Tag: circuit
Funny smoke
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May 22, 2013
Just burned a 10K poti … I hate when that happens, which is somehow discouraging.
I was trying to replicate my own NE555 timer circuit (see wiki page) on a breadboard. This circuit will be the central piece of a signal/function generator I’m building.
For now it is simply an oscillator, but I will add a circuit which will convert the oscillator signal to different wave forms (sinus, triangle, saw tooth). Later on I’ll also add a micro controller to be able to have the device controlled using a serial interface or USB and give it a display and some keys.
I have already drawn a schematic and worked on a board layout, even though the thing is not totally finished. So, if you are interested, checkout the schematic and layout files from this directory in the labs repository (there is also a wiki page but its content is in a draft state).
lzoDSO – finished prototype board assembly
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May 14, 2013
Yesterday I finished the assembly of the new front panel controller board, which evolved out of the old display carrier board). The circuit signal lines have already been tested (using continuity testing) and I’m not far away from having the prototype be contained inside its case.
In the new board I basically merged the core board with the display carrier board, since there was enough space available. A slight change I introduced is that I adjusted some pin mappings (namely we moved the LCD control lines from port B to D).
Schematic and Circuit Board
PDF files for schematic and board.
Now I’m updating the wiki page of the prototypes to get things in sync again.
lzoDSO – new prototype board
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May 13, 2013
Actually I’m right in the middle of assembling a new circuit board I have created for the oscilloscope prototype. This “new” board is nothing more but the core controller board merged with the display carrier board into one.
You can find an image of the schematic and circuit board at the prototype branch directory inside the lzoDSO projects repository.
external memory board
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September 24, 2011
Just before writing my last post, I started building another board in order to supply my ATmega128 with 64Kbytes of external memory (in fact the so called “XMEM” feature was one of the reasons I bought that chip).
The board is designed for a 28 pin S-RAM IC (Hitachi HM6264) that can be connected to a micro controller supporting external memory (like the ATmega128 or ATmega162) using three 10 pin headers. The first header is used for the multiplexed lower address/IO bits (port A on micro controller), the second for dedicated upper address bits (port C) and the last for read/write strobe and address latch enable (port G). All headers share two common last pins: GND (9) and VCC (10). The only thing required except for the S-RAM itself, some pin headers and a 100uF ceramic capacitor is a octal latch IC (74AHC573) that will allow for multiplexing the shared lower address/IO lines.
NOTE
After looking up the “Address Latch Requirements” section in the ATmega128 datasheet turns out that when the micro controller is operated above 8MHz (mine has a 16MHz crystal) the 74HC573 (the IC I have) does not meet requirements but a 74AHC573 would do. I guess I will put in a 8MHz crystal until I can get hold of a 74AHC573.
Download
base board for Olimex ATmega128 header board
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September 23, 2011
A couple of months ago I ordered a ATmega128 header board (AVR-H128) from Olimex. In order to make use of such a header board you need to mount it somewhere. For this purpose I created a sort of header board for the header board. It is very minimal, consisting of mechanical components only except for a LED and a resistor. The reason for that is that the header board on which the ATmega128 itself is placed already contains a +5V voltage regulator (LM78L05) and reset circuit (ZM33064). Using my board its very convenient connecting things to the pins of the micro controller. All ports (A, B, C, D, E, F and G) have a separate 10 (2×5) pin header where the last two pins of each header is connected to GND (9) and VCC (10).
The layout of the board was created with the intention in mind to be able to assemble it in a through-hole fashion. Needless to say that the layout can also be used to etch or mill the board.
There are still things that can be enhanced like adding a connector for the reference voltage of the ADC (AREF).
Download
Schematics and layout have been created using Eagle 5.11 with a non-commercial license. The outline of the board is 100x160mm, so for you folks that use the Eagle freeware you will not be able to modify the boards layout (since Eagle as freeware only allows for boards with a outline of 100x80mm).
