[mythtvnz] FrontEnds Controlling Audio Mains Power

[Tortise]

----- Original Message ----- 
From: "Nick Rout" <nick.rout at gmail.com>
To: "MythTV in NZ" <mythtvnz at lists.linuxnut.co.nz>
Sent: Sunday, October 03, 2010 11:21 AM
Subject: Re: [mythtvnz] FrontEnds Controlling Audio Mains Power

>Actually the gear pointed out on trademe will do it too.

Well maybe... with some (considerable legal fine print) limitations:

* does not have the software control possibility that I presume the kit does.  (See the circuit diagram)
* it is limited to 500W on the sensing circuit and
* the sense threshold appears fixed at 30W
* its not compatible with some plasma screens and laser printers

"Please note that some large Plasma televisions may need to be connected to a "SLAVE" socket instead of the "MASTER" socket of this 
product.

Some of the newer Plasma televisions draw over 30 watts even in standby, causing the powerboard to be unable to automatically detect 
that the Plasma has been switched off - and therefore not switching the "SLAVE" outlets off.

(The PT9778 Energy Saving Powerboard detects power usage under 30 watts to be "off").

If you experience this problem, please try connecting your Plasma television into one of the "SLAVE" outlets, and a connect a 
different device such as a DVD player into the master outlet. "
and
"WARNING: DO NOT CONNECT LASER PRINTERS TO THE SLAVE OR MASTER SOCKET OF THIS POWERBOARD. Doing so may damage both the printer and 
the powerboard. However, it is fine to connect a laser printer to the normal outlet of the powerboard. If you wish to turn off a 
laser printer while it is not being used, please use the printers on/off switch"

The kitset does not have these limitations and it is much more flexible, e.g. PS2 5V rail sensing can be easily added allowing USB 
keyboard power on to also continue to work.

I expect this is or is close to the kitsets circuit: 
http://www.electronicsinfoline.com/Projects/Electronics/Industrial_and_Manufacturing/Switch_and_Relay/usbsensing_mains_power_switch.shtml

BTW this is also published and has some merit:  http://www.gifford.co.uk/~coredump/usbpwr.htm using opto isolation, which means the 
LED draw on the 5V rail is negligible.

This http://www.siliconchip.com.au/cms/A_102979/article.html and its series of pics is also interesting: 
http://www.siliconchip.com.au/cms/gallery/article.html?a=102979&i=9 , using an 8 A triac, but presumably needing a heatsink for that 
load http://www.jaycar.com.au/images_uploaded/BT137FS1.PDF  At a guess 3 A / 750W is probably enough for our mythtv FE Audio / Video 
use.