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Wireless Sensor Tags

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The first I had read about Wireless Sensor Tags by CAO Gadgets was last year. I finally ended up ordering them in December. And as I begin to write this review, I came across an excellent review by Alasdair Allan – here it is: Teardown of Wireless Sensor Tags. I am going to defer to Alasdair for the fantastic overview and build on it. I would like to summarize from his post the hardware on the tag:

Processor: Microchip PIC16LF720 micro-controller

Wireless: Microchip MRF 49XA

Motion Sensing: Honeywell HMC5883L

The tags are using the 433MHz frequency – which does not need a license in the US.

Alasdair makes a remark on the choice of the sensor being based on a magnetometer – which would give good angular measurements. I have not tested the precision of the angular motion but it uses angular motion for setting the tag for door open/close sensing. The picture below from the Web App shows you can select different angles as threshold for triggering the alert.

Threshold Angle Selection

My experience with the software has been decent. It is at time somewhat confusing. With trial and error you will get it but given that the subject matter is complex and in my opinion the audience for this system is more of the geeky, hacker and DIY nature – we can live with it. For example – it is not clear the first time that you need to click on the “Motion Sensor” menu entry after you have clicked on the “Options” button under the tag you want to configure. There are small little things like this that make it challenging.

I have tried both Android and the IOS Apps – I would have to say that I am a bit disappointed because it is a short-cut. The Web App is implemented using HTML/jQuery and the UI of the mobile apps suggests that they are built using HTML/jQuery vs. a native application. One more thing that I still need to figure out – how do you “remove” the phones. Once you have installed apps on your phones and signed into your account – they will show up in the configuration. For each sensor – you can setup the trigger to notify the phone you have installed the app. Interestingly I had given my Nexus 7 to my son so I want to try and remove it (you can see it in the image), and the “Unknown” is a result of the app being setup and I missing an opportunity to name the phone. None the less I don’t see any mechanism of removing both these entries and starting over.

Notify Phones

The door open and close of the sensor tags seems to work well. I have tried both the Phone Notification, emails – and they work. Range has been pretty decent – at my home. I have the Tag Manager in my basement and two of the sensors on the floor above – one of them to detect garage door open or close. The third sensor – I wanted to use to monitor my refrigerator – its opening/closing and also the internal temperature. And the tag goes out of range when I put inside the refrigerator.

As a next step I need to do a couple of things: test the angular sensitivity / precision and try to understand the range impact of having the sensor inside the refrigerator. The picture below shows how the Wireless Tag Manager compares in size to the Twine (SuperMechanical), the Node (VariableTechnologies) and the Fitbit.

IMG_0384 - Copy


Written by Ashu Joshi

January 19, 2013 at 5:23 pm

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