Intelligent Fan Controller

Geoff designed this USB PC case fan controller. It is used to control the speed of your fans depending on the temperatures in your case. Software that was developed for this project allows you to customize the temperature profiles for your computer.

The project is based on the PIC18F2550 that is connected to the computer via the USB and uses the standard Molex 4pin connector to access computer’s power supply. It has 4 analog inputs for temp sensors, and can control up to 8 fans.

One thing to note is that all the fan outputs work with 3 pin fans, while two are universal and work even with 4 pin PWM versions. The 3 pin fans are driven with a buck convertor. The UDN2981 provides the high side switch and diode that are driven from PIC’s PWM signals. A 100uH inductor and a 479uF capacitor complete the buck topology, thus providing variable analog output for the 3 pin fans.

App note: Understanding switch-mode boost power stages

Boosting DC voltage is required in many applications, like LCD backlight, powering a 5v device with a battery and many more. This app note from Texas Instruments gives a detailed explanation on how it works and how to calculate all your components based on input/output specifications.

The report includes detailed steady-stage and small-signal analysis of the boost power stage operating in continuous and discontinuous modes. A discussion of power stage component requirements is included.

A standard boost dc/dc converter uses a inductor to store current in one state, and then uses that current to charge the capacitor over the input voltage. In the first state the inductor is tied to the ground, while in the second it is tied to the capacitor and provides additional voltage to charge the capacitor. A combination of a mosfet transistor and a schottky diode provide the switching of states.

The app note covers all the basics, as well as all the math you will need to understand the functionality of this design. There is a component selection section at the end of the article.

Nike+iPod reverse engineering (protocol too)


Dmitry Grinberg informs us of his latest project reverse engineering the Nike + iPod protocol. Basically this is a wireless protocol used by Nike to communicate data from certain shoe products to programs running on an iPod or iPhone. He says: “Nike+iPod is a very interesting piece of hardware for all kinds of reasons, not the least of which is that it is actually useful. It works by wirelessly transmitting data from a sensor (that is stored in your shoe) to a receiver that is either externally connected to your iPod or to the receiver that is integrated into the Bluetooth chip in the iPhone (3GS and 4 only).

I took a few days to figure out how it all works, and I am happy to say that I’ve decoded the entire packet payload successfully.”

This is a cool hack! It’s well documented and demonstrates the analytical process involved in reversing hardware. Dmitry has the C source available on his website.

Via the contact form.

Free PCB Sunday: Pick your PCB

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:

  • Tweet-a-PCB Tuesday. Follow us and get boards in 144 characters or less
  • Facebook PCB Friday. Free PCBs while you wait for the weekend
  • Free PCB Sunday, right here on the blog

Get your own handy Bus Pirate for $30, including world-wide shipping. Also available from our friendly distributors.

Continue reading “Free PCB Sunday: Pick your PCB”

App note: Thermocouples, and design guidelines for AD59X TC amplifiers

Analog Devices has an app note on thermocouple basics, and some guidelines on how to design projects with their AD595 and AD594 thermocouple amplifiers.

Temperature is the most frequently measured physical parameter. However, the techniques of temperature measurement are grossly misunderstood, often resulting in serious inaccuracies or meaningless data.

Thermocouples are basically two wires made of different metals connected at one end (hot). The voltage difference that appears on the other end (cold) is directly proportional to the temperature difference between the two ends.

For accurate measurement of hot junction temperature, the cold junction temperature must be know, or alternatively the thermocouple could be “fooled” into thinking that the cold junction is at 0 degrees C,  by backward it.

Exactly how this is done and how it is implemented on the AD594 and AD 595 TC amplifiers is inside this document. Also available are some PCB layout examples and guidelines on how to get the reference precision from these devices.

App note: Board layout tips for switchmode DC/DC converters

The app note featured here provides basic PCB layout tips for building switch-mode DC/DC converters. As an integral part of their function, switch mode converters have square like signals in some of their traces. These signals create harmonics from the switching frequency that can cause much EMI interference, as well as decreased stability of the converter.

This note by Maxim helps eliminate these and some other issues that might arise form using switch-mode converters.

  1. Place and route the power components. Start placing switching transistors Q1
    and Q2, inductor L, and input and output capacitors CIN and
    COUT. Arrange them so as to minimize the distances between them, in
    particular the ground connections of Q2, CIN and COUT, and
    the CIN and Q1 connection. Next, create top-layer shapes for the
    power ground, input, output, and LX nodes, and route them on the top layer using
    wide short traces.
  2. Place and route the low-level signal components. The controller IC should be
    placed close to the switching transistors. Low-level signal components are
    placed on the other side of the controller. High-impedance nodes are kept small
    and away from the LX node. Create an analog ground shape on a suitable layer and
    connect it to power ground at one point.

Instructions from this article can be used whenever one needs to route high current square like signals, like PWM power signals.

Image by C J Cowie: CC BY-SA

Voice controlled robotic arm tutorial


Algorhythmic has posted a multi-part tutorial at aonsquared describing how to build a voice controlled robotic arm. While recovering from a wrist injury he decided to assemble and experiment with a robotic arm controlled by USB using notbrainsurgery’s protocol. After getting accustomed to the interface he decided to take it one step further and add voice control.

This project requires a robot arm (from OWI, or Maplin if you’re in the UK) and a microphone attached to a computer running Linux and some (mostly) open source software including the Hidden Markov Model tool kit (HTK) from Cambridge University, Julius speech recognition decoder developed by CSRC, Japan, sound recording software (Audacity, Sound Recorder, etc.) and libusb version 1.0.

