First of all, this sounds like a really cool product, and it could not have come at a better time for me. I have been researching some options for remote sensors, and this is going to be a huge help.
I have a question about the power saving features of the Wixel and the CC2511. One of the features I was looking for was some kind of “Wake on Radio”, but I don’t see that anywhere in the datasheet so I’m assuming the chip doesn’t support it. I also don’t see it advertised for the Wixel - am I correct in assuming that there is no way to make it sleep and wake it up over the radio?
I would like to use one of these units (I bought two) as a wireless sensor in my garage. Ideally, it would run off of batteries which I would like to last for months. It will be idle 99.9% of the time.
I have considered putting it to sleep for a minute, waking up for a few seconds just to check for a signal. This would be an ok solution, but if there’s something more power efficient, I would love to hear it. I would like for it to respond on cue, but if I have to wait for a certain window, that will suffice.
There is no power-saving wake-on-radio feature on the CC2511: you will be using around 20mA if the radio is active, whether it is receiving or transmitting.
Is your garage sensor communicating with a base that can be plugged in to the wall? If so, you probably have a fine solution. An alternative would be to wake up once a minute and send a signal to the base; your base could be constantly listening and send an appropriate response when it receives the signal. This might take a little more power, but it would involve less broadcasting, so there would be less chance of interfering with other projects.
Ideally, it would not be plugged into an outlet, as there isn’t one conveniently located.
Basically, I want to be able to detect if my garage door is open or closed. I have a Maxbotix Sonar Range Finder that will interface with one Wixel, and be mounted to the back of the garage, facing the garage door. I want to be able to send an email/text message to a linux box, which will be tethered to the other Wixel, and have it read the current state of the garage door from the remote device.
Real-time responses would be ideal, but if I need to, I can do the sleep/wake cycles and just leave the linux box transmitting until it hears back from the garage. 99.999% of the time, the linux box will not be transmitting, and the range finder will not be in use and so the device in the garage should be able to last a while one a single charge, or set of batteries. I have no idea what to expect in terms of battery life with the sleep/wake cycle approach. Just as an FYI, I’m not attempting to monitor the state of the garage door, I’m attempting to query the state on demand.
The next step would be to open/close the garage door, in which case the device would be physically attached to the switch which is lighted, but I don’t think I would want to attempt to use it as a power source.
Is it not going to be hard to detect the garage door all the way from the back of the garage? That seems like it would require a pretty long-range sensor. Have you considered putting it on the ceiling, looking down at the door? It could plug into the same outlet as the opener.
In any case, what I was suggesting is that your garage Wixel could wake up once a minute and send out a short packet. If the Linux box Wixel is on, and if it wants to know the state of the garage door, it would immediately respond with a message that means “please take a reading”. Then the garage Wixel would read its sensors and send the appropriate response.
I have not tried anything with sleep modes on the Wixel yet, but you could probably be awake for less than 0.1s out of every minute, which would bring your average current down to around the 100uA minimum that you can get without modifying the hardware. See the User’s guide section on power for more information about power usage.
I have the maxbotix rangefinder that is calibrated to ~21’, which I think will be enough to reach from the back of the garage to the garage door, but I haven’t even taken it out of the bag yet, so I don’t have any actual experience with it.
Mounting the apparatus on or near the opener is a good idea, and might also enable me to use a cheaper sensor. I was also hoping to use the same Wixel as a parking guidance system too, which is part of the reason I was thinking mounting it to the back wall.
Thanks - so far, so good. I got my package today and got the wireless_serial app installed on both Wixels with no problems. Right now, I have one attached to my linux box, and started ‘getty’ up on the virtual serial port. I can now PuTTY from Wixel1 on Windows, to Wixel2 on Linux. Can’t believe how easy that was.
I measured my garage with a sonic tape measure, and it’s 24 feet long, so it looks like I’ll will be going with Plan B, of mounting everything on or near the opener. I also found an old 5v cell phone charger with a Mini USB B so everything else is just falling into place.
This is a pretty cool product - I have a feeling I’ll be buying more soon.
