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Check power consumption, costs, greenhouse gas emissions and more . . . How MUCH POWER are your appliances using? Despite international efforts to reduce the standby power requirements of appliances, this modern phenomenon continues to be a real problem. Virtually every mains-powered device is now in on the act, or soon will be. Standby power increases your energy bill and adds to the greenhouse effect. By PETER SMITH T V SETS, STEREOS, VCRs and the like have long relied on standby power. More recently, “convenience” electronics have been grafted into up-market household items such as dishwashers, coffee makers, cordless telephones and washing machines, all of which are designed to be permanently powered. Don’t think that these devices use much power when “off”? Well, you might be surprised to discover that 10-15% of all household power is consumed by devices in “standby” mode. According to a 2001 study by “Choice” magazine, appliances not performing their main task drew a constant total of 87W, on average. That works out to 760kWh in a year, for a cost of almost $100. And standby power consumption certainly hasn’t 76  Silicon Chip decreased since then. Consider the 100 million homes in the United States, for example. In total, they consume roughly 5GW of standby power. According to one source, this equates to about 8GW after distribution losses and generation reserves, or about the output of eight power plants. And that’s just for the domestic sector! With this in mind, you may wish to save some money and the environment by switching off appliances at the power point when not in use. Of course, it’s simply not practical to power off all devices. For example, microwave ovens and VCRs include a real-time clock that would need to be programmed at every power up, while cordless phones need to be on all the time. However, other devices such as PCs and their peripherals can be switched off. Measuring power usage Before you can make informed decisions about power usage, it’s necessary to know how much each device consumes, both during normal operation and in standby mode. Typically, the power rating printed on the label of a product indicates maximum input only, accounting for things like surge current at power up, motor start, etc. Real power usage is likely to be quite different. How you use an appliance will also have a major impact. For example, if you normally run your fridge in the middle of its temperature range, it will obviously consume less average power than on the cooler settings. The answer is to connect each device in turn to an electronic power meter. That way, you can determine the average power consumption, in line with actual usage. To help with this, a South Australian company, Computer Control Instrumentation, has come up with a great little handheld meter called the “Power-Mate”. It can measure instantaneous power use, accumulated energy consumption and more. Power-Mate, mate The Power-Mate is supplied in a 150 siliconchip.com.au Special Offer Table 1: Power-Mate Specifications Measurement/Calculation Range Watts 0 - 2500W Volts 170- 270V RMS Amps 0.000 - 10.000A RMS Cost & cost per hour 0 - 99.9999 ($) Cost per quarter & year 0 - 9999.99 ($) Energy 0 - 999.999 kWh Greenhouse gas 0 - 999.999 kg Run time (max). 99 hrs, 59 mins, 59 secs Basic accuracy: better than 1% for all measurements x 80 x 30mm plastic case. It features a bright red 7-segment display and includes a four-button tactile keypad. A 1-metre cable exits from the case, terminated in a combination mains plug and “piggyback” style socket. Hooking up an appliance for testing couldn’t be easier. The Power-Mate plug goes into the mains outlet first and the appliance simply plugs in on top. Maaaate! In all, seven primary measurements and calculations can be displayed. Repeatedly pressing the “Mode” button cycles through each of the possibilities, as well as the “Setup” and “Clear” functions that we’ll come back to shortly. There are also 15 additional display functions, accessed by pressing one of the other three colour-coded keys, labelled “Enter”, “+” and “-”. It’s easy to determine what information is available in a particular mode by referring to the matching colour-coded table below the keypad. Measurements include line voltage (volts), current drain (amps) and the power consumed (watts), all in real time. A simple press of the “+” or “-” buttons momentarily displays the maximum or minimum readings taken since power on. These measurements would be handy for service technicians, who often need to measure things like start-up and surge currents. The real power of this unit (pun intended) is to be found in its energy consumption and cost calculation functions. At power up, the PowerMate immediately begins to show the accumulated energy used by the appliance in kWh units; this is the default display in “Energy” mode. You can also see the projected hourly energy usage based on measurements thus far by pressing the “Enter” button. Pressing the “-” and “+” buttons extrapolates the measurements over quarterly and yearly periods, respectively. Hit the “Mode” button again and you can immediately see how much it’s costing you to run the appliance. Once again, you can have the option of displaying current, hourly, quarter or yearly costs. It surely doesn’t get The Power-Mate is designed, manufactured and approved for use in Australia. It is available from the Alternative Technology Association, on the web at www. ata.org.au or phone (03) 9419 2440. Currently, the unit is priced at $346 plus GST in one-off quantities, which includes a 12-month warranty. Computer Control Instrumentation is making 25 units available to SILICON CHIP readers at the special price of $315 plus GST. To take advantage of this special offer, e-mail Mike Russ at mike<at> c-c-i.com.au or write to PO Box 195, Goodwood, SA 5034. Note that only bank cheques, money orders or bank transfers will be accepted for this offer. any easier than this! For the environmentally conscious, the unit also calculates the equivalent amount of greenhouse gas liberated, based on the ratio of energy consumed to a constant. By default, this is calculated at 1.2kg of CO2 per kWh, which is the accepted value for fossil-fuelled electricity generators. Both the cost of electricity per kWh units and the constant used for greenhouse gas calculations can be programmed in “Setup” mode. Entered values are retained in memory at power off. Finally, a “Clear” function allows you to reset the accumulated values of time, energy, cost and greenhouse gas emissions without having to turn SC the unit off. COMING NEXT MONTH How Many Watts? For those who prefer to build their own, watch out for our Energy Meter in next month’s issue. It features a multi-function digital readout that will tell you energy usage, actual power cost and much more for the various appliances in your home. It’s easy to build and is based on a PIC microcontroller. 78  Silicon Chip PROTOTYPE SHOWN siliconchip.com.au