Solder mask

So, I have finally find time to improve my SMD work by adding a solder mask to pcb.

I've used the chinese UV-curable blue pcb solder mask paint, and it actually does great job, it takes some time and practice to do it right, but gives a professional look and quality. Again I might do a tutorial on this one, when I master it.

The final result was not so pretty, I still need to improve my soldering skills and get a new soldering station. My current iron is just useless. Also I might have burned the blue LED in my 5050 RGB, so that one is left unconnected. Actually, it is possible that it was already damaged. I did not test it before soldering.

Here is the final pcb:

Funny thing is that it looks like an aged pcb. I defiantly need to improve my skills:)

First lab, power supply, peltier elements...

I have finished my lab prototype. Got myself a bench power supply that is connected to a ATX power supply, so it is kind of silly, but it works. It has a panel meter and some banana plug terminals, so it looks and feels like a normal power supply. I can use only 3.3V, 5V or 12V connecting to different ATX-pins. For this state it is ok, I will redo it when I get the transformer and the pot. Also I got a bunch of different test leads and wires (thanks Franky Tong from http://99centhobbies.com). So now I can easily connect things.

I finally got the peltier element to play with. It is a small 27W element. It does the job quite well. I am thinking of automatic drink-dispenser, and those could make a good cooling device for it. I will do a proper post about those when I have some equipment to measure temperature.

SMD. First try

I’ve received my SMD 5050 RGB LEDs recently, and of course I wanted to test them. So I’ve decided to make a breakout board.

Few words about PCB creation. I’ve decided to use citric acid, hydrogen peroxide and salt for the etching process, I think someday I might do a tutorial on this. I liked this method very much. It is cheap, relatively quick and very simple, as you are not dealing with some hazardous chemical like ferric chloride.

Here is the result:

Arduino is contolling the LED to run through all the colors. It took me several hours to get to this state. But the fact that it a least works I think is great for the first attempt. I will improve it later using the solder mask and proper pins instead of wires. But for now it is a good result.

Updates on the PSU project

I've mentioned that I had changed schematic a bit:

This is the current version.

The input capacitor is changed to 3300µF to filter out the input ripple.
The transformer is changed to a center-tapped with two 12v coils. LM315 is rated to dissipate 15W max. The calculations are pretty easy: P = (Vin — Vout) * Current. When I have 24v transformer input voltage is 30-32V RMS, so on low voltages it will overload the regulator quite quickly even with not high current (500mA). The best Idea is to use a transformer with two coils and a switch to change the input voltage from 12V to 24V when I need it. I plan to improve this part of the circuit later that it could switch automatically using a relay and an npn-transistor.
Another good improvement was a R3 resistor it allows to use all turns of the pot. 5K pot is a bit too much to use with 100Ohm resistor, but this resistor should be low (120Ohm max.) as it will lower the current on the adjust pin and regulator might not work properly. So for the full range of the pot a parallel resistor R3 is needed.

I still need to check if there any issues with the output switch. As there in no path to discharge C4 capacitor after switching the input on it may still keep some high voltage in it, so it can damage the connected circuit. I need to test this one when I build this thing up on the breadboard.

I need to say thank you to a great guy mariush form Martin's forum. He helped me a lot with all the calculations and improvements.

First steps

I came up with my first project quite quickly. There are never enough power supplies and they are easy to build. So that would be it.

I've decided that it should be based on LM317, as it is easy to use and there are a lot of tutorials. Here is the first version of the schematic:

I have already change the schematic a bit, but it is a topic for the next post

And of course I've bought an enclosure for the power supply

Back to school

I’ve came to that period of my life when I need something to do. And I started to look for things I was interested in earlier. The first that came up was robotics. I remember that it was really cool to play with Lego NXT in the university.

But time changes and I got an Arduino. And after I’ve finished playing with the blinking LEDs I’ve realized that there is a whole big world behind that I was always interested it — Electronics. I’ve even used to take electronic courses back at school for a short period of time, and not much knowledge came from there. School physics did not help to understand all the electromagnetics either. But now I’ve decided to figure it out at last.

And I did. I’ve found a lot of resources for beginners. I’ve finally was able to realize what do I want and what do I need. Unfortunately there were not much Russian websites about electronics (Just want to mention http://radiokot.ru — cool project doing the right thing). But I di find a lot of cool videos on YouTube. There is quite a long list now in my subscriptions, but I want especially highlight this channel — http://www.youtube.com/user/mjlorton. Martin does not teach electronics, he’s learning himself, he makes mistakes and shows that there is nothing to be afraid of. I think it is the best way to teach.

A word about shops... There are some offline shops here in Saint-Petersburg, but often they have nothing to choose from, sometimes even some common used resistor values are not in stock. And need to say that pricing is quite high too. Of course there are some online-shops, but they are not much of a help too. So the only good option to get some really interesting materials, components and equipment is ebay or amazon, but Russian Post Service makes it nearly impossible to get something quick and not stolen. I think someday I am going to fill the lack of bits and pieces, but now I am watching videos and waiting till I can start doing all this myself.