GPS Puzzle Box – Reverse Geocache Box

For a good friend, I decided to make a GPS puzzle box, also known as a reverse geocache box. We have both shared an interest in electronics, how things work, and challenges. Not only is the box a puzzle to get open, but once it is open, he has a PIC based board with a GPS module, LCD screen, button, and an RGB LED that he can hack and make his own project, in addition to the contents of the box.

The GPS puzzle box is much like a treasure box, except that you are carrying the treasure inside of a locked box. The box only unlocks once a series of waypoints have been visited. The box looks like any other box, except it has an LED display and a single button. When the single button is pushed, a message displays greeting the treasure hunter and then proceeds to give a hint to the next waypoint. In my case, the box gives the distance from the waypoint. If the person is close enough to the waypoint, the waypoint is marked as visited and a clue to the next waypoint is given. Once all of the waypoints have been visited, the box unlocks itself, allowing the person to open the box and receive its contents.

In theory, the box is simple. It consists of a mechanized locking mechanism, a microprocessor, and a GPS module. However, in practice, as usual, the implementation is much more complicated. For this box power conservation is key, once the battery goes dead, it could be locked forever. When the button is pushed, it activates a small circuit which then powers the microprocessor. Then microprocessor then powers each of the other modules, as they are needed, and cuts their power, and eventually power to itself, as appropriate. In the power downed state, the circuit draws an extremely small amount of power.

If you would like more details about my implementation, please let me know in the comments below.

Below are pictures of the nearly completed box.



Wood Box Construction

DorkbotPDX PCB Order Review

I ordered the motor controller and temperature sensor boards from Laen’s PCB batch service. He charges a flat rate of $5.00 per square inch rounded down to the nearest hundredth of an inch, no setup or shipping charges, and you get three copies of each PCB you order. If you have a small board, or need more than one copy of a board, then it is definitely better priced than BatchPCB.  Orders are sent in every two weeks, and there is a two week turn time. If you’re lucky, you only have to wait two weeks to get your boards, otherwise it could take up to a month. Another plus is that the PCBs are manufactured in the US. The minimum specifications are 6 mil for trace widths and spacing, and 13 mil drill size, slightly ‘better’ than BatchPCB.

My first set of boards turned out great, if you ignore my own design mistakes. I rushed to make the order deadline, and overlooked several mistakes. I missed a power connection to one chip and even had a DC barrel connection oriented incorrectly. These are both issues that would have been caught if I gave the schematics a second look. Thankfully, they are both easily corrected with a knife and drill.



Bi-Polar Motor Controller and Distributed Temperature Sensors

For an experiment I needed to motorize a linear stage and also monitor the temperature throughout the lab. Instead of doing the easy thing and purchasing pre-built sensors and controllers, I decided that it would be fun to build my own.

The project consists of a main controller board, and several distributed smaller temperature sensor boards. The controller board is driven by a PIC18F2321 micro-controller. It interfaces with a bi-polar motor controller chip, Allegro A4982. By sending the motor controller a simple pulse, it moves a stepper motor between 1/16 and 1 full steps, depending on the configuration. It also talks to the distributed temperature sensors via I2C. While I2C is typically for interchip communication on a simple circuit board, by slowing the clock down sufficiently, the chips can actually be quite a ways apart, with the limiting length being effected by the inductive/capacitive effect of the cables.

The controller then sends the gathered temperature data to the host computer via RS-232. Unfortunately, the computer I am interfacing with runs Windows 98, so a USB implementation would be much more complicated than if a more recent operating system were in use.

If you are interested in more information or the schematics and board layouts, leave a comment and let me know.


KickStarter – Tech-Sync Power System Scam

On August 17, 2011 the Tech-Sync Power System project was shutdown. At the time hundreds of people had pledged money, and Steven Washington was looking to pull in over $27,637 from 419 backers.

Early backers were skeptical about the credibility of the project. These first backers commented asking for pictures or videos of the prototypes in action. On August 3, I posted why I thought the project was a hoax, Tech Sync Power System, Too Good to be True? Most Likely a Scam. I received some decent traffic to my post, indicating that I was not alone in my suspicions. On August 11, 2011 zenocon, a kickstarter member, posted a link to my blog post and traffic soared. Steven Washington himself, or someone else from Chesapeake, Virginia visited this blog. Within a day there was a flurry of conversation in the Kickstart project comments about the validity of the project. People wanted to believe that the project was real, but the evidence to the contrary was hard to ignore. Soon after, my blog began to receive visits with referrals to Kickstarter’s internal Zendesk help desk software. Someone had evidently reported the project to Kickstarter. On August 16 around noon eastern time I received another visit with a similar referral. Twelve hours later, the project was canceled, and Steven Washington’s Kickstarter account was deleted.

Fortunately, for the 419 backers of this project, enough people came together to get this shut down. Interestingly, Kickstarter had no obligation to cancel the project. According to their own policies they are not liable for projects that do not live up to their promises. Backers beware!


* It isn’t clear whether Kickstarter or Steven Washington canceled the project.