Itinerant Ham

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Danfoss BD50 Fridge/Freezer Controller Update

Project Update

Danfoss Fridge Controller

During the winter, I had to make my own fridge controller form my Danfoss BD35 compressor as the mechanical thermostat broke down miles from anywhere and many days away from getting a replacement.

Danfoss BD35/50 Smart Fridge Controller

The prototype was formed from an ESP8266 and a DS18b20 and programmed up pretty quickly to prevent the food spoiling.

It worked very well and it was very useful to have an accurate fridge monitor for the first time in over 10 years on the boat.

The first draft of a custom PCB for this project is ongoin – I expect to order it within days.

Agile Octobot

A side-project came up when I switched electricity providers to Octopus Energy. They have an Agile Tariff where you only pay the ‘going rate’ for electricity when you actually use it. Their day is split into 1/2 hour time slots and the price varies witht the wholesale price of electricity and is published in advance. I decided to write some Arduino code to allow some of my devices to make autonomous decisions on when to turn on. It uses the Octpus API. As an aside, I wrote a Telegram bot to remind me of upcoming electricity prices so I’m reminded to turn on my energy-intesive, not-so-smart devices. More detail at Agile Octobot.

Automated Irrigation

I decided to make an automated drip irrigation system and ordered up a few parts. To mount the valve, I made a 3D printed bracket. Control will be via relay and an ESP8266 running Tasmota integrated into Home Assistant.

This morning’s project was more mundane…


Oh yes, I almost forgot! I sent off some Rapberry Pi 3s to Hoveraid the charity I built a temperature monitoring system for a few years back. Its basically the same system with Node-red and Mosquitto running on Dietpi but this will give them more headroom for future expansion when they re-engine the hovercraft and need CANBUS.

I have a bunch of other upcoming projects so I’ll post more updates in the coming days.

Agile Octobot

I recently switched to Octopus Energy since they were not only cheaper but focussed on renewable energy. One of the most attractive aspect of switching was that they offer an Agile Tariff where you are charged for the energy used at the time you use it. That means that I can schedule electically ‘heavy’ tasks for a time of day when electricity is cheaper.

Pricing for the London area on 6/6/2020

Yes – there is negative pricing too! So you get money back when you use energy that is in excess. This seems to happen on windy, solar days but can also happen at night when overall demand falls really low.

To take best advantage of the flexible pricing I decided to write code for some of my ‘smart’ devices so that they could schedule themselves for when energy is cheaper. At the same time as I was writing the core, my friend Robin mentioned that he was having trouble getting pricing from the Octopus app on his older iPhone. So I thought it would be fun to write a bot that would just give you the prices. He uses it to plan his ‘energy day’.

So the Agile Octobot was born. Its on Telegram, a secure messaging platform and can be found at

If you then type /start, and choose your region, you’ll receive the prices for the next hour about 5 minutes before the hour.

There are other commands such as /now that will give you the current prices and /all that will give you the prices for the rest of the energy ‘day’.

If you have a play you’ll see that rather than paying a flat-rate price for every kW you can achieve significant savings on your energy bill.

There’s more about the Agile Tariff at If you are interested in taking advantage of those prices, there’s a discount when you switch to Octopus – if you use this link (, we can share a ¬£100 credit to your account.

The Agile Octobot is currently running on a very small platform, the ESP32 but the load is very light. Its not guaranteed to be available 24/7/365 but unless loads and loads of people start using it, it will be just fine. Please bear in mind, its a guide only ūüôā

Personal Report from Bahamas


Many pages of this blog tell the story of amateur radio operations in the Bahamas (C6). The northern Bahamas is in the middle of an unprecedented¬†crisis after the passage of Hurricane Dorian. I feel that before this crisis is buried by ‘local news’ in your part of the world, I should do my part in spreading the word.

If you feel that there is something that you wish to do, I attach a link to the Bahamian Government portal.

