Thursday, October 23, 2014

MyLight: Automated Night Lighting

The MyLight: Automated Night Lighting came across my social media transom this afternoon. 
The Mylight collection is a series of innovative LED-light products designed to enhance one´s lifestyle — delivering comfort and safety in your home. The Mylight is motion activated and turns on and off when you need it so no more fumbling for switches at night. It provides a soft indirect light for night time use.
While the individual pieces seem fairly simple and straightforward, it's a nice packaged concept - a couple of strings of warm LED lamps, a motion / light detector, a plug / power supply, and hardware to mount it under a bed or cabinet. Priced reasonably ($32 for a single sensor, $45 for a dual sensor unit, on sale). I'd be happy to put one under my bed - but the video makes me think that a nursery, bathroom or child's room would be even more useful.

Thursday, October 16, 2014

Checking Outlets

An electrical outlet tester is an invaluable tool for any homeowner, do-it-yourself-er, or professional working in the electrical or energy field. There are many different types of devices that all qualify as "outlet testers" - and here we'll review the capabilities (and limitations) of the various devices.

The basic outlet tester (~$5 from home improvement and big box stores) provides a quick check of outlet wiring, and the presence of voltage on an outlet.

It can spot an open ground, open neutral, reversal of hot / neutral, or hot / ground. And it gives a quick "OK" check. Perfect for a quick check of all outlets in a space, checking on a repair, or confirming power at outlets, plug strips, etc.

For a few dollars more (~$10-15) one can get this device with a GFCI test button - pressing the button places a small (~ 20 mA) load between hot and ground. A properly wired and functioning GFCI outlet or circuit breaker should trip. Again, a good "quick check" for GFCI outlets in kitchens, lavatories, exteriors, garages, and other wet locations. It's especially handy if (for instance) a string of outlets is supposedly wired from a single GFCI outlet - one can check each outlet to confirm it's actually fed from the GFCI outlet and wired correctly.

Now, both of these devices are fairly limited in capabilities. They do not place a significant load on the source, so cannot identify loose or corroded connections, nor determine voltage drop for distant outlets. They cannot discriminate between the grounded (neutral / white wire) conductor and the ground (green wire / safety) conductor. Mixing or intermingling neutral and ground connections can cause electrical noise, safety concerns, and magnetic fields.

More advanced outlet testers are available to provide more thorough inspection and analysis of electrical outlets.

The first feature is the addition of an electrical load to provide some indication of voltage drop. Typically measured in percent based on rated load - the National Electrical Code suggests that "5% voltage drop under rated load" is "adequate for good service". Voltage drops exceeding 10% are possible - depending upon conductor size, run length, and condition of connections / junctions. If one is (for instance) using such an outlet for a home office in the far end of the building, with a laser jet printer, space heater, or mini-fridge, light flicker, low voltage, transients, and other problems may ensue.

A quick survey of outlet testers that measure voltage drop include:
  • Suretest (Ideal Industries) - Various models, $300 - $400
  • Extech Instruments - CT70 / CT80 AC Circuit Analyzer, $150 - $250
  • Amprobe - INSP-3 Wiring Inspector Circuit Tester, $300 - $400
  • General Specialty Tools & Instruments - CA10-AC Circuit Analyzer, $100 (great value, especially as it's advertised to measure neutral and ground conductor impedance!)
These devices incorporate a variety of options and features (digital metering, testing of neutral and ground impedance, PC interface, etc.) 

As a power quality consultant, I carry a small outlet tester with me to any site that might involve 120 VAC AC power issues. Such a device permits a rapid survey of all receptacles in an area or space, often spotlighting the problem area quickly - my report includes a table of all outlets tested, eliminating the need to open up each and every outlet, and allowing me to focus on specific problems.

In addition, grounding issues (especially intermingling of neutral and ground wires) can cause ground loops, ground noise, and magnetic fields. So if I'm looking for noise issues on a higher voltage or dedicated electrical system, checking out all of the nearby AC outlets is a good way to be sure there's no sneak path for ground currents or noise.

Tuesday, October 7, 2014

Nobel Prize in Physics - Blue LEDs

The Nobel Prize in physics goes to three men who gave us blue light-emitting diodes, used daily in your smartphone screen - Washington Post / Oct 7, 2014

A little "Residential Power and Energy" shout-out to these gentlemen - Isamu Akasaki, Hiroshi Amano and Shuji Nakamura. When I was cutting my engineering teeth, there were red LEDs, amber LEDs, and green LEDs. But without blue LED's, it's impossible to make white light (red + green + blue) and as a result, low energy LEDs were not useful for things like video images or illumination. They were used quite early for traffic lights (red, amber, green - works out!)

Now, "white light" LEDs, based on this discovery, permeate our world. My smartphone, low power flashlights and lanterns, low power residential lighting. I'm pretty sure there is not a single room in my home that does not use these in some way.
Red, blue, and green light combine to make the bright white produced by LED lightbulbs. Bulbs using blue light-emitting diodes are more efficient and have a longer lifetime than old fashioned bulbs (up to 100,000 hours, compared to 1,000 for incandescent bulbs and 10,000 hours for fluorescent lights).
Wonderful to have something so practical, and uniquitous, recognized by the Nobel Committee.

