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Engineers: DIY Duty Cycle Monitor for appliances?
Old 08-03-2015, 10:14 AM   #1
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Engineers: DIY Duty Cycle Monitor for appliances?

I'd like to find a simple, cheap way to monitor the running on/off time of some of my appliances.

One example - I really can't tell when my well pump is running. It is at the bottom of the well, completely silent in the house. Years ago, we had an underground leak, and it was running a lot. I didn't notice until the pump could not keep up with the leak and the pressure dropped.

I finally took some action on this - I connected a cheap, analog 1.5V quartz clock to the 220V well pump circuit. I used a wall-wart power supply rated for 110/220V, and a resistor divider to take its 5V DC output to ~ 1.2V, so the clock runs when the pump is powered. I set it to 'midnight/noon' each Sunday evening, and I'm finding it runs ~ 9-12 hours per week.

So that's 'solved'. But I'd also like one on our freezer and fridges. I recently did a long overdue manual defrost of our freezer. I monitored it with my Kill-a-Watt meter, and it was running ~ 90% duty cycle before defrost, and still about 80% after (freezer is in a hot garage at this point - duty cycle is far less in winter).

But that requires keeping the meter connected, and doing a calculation on the hours, kilowatts, and an estimate for the average 'on' watt draw. What I'd really like is something that tells me the duty cycle at a glance.

I haven't been able to figure out anything simple and cheap. The standard RC averaging network would be non-trivial with hour long cycles, and probably take weeks to settle. Everything seems to involve some fairly complex circuitry, and I just don't want to bother. I want simple.

A clock like on my well pump is probably the easiest, but would require more manual input with the high duty cycles. But I guess anytime I'm curious, just reset it at some point in the morning, and check 12 hours later.

Hmmmm, writing this spurred another idea. We have a few old ipods and smartphones laying around - if I were clever, I could actually write a little program for this. Tap the 120V circuit with a wall-wart ( isolated step-down transformer with AC output), feed that through a resistor divider into the mic input of the phone, and have the program sample every ten seconds or so to look for a voltage at the mic. With a program, you could do all sorts of running reports. Max and Min ON time, Max and Min OFF time, last ON/OFF times, duty cycle % for the past 8 hours, past 24 hours, past week, month, year...

I'd have to learn how to code for android or IOS though. But this might be a good motivator? I could put output jacks on various things I want to monitor, and move the phone around if I didn't want to commit an old phone to each appliance and monitor all of them 24/7.

Yeah, I know.... WDYDAD?

-ERD50
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Old 08-03-2015, 10:31 AM   #2
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I haven't tried it, but you moist look at this

Hijack - Wiki

Quote:
HiJack is a hardware/software platform for creating cubic-inch sensor peripherals for the mobile phone. HiJack devices harvest power and use bandwidth from the mobile phone's headset interface. The HiJack platform enables a new class of small and cheap phone-centric sensor peripherals that support plug-and-play operation. HiJack has been tested with the iPhone 3G/3GS/4G, iPod Touch, and iPad devices.
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Old 08-03-2015, 10:57 AM   #3
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Thanks, I did a little more googling after looking at that site, and I found this, which might be just the ticket for an old-school, lazy quasi-programmer like me:

Learn RFO Basic - The Easiest Way To Create Android Apps

https://play.google.com/store/apps/d...fo.basic&hl=en


That looks powerful and simple, and something I might actually be capable of.

-ERD50
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Old 08-03-2015, 02:26 PM   #4
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I vaguely recall seeing something that looked at the power draw from the entire house. I don't remember whether that device came with software to mark the on/off signature of each appliance or whether I was thinking that it could be modified to do that. Doubt you could catch the smaller draws with such a device but bigger things with motors should certainly be possible.
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Old 08-03-2015, 03:34 PM   #5
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How about just an hour meter wired in parallel with the compressor motor?

http://www.amazon.com/AC100-250V-Ele...rds=hour+meter
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Old 08-03-2015, 03:37 PM   #6
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Would something like this work? https://www.ubnt.com/mfi/mpower/

The Amazon reviews are mixed, but it looks like a family of controllable power outlets. Parameters such as power, energy, on/off state, etc. are monitored. Looks like desktop and phone/tablet software is available. All of the units have wi-fi. Some have wired ethernet.

