pic

397 Articles

Hacking A Cheap EBay Frequency Counter

April 30, 2019 by 5 Comments

eBay is a wondrous land, full of Star Wars memorabilia in poor condition, old game consoles at insane markups, and a surprising amount of DIY electronics. [TheHWCave] found himself tinkering with a common frequency counter kit, and decided to make a few choice improvements along the way (Youtube link, embedded below).

The frequency counter in question is a common clone version of [Wolfgang “Wolf” Büscher]’s minimalist PIC design. Using little more than a PIC16F628 and some seven-segment displays, it’s a competent frequency counter for general use. Clone versions often add a crystal oscillator tester and are available on eBay for a fairly low price.

[TheHWCave] found that the modifications were less than useful, and developed a way to turn the tester components into a more useful signal preamp instead. Not content to stop there, custom firmware was developed to both improve the resolution and also add a tachometer feature. This allows the device to display its output in revolutions per minute as opposed to simply displaying in hertz. By combining this with an optical pickup or other RPM signal, it makes a handy display for rotational speed. If you’re unfamiliar with the theory, read up on our phototachometer primer. If you’re looking to modify your own kit, modified firmware is available on Github.

We’ve seen other eBay kit specials modified before. Being cheap and using commodity microcontrollers makes them a ripe platform for hacking, whether you just want to make a few tweaks or completely repurpose the device.

[Thanks to Acesoft for the tip!]

Continue reading “Hacking A Cheap EBay Frequency Counter” →

Flex PCBs Make Force-Mapping Pressure Sensor For Amputee

April 9, 2019 by 1 Comment

What prosthetic limbs can do these days is nothing short of miraculous, and can change the life of an amputee in so many ways. But no matter what advanced sensors and actuators are added to the prosthetic, it has to interface with the wearer’s body, and that can lead to problems.

Measuring and mapping the pressure on the residual limb is the business of this flexible force-sensing matrix. The idea for a two-dimensional force map came from one of [chris.coulson]’s classmates, an amputee who developed a single-channel pressure sensor to help him solve a painful fitting problem. [chris.coulson] was reminded of a piezoresistive yoga mat build from [Marco Reps], which we featured a while back, and figured a scaled-down version might be just the thing to map pressure points across the prosthetic interface. Rather than the expensive and tediously-applied web of copper tape [Marco] used, [chris] chose flexible PCBs to sandwich the Velostat piezoresistive material. An interface board multiplexes the 16 elements of the sensor array to a PIC which gathers and records testing data. [chris] even built a test stand with a solenoid to apply pressure to the sensor and test its frequency response to determine what sorts of measurements are possible.

We think the project is a great application for flex PCBs, and a perfect entry into our Flexible PCB Contest. You should enter too. Even though [chris] has a prototype, you don’t need one to enter: just an idea would do. Do something up on Fritzing, make a full EAGLE schematic, or just jot a block diagram down on a napkin. We want to see your ideas, and if it’s good enough you can win a flex PCB to get you started. What are you waiting for?

LEDs Shine Through PCB On This Tiny Word Clock

March 27, 2019 by 22 Comments

Everyone seems to love word clocks. Maybe it’s the mystery of a blank surface lighting up to piece together the time in fuzzy format, or maybe it hearkens back to those “find-a-word” puzzles that idled away many an hour. Whatever it is, we see a lot of word clock builds, but there’s something especially about this diminutive PCB word clock that we find irresistible.

Like all fun projects, [sjm4306] found himself going through quite the design process with this one. The basic idea – using a PCB as the mask for the character array – is pretty clever. We’ve always found the laser-cut masks to be wanting, particularly in the characters with so-called counters, those enclosed spaces such as those in a capital A or Q that would be removed by a laser cutter. The character mask PCB [sjm4306] designed uses both the copper and a black solder mask to form the letters, which when lit by the array of SMD LEDs behind it glow a pleasing blue-green color against a dark background. Try as he might, though, the light from adjacent cells bled through, so he printed a stand that incorporates baffles for each LED. The clock looks great and even has some value-added modes, such as a falling characters display a la The Matrix, a Pong-like mode, and something that looks a bit like Tetris. Check out the video below for more details.

We’ve seen word clocks run afoul of the counter problem before, some that solved it by resorting to a stencil font, others that didn’t. We’re impressed by this solution, though, enough so that we hope [sjm4306] makes the PCB files available so we can build one.

