Some days ago I received my new PCBs. This time I tried Sparkfun’s BatchPCB. BatchPCB is a specialized service to enable even smallest orders. They collect some smallers orders and have them produced in a batch at Gold Phoenix. So the smallest order is a square inch.

The quality looks really good, as far as I can tell. Especially the edges of the PCB are smooth and not as rough as the ones from Olimex.

To get them produced, BatchPCB has a nice tutorial. It shows you how to process your Eagle CAD files to the needed Gerber files. When you are done with that, it’s time to get an account at BatchPCB. Next you can upload your zip of Gerber files. There is a check, that every file you uploaded is recognized correctly and that no files are missing. A couple of minutes later you will receive an email with an in depth check of you files and with images of your design. That way I noticed, that the bottom left corner of the boundary was not centered. That resulted in displaced drill holes. I corrected that error and uploaded the design again. This time it looked good. Now I went to the shop (!) and ordered my design. Hmm, I take 5 of these today.

It took 22 days until I received my boards, 15 days until shipment and 7 days for shipping to Germany. I payed 31.52€ ($48.45) overall for 5 tiny boards. Actually the price includes shipping ($25.95) and handling ($10 setup fee). The board itself costs only $2.50 (1 square inch).

This order at Sparkfun cost me 1.05€/cm², compared to 0.34€/cm² from my last order at Olimex. That is a huge difference, but my boards were tiny and shipping and handling was high. At the end I am very pleased with the outcome. Handling and payment completely online was perfect and better as with Olimex, but Olimex was faster, 11 days to 22 days. The price is higher at BatchPCB, but therefore you can start with really small boards and don’t have to pay for a complete board of 160×100mm. At last they send me 10 instead of the ordered 5 boards, that reduces the price to 0.53€/cm². That’s cool.

Links

• PCBs from Olimex
• BatchPCB
• Olimex

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.

Materials

• Tengu PCB
• Everlight 8*5 LED dot matrix
• ATmega48, 4kB Flash RAM, 512 bytes RAM
• 4 MHz crystal
• LM386 Op-Amp
• 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

As this is my first design, there are a couple of things that I would redesign.

As 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.

All 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.

What would you think of an Arduino version of this circuit? The controller could be replaced with an Arduino compatible ATmega168. Or maybe as an Arduino shield?

Conclusion

It is great to see your first produced PCB. Even 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.

As I have still two boards left, you can email me at alex at this domain and I will send you the PCB for free. The only requirement would be, that you really want to build it and that you give me feedback on how it worked, what you would change or how you modded it.

Links and Downloads

• Crispin Jones Tengu, the original idea of this device
• Mini Amplifier with LM386
• Tengu clone on prototype board
• Tengu clone on a breadboard
• tengu-clone-rev-1.0a.zip source and Eagle schematics

More at Flickr.

Today my first PCBs arrived. Hooray! For me, this is definitely like reaching the next level in DIY technologies.

I chose three simple circuits that I wanted to be produced. After some research I decided to go with Olimex, a PCB service in Bulgaria. They are offering a very good price even for small quantities. A double sided PCB with 160mm x 100mm costs 30 €. And you can have multiple layouts on one board.

So I made up my eagle files and produced gerber files. I had to adjust the precision for drilling (EXCELLON step) according to the FAQ. Next, I zipped all gerber files and a readme file and send it to Olimex. As this was my first order, it took some time and several emails until everything was ready for production. First I didn’t check exactly if my circuits fit on the board as I layed them out. Second I designed a custom part, an LED matrix, in Eagle. That part had circles all over to represent every LED. But that confused Olimex and they thought something went wrong when I did the gerber files.

They confirmed that now everything was ok with my files and that they were ready to go. I received a PDF which I had to print and fill out with my address and credit card details. That print out had to be faxed back to Olimex. Hmm, that looks a bit like 1996 to me. I would prefer to do everything online, including the payment. After they received the payment, it took 5 work days for them to finish my boards and it took another 4 days until I received my boards here in Hamburg.

After all it cost me 52 € for my 11 boards. Thats including VAT, shipping and some extra euros for correcting my errors. The price is still ok, I think. And if I had been more precise with my layouts, it would have been faster. Olimex did a great job in supporting me with my first order. Friendly and fast.

Maybe I will try out other PCB houses as well, but I suspect that Olimex is one of the better ones.

Links

• Olimex PCB manufacturer
• Eagle tutorial at Sparkfun
• Eagle tutorial at Instructables