LowPowerLab Forum
Hardware support => Projects => Topic started by: wile1411 on April 08, 2015, 09:16:31 PM
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Is there any plan to add any capacity to read the voltage / current of the load being used by the SwitchMotePSU?
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No plans for now, and here's why.
Measuring power is a hard thing to do right, but it's very easy to just get a "ball park". If you want to get an accurate sense of what a circuit is consuming, you should measure it as close to the source as possible (ie in your panel). Otherwise you are only measuring the device draw (which in most cases is sufficient) but the power loss in the circuit wiring are not accounted for. The AC voltage drop is significant in residential circuits.
The SwitchMote PSU is basically the PSU side of the SwitchMote and it's there to provide power and switching capability. Measuring power would mean this would no longer be a through hole product and would very significantly increase complexity/size and cost. Plus you have devices like KillAWatt that are really cheap and can be hacked to transmit power readings via Moteino (http://lowpowerlab.com/blog/2012/12/28/wattmote-moteino-based-wireless-killawatt/).
I hope this explanation puts into perspective why bundling that functionality in SwitchMote is not really ideal.
To me measuring circuits in the panel is a much more interesting problem.
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<...snip>
To me measuring circuits in the panel is a much more interesting problem.
How timely! I just deployed two of the power monitor mote I referenced in this post: https://lowpowerlab.com/forum/index.php/topic,998.msg6450.html#msg6450
It's a 4 channel 'honest'(1) RMS power monitor that uses inexpensive clamp-on current probes with wireless reporting, of course. I have guests visiting for a couple of days and can't post right now, but I'll try to post the circuit and software by this weekend. I'll provide a link in this thread when its posted.
Tom
Note 1: 'Honest' RMS is 'close' to 'True' RMS.
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Thanks Tom for the reminder and link, I totally forgot about Tom's project.
I would make something similar to him if I needed to, something modular, I look forward to his completed project.
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The SwitchMote PSU is basically the PSU side of the SwitchMote and it's there to provide power and switching capability. Measuring power would mean this would no longer be a through hole product and would very significantly increase complexity/size and cost. Plus you have devices like KillAWatt that are really cheap and can be hacked to transmit power readings via Moteino (http://lowpowerlab.com/blog/2012/12/28/wattmote-moteino-based-wireless-killawatt/).
Completely understand the reasoning of keeping the PSU simple - just putting the question out there as the Kill-a-Watt option isn't an option for Non-US people that want to use moteino as the means for reporting of power usage.
It only occured to ask as while in the nitty gritty of wiring up remote controlable switches using a switchmotePSUs, I figure that would be a good two-birds-1-stone possibility there to also grab the current measurement of the load being switched on. The alternative currently being planned is to throw a ACS712 module in as well and have that monitored via the moteino used by the switchmote.
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I figure it could be easy to add an ACS sensor as you mention, but for now there is no integration on SwitchMotes, they are all through hole components and modular.
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<...snip>The alternative currently being planned is to throw a ACS712 module in as well and have that monitored via the moteino used by the switchmote.
I've used the ACS712 with Moteino and it's pretty straightforward other as long as you level shift from the 5V required by the ACS712 module. I use this, both as a soldered down chip and an add-on breakout board where I need a second channel, in my DC Remote project: https://lowpowerlab.com/forum/index.php/topic,934.msg5903.html#msg5903
Tom