Crosby Beach

Just north of Liverpool is a beach, Crosby Beach. It’s one of my favorite places.

It’s windswept and not at all sandy (well, not until the tide goes out). It’s not even a pebble beach. It’s a Brick beach. Full of bricks. All different shapes and sizes.

As many will know, Liverpool was very badly bomb-damaged during the Second World War. It was Crosby Beach where all the bricks and rubble from the destroyed homes, factories, shops, streets was dumped. Fragments of everyday life, written in wind and wave blasted stone can still be seen there

Walking along the beach you see all these shapes and colours. Some have writing speaking of a time when local factories proudly produced the very fabric which Liverpool was built with. So much pride, their names are clearly stamped there. Are our modern Wimpy housing estates built with the same pride?

Of course, you might know Crosby beach for another reason. It’s the home of Antony Gormley’s ‘Another Place’ which was permanently installed on the beach in 2007. I have always loved Gormley’s work, but Another Place is so extraordinary, the way it sits in the landscape, and yet at the same time, is the landscape.

If you are in the area, it’s well worth a visit.

MongoDB passes Jepsen Test! – The Industry’s Toughest Database Test

I’m really pleased to share the news that MongoDB has been acknowledged by the creators of the formidable Jepsen Test as demonstrating Data Safety, Correctness & Consistency. On February 7th 2017, Kyle Kingsbury, creator of Jepsen, published the results of his tests against MongoDB 3.4

His Conclusions are:

MongoDB has devoted significant resources to improved safety in the past two years, and much of that ground-work is paying off in 3.2 and 3.4.

MongoDB 3.4.1 (and the current development release, 3.5.1) currently pass all MongoDB Jepsen tests….These results hold during general network partitions, and the isolated & clock-skewed primary scenario.

Read more about the news here: https://www.mongodb.com/mongodb-3.4-passes-jepsen-test

Sensing VCC with an ESP8266

Part of the plan in the previous post showed me attempting to sense the voltage level of the VCC supply by feeding it into an external ADC. Well I’ve just discovered, thanks to Tzapu’s (he of “WifiManger” fame) Minimalist temperature sensor project, that the ADC on the ESP8266 can be configured at boot to read the internal voltage at VCC. This would mean that using an external ADC would be essential, but then seeing as the ESP’s A0 only goes from 0-1v it isn’t a devastating loss to not have it available.

Tzapu is also using a current regulator (with a 18650) cell to power it. This will also require some investigation.

The Plan

I’ve been working on the plan, or what passes as a plan for the soil sensor. Right now it looks something like this.

the plan

I don’t know if it will work yet, I’m not really clever enough to work through the numbers, but I’ve ordered all the components, so they should trickle in over the next few weeks from china. While several people have mentioned that trickle charging lithium cells is a really bad idea, I’m hoping that two layers of protection firstly within the 18650 cell and then on the TP4065 charging board will cut down the risk of explosions and fire to a manageable level. The 5v Solar Panel has already arrived and looks to be suitable for the job, but as I’ve nothing else yet, we’ll have to wait and see.

I may yet drop an Arduino into the picture in place of the ADS1115 i2C if the ESP8266 seems to be a bit too unstable and needs supervision or an external watchdog. It never really sat well with me before, but when you think about it, you can buy a knock off pro-mini for the same price as an ESP-12 so it’s not going to break the bank.

ESP8266 Analogue input expansion

I’ve just read on the Internet of Home Things blog, a great idea for expanding the number of analogue inputs that can be read by an ESP8266.  Using an 74HC4051 CMOS analog multiplexer chip you can get 8 Analogue inputs selectable from a matrix of 3 digital inputs.  Great idea.

I’ve ordered some samples of the Maxim MAX4617CPE multiplexer to see if I can get any analog(e) joy out of it.

To be fair, A Reddit thread I just started seems to come down in favour of a separate ADC. It seems the ESP8266 only has a +/- 1v on it’s solitary ADC pin, so a i2C ADC makes sense. I’ve been pointed in the direction of this Adafruit product (ADS1015 12-BIT ADC – 4 CHANNEL) and while I love Adafruit, their shipping to the UK kills me. Luckly there seem to be some chinese clones floating about which profess to do the same job.

Suffolk Harvest

I’ve just got back from a holiday in Suffolk, where is was great to see this year’s harvest in full swing.  For an engineering geek like myself, seeing the huge Combine Harvesters running through the night was a great sight.  Even better were the large stubble fields which I took the liberty of trespassing on.  Specifically, I’ve been wanting to perform an autotune, which sees the quad throw itself around a bit so that it can tune it’s PID settings.  I managed to get it into autotune, but my batteries didn’t have the staying power to see it through to the end.  I’ve given up on the Turnigy 2200mAh 20c batts now, five out of the six that I got have puffed, and I’m not willing to use them anymore.  I think the voltage sag was taking cells down below their healthy voltage and damaging them permanently.

I’ve splashed out on some turnigy nano-techs, which depending on who you listen to are either just as bad or amazingly good.   They should be a little bit more resistant to sag and perhaps will give me enough juice to get an Autotune complete.

With the camera and gimbal in place and with the new 4000mAh battery (333g) it’s now weighing in at over 1600g.  That’s a fair weight and I’m going to be ultra cautious about flying with this config.