Tengu Clone on PCB
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Transcript of Tengu Clone on PCB
5/12/2018 Tengu Clone on PCB - slidepdf.com
http://slidepdf.com/reader/full/tengu-clone-on-pcb 1/4
Tengu clone on PCB
May 3rd, 2008 · 40 Comments · PCB, avr, led, sound
This is a new version of my Tengu clone. This time on a printed circuit board (PCB). I have them
produced by Olimex and I am very pleased with the quality. The PCB worked on the first try and
has some minor issues only.
MATERI
ALS
Tengu PCB
5/12/2018 Tengu Clone on PCB - slidepdf.com
http://slidepdf.com/reader/full/tengu-clone-on-pcb 2/4
E verlight 8*5 LED dot matrix
A Tmega48, 4kB Flash R AM, 512 bytes R AM
4 MHz crystal
LM386 Op- A mp
28 pin header
8 pin header
2 * 22pF capacitors
3 * 100nF capacitors
10k potentiometer
100k potentiometer
100k resistor
5 * 1k resistors
2 * 7 pin header sockets
2 pin headers for power supply and microphone (optional)
Electret microphone (not on the picture)
Note, that the electret microphone has a polarity. On the PCB the inner pin is the positive one. If
you connect it the wrong way, it is heating up really quick.
The microphone that I used here has an impedance of 2k. You may have to experiement a bit
with different microphones.
The capacitor C2 is used to control the amplification of the LM386. I used 0.1uF but you can use
up to 10uF to get a stronger amplification. Here is the amplifier circuit that I used.
PCB DESIGN ISSUES
5/12/2018 Tengu Clone on PCB - slidepdf.com
http://slidepdf.com/reader/full/tengu-clone-on-pcb 3/4
A s this is my first design, there are a couple of things that I would redesign.
A s I tried to insert the pin header sockets, I realized that the drill holes were a bit too narrow.
You have to use a bit of strength to insert the headers, but it works.
A ll solder pads used for resistors and capacitors are a bit too small. It was a bit difficult to solder
them. I would make them a larger next time.
I think I should use a bit less of the silk layer. Some solder pads are covered with silk. Most of
the time that does not hurt as it is on the top side. But there are pins that you may wont to solder
on the top side, e.g. the power connector.
IMPROVEMENTS
The component count could be reduced if I had dropped crystal. For the animation of the LED
matrix the internal oscillator would be sufficient. On the other hand, with a suited crystal, this
circuit could be modified to display the time.
I would add an ISP (in system programming) header for easier programming. Now you have to
flip off the display, take out the controller, program it, re-insert it and put the display back in
place. Not a fast turn around if you want to modify the firmware.
5/12/2018 Tengu Clone on PCB - slidepdf.com
http://slidepdf.com/reader/full/tengu-clone-on-pcb 4/4
W hat would you think of an A rduino version of this circuit? The controller could be replaced
with an A rduino compatible A Tmega168. Or maybe as an A rduino shield?
CONCLUSION
It is great to see your first produced PCB. E ven better if it works on the first try. Maybe I can
even build a kit out of it with the next revision of the board.