On Wednesday, May 1, 2013 1:54:36 PM UTC+1, whisky-dave wrote:
On Wednesday, May 1, 2013 12:21:38 PM UTC+1, wrote:
On Wednesday, May 1, 2013 11:11:28 AM UTC+1, whisky-dave wrote:
On Wednesday, May 1, 2013 12:33:51 AM UTC+1, wrote:
On Tuesday, April 30, 2013 11:35:49 PM UTC+1, The Other Mike wrote:

If the government keep their stupid fingers out, it won't be long before appliances with this feature are available for an extra £5.
No you'll be entered into a free prize draw....


An 8 bit cpu can respond to frequency,

Not that easily, and I doubt using that method would be very successful.

its not hard to divide the clock frequency down to 50Hz ..

But you need a dedicated clock you can;t use the average MPUs clock as it's too inaccurate, you need a proper RTC, you do know that computers keep pretty crap time unless they get it from a server.
You wouldn;t use that method anyway as you need to mearuce the actual frequency of teh main not simulate it.
and time the period from local zero crossing to mains zero crossing, and log the latest value to see how far it moves.
Not necessary.

All one need do is
a) xtal control the cpu clock, an xtal with no oven is more than accurate enough to read 50Hz +/- 0.1%.
b) count a divided version of the clock from one mains zero crossing to the next. Problem solved.

The slight frequency spread of the xtals prevents all appliances going off at the same time.


Far better to have teh aplience switched off on demand from the suplier than wait for the frequency to alter which would be difficult to measure cheaply.

well, thats what checking the frequency achieves. How would you do it cheaper?

Measure the frequency at the power station and if it's condered that power needs reducing lower the overall voltage supplied to the grid.

Voltage control would be quite unreliable, V swings about in normal healthy use for various reasons.


If yuo really need to switch things off then measure the frequency of the grid and if it's below what you see as a miniumium then send a single to turn off particular devices that are in yuor home that the smartmeter recognise.

So you're proposing that appliances have 2 way communications, and that smart meters talk to each appliance in each house. Doable of course, but its more money, so not attractive.


Be silly to have to measure the frequency of every device.

Either you measure locally or decide centrally and communicate. Do you think 2 way communication's cheaper?

Yes.

I'm struggling to see how enabling 2 way comms and playing with MACs is cheaper than a divider in the chip.

Measuring low frequecies accuratly is more difficult than you think.
What you have to do is count cycles in one second yuod get perhaps 47 or 53 so you need to average it out especailly in times of high or low demand.
So you need to sample it for at least 10 seconds to giove you 0.1 resoultion and in that time the situation can change.

Its not hard at all, just time the number of clock cycles between 2 successive crossings. You could average lots of counts but I don't believe there's a need to, a small percentage of mistimes is immaterial in practice. Simply averaging several yes or nos would be trivially easy.


Anyway it would be cheaper to have just one device measuring frequency rather than every electrical device each reading it. If I were designing such a thing it'd use teh smart meter to measure it rather than install the ciruitry in my kettle and fridge.freeze, TV cooker shower , washing machine, coffee maker storage heaters fires hair dryer etc.....

but you'd still need to install everything in the appliances, you'd only miss out the clock divider, which inside a custom single IC costs close to nothing.


What I'd get manufactiers of such devices to do it allocate a specific number to each product a bit like a MAC address which my smart meter can locate and be able to either just switch off/on or reduce it's power.

more costs

idf all 2KW+ kettles had a 1/2 power switch then my first try would be to turn those kettles is 1/2 power them, I wouldn't turn off motors or mmoving things such as food blenders.

I'd agree there. There are many things can be turned off or down if its ever worth it. Today its mostly not though.


and send the appliance serial number down the wiring now and then, and the power co software will automatically knock £1 off the bill.

Too much hassle and no need for it.

The user needs some reason to spend the cost of the control unit. If I were offered 20% ROI I'd buy, for a prize draw I wouldnt.

You don;t need to you make it cheap enough that no one would bother

that'll happen, but only after its already being widely bought, ie produced on a mass scale, with all the upfront investments paid off. To get to that point its going to cost, so there must be a customer upside.

or you make it illegal to sell products without such things.

but then its a protected parasite, & the cost stays high.


We do this in the name of H&S, you can't normally buy appliences without leads, you have to buy them with the product or buy them seperatly.
I remmber the days when buying electrical equipment you HAD to purchse a lead or plug and put that on yuorself. Nowadays that's not possible for most people you can;t go and buy even a £5 kettle without a moulted lead.
You can't say IO'm not buying an electrical product that comes woth a free lead because i have plenty. I have about 150 IEC leads I'm not using in a box.

Firstly this isnt a H&S issue, and there isnt anywhere near justification to force it on everyone. Second, phones are beginning to be sold now without chargers, and with IEC leads so common theyre moderately likely to become optional with cheap appliances. Government interference gets in the way of progress more than it helps it.


NT