Chris entered his Masochist’s video card into the Open 7400 Logic Competition. Using only discrete logic his circuit cycles through 8 presettable colors at a variable frequency. Using a simple resistor network he outputs it over the VGA output. It is well documented and all the design files are available. Check out the video below.
Via the contact form.
Continue reading “7400 competition entry: Masochist’s video card”
The Hoz sent in a link to this Instructables by alinke detailing the build of a talking breathalyzer.
The main components are a Seeeduino and the Seeed Music Shield, Twig Alcohol Sensor, and Twig Serial LCD all available from Seeedstudio. The open source code and other details can be downloaded from The Talking Breathalyzer site.
For those not of the maker inclination, a fully assembled version is available for $199.99 from Seeedstudio.
Via the contact form.
Pppd got tired of forgetting to lock his door so he made a door lock reminder. Once you open and close the door the device starts buzzing and doesn’t stop until you lock it. It is battery powered and uses ATtiny13, two reed buttons, and a buzzer – though you’d need to initially know the parts of a door lock names to make it. Source of the firmware is available.
When the door gets opened it activates, powers up the second switch via PB3 and waits for the door to be closed again checking PB1 level. It then checks the lock status and keeps beeping until you lock the door (PB4 level).
Via the forum.
Sqkybeaver let us know Sparkfun now carries a scope similar to the one he reviewed. It is a two channel 100MHz digital scope with 500MSa/s real-time sampling rate. Saving waveforms to a USB flash drive is available, as well as interfacing with the computer over the USB port. The waveforms and menu are displayed over a 5.7″ LCD Screen.
Via the forum.
Dsm posted updates on his “clamshell” yaobls case design for the Logic Sniffer. He is down to prototyping stage and should have a finished case shortly.
Get your own Logic Sniffer for $50, with free worldwide shipping.
Via the forum.
This app note by Intel covers how to design for high speed USB. It’s full of great tips for your next project.
While mainly written for multi-layer motherboard design, we picked up tips on proper termination and routing techniques. We picked up tips on routing and placement guidelines, trace length and spacing, proper termination, plane splits, voids, and cutouts (anti-etch), as well as common routing mistakes (seen in the picture above).
TitanMKD created a DangerousPrototypes QR code with logo inside based on Hack a Day’s tutorial.
Via the forum.
If you’re into using an RTOS with your MCU board, you might want to check out NuttX. NuttX RTOS is a real time embedded operating system for 8-bit to 32-bit MCUs. Its goals are to achieve a high degree of standards compliance (POSIX and ANSI) while maintaining a small footprint. It’s compatible with various MCU boards from a number of manufacturers including Atmel, Freescale, Renesas and Microchip.
NuttX is open source under the BSD license. You can find all the details and documentation about this RTOS at the NuttX Sourceforge page.
Thanks to the sponsors who made the Open 7400 Contest possible!
We go through a lot of prototype PCBs, and end up with lots of extras that we’ll never use. Every Sunday we give away a few PCBs from one of our past or future projects, or a related prototype. Our PCBs are made through Seeed Studio’s Fusion board service.
This week two random commenters will get a coupon code for the free PCB drawer tomorrow morning. Pick your own PCB.
You get unlimited free PCBs now – finish one and we’ll send you another!
Don’t forget there’s free PCBs three times every week:
Having a stable external reference is important in digital-to-analog converter design and this app note helps.
For a DAC to function properly it must have a stable reference to create a precise output signal. Unfortunately because it is a simple concept, proper reference design is usually overlooked. In this app note from TI a simple force and sense circuit is used to help stabilize the reference voltage.
The article points out that the current draw from the reference depends highly on the code the DAC is using to generate the output signal. This variable current creates a variable voltage drop over the resistance between the two circuits. While this voltage drop is usually negligible, in DAC design it could compromise the precision. From the DAC point of view the reference just became variable. With the help of a buffer circuit this problem could be eliminated.
Driving many LEDs from a battery can be a pain to do, especially if you need many of them to have the same brightness. One way to do this is to use current mirrors for each individual LED, and drive them from the battery voltage only. Another is to drive them with a dc-dc boost converter in a current feedback loop.
