door spring

Compliant Contacts: Hacking Door Locks With Pen Springs

As you may have guessed given our name, we do love hacks around here, and this one is a great example of making some common, everyday things work in uncommon ways. [Nathan] sent in his hack to detect the door lock position in his basement.

Having a house that dates back to the 1890s, much of it was not very conducive to using off-the-shelf home automation devices. [Nathan] wanted a way to check the status of the basement deadbolt. He went about putting together a custom sensor using some spare parts, including a spare BeagleBone Black. Going full MacGyver, [Nathan] used springs from a ballpoint pen to craft a compliant contact for his sensor.

The pair of springs sat in the door frame and came in contact with the deadbolt; given they are springs, the exact position of the sensor was not very sensitive, as if too close it would just compress the springs slightly more. The springs were wired to the BeagleBone Black’s GPIO, acting as a switch to sense when there was conductivity between the springs through the deadbolt.

This wasn’t just a plug-it-in-and-it-works type of project, mind you; the BeagleBone Black was over 15 ft away from the sensors, lending plenty of opportunity for noise to be introduced into the lines. To combat this, [Nathan] created an RC filter to filter out all the high-frequency noise picked up by his sensor. Following the RC filter, he added in some code to handle the debounce of the sensor, as the springs have some inherent noise in them. Thanks [Nathan] for sending in your resourceful hack; we love seeing the resourcefulness of reusing things already on hand for other purposes. Be sure to check out some of the other repurposed components we’ve featured.

Buyer Beware: Cheap Power Strips Hold Hidden Horrors

We’ve got a love-hate relationship with discount tool outlet Harbor Freight: we hate that we love it so much. Apparently, [James Clough] is of much the same opinion, at least now that he’s looked into the quality of their outlet strips and found it somewhat wanting.

The outlet strips in question are Harbor Freight’s four-foot-long, twelve-outlet strips, three of which are visible from where this is being written. [James] has a bunch of them too, but when he noticed an intermittent ground connection while using an outlet tester, he channeled his inner [Big Clive] and tore one of the $20 strips to bits. The problem appears to be poor quality of the contacts within each outlet, which don’t have enough spring pre-load to maintain connection with the ground pin on the plug when it’s wiggled around. Actually, the contacts for the hot and neutral don’t look all that trustworthy either, and the wiring between the outlets is pretty sketchy too. The video below shows the horrors within.

What’s to be done about this state of affairs? That’s up to you, of course. We performed the same test on all our outlets and the ground connections all seemed solid. So maybe [James] just got a bad batch, but he’s still in the market for better-quality strips. That’s going to cost him, though, since similar strips with better outlets are about four times the price of the Harbor Freight units. We did find a similar strip at Home Depot for about twice the price of the HF units, but we can’t vouch for the quality. As always, caveat emptor.

Continue reading “Buyer Beware: Cheap Power Strips Hold Hidden Horrors”