Junkbox Freezer Alarm Keeps Steaks Safe

October 29, 2017 by Dan Maloney 24 Comments

A fully stocked freezer can be a blessing, but it’s also a disaster waiting to happen. Depending on your tastes, there could be hundreds of dollars worth of food in there, and the only thing between it and the landfill is an uninterrupted supply of electricity. Keep the freezer in an out-of-the-way spot and your food is at even greater risk.

Mitigating that risk is the job of this junkbox power failure alarm. [Derek]’s freezer is in the garage, where GFCI outlets are mandated by code. We’ve covered circuit protection before, including GFCIs, and while they can save a life, they can also trip accidentally and cost you your steaks. [Derek] whipped up a simple alarm based on current flow to the freezer. A home-brew current transformer made from a split ferrite core and some magnet wire is the sensor, and a couple of op-amps and a 555 timer make up the detection and alarm part. And it’s all junk bin stuff — get a load of that Mallory Sonalert from 1983!

Granted, loss of power on a branch circuit is probably one of the less likely failure modes for a freezer, but the principles are generally applicable and worth knowing. And hats off to [Derek] for eschewing the microcontroller and rolling this old school. Not that there’s anything wrong with IoT fridge and freezer alarms.

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Fight Frost With An Internet Of Things Fridge Alarm

August 23, 2015 by Dan Maloney 12 Comments

It has been incredibly humid around these parts over the last week, and there seems to be something about these dog days that makes you leave the fridge or freezer door open by mistake. [pnjensen] found this happening all too often to the family chill chest, with the predictable accretion of frost on the coils as the water vapor condensed out of the entrained humid air and froze. The WiFi-enabled fridge alarm he built to fight this is a pretty neat hack with lots of potential for expansion.

Based on a Sparkfun ESP8266 Thing and home-brew door sensors built from copper tape, the alarm is rigged to sound after 120 seconds of the door being open. From the description it seems like the on-board buzzer provides a periodic reminder pip while the door is open before going into constant alarm and sending an SMS message or email; that’s a nice touch, and having the local alarm in addition to the text or email is good practice. As a bonus, [pjensen] also gets a log of each opening and closing of the fridge and freezer. As for expansion, the I2C header is just waiting for more sensors to be added, and the built-in LiPo charger would provide redundancy in a power failure.

If frost buildup is less a problem for you than midnight snack runs causing another kind of buildup, you might want to check out this willpower-enhancing IoT fridge alarm.

Over Engineered Kegerator Is Glorious

December 13, 2013 by Adam Fabio 12 Comments

keger

When [Joey] decided to build a kegerator, he didn’t skimp. No commercial unit or simple kit would do. [Joey] wanted complete temperature monitoring, with a tap on the kegerator itself and a cooled tap remotely mounted at his bar. He started with a box freezer, which was a bit short for his purposes. Not a problem, as [Joey] cut an extended collar for the freezer from HDPE on his shopbot. The new collar gives mounting points for the beer lines, gas lines, as well as all the electronics.

Temperature control is handled by a commercial controller, however temperature monitoring is another thing altogether. An Arduino sits in a custom aluminum case on the outside of the kegerator. The Arduino reports temperature, beer type and also controls the cooling system for the beer lines. The cooling system alone is incredible. [Joey] designed everything in CAD and cut the parts out on his shopbot. Two fans sit in an aluminum air box. One fan is used to push cold air out from the freezer around the beer line. A second fan pulls air back in, keeping the kegerator/line/tap air system a (relatively) closed loop. The entire line set is insulated with 2″ fiberglass flex duct.

Temperature data and trend graphs can be monitored on the web, and [Joey] is using a Raspberry Pi to create a wall mounted status screen for his bar room. We love this build! [Joey] we’d buy you a beer, but it seems like you’ve got that covered already!

Freezing Android To Crack The Encryption

February 20, 2013 by Mike Szczys 40 Comments

frozen-phone-encryption-hacking

Build a better lock and someone will make a tool to open it without the key. Or in this case they’ve made a tool to discover the key using a trip to through the deep freeze. The Forensic Recovery of Scrambled Telephones — or FROST — uses cold temperatures and a custom recovery image to crack Android encryption keys.

Cold boot hacks go way back. They leverage use of low temperatures to slow down the RAM in a device. In this case, the target phone must already be powered on. Booting a phone that uses the encryption offered by Android 4.0 and newer requires the owner’s pass code to decrypt the user partition. But it then remains usable until the next power cycle. By freezing the phone, then very quickly disconnecting and reconnecting the battery, researchers were able to flash their own recovery image without having the encryption key cleared from RAM. As you can see above, that recovery package can snoop for the key in several different ways.

[Thanks Rob]