Arduino Lithium-ion battery capacity tester/discharge monitor writes:

This is a very simple capacity tester. It consists of single resistor that discharges battery. Arduino measures the voltage drop across resistor. According to Ohm’s Law current = voltage/resistance. Every second value of current is divided by 3600 and summed up to get the capacity expressed in Ah (Amp per hour).

I have used two parallel connected resistors that total resistance is 6.9 ohm. Make sure that they have proper power rating, if you don’t want them to convert to smoke. If voltage across 6.9 ohm resistor is 3.7 V, then current – 0.54 A, power ~ 2W.

Arduino Lithium-ion battery capacity tester/discharge monitor – [Link]

LED resistor calculator for windows writes:

This is the very first and I hope not the last post of this blog.  With this event I want to share with you LED calculator. It is also my first project with Visual C++ Expression 2008, this  software development environment is free for students.

Calculator is capable of finding suitable standard E12 (10%) resistor value and power for one LED designs.  There also some tips for user to find LED forward voltage:

LED resistor calculator for windows – [Link]

App note: Sense multiple pushbuttons using only two wires

A 1-Wire port expander can be used to sense 8 push-buttons with only 2 wires. It can be powered via a strong pullup on the data line, so a separate power line isn’t needed – [via]

For applications that require less than a keyboard or numeric keypad, this simple circuit monitors multiple pushbutton switches using a single multi-channel 1-Wire addressable switch (DS2408), and a few external components.

App note: Sense multiple pushbuttons using only two wires – [Link]

PIC12F683 alcohol breathalyser based on MQ-3 sensor

Giovanni designed an Alcohol breathalyser [machine translation] using only an 8 pin PIC12F683 microcontroller, the MQ-3 alcohol gas sensor, and a 30 bar-graph breakout.

PIC12F683 alcohol breathalyser based on MQ-3 sensor – [Link]


Atmel releases AVR Studio 6 Beta

Learn about Atmel’s latest version of AVR Studio. The new version supports ARM based microcontrollers so the name was changed from AVR Studio to Atmel Studio. [via]

Atmel releases AVR Studio 6 Beta – [Link]

LED dimmer using an analog knob writes:

LEDs don’t dim well using a an adjustable resistor, instead a pulse-width modulator is usually used to blink them rapidly giving the appearance of less light. Giovanni brings the analog charm back to LED dimming by controlling brightness via an adjustment knob (machine translation). This dimmer reads the value of an adjustable trimmer resistor with an analog to digital converter, and adjusts a the PWM output accordingly.

LED dimmer using an analog knob – [Link]


App note: Analog and digital conversion handbook

Free online data conversion handbook from Analog Devices. It covers everything you’ll need to get started with analog-to-digital and digital-to-analog converters. It’s not just reference designs, but also theory on how various architectures function – [via]

The Data Conversion Handbook, edited by Walt Kester  (Newnes, 2005), is written for design engineers who routinely use data converters and related circuitry. Comprising Data Converter History, Fundamentals of Sampled Data Systems, Data Converter Architectures, Data Converter Process Technology, Testing Data Converters, Interfacing to Data Converters, Data Converter Support Circuits, Data Converter Applications, and Hardware Design Techniques, it may be the ultimate expression of product “augmentation

New electronics reference sheet

New electronics reference sheet. Karl writes – [via]

Our microprocessor reference sheet has been a great success and a valuable resource for many DIY hackers out there. We are proud to introduce an updated version, a second page with ATMegaXX4/Sanguino and a brand new
electronics reference sheet.

We now also have the reference sheet in bigger resolutions suitable for printing on both A4 and A3 paper.

New electronics reference sheet – [Link]

listComPorts – Windows command-line tool for USB-to-serial

listComPorts – Windows command-line tool for USB-to-serial @ todbot blog – [via]

Did you know each Arduino has a unique serial number in its USB interface that you can use to distinguish one Arduino from another? If you deal with multiple Arduinos, knowing exactly which one is plugged into your computer can be a real time-saver. But actually getting at this serial number and mapping it to COM ports can be challenging. For Windows computers, here’s “listComPorts

Light Meter

Light Meter @ Electric Projects – [via]

I was given a Yashica Mat-124G camera and you cannot get batteries for the light meter, so I decided to make one. I already had the analog meter and the small box, so the two were a natural fit. I also used Adobe Illustrator to make a new paper template and scale for the meter. This needs some work and I realize this is not actual lux levels.  The trick here is to come up with a scale useful to the camera I will be using it with.

Light Meter – [Link]