[ATtiny2313] Check out my first working circuit board!

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Jamison
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Posted by Jamison: Sun. Oct 4, 2015 - 06:41 PM
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Hello fellow Freaks!

 

I wanted to showcase my very first functional printed circuit board (all homemade)! After two failed boards, my third board came out great.

I used the photo resist method using positive pre-sensitized boards from Jameco. It's just a simple Simon says game but I'm so excited to build more projects in the future!

I would love to hear what you folks think of my board. My soldering skills certainly need a bit of work but I'm satisfied with my results so far. Check out some photos below.

 

The controller is a small ATtiny2313.

 

Here's the board after the etch process:

 

The bottom side of the board after drilling and soldering:

 

Here's the top of the board:

 

Here's a video of the board in action: https://www.youtube.com/watch?v=RyCQQdY5ZwA

My digital portfolio: www.jamisonjerving.com

My game company: www.polygonbyte.com

Tags:

AVR Microcontrollers, megaAVR and tinyAVR
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DocJC
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Posted by DocJC: Sun. Oct 4, 2015 - 08:41 PM
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Nice job!

 

It is great when your first home made PCB works!

 

I might add a suggestion or two for your next PCB.

 

It is worth putting a small Pin #1 Marker on the PCB for the uC's Pin #1.

Likewise, put a small "+" sign next to the V+ pin on your power header.

It is good to put a Version number on the PCB, also.

 

In 6 months, if you have been working on other projects, you won't remember exactly how you laid out the PCB, and you will spend a lot of time following traces on your own PCB.

It is much easier when you have even a few identifiers, such as suggested above.

 

The other thing that caught my eye was the absence of any By-Pass capacitors.

Although your project is working without them, you should really get in the habit of including them in your schematics, and projects, for reliable operation.

This Thread has some further discussion in that regard.

 

Ounce again, Congrats on your Project!

 

JC

 

 

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Torby
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Posted by Torby: Sun. Oct 4, 2015 - 09:15 PM
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Nice work.

 

Yea. I put lots of text on mine, right in the copper. Usually 2 letters and the date I started laying it out. I also name the file the same, and keep a document with the same name. This doc usually just says what's wrong with the board that I'd want to fix before I make another.

 

Also, look into surface mount parts. LOTS easier than drilling all those silly holes.

The largest known prime number: 282589933-1

Without adult supervision.

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Jamison
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Posted by Jamison: Sun. Oct 4, 2015 - 11:13 PM
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@DocJC:

Thanks for the tips on the pin markings and version labels . Great suggestions!

Also, I've known a little about by-pass caps but I have not used them on my breadboard projects. I will be sure to look at that topic and look for more reference material on proper utilization of by-pass caps before I build my next board.

 

@Torby:

Thank you as well for the suggestions for labels and the like. I also like your idea for a document maintained with board changes and such. This will certainly come in handy for larger projects in the future (I've got so many in mind and so many breadboard projects I want to turn into boards!). As for surface mount parts, before I got all of my circuit board equipment, I honestly thought through-hole components would be easier. Now I'm realizing drilling holes is a difficult process (primarily the alignment and the time consumption). I've got a few surface-mount ATmega644ps and SAM devices. I honestly dread the idea of soldering SMT resistors and caps, as they seem SOOO small. I'm worried I will not do so well soldering them. But I do intend to try it when I get a chance to purchase my next batch of components. Who knows, I may be pleasantly surprised that it might be easier than I think right now.

 

Again, thank you folks for the kind words. I've learned so much from this site and I look forward to many more years of electronics and being apart of the community!!

My digital portfolio: www.jamisonjerving.com

My game company: www.polygonbyte.com

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DocJC
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Posted by DocJC: Mon. Oct 5, 2015 - 12:50 AM
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There are many Threads discussing the migration from through hole to smd PCB's.

 

For example:  Here.   (Old Forum, you'll have to click on the images to see them)

 

And Here.

 

JC

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DocJC
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Posted by DocJC: Mon. Oct 5, 2015 - 12:52 AM
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BTW, get a red marker pen and put an ">" or "#1" next to the programming header's pin #1, also, right on the top of the PCB.

 

JC

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Jamison
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Posted by Jamison: Mon. Oct 5, 2015 - 01:17 AM
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@DocJC

Thanks for the links. More reading material is always fantastic!