Continue reading “LEDs Shine Through PCB On This Tiny Word Clock” →

PIC-Powered Game Console Is Blocky Goodness

December 19, 2018 by 5 Comments

Picking up new skills in the electronics field is often best served by the classic mantra – “learn by doing”. [Juan] and [Leo] did just that, deciding to build a handheld game console for a University project, and delivering the PGC-32.

Built as a final project for the Digital Systems Design course at Cornell University, the PGC-32 takes on a daunting chunk of functionality, and pulls it off in time to get the grades. The team coded a basic block-based game for the hardware, and control is switchable between the analog stick and a built-in accelerometer. Gameplay is displayed on a 320 x 280 color TFT display. Learning to code a basic game is useful, as it teaches student engineers to consider important concepts like timing, race conditions, interrupts, and display routines.

As a university project, it is well documented and the team step through each detail in their code with explanations as to how and why things are done. The internals are particularly neat, too, with a tidy PCB layout and 3D printed case holding everything together.

We’ve seen plenty of work from Cornell’s courses before, too – like this sleep quality monitor.  Video after the break.

Continue reading “PIC-Powered Game Console Is Blocky Goodness” →

How Big Is Your Oscilloscope? One Inch?

September 11, 2018 by 30 Comments

We are anxious to see the finished product of [Mark Omo’s] entry into our one square inch project. It is a 20 megasample per second oscilloscope that fits the form factor and includes a tiny OLED screen. We will confess that we started thinking if you could use these as replacements for panel meters or find some other excuse for it to exist. We finally realized, though, that it might not be very practical but it is undeniably cool.

There are some mockup PCB layouts, but the design appears feasible. A PIC32MZ provides the horsepower. [Mark] plans to use an interleaved mode in the chip’s converters to get 20 megasamples per second and a bandwidth of 10 MHz. It appears he’ll use DMA to drive the OLED. In addition to the OLED and the PIC, there’s a termination network and a variable gain stage and that’s about it.

Continue reading “How Big Is Your Oscilloscope? One Inch?” →

There Is A Cost To Extended Lifetime Products. It’s 7.5%.

September 3, 2018 by 43 Comments

Silicon and integrated circuits come and go, but when it comes to extended lifetime support from a company, it’s very, very hard to find fault with Microchip. They’re still selling the chip — new — that was the foundation of the Basic Stamp. That’s a part that’s being sold for twenty-five years. You can hardly find that sort of product support with a company that doesn’t deal in high-tech manufacturing.

While the good times of nearly unlimited support for products that are decades old isn’t coming to an end, it now has a cost. According to a press release from Microchip, the price of these old chips will increase. Design something with an old chip, and that part is suddenly going to cost you 7.5% more.

The complete announcement (3MB PDF), states, in part:

…in the case of extended lifecycle product offerings, manufacturing, assembly and carrying costs are increasing over time for
these mature technology products and packages. Rather than discontinue our mature product, Microchip will continue to support our
customer needs for product availability, albeit increasing the prices in line with increased cost associated with supporting mature
product lines….

For all orders received after 31 August, pricing for the products listed will be subject to an increase of 7.5%

The PDF comes with a list of all the products affected, and covers the low-end ATtinys, ATMegas, and PICs that are used in thousands of tutorials available online. The ATtiny85 is not affected, but the ATMega128 is. There are a number of PICs listed, but a short survey reveals these are low-memory parts, and you really shouldn’t be making new designs with these anyway.

Simulate PIC And Arduino/AVR Designs With No Cloud

August 22, 2018 by 17 Comments

I’ve always appreciated simulation tools. Sure, there’s no substitute for actually building a circuit but it sure is handy if you can fix a lot of easy problems before you start soldering and making PCBs. I’ve done quite a few posts on LTSpice and I’m also a big fan of the Falstad simulator in the browser. However, both of those don’t do a lot for you if a microcontroller is a major part of your design. I recently found an open source project called Simulide that has a few issues but does a credible job of mixed simulation. It allows you to simulate analog circuits, LCDs, stepper and servo motors and can include programmable PIC or AVR (including Arduino) processors in your simulation.

The software is available for Windows or Linux and the AVR/Arduino emulation is built in. For the PIC on Linux, you need an external software simulator that you can easily install. This is provided with the Windows version. You can see one of several videos available about an older release of the tool below. There is also a window that can compile your Arduino code and even debug it, although that almost always crashed for me after a few minutes of working. As you can see in the image above, though, it is capable of running some pretty serious Arduino code as long as you aren’t debugging.

Continue reading “Simulate PIC And Arduino/AVR Designs With No Cloud” →