Test your etching chops with PCB map making


[Martin] had been using standard perf board for most of his electronics projects, but as he was starting to utilize more surface mount ICs, he quickly realized that it was time to start making his own PCBs. Having never etched any PCBs using the toner transfer method, he figured it was as good a time as any to give it a try.

Rather than make a board for a particular project, he decided to try his hand at etching a very detailed map of the Paris Metro as a test pattern instead. He grabbed a large image of the subway map, then printed it out on the back of a supermarket flyer. He attached it to his PCB and ran it through a lamination machine to transfer the toner. He figured that the laminator would be easier than an iron to use, and was right for the most part. The only issue he had was that the laminator did not generate enough heat, so he supplemented the its heat output with a hair dryer.

When everything was said and done, he had a pretty good looking PCB on his hands. Most of the Metro tracks and text came out just fine, though he admits there is a bit of room for improvement. It looks nice when mounted in a frame, though we would love to see a functional circuit made out of a PCB map like that. Heck, we’d even settle for a double-sided PCB with a street-level map on one side an the Metro on the other!

Building a home automation mesh network

[Ian Harris] designed a bunch of home automation for his parents using X10 hardware. He was a bit disappointed by the failure rate of the modules and the overall performance of the system so he set out to replace it with his own hardware. Lucky for use he’s documented the journey in a four-part series about mesh networks.

The hardware seen above is his test rig. He’s using a couple of Sparkfun breakout boards to develop for nrf2401a RF transceiver chips. These could be used as slave modules, with a central command device, but due to the home’s architecture wireless signals don’t propagate well from one end of the house to the other. The solution is to build a mesh network that will allow each module to act as a network node, receiving and passing on messages until they arrive at the target device. He’s trying to do this with cheap hardware, selecting the PIC 16F88 which boasts 7 KB or program memory and 368 bytes of ram. In the end it doesn’t take much code to get this running, it’s the concepts that take some time and research before you’ll be comfortable working with them.

[Thanks Oakkar7]

Hardware-based security keypad keeps it simple


Instructables user [trumpkin] recently built an all-hardware based keypad lock for a contest he was entering, and we thought it was pretty neat. The lock uses mostly NAND gates and 555 timers to get the job done, which makes it a nice alternative to similar software-based projects we have seen in the past.

The lock has 6 keys on the keypad, which is connected to the main logic board. The keycode is set using a series of headers at the bottom of the board, and you get 10 chances to enter the proper code before the board locks up completely. If this occurs, a “manual” reset via a button built into the main board is required before any more attempts can be made.

As you can see in the video below, the lock works quite well, but suffers from one shortcoming. Any permutation of the key code can be used to deactivate the lock, which is something [trumpkin] says he would like to improve in the future.

If you are looking for some more security-related reading, be sure to check out these other hacks we have featured in the past.

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More radiation test gear

This is a multifunction too for measuring radiation (translated). The measurements center around gas discharge tubes that react when ionizing particles pass through them. After reading about the counting circuit for the pair of tubes used in this handheld it’s easy to understand why these are tricky to calibrate. The handheld features a real-time clock as well as a GPS module. This way, it can not only give a readout of the radiation currently measured, but can record how much radiation exposure has accumulated over time (making this a dosimeter). An accompanying dataset records the location of the exposure. An ATmega128 drives the device, which is composed of two separate boards, a series of five navigation buttons, and a salvaged cellphone LCD for the readout. The translated page can be a bit hard to read at times, but there’s plenty of information including an abundance of schematic breakdowns with accompanying explanations of each.

This is certainly feature-rich and we think it goes way beyond the type of device that Seeed is trying to develop.

[Thanks Andrew]

Add a shutoff timer to your bathroom fan

Adding this board (translated) to your bathroom fan will turn it into a smart device. It’s designed to automatically shut off the fan after it’s had some time to clear humidity from the room. It replaces the wall switch which normally controls these fans by converting the fan connection to always be connected to mains.  The board draws constant power to keep the ATtiny13 running via a half-wave rectification circuit. A single LED that rises from the center of the PCB lights up to signal that the fan is in operation, but it is also used as a light sensor, similar to the LED communications hack from a couple of days ago. When the lights go on in the bathroom the microcontroller will turn on the exhaust fan via a Triac. It will remain on until the light level in the bathroom drops.

There’s an interesting timing algorithm that delays the fan startup, and varies the amount of time it will stay on in the dark depending on how long the bathroom lights were on. This way, a longer shower (which will build up more humidity) will cause the fan to remain on for the base of five minutes, plus one minute longer for every two minutes the bathroom was in use. Pretty smart, and quite useful if your bathroom sees high traffic from several family members.

Building a zoetrope using Kinect, processing, and a laser cutter

A zoetrope is a device that contains a disk full with a series of images that make up and animation. A couple of different methods can be used to trick the eye into seeing a single animated image. In the past this was done by placing the images inside of a cylinder with slits at regular distances. When spun quickly, the slits appear to be stationary, with the images creating the animation. But the same effect can be accomplished using a strobe light.

The disk you see above uses the strobe method, but it’s design and construction is what caught our eye. The animated shapes were captured with a Kinect and isolated using Processing. [Greg Borenstein] takes a depth movie recorded while someone danced in front of a Kinect. He ran it through a Processing sketch and was able to isolate a set of slides that where then turned into the objects seen above using a laser cutter.

You can watch a video of this particular zoetrope after the break. But we’ve also embedded the Pixal 3D zoetrope clip which, although unrelated to this hack, is extremely interesting. Don’t have a laser cutter to try this out yourself? You could always build a zoetrope that uses a printed disk.

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