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Belkin Wemo devices

In May 2016 I signed up with Ohmconnect.com so I could help prevent the dirtiest electric powerplants from coming on line by reducing my use at critical times. Ohmconnect knows when those times are.

So what could I let Ohmconnect get to while feeling reasonably safe about having devices connected to the web (Internet of Things)? Wemo comments follow after some motivation.

Seti computations.

I do scientific computing for seti@home and einstein@home and it amounts to about one-half a kilowatt-hour per hour. And can be turned on/off during critical power situations with no significant onsequences. This is an opportunity.

There are lots of devices to choose from. The ohmconnect connect page 'Smart Device' button has a list. After looking at devices from all these folks I decided to go with one that uses wifi, not zigbee or the power wiring. With Wemo there is no local 'central station' to buy. Nor wiring to do. I don't want a thermostat device as our radiant heating rarely runs at all, and never in spring,summer, or fall.. And in summer we use air conditioning as little as possible (just a few days a year).. So there is no good reason to interface to a thermostat. I did not agonize of the choice. I'm not saying one is much better than the others. But Belkin WeMo seemed to tick all the boxes for me.

Wemo devices.

When you open a Wemo device the instructions have just 4 points. It's easy, but... I found it unintelligible.

1. Plug in...is clear enough. But before you plug it in find the serial number on the device and write it down.

2. Clear enough. You can perfectly well do the download/install as step 1. Or maybe you already downloaded and installed. Fine.

3. Now this is clever. The instructions meant nothing at first glance. The instructions say to connect to the WeMo network. They mean it. The Wemo device creates a wifi network called.... wait for it... Wemo Switch.xxx (something like that). Select it (using Wifi settings on the phone/tablet) as the wifi network to use.

4. Now launch the WeMo app. Your first task is to rename the device to something meaningful to you (the default name involves part of the serial number you noted down earlier). Since the network you are using has just that device there is no ambiguity.

So basic setup is done. The WeMo wifi channel is gone, vanished, kaput. You will now be on your local WiFi. (You can always press the reset button on the WeMo device with a paperclip and redo step 3.) You can use your phone/tablet to set static rules for the switch such as on/off times if there are any you wish to set.

Using Wemo for controlling Seti etc cpu/gpu use.

The elevator speech:. The system uses WeMo to turn a relay on/off which a Raspberry Pi watches for and the Raspberry Pi sends messages to the Seti etc computers telling them to start/stop Seti etc calculations. The goal is to let OhmConnect turn the Seti etc calculations off when there is a need to do so (per Ohmconnect.com), which seems to happen at least once a week. (I won't describe the messages between computers. That is beyond the scope of this web page.)

OhmConnect uses ifttt.com to actually control the device. OhmConnect wrote methods (on ifttt.com) for ohmconnect.com to use. Going to ifttt.com I discovered that the WeMo Maker device is not supported by an OhmConnect method. Yet. But WeMo Switch is supported.

Going to ohmconnect.com's Connect page and trying to connect ohmconnect I discovered that the documentation about this with WeMo does not exist (there is a dead link). On 23 June 2016 I contacted Ohmconnect's Chat support and they filed a bug report on the omission.

GOOD NEWS: If you set up an ifttt.com rule you can connect things up even without any help from documentation.

Step one. Set up an account on ifttt.com (it is free). Search for OhmConnect rules and select OhmConnect for the 'if' Wemo Switch. And for the then clause select Wemo Switch. It will ask for wemo data like login, password, name of switch (which you set on your switch when you set the switch up). This creates an ifttt recipe and assigns a number to the recipe. Write down the recipe number (recipe id).

Step two. On the connect page select an unused device blob and clicked configure. A menu gave a choice of devices (chose Wemo Switch). Ignore the login/password fields. Click the configure button. Now there will be three fields you can and must fill in. A) Email you use as ifttt.com username. B) ifttt.com password C) ifttt.com recipe id

Step three. Click configure. It will check your ifttt.com account and if all matches ok you are set up! I have no guarantee ohmconnect can do the shutoff during ohmhour, but I hope it can! I keep records using the Rasberry Pi so I'll know if it works.

Raspberry Pi.

I use a Raspberry Pi B+ (it was on hand gathering dust). I'm not covering this in detail. Install raspian and find instructions on the web for coding in python to control (turn on/off and sense) the pins. It's amazingly easy.

Wemo Switch Wiring.

I just wanted the WeMo to open or close a circuit so I bought a WeMo Maker. Does that job exactly. but as I learned it's useless for ohmconnect at the present time so it is on the shelf.

With a Wemo Switch I use an 110VAC to 5VDC transformer wall-wart from some defunct electronic thing and added a 5VDC relay to switch on/off. I connected to WeMo pins with about 230Ohm resistor. It Works! Picture of Raspberry Pi B+ The picture also shows the green LED (a 330 Ohm resistor is hidden in the blue wire covering) which is just there so I can glance at this and know that Raspberry Pi thinks Seti etc is running.

Notice that as of July 1 there are two blue relays in the picture. One is connected to the WeMo Switch. OhmConnect is able to turn this relay off (and on) to save electricity when appropriate (or resume normal when saving is not critical). The other lets the Raspberry Pi know when PG & E power fails. The power to that relay is not on UPS (Uninteruptible Power Supply) devices (unlike everything else in these computer systems) so a power fail is seen within seconds. In case of power failure Raspberry Pi turns off the calculations just like a WeMo can. Turning off Seti calculations on power fail ensures the UPS batteries will last at least 40 minutes instead of lasting under 10 minutes..


Letting Ohmconnect turn off charging to the Tesla at critical times is easy enough. But will not save much because the home Tesla charging is done in the middle of the night. Normally there are no issues with power in the earliest hours of the day.


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