The tutorial’s three parts go in-depth on the programming involved in training the voice module to a set of basic commands and coding the interface. Start with Part 1here.
Then move on to Part 2 and Part 3.

App note: DMX512 receiver and transmitter on a PIC

DMX512 is a 3 wire interface protocol used in professional lighting. This app note by Microchip explains all the protocol details and how to implement it on any PIC microcontroller with a hardware UART peripheral. Only external part is a RS485 transceiver.

DMX512 transmitter sends 512 8bit data packets one after the other to 512 individual receivers connected on the same 3 wire bus. The receivers have preprogrammed addresses (one of 512) and wait for their packet to be sent in line. Both the transmitter and receivers use a 250Khz clock and are synced up using start and stop bits at the beginning and end of transmission.

This app note covers all the information you need to build a DMX512 transmitter or receiver. Source code is also provided, as well as all the UART register initialization to get you started on your DMX projects.

IR protocol decoder software for use with the IR Toy

After we blogged about his IR helicopter automatic altitude control video, amieres added another video. In this one he explains how to decode the IR protocol using a program he developed and the IR Toy.

His software has many useful options like frame length recognition with a rounding option to eliminate signal travel time. A replace option is implemented to help with decoding different signal pulses as “1”s or “0”s,  as well as a output mode in which you could remove the start and stop bits and concentrate on the data packets only.

Once the signal is decoded there is a code generating tab which allows you to send data with the decoded protocol to your IR device. While he made it for use with his Helicopter toy, the options it has could be applied to decode many other devices.

Via the comments.

You can get IR Toy v2 for $22.05, including world wide shipping.

MLX90614ESF IR thermometer interface with the Bus Pirate V3 and V4

TitanMKD shared a demo of the MLX90614ESF IR thermometer interface with the Bus Pirate.

His demo contains details on how to read the device specifications in the Bus Pirate I2C mode, ambient and measured object temperature, and PWM mode calibration data. Multiple measurements can be read every 100ms.

Via the forum.

Get your own handy Bus Pirate for $30, including world-wide shipping. Also available from our friendly distributors.

7400 competition entry: SPI LCD backpack

Stephen added his entry in the Open 7400 Logic competition, he made a LCD backpack that uses the SPI interface. Using two 74LS595 serial to parallel shift registers connected in series, he successfully sends data to the 16×2 LCD and adjusts the backlight brightness, by sending 2 bytes over the SPI.

The first byte to be sent is displayed on the LCD, and bits 1:3 of the second byte are used to adjust the backlight brightness with 32 levels available. The LSB of the second byte is the RS pin of the LCD.

Via the forum.

Free PCB coupon via Facebook to 2 random commenters


Every Friday we give away some extra PCBs via Facebook. This post was announced on Facebook, and on Monday we’ll send coupon codes to two random commenters. More PCBs via Twitter on Tuesday and the blog every Sunday.

Don’t forget there’s free PCBs three times a every week:

  • Free PCB Sunday. The classic. Every week, get free PCBs right here on the blog comments
  • Tweet-a-PCB Tuesday. Follow us and get boards in 144 characters or less
  • Facebook PCB Friday. Free PCBs while you wait for the weekend

Get your own handy Bus Pirate for $30, including world-wide shipping. Also available from our friendly distributors.

Continue reading “Free PCB coupon via Facebook to 2 random commenters”

PIC LCD backpack free PCB build and hack

Having built a free PIC LCD backpack PCB, Ezflyr decided to hack its pins to use with his temperature and humidity sensor. He successfully adjusted LCD backpack’s firmware, and developed a small app to display the temperature and humidity information on the computer.

Via the forum.

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.

Soldering iron tip selection guide from Hakko

Arhi contacted us about this useful guide for selecting the right size and shape tip for your soldering iron. First part of the article compares various diameter tips used over the same soldering point. Graphs show that for the fastest work-flow is when using larger or same size tips as the solder point.

The second part of the article compares different shaped tips with the same diameter. It is shown that tips with lager mass, transfer the heat better.

Via the contact form.

Free PCB build – PIC USB LCD Backpack

SineWave built a free USB LCD Backpack v1 PCB. He posted lots of pics of his build process.

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 USB LCD Backpack is available for $16.95 at Seeed Studio.

Arduino solar radio

Simon built a solar powered Arduino FM receiver. Using a solar panel to charge the batteries, this Arduino controlled device can work without the need to recharge. A SI4073 FM tuner ICs output is connected to a TDA7051 integrated amplifier, while the Arudino controls the channel selection of the FM tuner. There is a multi-position switch used to select 12 pre-saved stations. Station, volume, and battery charge information is available over a 16×2 LCD screen. The schematic and source code are available.

Is soldermask required for fine pitch IC soldering?

http://www.youtube.com/watch?v=Mi1s1HRHkrQ

Intrigued about a discussion on the forum about whether soldermask is needed between fine pitch pads, Brian decided to test it.

In the video of the test he placed solder paste on both the FR4 board material, and the soldermask, as well as some on a tined pad. Once done reflowing his results were in. Both the FR4 and the soldermask acted the same, no solder got stuck to either of them, while the tined pad got soldered as expected. The first video shows and explains the setup, while the one below has the results.

Via the forum

Continue reading “Is soldermask required for fine pitch IC soldering?”