[clug] [OT] Remote control powerboard

Robert Edwards bob at cs.anu.edu.au
Wed Nov 25 19:01:12 MST 2009

Angus Gratton wrote:
> On Tue, Nov 24, 2009 at 10:34 PM, Rainer Klein <rklein at tpg.com.au> wrote:
>> The remote control is based on RF and comes with 4 buttons. It can be easily
>> attached to a key chain.
>> If you want to control it from your computer, you might want to use Jonathan
>> Oxer's idea and use an Arduino board.
> In fact, there's already an Arduino library for many of the common RF
> remote-control switches.
> I recently built a project using a single remote control power point.
> The Arduino is wired to a 433Mhz ASK transmitter from Jaycar. Very
> similar to a PIC-based design that Bob had posted on the web.
> Arduino library: http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1216065789/3
> Power point: http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=360196127267
> Wireless module: http://jaycar.com.au/productView.asp?ID=ZW3100
> That library supports 3-4 slightly different encoding schemes, so
> there's a good chance it will work with the power board as well.
> Getting the power point working was really simple. I was a tiny bit
> disappointed that I didn't have to do any coding from scratch. ;)
> Hth,
> Angus

I haven't yet tried to determine if the R/C in the 4-way remote power
board is using a one-time sequence or not. If so, it is much harder to
program your Arduino to come up with the same sequences, and using Jon
Oxer's approach with relays etc. would need to be done. Note that Jon's
approach requires a battery for the original remote, unless a power
supply is substituted. The relays are only one for short periods (the
time of a typical button press), so not too much power consumption

Note that the actual power board itself, like most small 240VAC devices,
uses a capacitor/reactance voltage divider power supply, which is cheap,
relatively small and can be relatively efficient. These power supplies
typically have a large yellow "X2" rated 275VAC capacitor acting as an
impedance device, but with very low real losses. These work really
well for devices with a small constant well-known load (like a little
microcontroller, a radio receiver etc.), but not so well for variable
loads (like what happens when a power control relay switches on).

In the case of Angus's single remote control power point, there is only
one such relay and the associated losses for when the relay if off is
not too great.

In the case of my 4-way board, the power supply needs to be able to
supply enough current at sufficient voltage to turn all four relays
on together. In order to do this, they had to design for a much higher
"no-load" voltage and throw away the excess power (as heat). Mine had
a 1uFd cap and was running at 23V with no-load and getting quite hot.
I eventually replaced this with two 0.33uFd caps in parallel (to give
0.66uFd) which reduced the no-load voltage to 17V, but still gave
enough to switch the 4th relay (at which stage the P/S voltage had
dropped to little under 9V). The resulting power consumption of the
power board dropped from about 17W to about 2W on standby, and 4W with
all the relays on.


Bob Edwards.

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