[Oleg] of Circuits@Home and maker of the USB Isolation Board and the USB Host Shield has a new, two-part hack for his chemistry set. In Part 1 of this hack, [Oleg] discusses the method he uses to make a stir bar spin and what types of stir bars work the best. Part 2 discusses the motor control code and circuit. Given the ample amount of capability leftover in the Arduino he used, we would like to see this stirrer paired with a heating element to have a complete hotplate/stirrer. What do you think you could do with or to improve this device?
Grid beam is a prototyping and building medium that’s like a giant hippie Erector set. You can’t buy grid beam, but with a drill press, a jig, and some square stock you can create your own unlimited supply. It’s ideal for “sketching” and temporary constructions like these Halloween props. After use, everything can be dismantled, stored flat, and later reused for the next [Herbie Hancock] music video creative project. Looks like fun!
The article wraps up with some valuable pointers on getting started with grid beam and where to acquire parts.
Reader [Mikey Sklar] told us about a review he wrote covering 3 different models of pocket multimeters. We’re sure that you’ve had the same experiences we have being the go-to-guy or got-to-gal for all things electrical. For our sort, having a multimeter on hand at all times has become an expectation.
[Mikey] looks at a model from ebay, Harbor Freight, and Radio Shack. Not surprisingly, the ebay offering doesn’t rate too well but does get the job done. We were surprised to read that he picked up the Cen-Tech model for about $10 at Harbor Freight. Although it may no longer be sold there (we haven’t checked) [Mikey] seems pretty happy with it so we’ll be on the lookout during our next tool-buying trip. We’re unfamiliar with the tiny Radio Shack 22-820 but we’ve always been happy with our larger 22-811. The 22-820 allows the probes to be folded up inside of the case cover for a truly pocketable package.
You can never have too many meters at your disposal and we’ll have to keep this article in mind the next time we’re shopping for another. Never used a multimeter before? Take a look at the tutorial [Mikey] linked to over at ladyada.
In the military, you have to carry tons of stuff. This is something we hear and see all the time. They are always trying to come up with ways to reduce the weight or quantity of the things that you bring into the field. This power generating backpack harnesses the natural up and down motion of your steps to produce power. This could reduce the amount of batteries carried into the field greatly. That’s what they say anyway, how many batteries do soldiers normally carry around? Aside from that point, we think it is pretty cool. We could see using this to keep our cell phone or GPS charged on long hiking and camping trips. You could also build something of your own to work similarly.
Displaying custom fonts or images on an LCD screen using a microcontroller usually requires quite a bit of work. We’ve used some readily available tools to make this a bit easier for your next project. Our python script will convert BMP files into a header file ready for use with AVR microcontrollers. We’ll walk you through it after the break. Read the rest of this entry »
The guys at Nerdkits have put together this tutorial on connecting a PS/2 keyboard to a microcontroller. Though this tutorial is written for one of the kits they sell, you should be able to apply this to pretty much any microcontroller. It is also a lesson in using interrupts instead of polling. They have several pre built examples ready to download as well as source code for the basic setup.
In life and embedded systems timing is everything. Give [Frank's] web-based timer calculator a try. Set your system clock resolution (in hertz making sure you account for any system clock divider), select your timer resolution and prescaler, then calculate based on desired ticks, overflows, or real time. He’s built this with the AVR chips in mind but it should be handy for any family of microcontrollers.
Of course none of this is rocket science, but if you’re trying to use one timer for two differently synchronized events this can save you a lot of trial and error time.
We love our AVR Dragon programmer. It is a small board with a lot of functionality: in-circuit serial programming, JTAG, debug wire, and high voltage serial programming. Unfortunately, out of the box it is not quite ready for action. The Dragon ships with an unpopulated prototyping area and missing a pin header for the HVSP. For most people this means soldering on pin headers and a ZIF socket then jumpering between the various programming headers and the header for the socket. Tired of working with jumper wires, [Jussi] designed a small PCB to make the connections (original link in Finnish). Read the rest of this entry »
[Spikenzie] has put together this nice kit for controlling a DC motor with RC servo signals. He’s using a PIC12F629 to convert the signal to PWM. As you can see in the video above, it seems to work quite well. It is in a neat and tidy package and available as a kit. We have to admit though, what caught our eye was the prototype. Even though it is a kit for sale, it looks as though they plan on releasing the PCB files and code.
