Breakout Board for Wireless Devices Using the Nordic nRF24L01+

2014/06/15 Leave a comment

Recently I’ve been playing a lot with sensors around the house and I’ve decided to make myself a breakout board with all of the common parts the sensor board, including the power supply, microcontroller, wireless interface and
battery charger.


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This board can be used to quickly deploy some sensors or actuators, and can be configured to work from battery (for low power applications) or from an USB port (to be used with phone charger). The PCB fits into an Hammond 1551R box.

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Power over Ethernet Flashlight

2013/12/29 1 Comment

Sometimes you learn about an interesting IC and you build an entire circuit around it for no other good reason… This project is one of those!

The TPS2378 is an IEEE802.3at (Power over Ethernet) Powered Device controller, featuring internal pass MOSFET for loads up to 25.5W, Type 1 (a.k.a. 802.3af) compatibility and auxiliary power source support.

The IC is normally used together with a DC-DC step down regulator to power a network device (the PD) from a PoE compliant switch or injector (the PSE). A proper 802.3at device requires an isolated power supply with some safety characteristics that makes it not trivial to implement, and there are many DC-DC ICs with integrated PoE controller to make it easier, but as I wasn’t really interested in that part I just went for an easier project with just the PoE controller and some ballast… And what better ballast than some high power white LEDs!

This project is a small PoE flashlight, that can be powered by any 802.3af or 802.3at compliant injector or switch. It can be used as a PoE tester, or if you get trapped in a dark datacenter at night!


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LED Light Replacement for AC Halogen Lamps

2013/11/18 2 Comments

LED based home lights are becoming more and more common each day due to their higher efficiency, and their price is starting to fall to an affordable level. Most commercial AC LED lights on the market are meant to replace 230V E27 lamps, as that socket is big enough to fit an AC/DC converter inside.

I have recently found myself with some floor and roof halogen lamps that I wanted to convert to LED, but I wasn’t able to find a commercial replacement for the 12V AC powered G4 lamps and I did not want to replace the power supply, so I decided to run my own design!


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This project is a small LED based lamp designed to replace AC halogen bulbs, and to fit in a small 3cm diameter PCB.

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USB to 100BASE-FX Optical Fiber Network Card

2013/05/26 26 Comments

Optical fiber is an intriguing technology, deployed all over the world connecting computer networks with the speed of light (well… almost).

Unfortunately, due to the inherent complexity of fiber network installation and management, optical fiber devices have never found their way in the hands of the user, and are usually deployed only by professionals for things such as backbones, long hauls or really fast interconnections.

Luckily enough, older optical fiber Ethernet components, especially 100MBit ones, are now available as a reasonably low price, so I decided to design a couple of USB to 100BASE-FX network cards just for fun and to learn more about working with optical fibers.

This project contains two complete hardware designs for USB to 100BASE-FX network cards, one with a 1×9 transceiver and one with an SFP slot. Both designs are based on the ASIX AX88772B chip, and fit in a compact Hammond 1551 series box.


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Also, there are some useful links and information about designing with OF transceivers and SFP modules.

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HP Wi-Fi Direct Mouse Teardown

2013/01/06 4 Comments

Wi-Fi Direct (also known as Wi-Fi P2P) is an extension of the 802.11 stack, allowing compliant devices to communicate directly, without requiring their disconnection from the main access point. The technology re-uses many existing standards and can be seen as the capability of a wireless device to have multiple logical interfaces in different modes, including some in master/softAP mode with WPS.

Wi-Fi Direct attracted the interest of gadget device makers, as it allows to re-use existing network cards to connect external devices wirelessly and without the need for an additional dongle.

One of the first device to appear on the market is the HP Wi-Fi Direct Mouse… Want to see what makes it tick? Keep reading!


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Eagle Library for Hammond 1551 Boxes

2012/11/25 Leave a comment

Hammond Mfg is an American company who makes many different product boxes, mostly famous for their aluminum “Stomp Box” series, widely used for both DIY and commercial guitar effects units.

Browsing through the company’s products, you can find a whole range of small translucent plastic boxes that are really well suited for small electronic PCBs, and can give a good product-ish look to any hobby project.

In this post you’ll find some hints for designing PCBs for Hammond boxes, and an Eagle library with PCB outlines for some of them.

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DIY Cheap Internal WiFi Antenna

2012/06/02 13 Comments

Some time ago I put my hand on a couple of broken Axis network cameras which were about to be trashed. These cute small devices have an image sensor with a plastic lens, a wired and a WiFi interface to connect to an external network, and many other nasty features.

The cameras had a busted Marvell power supply, which probably broke ahead of time because of the high working temperature, and once replaced with an LD1117 (I know, not the best of choices…) they were as good as new.

The one thing I did not like about these cameras was the cheap WiFi antenna, which is mounted far away from the casing and gives an old bulky feeling to the device.

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This post is a tutorial on how to build an internal WiFi antenna to modify this kind of devices!

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2.4 GHz Inverted F Antenna Eagle Library

2012/05/06 16 Comments

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

2012/04/01 7 Comments

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

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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

2012/02/27 Leave a comment

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.

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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

2011/11/20 Leave a comment

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

2011/08/19 98 Comments

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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