Lars

January 28, 2013

I’m quite busy with my PhD and some other things these days, so I haven’t been able to update the blog lately. I will get back with more projects later on, so please check back.

Square wave generator on the Stellaris Launchpad

I’ve coded a very simple square wave generator. It uses the buttons on P1.0 eh… ooopps… PB5 and PB0 (the two first buttons on the LarsLCD board), and prints the kHz value on the LarsLCD. It should run without the LCD also. The output is on PA2 (bottom right).


The LCD library is from CorB’s post on stellarisiti.com and is mainly his code by now. The generator code is adapted from the example timer code in the project documentation. If you have input on ways to write it better (button presses etc), I’m very happy to receive feedback.

The code is available here.

ds2202-large

Rigol DS2202 oscilloscope, function generator and DSA815-TG spectrum analyzer

I just bought a new Rigol DS2202 200MHz oscilloscope and I’m very happy about it. It is very useful to see the analog effects on the digital circuits, like noise, decoupling capacitors etc. This scope also has some decoding of digital signals, but I already have a logic analyzer from Dangerous Prototypes that I’m quite happy with.

It was a race between the Owon and Rigol brands, but Rigol seems much more solid in terms of firmware and build quality, though their scopes are also almost twice the price. There are quite a lot of bugs in the DS2202 (it’s a new product), but none of them really bother me. I hope they will be fixed soon. I’ve also ordered a Rigol function generator and a Rigol DSA815-TG spectrum analyzer with a tracking generator. This equipment will definitely help me make better products. I have not received the spectrum analyzer and function generators yet.

A cheaper alternative for DIY-ers is the Rigol DS1052E, which has a smaller screen, less functions and a much smaller price. If you get the right firmware, you may be able to hack it to run a higher bandwidth. This is a very common DIY/hacking scope, though the new ones have more functions.

eevblog.com is a great site for reading about oscilloscopes and getting advice. The blog author has some really funny and educational Youtube videos. I can really recommend them. He has some tear-down videos of various components (like two Apple chargers) that are quite educational. For spectrum analyzer youtube-videos I’d recommend jimeagle.

I bought the equipment from Tekequip.com since Batronix don’t do free shipping to Norway. They seem to consider customers outside the EU less interesting. (Even though Norway even is within the EEA and Norwegian consumers should have the same rights as EU citizens). Tekequip.com have been very service-minded and prompt in their responses and shipping. And I did not get any specials for mentioning them here :-)

reflow_oven

T-962 Reflow oven

I’ve wanted a proper reflow oven for a while. The hot-plate works well, sometimes together with the hot air gun. But for some projects it would be better with an oven. Many people build their own, but while I’d love that project, getting hold of an oven here in Norway would end up being almost as expensive as this cheap alternative: T962 from Puhui. I did a lot of googling before buying one, and it has some bad reviews. In fact I’ve found it difficult to find positive reviews. But I bought it anyway, and so far it seems the reviews are wrong and it works fine. The reviews do indicate that the soldering profile is slow (the watch is not real-time), which seems correct, but the oven works well. I’ve only used it a few times, but except two tomb-stoned resistors (attached on one end and lifted up so it doesn’t attach on the other end), I’m happy about the results. I think the tombstone is probably just a matter of tuning the profile + stencil, and since I’ve only used the default profile No. 1, I can’t say I’ve tuned it to perfection. My first impression is at least that I can recommend this product and that the reviews are not balanced. It seems many of the reviews are people who bought it from ebay or aliexpress, but I bought it straight from the company website, which might be better. It arrived here 4 days after I ordered it, shipped with DHL.