PCB is here

New PCB version 1.6. is here, and I have started to put all components on it. All I had at home already is there and it is good so far. New switching power supply is delivering right around 4V required for SIM900. GSM module is starting up and when I put SIM in the socket it registers automatically to home network. W5500 also lights up the ACT and LINK leds when Ethernet cable is plugged it. I have to wait mainly for the UART multiplexer/demultiplexer to really start the tests. Waiting for you Mr. Postman :).

PCB for new GW board.

Little later that I wanted here is 3D picture of new GW PCB version 1.6. I have already send it for fabrication. Wish me luck. :)

There is still 1284P, new WIZ5500, SIM900, new dual power supply, new analogue protection circuit and RFM69HW. It comes in 10*13cm size and will have nice big connectors.

Battery node

New node boards have arrived. I've ordered first time from seeed, and they look quite good. Nice sharp traces, I use usually bigger ones, as I tend to hand solder sometimes. Nicely aligned solder mask, and silkscreen without smudges. I will use them in future for sure.
This board was also for me first board to be made in KiCad, instead of Eagle, as I needed bigger PCB area for new gateway(main board). I can just say all as expected, if you check your Gerbers, there should not be any surprise. I feel a bit more confident to spend $50 for the big boards.

So, speaking of hardware, I soldered the battery option node. There is place on PCB for either battery or DC or even both if you want dual power (3.3V and 5V). And it works! Happy man :). To put it in numbers:

Battery voltage is more then 3.4V:
ATMega328P, and HW69W both sleeping:  0.09mA
ATMega328P working , and HW69W sleeping:  7.2mA
ATMega328P working , and HW69W receiving: 8.5mA 
ATMega328P working , and HW69W sending: 61mA

Battery voltage is less then 3.4V:
ATMega328P, and HW69W both sleeping:  0.12mA
ATMega328P working , and HW69W sleeping:  14mA
ATMega328P working , and HW69W receiving: 17mA 
ATMega328P working , and HW69W sending: 123mA

I tend to use it with li-po batteries, in theory they have self discharge ranges about 5% in month, then 1–2% per month (plus 3% for safety circuit). By raff numbers, and using the scenario of a remote sensor sleeping for 5-10 minutes, reading the sensor and doing the math for 500ms. Finally transmitting for at full power for 10ms, it gives me battery life for about 2 years with 2000mAh battery.

Now the question here is where it is a practical and economical solution to buy a li-po and let it basically drain by self discharge. Eneloops NiMH have seems to be more suitable, but li-po's are getting cheaper on eBay or such. Another solution is to go for a small li-po, around 200mAh and tiny solar panel. This or another, I'm happy with its wide input voltage and consumption. With this setup I can go from AA, to li-po or NiMH.

Going back to design, it uses MCP1252, which is inductorless, buck/boost, DC/DC converter with low quiescent power: 80 μA (Typical), and giving 120 mA (150mA max, high power RFM69HW can be used) output current. Add couple of ceramic capacitors, and you are set. On picture capacitors a a bit bigger then pads, since I have put what I found in drawer, and not the proper 1206.

New main unit.

As new node PCB is in transit, I have some time to move forward in design of new PCB for main board. It will be bigger with all necessary components on it. As I have moved from Eagle to KiCad, I will wait for the new node PCB to see what mistakes it will bring. Lately I was in search of new fabrication house, but boards bigger then 10x10cm are rather expensive.  My new board will be most probably 10x13cm and it is about 50USD without shipping for 5 pcs at least. It becoming a bit expensive fun, hope to not make serious mistake.

But new board is getting into final shape. It has WizNet W5500 Ethernet chip, SIM900 for GSM, and also some other improvements like better analogue protection, and RFM69HW. It will be drop in replacement for any old wired burglar alarm. It will also have new nice big and 45° angled screw terminals.

I have also in mind extension board the will plug on top of the analogue part that is on right side and allow 8 ports to be added. They will be stackable up to maximum of 4 boards, together 40 wired analogue inputs connected directly to main board.

Also I'm thinking now, it as it looks like final product, I will sell the finished boards and nodes. I guess it can be a good jump start to any one who wish to do some security alarm at home and use as sensor gateway for home automation as well. And still use the Arduino code and various libraries to tweak it, add new functionality or features. Believe me the old 8bit atmega has still power to do all these things fast and reliable.

Remote node code

Just created new GitHub repositories for remote node code and put links to them on the page here on blog.

In the code there is visible declaration of sensors and authentication units, and their way of registration to gateway. In the iButton node, there is also sound and led code that is based on tone library and performs feedback to user. Wired nodes use my own RS485 library, otherwise standard Arduino libraries are used.

New node

In past week I have created new board for remote node. Here is render from KiCad, how it should look like. It is my first board after switching from Eagle to KiCad, so we'll see what it will look like in real.

There are many changes, while keeping the current format 5x5cm, I have replaced most of the components. There is new switching power supply, actually two of them. One is for standard DC 5 - 20 V and up to 500mA. Second is for batteries and support voltage from 2 to 5.5 V but only 120mA. There is still present the RS485 half-duplex IC, speaker, and header for 1-Wire touch probe with 2 LEDs. IO Header grew with new pins and most importantly there is place for new RFM69W radio module on the back.

I have plans to use more battery powered nodes that should last long. Either to run them from rechargeable batteries like li-on or li-po or from standard packs or bigger button batteries. Waiting for the boards to get them alive :).

Redesigned UI

Last week I put some effort into creating fresh new look with CSS. I was so happy with the look, that I have rewrote all the UI into it. Look at the screen capture below, it is best viewed in HD. Just remember that the web service is provided by the 8bit ATmega MCU, still amazing. I'm not showing the Key and Phone parts, as this is unit is already guarding my property and the iButtons codes and phone numbers are listed there.

As always, I will push all updates to GitHub.