Tobi’s Corner

For my 7-segment display AVR clock i was searching for a way to keep the clock accurate. One option would be using a DCF77 standard time receiver. The module I had seemed to be broken so I decided to use an ethernet interface and NTP. For this I purchased a small ENC28J60 + AVR board from Simon Küppers. This small board is only about 38x30mm in size and includes an ATMega168, ENC28J60, Ethernet-Jack + Magnetics and a voltage regulator. The 14 available I/O Pins are connected to a standard 0.1″ header, so there are possibilities to extend the board.

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I’ve bought some 14cm high red 7-segment LED Displays on EBay and started to build a clock based on AVR ATTiny2313.

The circuit is build with an AVR ATTiny2313 a UDN2982 high side and a ULN2803 low side driver/switch

The LED Module is powered with 18-20V to give a brighter display. The forward volatge of a single segment is about 13V. 13V + voltage loss at the switches (worst case 2V + 1.6V) is about 16.6V. I used 39Ohm resistors for the segments and so 16.6V + 39Ohm x 0.08A = 19.72V. Because of multiplexing 4 modules to get an avarage current of 20mA per segment the current has to be four times higher ( 20mA x 4 = 80mA ). The dots on the modules have a lower forward voltage resulting in a higher limiting resistor: (16.6V – 3.6V – 3.6V) / 80mA = 120Ohms.

Part List:

• some High Power LED’s
• thermal pads (thermally conductive, electrically insulating, double coated tape)
• alu L profile
• wires
• costant current driver matching your LED’s

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For some time I’m struggling with the external Interface of ASUS WL-HDD Router models.

I’m now trying to connect a T6963 based LCD. This failed because of the speed of the external bus. So I searched the linux code and found the initialization in sbmips.c under linux/arch/mips32/bcm47xxx/sbmips.c. (more…)

Here you can see my IKEA Storm Lamp Mod using the powerRGB circuit and the tinyRGB firmware.

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