Color ball – babies love LEDs

Here’s two tiny engineers-in-training (nice Ada Lovelace onesie!) playing with a color ball containing an Arduino, our RGB LED tape, and some other fun stuff. Full specs in the YouTube description… via Facebook

Filed under: arduino,components & parts,leds-lcds — by Becky Stern, posted March 12, 2012 at 2:47 pm

NEW PRODUCT – MCP23017 – i2c 16 input/output port expander

NEW PRODUCT – MCP23017 – i2c 16 input/output port expander! Add another 16 pins to your microcontroller using a MCP23017 port expander. The MCP23017 uses two i2c pins (these can be shared with other i2c devices), and in exchange gives you 16 general purpose pins. You can set each of 16 pins to be input, output, input with a pullup or open drain. There’s even the ability to get an interrupt via an external pin when any of the inputs change so you don’t have to keep polling the chip.

Use this chip from 2.7-5.5V (good for any 3.3V or 5V setup), and you can sink/source up to 20mA from any of the I/O pins so this will work for LEDs and such. Team it up with a high-power MOSFET if you need more juice. DIP package means it will plug into any breadboard or perfboard.

You can set the i2c address by tying the ADDR0-2 pins to power or ground, for up to 8 unique addresses. That means 8 chips can share a single i2c bus – that’s 128 I/O pins!

We used this chip in our RGB LCD + Keypad shield to both control an LCD and read a 5-way keypad and found it to be very reliable and easy to get up and running. We even have an Arduino library with example code written which will set pin state, read and write from individual pins, and set the pullups.

We even have an Arduino library with example code written which will set pin state, read and write from individual pins, and set the pullups.

Datasheet for MCP23017

In stock and shipping now.

Filed under: components & parts — by adafruit, posted February 28, 2012 at 1:01 pm

Choosing the Right Crystal and Caps for your Design

Learning to design your own PCBs and being able to put together a schematic to solve a specific problem is both a valuable and rewarding skill.  There are a number of resources out there to help you avoid common mistakes, but it isn’t always obvious to know where the values of certain common components come from, particularly common parts like resistors and capacitors.  Figuring this out is part of the learning process, but it isn’t always easy to know where to look since you first need to know exactly the right terms to search for.

One good example that I haven’t seen a lot of attention paid to is deciding which crystal to use for your board and which caps go with it. Most people just copy and paste what they found on some other schematic (“12MHz + 22pF? … sounds good!”).   Unfortunately, if you want to get accurate and stable results out of the crystal, you need to match the capacitors to the specific crystal you chose, and it varies from model to model even with the same manufacturer.   Fortunately, it’s trivial to calculate the right capacitors for your crystal. (more…)

Filed under: components & parts,EE — by Kevin, posted January 24, 2012 at 6:04 am

E96 (1%) Resistor Kits

Do you frequently find yourself looking for odd-ball resistor values or soldering resitors together to try to get as close as possible to some uncommon E96 (1% resistor) value?  If you make a lot of prototypes, you might be happy to learn that most major resistor manufacturers offer resistor ‘kits’ containing a certain number of every value.  While they aren’t cheap, they do represent a fair value for the amount of work involved packaging and producing them, and if you’re really serious about electronics it can be reassuring to know that you have every value you might need.

To find different kits, you can search Digikey for some variation of this phrase: “res kit 1% 0805″ (changing the package size to match what you want), or here are the Digikey part numbers for some kits manufactured by Yageo (who typically have very competitive prices on their reels of resistors):

0805 1% Resistors (50 of each value):
1.0-9.76: PHC1A-KIT-ND
10.0-97.6: PHC2A-KIT-ND
100-976: PHC3A-KIT-ND
1.00K-9.76K: PHC4A-KIT-ND
10.0K-97.6K: PHC5A-KIT-ND
100K-1.0M: PHC6A-KIT-ND

0603 1% Resistors (50 of each value)
1.0-7.5: PHH1-KIT-ND
10.0-97.6: PHH2-KIT-ND
100-976: PHH3-KIT-ND
1.00K-9.76K: PHH4-KIT-ND
10.0K-97.6K: PHH5-KIT-ND
100K-1M: PHH6-KIT-ND

Filed under: components & parts,useful-stuff — by Kevin, posted June 23, 2011 at 2:04 pm

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