Cheese fridge repairs

My cheese fridge was partially destroyed at the start of July.

A car crashed into a power pole carrying both a 22kv distribution line and the 230v line for our house.

They . touched . briefly

It turns out a lot of devices made to run on 230v are not so happy running on 22kv which caused a lot of magic smoke to be released from our prized belongings.

The temperature and humidity controller in my cheese fridge literally blew up, sending plastic pieces six metres across the garage. Fortunately these controllers protected the fridge itself so it’s just the controllers that need replacing.

The ZL-7801A, these look interesting

I started looking for new controllers and found the ZL-7801A, which is a combined Temperature and Humidity controller in one. It’s also got a timed on, timed off relay output intended to be used by an egg turner (in an incubator), but I think I should be able to use it to turn on circulation fans for 30 seconds once every 30 minutes.

I plan to use one half of the “Egg turning motor” output to turn on a circulation fan on a 1% duty cycle

I’ll do another blog post once I receive the controller.

Posted in Cheese Fridge, Electronics, General Randomness, Projects

Setting up a CA SSL certificate in hMailServer

I’m a big fan of hMailServer, but the documentation for setting up SSL certificates and the certification chain is a bit lacking.

The easiest way to check if hMailServer is setup correctly is to use OpenSSL.

openssl.exe s_client -showcerts -connect mail.yourserver:995

If one of the last lines has the message “unable to verify the first certificate”, the certification path is incomplete.

If one of the last lines has the message “self signed certificate in certificate chain” and you are NOT using a self signed certificate, things are probably set up OK.

You can also use web based tools such as – just remember you need to add a port number (SSL POP3 normally runs on port 995)

hMailServer requires you to provide all certificates in the certification chain. For the image below, this is the SSL cert, TWO intermediate certificates and the Root certificate.

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Posted in General Randomness, PC Tips, Tips

1,500,000,000 the Epochening

Don’t forget that at 2:40am, 14 July 2017 (UTC) the Linux epoch will hit 1,500,000,000 (1.5 Gigaseconds).

Visit to watch the excitement!

It hit 1,000,000,000 back in September 2001 and it won’t hit 2,000,000,000 until May 2033.

Posted in General Randomness, Linux Tips

Modifying float voltage of a TP-SCPOE-1224

Adjusting the float voltage of a Tycon Systems TP-SCPOE-1224

The Tycon Systems TP-SCPOE-1224 is a Solar and Power over Ethernet powered DC UPS.
You connect it up to a 12v battery, power it over ethernet, add an optional solar panel and it will output 24V DC until the supply stops and the battery runs flat.

The units are very reliable, but the battery float voltage seems to sit at around 13.3 volts. This is a little low for AGM batteries which should be kept in the 13.6-13.8 volt range.

I’ve had multiple batteries fail within 16 months after being held at a 13.3v float. I recently decided it was time to see if it was possible to increase the float voltage.

I got in touch with the team at Tycon Systems. After receiving (and not accepting) an initial “Not possible” response, they came through with the goods – A section of the schematic specifying that resistors R45 and R49 control the float voltage. They also advices that the charge voltage increases relative to the float voltage, so just changing the float voltage will increase the charge voltage by a relative amount as well.

It’s easy to open up the unit. Turn it over, remove the four rubber feet to reveal four screws. Remove these screws and the two halves separate with ease.

Resistors R45 and R49 (circled) are very difficult to access

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Posted in Uncategorized

Power meter optical pulse detection

I’ve always planned to monitor my electricity usage. I had previously (about a year ago!) ordered some power transformers from seeedstudio and a six channel ADC for simultaneous three phase current and voltage measurement but never got around to starting the project.

We’ve since had a “smart meter” installed which has a handy LED on it that flashes once every watt hour of energy is consumed. It also has and IrDA port on it but I believe the communications protocol is password protected and will report a tamper state if the password is tried too may times. Because of this, I decided it was best to optically interface with the meter, and best of all, I’ll be measuring the exact amount of power we get billed for. Unfortunately I won’t be able to predict the bill amount (in dollars) as the three phases that come into the house are billed at different rates while this LED pulses the combined usage.

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Posted in Electronics, Embedded Systems, Power monitoring, Projects, Wino-Board

Wiring up the ESP8266

Before you can program the ESP8266, you need to wire it up.

First things first, the ESP8266 uses a 2mm pin spacing so you can’t use a standard breadboard as these use a 0.1 inch spacing. It also uses 3.3V logic, so you need to use a 3.3V serial adaptor or a 5V one with a level shifter.

Ideally, you will need the following things:

  • USB to 3.3V TTL serial adaptor (I use an FTDI TTL-232R-3V3)
  • ESP8266
  • 3.3v DC supply (capable of providing ~400mA)
  • Small SPST switch – Optional to switch between Run/Program mode
  • Momentary push button – Optional reset button
  • 4 x ~10k resistors
  • ~100nF capacitor

I wired up my ESP8266 like this (Source:

Note: The pin CH-PD is marked EN on the ESP8266 12E

Note: The pin CH-PD is marked EN on the ESP8266 12E

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Posted in Electronics, Embedded Systems, ESP8266, Projects

Introducing the ESP8266

About a year ago I put up some money for the Wino-Board kickstarter project, received my Wino-Boards and did nothing with them for 12 months. They are effectively a tiny Arduino board attached to the innards of an ESP8266 WiFi module.

I finally had a play with them last week and after making a few changes to the Wino-Board libraries (The current version could not do an HTTP GET), I found them very easy to use.

The more intriguing thing about the Wino-Board was finding out more about the ESP8266 module and that it is now possible to directly program the module itself using the Arduino IDE.

Front and Back of the ESP8266 (12E)

Front and Back of the ESP8266 (12E)

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Posted in Electronics, Embedded Systems, ESP8266, Projects, Wino-Board

Fridge Wiring

My Humidity controller finally arrived this morning so I’ve started wiring up the control box.

It's still looking like a bit of a birds nest, but I can assure you, It's safe!

It’s still looking like a bit of a birds nest, but I can assure you, It’s safe!

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Posted in Cheese Fridge, Projects

Fans in the Fridge

I’ve finally found a bit of time to get my fans installed in the fridge.

I’m still waiting on the humidity controller to arrive from China. Everything else took about 8 days to arrive, but the humidity controller has so far been 36 days – The tracking number shows it in NZ now, so it should arrive very soon.

I’ve lined one of the holes with a short length of PVC pipe, the other has a longer piece to reach lower to the bottom of the Fridge section – The longer length “sucks” air from the bottom of the fridge, effectively trying to fight convection and move the cold air from the lowest point back to the highest point.
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Posted in Cheese Fridge, Projects

Drilling vents in the fridge

When I was investigating the wiring diagram of my fridge freezer, I was also trying to find out if there is anything important in the divider between the fridge and freezer. Based on the diagrams I was confident that there was nothing in this area so I was free to drill holes.

I opted to put one hole in the front left and one in the back right.
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Posted in Cheese Fridge, Projects