but that would entail drilling through the wood or UPVC
doorframe, which is what they wanted to avoid when they chose the
wireless option.

--

Graham.

%Profound_observation%