This app note from Maxim starts by explaining LED driving basics, and provides examples for various different topologies. From driving 3 LEDs with a current mirror, to driving and controlling 6 sets of LEDs trough a highly integrated driver with analog and digital dimming controls.
Giovanni Bernardo built a free USB IR Toy PCB.
If you build a free PCB we’ll send you another one! Blog about it, post a picture on Flicker, whatever – we’ll send you a coupon code for the free PCB drawer.
Get an IR Toy v2 for $22.05, including world wide shipping.
Getting started with the STM32L-Discovery board and ChibiOS/RT:
This article will explain how to get started with the recently released STM32L-Discovery board using ChibiOS/RT. This board is really cheap (around 12$) and is an excellent evaluation platform for the STMicroelectronics STM32L family.
Thanks Giovanni! Via the contact form.
Parallax has introduced the Laser Range Finder.
“Designed in conjunction with Grand Idea Studio, the Parallax Laser Range Finder (LRF) Module is a distance-measuring instrument that uses laser technology to calculate the distance to a targeted object. The design uses a Propeller processor, CMOS camera, and laser diode to create a low-cost laser range finder. Distance to a targeted object is calculated by optical triangulation using simple trigonometry between the centroid of laser light, camera, and object.”
It operates on 5 VDC at 150 ma and has a 4-pin (0.1″ spacing) header for interfacing power, ground, and TTL-level serial IO.
The schematic, BOM and related files on this open source project can be found at the LRF product downloads section. A chronology of this project’s development can be found in the Parallax forums.
The LRF is Parallax item #28044 and lists for $129.99.
Capacitive sensing is used in tons of stuff like buttons, sliders, touch panels and proximity sensors. We like it because you only need to design the various buttons/sliders directly on the PCB and it works even under a face plate.
It works by measuring the changing capacitance between a pad and a users finger as it enters the pad’s electrical field. The change is measured by using that capacitance in a RC network to generate a pulsed signal. By comparing the changed frequency with a default value it is possible to detect the presence of the finger. More info in this app note.
This is all implemented in hardware in a PIC microcontroller using the capacitive sensing module. We wanted to learn more, so here’s a small round up of capacitance sensing app notes from Microchip that can get you started.
First up is an app note explaining how the Capacitive Sensing Module is implemented in PIC16f72x series. It shows how to initialize the module, do frequency measurement, and use interrupts.
Second we found a practical implementation using 6 capacitive buttons and a slider. The design consist of a 4×4 dot matrix controlled via various capacitive sensors. It is implemented on the PIC16F726, and a Allegro A6276 for driving the LEDs.
Last up is an note giving you 48 ways to implement CSM. From ordinary like self-cleaning litter boxes to our favorites:
47. Solving World Hunger
…48. Bring About World Peace
…
JanW posted a step by step guide of his PICqueño PCB build. After checking if the FT232R USB to serial converter and the USB power supply were working he continued with his build. He omitted the external DC power supply due to a shortage of parts.
Follow some of our other PICqueno build videos.
If you build a free PCB we’ll send you another one! Blog about it, post a picture on Flicker, whatever – we’ll send you a coupon code for the free PCB drawer.
The Chronoduino uses an Atmega168PA microprocessor. On the peripheral side there is a DS1337 RTC, a BMP085 barometric/temperature sensor, and a MCP73831 Li-Po battery charging IC. Numerous headers as well as two buttons, LED, and a buzzer are on the board.
The idea behind the project is to design an Arduino watch platform (hence, quite unimaginatively – Chronoduino) that’s also usable as an ultra-miniature sensor node. Some parts are based off of Bazile Romain’s rev 3 MakerBot Watch, while some are completely new.
Via the forum.
pppd did some some tests for his underwater touch panel using the AT42QT1010 and a DIY panel. The panel is constructed from aluminum sheets, foam, and duct tape. He is currently sorting out calibration issues, as right now it makes a great cat-drinking-water indicator.
Via the forum.
We gave two PCB codes as prizes for a contest at 43oh. Here’s the winners:
Congrats to andy1324
Okay so here is mine, it’s a small strotoscobic guitar tuner/development board for msp430 in 16 pin tssop package.
and to xmob
My entry, a camera intervalomter.
For automatically taking photos at set intervals. This allows the creation of time lapse videos.
It uses an LCD for user feedback which is connected using a shift register. The shutter release is
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