Here is the report:

From Fr. Keith Cartwright, Anglican Arch Deacon, Nassau

In order to dispel rumours and untruths, My Priest, who just got back from Marsh Habour 6 am this morning and has been on the ground every day since from the day after storm departed gave our Church a full report on the situation in Marsh Harbour and Grand Bahama. In Marsh Harbour he said that with the exception of a few souls who are still refusing to leave what little they have, the entire affected areas have been completely evacuated. There is nothing left, he said. The stench is unbearable. There are countless medical personnel there doing an excellent job. There is a clean up team on the way from the Netherlands whose function is uncovering, containment & sanitizing of dead bodies and should be there now on the ground. ¬†There are plenty dead and unaccounted for still under debris and swept out to sea. ¬†The bodies they have recovered so far are stored in large constructed coolers run by generators. The clinic and one of the government buildings left standing have been cleaned and sanitized. They are in the process of doing the same to the building that was taken over by the Haitians. He said that the clinic and the two government buildings were the only structures not damaged, which was a testament to the builder who passed away last year. ¬†Also, the uproar about the Bahamasair charging $75 was partly true. He was present at the airport when the flight came in. It was the very first flight and was a regular scheduled flight for Bahamasair. Persons had previously purchase tickets prior to the storm and before consulting with the powers that be, made the decision to charge that fee. My Priest intervened immediately and told them that will not be happening. He got on the phone with the Prime Minister himself and explained what was going on. The Prime Minister then got in contact with the man in charge and was instructed to let that be the first & last flight they charged those people as Bahamasair was the People‚ÄĚs airline etc. etc. Every flight after was completely free and they went above and beyond getting the people out. There was looting and unrest, and order has now been restored. As for Freeport, there is still a lot of flooding and damage although not to the degree of ¬†Abaco. He said there are plenty dead and unaccounted for there as well. He told us stories of survivors who watched loved ones die and got swept away right before them. My head is still spinning from the horrors and grief that I can‚Äôt begin to tell you all everything, but this is what I recalled.

D1 Mini Lighting Shield

So we have a home renovation project underway and lighting is one of the major improvements as well as a new kitchen.¬† Led lighting is so much more efficient than incandescent anything and I like the way that we can set the colour temperature for certain strings to suit the mood.¬† We’re going to embrace certain aspects of home automation as well and some intelligent features such as being able to detect when to turn the lights on – less fumbling for the switch in the middle of the night when you go to the kitchen for a glass of water.

So, particularly for the kitchen, I had the need to control strings of WS2812B and strings of many RGB or white LEDs so I set about designing a shield for my trusty Wemos D1 Minis.  The D1 mini is a very cheap board with the wifi enabled ESP8266 soc which is ideal for the purpose.  The form factor is especially important the whole board being just over 840 mm sq (or 1.25 inches sq).

Power is important. Modern lighting systems are low voltage – more important in ‘wet’ areas. The ESP8266 runs at 3.3V but the D mini has a linear voltage regulator on board that works from 4.x volts up. Of course, being linear its best not to go too much above 5V for efficiency’s sake.¬† There are simple shields available that allow higher voltage supplies but I didn’t really want another layer on the stack of boards.

Here are the specs of the final shield:

  • 6-24V voltage regulator at up to 3A
  • 3 pwm channels (up to 2.5A) for controlling RGB led strings
  • 1 channel with WS2812B ‘driver’
  • 1 other breakout pin
  • Voltage divider on board for battery monitoring and switching
  • Stackable! You can use more than one lighting board per D1 Mini
  • Serial pins unused should you need to wire to an array of other microcontrollers.
  • Configurable.¬† Only populate the areas you need on the board for the required functionality




Testing confirms the following:

  • Power supply good to 2.5A continuous at 30C
  • Drives a string of 120 WS2812B at 80% brightness
  • PWM channels (current sink) good for 2.5A per channel
  • McLighting, Tasmota, and consequently Home Assistant compatible
  • PWM and WS2812B drivers work separately or concurrently

All in all its a decent shield and integrates well with the D1 Mini.

If you want to build one of these, I may have some boards and components available from time to time, so drop me a comment and I’ll be in touch!




August 2020