A single outlet unit starts at $39 on Amazon.
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Old 08-03-2015, 07:24 PM   #7
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Quote:
Originally Posted by Walt34 View Post
How about just an hour meter wired in parallel with the compressor motor?

Amazon.com: AC100-250V Electromechanical Hour Meter Counter: Automotive
Wow, that's cheap at $8.99!

My RV has a counter like this to log the time that the generator is run. It is however digital, and some segments of its display have gone dead and I am looking to replace it.
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Old 08-03-2015, 08:13 PM   #8
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Some interesting ideas, thanks for the input.

Yes, the hour meter is pretty cheap. I found a few others, none seem to be reset-able to zero (meant to be tamper-proof I assume), which isn't a big deal, but a little inconvenient when moving from appliance to appliance (just write the # down). But for the most part, my basic standard cheap clock works almost as well (just not so well for over 12 hours of run time).

Here's a hardwired, cheaper version of the Kill-a-Watt ($9.44):

20A Power Monitor Module AC Meter Panel Sale-Banggood.com

You'd still need to track total hours though, I don't think it displays that, only cumulative kWh.

The mpower thing looks interesting, but those reviews scare me. If you can't get the SW to work, it's a brick.


I did download the RFO-BASIC SW to my tablet and played a bit. Pretty nice for running up some code. You don't need to get in and learn all this 'development environment' overhead, just some simple BASIC coding. I had some simple loops and stuff running in no time, and just a couple commands to record audio to a file. EZ.

Unfortunately, it does not provide direct access to the microphone. It might be possible to record something like 2 seconds of audio every minute , and then read the file to see if it recorded a level to indicate it was on. That might be a fun learning experience.

I also came across REBOL,

Cross Platform App Development with Rebol 3 Saphir

This is supposed to be totally cross-platform, Win, IOS, Linux, Android - but I had trouble getting it installed on my 64-bit version of Linux, but I just got it loaded on my old 32-bit machine. It looks pretty darn cool, but I only had a few minutes to play before dinner. So far, I don't see anything about accessing the mic.

Maybe I can read the USB power status? For something like the fridge freezer, I could connect a USB 110V charger to the compressor, it would power the device and recharge the battery to power the device in the off cycles. That wouldn't work for things with long off times though.

This is 90% puzzle, and 10% practicality for me. So far, it's been worth it just to find some simple program languages for my tablet/phones.

-ERD50
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Old 08-03-2015, 10:51 PM   #9
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This might meet your needs!

Cost = $160

Dent TOUCT-4G Time-of-Use & Run-Time Datalogger with Current Transformer

Dent TOUCT-4G Time-of-Use & Run-Time Datalogger with Current Transformer Model: TOUCT-4G
A compact datalogger that provides a simple way to measure the run time and time-of-use for any device that draws electric current. Simply clamp the attached current transformer around the insulated live conductor and toggle the sensitivity.

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Old 08-03-2015, 11:18 PM   #10
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There's now a Kill-A-Watt wireless version. A display head can be used with up to 8 sensors, each placed at an appliance to be monitored.

It so happens that Amazon is having a sale for $29 for a display head and one sensor. Regular price: $80. Hurry up. Buy, buy, buy...

P3 P3 P4250 Kill A Watt CO2 Wireless - - Amazon.com

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Old 08-04-2015, 05:53 PM   #11
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Quote:
Originally Posted by johnsope View Post
This might meet your needs!

Cost = $160 ...
Sure, if one of those Chinese suppliers gets the price down to $19.99!

Quote:
Originally Posted by NW-Bound View Post
There's now a Kill-A-Watt wireless version. A display head can be used with up to 8 sensors, each placed at an appliance to be monitored.

It so happens that Amazon is having a sale for $29 for a display head and one sensor. Regular price: $80. Hurry up. Buy, buy, buy...
I was confused because they talked about it being a CO2 monitor? Hmmm, CO (carbon Monoxide?), no CO2. Heck, it might alarm when I'm fermenting beer in the basement!

But no, it seems that instead measuring 'power', they want to tie it to the amount of CO2 the energy must be producing to power that device

Also, the base and one sensor is cheaper than a sensor alone. And the reviews are terrible. Might be a cool concept, but I want something reliable.

-ERD50
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