Wednesday, October 1, 2014

Efergy E2 Classic Energy Monitor

I recently picked up a small energy monitor for my home / condo, made by Efergy Technologies Limited. I'm always looking at new / low cost ways to monitor, measure, quantify electricity and power. The price point here was minimal ($100). The functions and feature set (monitoring demand, wireless display that can be moved throughout the home, USB interface to access data and produce reports, software to facilitate all that) all looked great.

Here's a quick review.
Technical Capabilities

Strictly speaking, the device is a CURRENT monitor. There are two clamp on current probes, but no voltage connection point - it calculates demand based on a fixed voltage, and presumably a unity power factor. I have not determined it it measures average current or true RMS at this point. It samples data on a 10 / 15 / 20 second rate. It's not super accurate, as a result, but it's "close enough" and certainly can provide a good comparative measure of energy usage over time.

It also has a third current probe "port" so can presumably monitor three phase power as well. It appears to be designed for a world market: 50/60 Hz, multiple nominal voltage settings, and multiple rate / tariff units.


The monitor was easy to install. Two clamp-on current probes (A) were connected to the mains coming in. I have a 100A panel, the probes appear to be sized for 200A maximum. The probes are not spring loaded, but use a nice little plastic latch / clip for secure connection, and since there is no voltage monitored, the vector / direction of the probe does not matter. I'm comfortable sticking my fingers in a live panel, but to be safe, kill the power before installation.

These are connected via a fixed cable to a transmitter (B) which is powered via 3 x AA batteries, or an optional DC supply. The company claims battery life of 8-10 months is typical for both transmitter and monitor.

The wireless display / monitoring unit (C) can be located anywhere convenient; I placed it atop the panel for the photo. It's powered via 3 x AAA batteries. The transmitter / monitor are linked via a simple push-button procedure. I had no problems getting them to talk. The expected range is 100 - 200 ft. although I found signal was sketchy up on the second floor. 

The past week I've had the wireless display sitting on my desk as I've worked, and have enjoyed (yeah, I'm an engineer, what do you want) watching the kW measurement track up and down as I work throughout the day. 

Monitor / Display Unit

The display for this device has some rudimentary information. There are three values available:
  • Energy Now (KW) 
  • Cost (per day) based on present energy ($)
  • CO2 (per day) based on present energy (KgCO2) 
In addition, the device displays all of these parameters as an Average (over the life of monitoring, with energy in KWHr) and History (scroll through a daily, weekly, or monthly tally of demand, cost, and CO2)

The device allows you to set up variable rate (single or multiple) in cost / kWHr, and a CO2 usage factor.

The display is pretty rudimentary; and if I were relying on that I'd probably check out the Efergy Elite True Power Meter (more sophisticated measurement, more advanced display, temp & humidity) but that  device does not have "in the box" communications capability to a PC, and I am all about the data.


The free to download software, elink, is pretty spiffy.  The basic HISTORY function displays demand on an hourly basis (per day), a daily basic (per month), or a monthly basis (per year)

Under the MANAGE function, the user can look at individual days, do a weekly comparison (for instance compare individual weekdays or weekday vs. weekend), as well as a month by month comparison.

Finally, there are some advanced options of tracking actual usage vs. planned usage, setting up complex utility tariff schedules (for those working with peak / off-peak billing) and adding multiple utilities (so one could presumably compare different rate schedules with actual historical demand data)


Last but not least, the software gives the option of generating a Daily or Monthly report - selecting a specific time period, and creating a PDF report. The "Add Stickie"feature is not all that intuitive or well documented, but from the main HISTORY page you can create comments on notable usage or patterns which would be great if one were creating a report for users, management, clients, etc.

The exported spreadsheet is pretty rudimentary: Date / Time / KWHr / Daily Max / Cost / Stickie Note(s). Including the Stickies is a nice touch. But really, the PDF report is pretty much all I might need.  

Using the Efergy Demand Meter

I can think of a lot of ways to use this device.

Professionally, it would make a great tool to do short and simple residential / small business demand audits. Hook it up, perhaps do some walking around turning things on and off and recording the demand, then leave it connected for a week and generate a report, with recommendations for savings.

As an end-user, I'd probably first characterize the household energy consumers. I'll be able to (over time) generate the cost (in electricity) for things like a load of laundry, a shower, a hot bath, and factor those in a bit. Might even consider replacing older / less efficient appliances. And although I've gone through the condo pretty well in terms of replacing incandescent bulbs and other energy hogs, perhaps I'll find something I've missed - most consumers who have been less fanatic than I will probably find a lot of room for improvement.

I can also watch the electrical demand on a real time basis, and if I've left something on (stove burner, iron, etc.) I should be able to spot that quickly.

Bottom line, really nice piece of technology - really well designed (hardware and software) and useful.