Ordering parts for the cheese fridge

After working out how my fridge works, I’ve now decided what I’m going to do to make it into a cheese fridge.
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Posted in Cheese Fridge, Projects

Understanding how a fridge freezer works

The fridge I’m using for my cheese fridge is a fridge freezer, this means that during normal operation, the two boxes are different temperatures – around 20 degrees C.

I want both the fridge and freezer to operate at the same temperature, so first job is to find out exactly how the cooling system works. I’m not talking about the Vapor-compression refrigeration process, but the specific details about how this specific model works.

The circuit diagram is a good starting point:
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Posted in Cheese Fridge, Projects

Cheese Fridge project

Wow, almost six months since my last post! Yes, I’ve been busy.

I’ve recently started making cheese. Generally you start off making soft cheeses like Brie & Camembert. After a little while these cheeses no longer do it for you and you move onto the gateway cheeses such as Gouda. Before too long, you’re an addict and you need something harder – Yep, I’m talking Cheddar and Parmesan.
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Posted in Cheese Fridge, Projects

Petit Studio Raspberry Pi HDMI extender cheap cable fix

Note: This fix is NOT due to a fault of the Petit Studio Raspberry Pi Camera extension kit, it’s due to the use of cheap HDMI leads.

I brought some Petit Studio Raspberry Pi HDMI camera extenders from Tindie. These boards passively convert the 15 pin ribbon cable into a convenient HDMI connector so the cable can be extended using HDMI cables. It doesn’t convert the signal to HDMI, it simply uses the HDMI cable as an extension. Sidenote: The $5 shipping only took 4 days to get to New Zealand from Japan!

I brought some cheap 3m HDMI cables from a supplier on TradeMe and thought I was all set.

It turns out not all HDMI cables are made the same. The cables I brought work perfectly between a PC and monitor, but not at all on the Tindie camera extender.

A quick Duck Duck Go (That’s so much harder to use as a verb than Google) and I found a fix – There are meant to be shields for each data pair but in cheaper cables these are not connected. It’s an easy fix, just use the metal shield of the HDMI plug as ground…..

Or not..
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Posted in Electronics, Raspberry Pi, Weather Station

EP Solar MPPT Tracer charge controller serial code

Following on from my previous post working out the EP Solar Tracer serial protocol, I’ve got code working on a Raspberry Pi. It’s even validating the CRC checksum.

How to connect a Raspberry Pi up the the EP Solar Tracer

How to connect a Raspberry Pi up the the EP Solar Tracer

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Posted in Electronics, Embedded Systems, General Randomness, Solar power

EP Solar MPPT Tracer charge controller serial interface

I’m currently involved in a project to set up a solar powered wireless station and wanted to remotely monitor the battery charge process. I looked into a number of charge controllers to see if any of them could be connected to a computer. Many of the controllers have ethernet and built in web servers, but these come at a cost.

The (relatively) cheap chinese made EP Solar Tracer MPPT Solar charge controllers have an RJ45 interface for an MT5 remote display which means that there must be some way to get data out of the charge controller.

The MT5 remote display

The MT5 remote display

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Posted in Electronics, Embedded Systems, General Randomness, Raspberry Pi, Solar power

dump1090 binary built for Raspberry Pi / Arm

If you’re after a binary of dump1090 for the Raspberry Pi without having to build it, here’s a compiled binary for you.

I built it on Arch linux, but it also works on Raspbian, or likely any other Arm processor as well.

It’s version 1.09.0608.14 of the MalcolmRobb fork

You can download it from here: Read more ›

Posted in ADS-B Aircraft tracking, Embedded Systems, General Randomness, Linux Tips, Raspberry Pi

Pulsecounter PCB’s have arrived

I posted recently about detecting power loss in an AVR and quickly writing values to EEPROM before power is lost completely and have since received the PCB’s I ordered from oshpark.

This is the first time I have ever ordered professionally made PCBs. I’ve made many using photo resist or toner transfer, but at US$5.00 per square inch for three boards (including worldwide postage) I decided to give it a go. It took a total of three weeks from placing the order to arriving in New Zealand.

This is OshParks render of what the Top was meant to look like

This is OshParks render of what the Top was meant to look like

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Posted in AVR, Electronics, General Randomness

This website is now exclusively SSL

Google have announced (Ironically via a non SSL website) that they will now take into account whether sites use secure, encrypted connections as a component of their ranking algorithm.

On this announcement I’ve switched my website to exclusively use SSL. It will now silently (but forcefully, like a Ninja) redirect you to the https version.

Posted in General Randomness

AVR – Detecting loss of power and writing to EEPROM

As part of a recent AVR project, I wanted a way to increment a counter and store it even if the power was lost. This could be done with an external flash memory device, but I wanted to use the internal EEPROM of the AVR.

The internal EEPROM is limited to around 100,000 writes. Independent tests have shown this can be doubled, but 100k writes is only about 27 hours if saved once every second, so not practical for a device I wanted to last at least five years.

It takes a maximum of 34ms (8448us per byte) to write a 32 bit (4 byte) integer to EEPROM. Due to the low power requirements of an AVR, I was confident that a decent sized (say 2200uF) capacitor would allow an AVR plenty of running time to complete EEPROM writes/saves before power is totally lost.
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Posted in AVR, Embedded Systems, Weather Station