Variable rate electricity and using a big part to prototype a small job.

[blueroomelectronics]

Here in Toronto, Ontario, Canada we have variable electricity rates.
I thought it would be fun, practical and educational to build a wee rate indicator using a BiColor Red / Green LED.
So when rates are high it's Red
medium Yellow
cheap Green

Here's the hardware spec
PIC12F629
32,768Hz crystal
Red / Green (yellow) LED
Simple serial port 9600 for setting the time & date

Pin count
1 reset (set time date) or DTR input via 22K from serial port
1 RX via 22K resistor
1 Red LED lead and TX on same pin
1 Green LED lead
2 Crystal on TMR1 osc

Thoughts
DB9 connector with RI used for power when not connected to a serial port
Supercap for backup power
4MHz running but only when used briefly when the PIC wakes up every second or two
Could be run from a small solar panel (want to be green after all)
Sleeps (no LEDs) from 2am till 6am (for a small solar cell)
LEDs could flash to save power but this might be annoying
Fairly fancy RTCC as it needs to determine DST and different rate tables depending on day of week and time of year.
Doing the tables in EEPROM would allow reprogramming via the serial port as I'm sure these rates vary from place to place.

How I'm going to go about it
I like using hardware debugging but the wee 12F629 doesn't have hardware debug built in (you need a special version of the chip if you want that) so I'll prototype with the similar 16F88 which has hardware debug. It's also the type of project that most of the debugging could be done with MPLAB's built in simulator or even OshonSofts simulator.
Just thinking aloud. Comments welcome.
**broken link removed**

 

[birdman0_o]

I guess the purpose is just as a reminder only because the rates change at a different time every day? Just wondering because if it's at the same time every day...otherwise sounds like a fun project. Here in Quebec we always have the same rate! Go Hydro

 

[blueroomelectronics]

It's a new thing here in Toronto, not sure what other parts of the world use variable rate. As it's new it takes some getting used to when running high current devices. I'm new to OSX too and quickly reading up on Cocoa (would be a nice reminder program for the taskbar / menu bar)

 

[colin55]

Initiated by your desire to monitor tariffs, I conducted an experiment to determine the energy from a 2400watt kettle and a gas ring – commonly called a wok ring.
I heated water and measured the temperature after a calculated period of time. The kettle provided 1.9kW while the wok ring produced 1.3kW. It was advertised as a 4.3kW burner.
This leaves me with some suspicions.
What is the genuine calorific value of gas, and what is the efficiency of a gas ring?
We know electricity is 100% efficient – minus the heating of the kettle and losses during heating, but we could be entirely duped as to the calorific value of gas.
It is much more difficult to monitor a gas supply and they may be diluting the gas – who knows?
However I will let my 120 litre hot water tank go cold and monitor how many cubic metres it takes to heat the water to a specified temperature.
We are getting Smart Meters in Australia for electricity consumption. Not only are the consumers being charged for the meters but the overall electricity bills are rising 10%.
What a clever CON.
In addition, solar rebates have dropped from 60 cents per kwHr to 20 cents.
This is another CON. Why rebate someone 60 cents for something that costs 10 cents?

 

[blueroomelectronics]

I think that variable rate power is coming to most cities. It does take some getting used to.

 

[Mr RB]

Bill, you could power your device from the mains which would be quite easy since it uses so little power. And sync the device to the mains too, which should give you a very accurate clock as your mains freq will be very accurate. I'm imagining something like a little night lite button plugged in any power point and you can still use the supercap to keep its clock running during blackouts etc.

 

[colin55]

What's a blackout?

 

[bryan1]

What's a blackout?

goin a bit senile here Colin !!!!!!! just wait untill full summer hits and it's 46C in the shade in melb, when the power goes out I'll be on my side laughing as I'll be doing my best to use all that power I'm making........

 

[colin55]

Can't remember the last time we had a disruption in the supply. I have never used the candles we bought 10 years ago and the torches have never had the batteries replaced.
I must be in a good location.
.

 

[blueroomelectronics]

Thanks all, yes a small mains phone charger would work like charm. I think it would be an amazing little product if could make a wallplate glow (light switch / mains outlet) as a gentle reminder. Trick would be setting the clock and powering the device.

 

[ericgibbs]

Thanks all, yes a small mains phone charger would work like charm. I think it would be an amazing little product if could make a wallplate glow (light switch / mains outlet) as a gentle reminder. Trick would be setting the clock and powering the device.

hi Bill,
I guess as the 'unit' will be connected to the mains supply it will be in an isolated casing of some type.??

If yes, then a transformerless psu would be OK, say a 470nF cap, 4.7Vz etc.....
The LED could be mounted thru the facia of a wall switch which could also house the PIC etc.

 

[Mike - K8LH]

Use a crystal to maintain its own RTC. That way you can have it drive a relay that completely disconnects mains to the house during those high cost periods (grin).

 

[Mr RB]

Could it utilise a simple VB program to format the time/day/date/rates into eeprom data and make as a text file?

Then you could just run that VB program, program the PIC (including eeprom from the text) and it would be working, no need to set the clock at all.

You just need to program it and plug it in to the device and the clock keeps going from there...