It has been on my mind for sometime: how are those digital electric meters made? I guess you'll need things like keypad(for entering recharge code), an LCD for display, a microcontroller for driving the LCD and the memory stuffs, a relay for cutting off power supply when the recharge has been exhausted.
A VERY interesting and challenging project for anyone to occupy himself with.
Look into Analog Devices' "Energy Management" category. They have chips optimized for power meters, samples, demo boards, and app notes on power metering.
I've got a pre-pay card system in my house as well, although it's not because I don't pay my bills - the meter was already installed when I moved into the house and I've never bothered to have it exhanged for a standard type.
It's actually worked out to be quite handy for me because my girlfriend, who's moved in with me, contributes towards the bills by looking after the electric meter - so I don't get a bill for my electric at all.
yes, it was quite a clever method. Then the operatives wouldn't have to be going to people's houses checking up their bills; in this case the customer's do all the running .
it is not anti-fraud though and there have been cases of people shunting the meter and getting unto the grid :lol: It is still on trial in my place.[/quote]
By-passing the meter is certainly well-known to us here - but it is quite easy to detect - the accounting system checks each bill against the previous few, and if usage drops dramatically, it raises an alarm on the system, and we go out and investigate.
People steal electricity all the time - but it's the greedy ones who get caught. One guy here got caught, because he installed a switch in a cupboard, to switch between Metered and Bypassed (thinking that, if he paid for SOME of his power, it would go un-noticed), but when he was selling his house, he actually pointed it out to the potential buyer as a "feature"... :lol: ahhh... the stupidity of some :lol:
yes, it was quite a clever method. Then the operatives wouldn't have to be going to people's houses checking up their bills; in this case the customer's do all the running
What we have here, for some commercial customers, is 'remote metering', where the meter is connected to a cellular modem, and the control centre simply 'rings' the modem every few days to collect the readings, thus removing the manual checking. (Unless the modem screws up, which they seem to do fairly often)