BT_Sentry : Sentry Power

This is the 4th of my Blogs for the Bluetooth Unleashed Design Challenge

The other posts are here :-

Concept

The idea is to detect the bluetooth transmitted from the vehicle and signal other Home Automation functions.

If the vehicle is known then it can open the garage door, and inform the home owner that xx is home.

Hardware

The detection point needs to be at the start of the driveway, and because there is no power source, this will need to be low power with solar charging.

The PSOC range seems a very good fit, but because of the timeline and my need to upskill, the inital design will be Arduino based and some form of RF transmitter/transceiver.

Adding a vehicle detection loop or beam is necessary to ensure those vehicles without bluetooth will also trigger the system.

By now I'd hoped to be blogging about Bluetooth detection, but it hasn't been progressing very fast ... in fact I haven't had it running at all.

That isn't to say I haven't been doing some research, understanding and a few examples.

Solar Power

Because the gateway (Sentry) location is unpowered, I'm going to require solar (or wind) to charge the battery.

While it might be ideal to use the BLE characteristics, the reality is that I need to advertise, and that takes energy.

Most of the BLE (Bluetooth Low Energy) devices are the receiving end, so they simply wait until they wake up and detect someone advertising, and then connect and communicate.

Obviously most 'visitors' that I'm interested in, aren't going to connect, or be connected previously, and since I don't intend providing any services, its will just be a MAC address gathering exercise.

Ideally I'd like to know just how much power I need, but the reality is I don't, so I thought I'd look at some possible options.

Solar Lights

I recently visited a friends place where he runs off solar power.

The cost of getting the power even to his gate, is prohibitive, and his permanent house is still being planned (and financed).

He was using some low cost solar lights that one of the local retailers had, and they worked very well.

When I was visiting another retailer, I spotted these, and the importance was they used a 3.2v battery, rather than the single cell many others have.

The costs was NZ$15, and if they weren't suitable, I could still use them as they were designed.

Strangely they must be designed for another use, as the mounting bracket seems to also fit the solar panel ....

You can see there is room inside for some electronics, so it could be very useful even as a solar powered PIR detector.

As the pictures show, the construction is simple, with plenty of hot glue to hold the board and lens in place, while a bit of foam supports the 3.2v 400mAH battery.

Shed Light

While I was picking up 2 more of the above, I looked at a Shed light.

The idea is you have a solar panel outside, and a LED light inside where it would otherwise be dark.

The LED is just a few LEDs in parallel with a small resistor, so not exactly efficient, but I wasn't after it for the Light .... just the panel.

The box suggested it used 3 rechargable cells, which by my calculation is 3.6 volts.

Once opened it reveals three standard rechargable cells 1.2v 200mAH.

So not as high as the other lights, but I'll need to do some tests to see what the panel can deliver before seeing if it is useful.

The last photo shows the build quality you can expect with these cheap devices.

The battery clip on both sides has been installed upside down, while the soldering has been while the battery is installed.

I do like the pull switch. It's a rather clever way to achieve it.

Unlike the other lights, this is definately not an outdoor unit.

BUT having seen the poor design of other 'outdoor' units, I tend to treat them all with some scepticism nowdays

Parts

My shopping basket is on it's way thanks to the generousity of element14/Newark and the work by danzima and UPS.

I'm not sure if that arrives before I go, but it isn't a requirement just yet.

After a discussion between Jan Cumps and myself regarding the current consumption

https://www.element14.com/community/community/design-challenges/bluetoothunleashed/blog/2018/04/30/btsentry-introduction…

I purchased a Cypress Low Energy BLE kitCypress Low Energy BLE kit  and I've ordered a solar powered version Cypress Solar BLE

Sadly there are none available on the NZ website and e14phil kindly checked his cupboard, but alas there were none lurking, so it is coming directly from Cypress

It could be that after all this, I just use the CY8C4248LQI-BL583 module on its own as the size is right and it seems that the MCU is onboard.

Whatever the outcome, fvan is safe from blame for buying these ....

Next Blog

I'm away on holiday next week, so I'm going to see if I can prepare the next blog, and try the scheduled posting.

Unless you'd all prefer photos of cars and a warm beach with people swimming ...

Mark