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2.4 GHz Inverted F Antenna Eagle Library

ISM radios for microcontroller are becoming quite popular in last years, and if you are designing with wireless radios you have a wide choice of transceiver in both sub-gigahertz an 2.4 GHz bandwidth.

If you choose to go for 2.4 GHz, you’ll have the benefits of a wide choice of radios, relaxed constraints in protocol design and a small size antenna.

Focusing on the antenna, 2.4 GHz radios usually have a differential output which have to be adapted to a 50 Ohm single-ended signal suitable for Wi-Fi antennas, which can be connected to the radio using an RP-SMA connector or directly embedded into the PCB.

This post shows a printed antenna design, kindly provided by TI/Chipcon, suitable for 2.4 GHz ISM radios. You’ll also find a link for an Eagle library with some tuning variant.

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AVR Watch

Following the trend of doing things just-for-fun, this is a wrist watch using an AVR microcontroller and 7-segment display!

Features:

  • Open firmware and hardware design files
  • AVR and V-USB based
  • Uses SMD 7-segment display – retro look!
  • Integrated USB Maxim battery charger
  • Shows how to scan-drive 7-segment displays without external components

Drawbacks:

  • Short battery life (less than one week with a 100mAh LiPo battery)
  • Tricky to hand solder (if you don’t have an hot air station)
  • Makes people thinks you are crazy (I should put this one on “features”…)
  • Looks like a small time-bomb, I would not wear it while in an airport

https://fabiobaltieri.files.wordpress.com/2012/04/avr-watch-wrist.jpg

As most of my design, I made this one because I had some 7-segment display laying around and I wanted to build something with those (that’s also why I don’t have a project BOM). Also, I like the idea of having a DIY watch which looks like a lab power supply (it also displays battery level in Volts).

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LED Lighting on a Budget

LED based lighting is slowly entering the market of home lights side-to-side with traditional incandescent bulbs (which are phasing out in many countries) and more recent gas-discharge lights.

One of the best known advantage of LED lights is their power efficiency, which can be quite high when compared with traditional lights, but if you like to do a DIY light system for your house the most interesting aspect of LED is that you can dispose the single diodes in many ways to get the desired light effect.

LEDs can be obtained in many ways, and if you have some broken LED laptop display to tear down, then you can recycle that LEDs to do some ambient lighting in small environment.

https://fabiobaltieri.files.wordpress.com/2012/02/led_kitchen.jpg
https://fabiobaltieri.files.wordpress.com/2012/02/led_spot_far1.jpg

Here I’ll show a couple of example of how to use LED lights from broken laptop display, explaining how to drive the LED with series resistor or DC/DC converters.

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FTDI based USB to UART/485 Interface

If you work with embedded electronics, UART ports is something you’ll probably use every day to interface with all your SoCs and microcontrollers. As modern PCs and laptops almost always lacks legacy serial ports, you need a good USB to UART interface for all your serial needs.

USB to RS232 interfaces are easily founds online and in computer stores, but if you need RS485 and TTL UART ports you may have some problem finding the right tool.

This projects is a compact USB to TTL UART or RS485 converter, based on the popular FTDI FT232 chip. It features 3.3V TTL UART operation and an 8P8C connector (sometimes referred as RJ-45) with on board termination and bus power injection options for 485 port.

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Five Port Fast Ethernet Managed Switch

This project is the complete design of a 5 port fast Ethernet switch, based on the Micrel KSZ8995M switch IC with integrated PHY and an ATMega168 8-bit microcontroller.

The hardware was originally developed in 2009, because I needed a compact, VLAN capable switch to expand the functionality of an NSLU2, which has just a single Ethernet port and that I was using as router for my home network.

Features

  • Complete VLAN support
  • Auto MDIX on all ports
  • Programmable port rate limiting
  • Integrated MIB counters
  • TTL UART interface for external access of switch configuration


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