andyc – CatTrack

CatTrack 3.0 Low Power Radio Receive (and a swollen LiPo battery fixed in software)

The issue 2 boards are here, I’ve soldered them up and tested them and the good news is that they match the performance I managed to prototype with the issue 1 boards (thereby rendering all the effort I put into making the supplies easy to isolate pointless, ah well!):

Sleep mode current (10.00 seconds): 0.00147 mA Active mode current (0.060 seconds): 8.97500 mA

This equates to an average current consumption of 0.0559mA, or 55.9uA. This means that a 200mAh battery will last (hopefully!) around 4.9 months.

CatTrack v3.0, Posts 0

CatTrack 3.0 Minimising Current Consumption…

It’s been a couple of months without an update, but I have been busy with CatTrack. I’m currently waiting for oshpark to send back an issue 2 PCB.

The only real change from the issue 1 PCB to the issue 2 PCB is a change in voltage regulator. I have spent a long time over the last couple of weeks scalpeling my existing board and isolating everything in order to measure how much current each of the devices on the board is consuming.

I initially measured the current consumption of the whole board with everything in ‘sleep’ mode as 3.5uA. This didn’t really add up with what I expected, so I isolated each device in turn (MUCH easier said than done!) and measured the current of the PIC, RF95W and regulator seperately.

I started with the PIC. There are plenty of guides around the Internet detailing how to reduce the current consumption of a PIC to a minimum. Microchip themselves have a good guide.

CatTrack v3.0, PCBs, Posts, Schematics 4

CatTrack 3.0 Schematic, PCBs and Software!

Motivation and dedication are still high!

I’ve managed to complete the schematic and PCB, get it sent off to oshpark (my favourite PCB fab!), get them back, and solder them up, phew. I went for oshpark’s 0.8mm board thickness in order that my stacking heights would work inside the case, so they took a little longer to arrive than normal.

The schematic is below (click to enlarge). It’s quite simple and comprises the following:

CatTrack v3.0, Posts 6

CatTrack 3.0?! It’s August 2023!

It’s been over 2 years since CatTrack 2.0 was “on it’s way”….

Well… umm… it hasn’t progressed much since the previous post. I’ve had some good email chats with a good guy called Robert, who has been working on something very similar over in the Czech Republic. He has made many prototypes and has shared his thoughts with me around getting decent GPS reception. In the end he has settled on a Quectel LC86L GPS module and engineered the box such that the antenna sticks out a little, drastically improving reception.

I was having some reception issues with the u-blox GPS module I was using for CatTrack 2.0, which caused me to think about making a slightly different device…

Posts 12

CatTrack 2.0 is on its way…!

It’s been a while!

The last post I made here was July 2018… quite a lot has happened between then and now. Not only did Buttons sadly get involved in a car accident and need to have a leg amputated (don’t worry he’s fine and still himself!), but I also moved house and had a child.

Also there was a global pandemic.

Anyway enough of all that rubbish, the most important thing is that I’ve been working a little on Version 2 of CatTrack.

Posts 8

tl;dr complete version 1 build summary

There are a lot of posts to trawl through in this blog if you’ve not followed it from the beginning. Hopefully this summary makes everything a bit clearer…

The first thing I did was to have a look at other cat tracking products on the market. I found that they all have a big flaw… battery life. I wanted GPS level accuracy and a battery life measured in months. Nothing on the market offered that, so it was down to me to design it!

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Posts 3

Everything’s working!!!

Everything is working!!!

This is the CatTrack Basestation communicating with the CatTrack unit on Buttons’ collar, showing his position on it’s LCD screen whilst simultaneously sending position information via Bluetooth to my laptop, which you can see on my screen in the background.

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Posts 3

Long Range Communications with the CC1125

I’ve now written enough code for the PIC on the CatTrack base station such that I can begin to test it!

I’ve already tested comms with the CatTrack collar, using a development board instead of the base station. Read about that here.

Unfortunately, when testing my base station I found that it was nowhere near as sensitive as the development board – the base station was getting CRC errors whilst the development board was still receiving the signal fine. After a small bit of investigation I found out why. The problem is all down to the fact that I want to use the CC1125 at the lowest baud rate (300 bps), and consequently a very narrow receive bandwidth (3.8 kHz).

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PCBs, Posts 1

Base station PCBs have arrived – time to solder!

Well, the boards actually arrived several weeks ago, but I’ve only just got round to doing the soldering. As ever, I’ve ordered all my components from Farnell in the UK.

All of the passive components I’ve used are 0402 sized (0.5mm by 1.0mm). The advantage of components this small is that you can squeeze a lot into the RF sections of the board, most notably at the output of the CC1125. This decreases board size and improves the RF performance. You can go much smaller than 0402 – 0201 is the next size down, followed by 01005 – only 0.2mm by 0.4mm! Getting decent performance out of an inductor or capacitor that small will be difficult, so it’s a tradeoff between size and performance.

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PCBs, Posts 1

Base Station PCB

I’ve finished laying out the base station PCB, hurrah!

As ever I’ve laid it out using Eagle – this time I’ve managed to keep it to two layers so that’ll save me some money in PCB manufacture costs. Click it to enlarge.

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