I like the idea of using a red marker to mark the headers as well. Great for when I need to go back to a project and don't remember the orientation.

My digital portfolio: www.jamisonjerving.com

My game company: www.polygonbyte.com

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valusoft
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Posted by valusoft: Mon. Oct 5, 2015 - 01:34 AM
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Even better is to put a diode in series with your positive power supply pin so that you don't reverse connect your battery and blow the bejesus out of your new project. Personally I use a bridge rectifier, smoothing cap and low drop out (LDO) linear voltage regulator so that if I accidentally connect an AC wallwart I can still power the unit safely. Pennies to save dollars and your precious time and sanity.

 

Cheers,

 

Ross

 

Ross McKenzie ValuSoft Melbourne Australia

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Jamison
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Posted by Jamison: Mon. Oct 5, 2015 - 02:25 AM
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@valusoft:

Thanks for the tips. If I am understanding those correctly, the diode in series on the positive supply pin prevents reverse flow back to the battery if it is connected backwards on accident? Thus allowing it to only work in the correct orientation?

And the linear voltage regulator ensures voltage drop down to the required supply voltage in case a higher voltage needs/is supplied?

 

I looked up some info on a smoothing cap and it seems to primarily be to ensure an AC supply waveform doesn't dip down to zero. Is this only required when an AC supply is used than?

I will look up more information on this topic.

 

Please forgive me if my understanding of this stuff is way off. Electronics has just been a hobby of mine that I do when I have free time, so my understanding of the electrical parts and terminology is lacking (I'm a software engineer by day, so the programming is really my area). I'm certainly trying to learn more though as I really enjoy it!

My digital portfolio: www.jamisonjerving.com

My game company: www.polygonbyte.com

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valusoft
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Posted by valusoft: Mon. Oct 5, 2015 - 08:57 AM
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Jamison,

 

There are at least 4 ways of preventing accidental disaster when connecting power to your latest masterpiece, and mine...

 

#1. Be a human who NEVER connects power the wrong way. Unfortunately I haven't met such a rare creature.

 

#2. Have a diode connected in parallel across the power terminals so that if power is incorrectly connected the diode conducts and limits the "damage" to -0.6 volts (well it can be worse... you may destroy your source of power)

 

#3. Use a series diode. It only allows a correctly connected DC power source to power your masterpiece... but it does reduce your power source by 0.6volts.

 

#4. Use a bridge rectifier (or 4 separate diodes). If your power source is DC, irrespective of how you connect it, it will always result in the correct polarity power to your masterpiece. You will lose about 2 x 0.6 volts, but if your power source is sufficiently large compared to your desired voltage, the low drop out regulator will take care of the excess voltage. If your power source is AC, the bridge rectifier will convert it to a DC supply which will be smoothed by the capacitor. In this way you can almost be careless about which wallwart you connect to the input terminals.

 

 

Cheers,

 

Ross

 

Ross McKenzie ValuSoft Melbourne Australia

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Torby
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Posted by Torby: Mon. Oct 5, 2015 - 02:09 PM
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Yes. Soldering SMD's can be frightening.

 

Next time you're ordering parts, order some soldering paste. I have "chipquick" here that comes in a syringe and some really small desoldering braid. Squeezing it through the needle is nearly impossible, so I use the needle as a cap and just take it off to get some out. Also get a good magnifier. I have a 30x jewler's loupe and a magnifying visor. Then go to your local thrift store and find a cheap electric skillet. Also, you want a box of toothpicks.

 

When I go to build a board, I clean it again. Squeeze a bit out and use a toothpick to put a small dab on each pad. There's a pretty big difference between not enough and too much, so it's not hard to do. Avoid having extra paste laying around as this forms little conductive balls. Then, with a tiny tweezer, you can stick the parts onto the paste. Try to get about the same amount on each side of small things like 0603 capacitors or they can "tombstone" and stand up on one end.

 

Set the gooey board on the cold skillet and turn it all the way up. Watch closely as it slowly warms up. When it gets to the right temperature, all the dark gray paste turns bright silver, then sucks itself together around the joints. Take a quick look around for any tombstoned parts. You can push them down with a toothpick. Turn the skillet off and let it slowly cool down. This is a VERY rough approximation to a "reflow profile."

 

Once it's cool, I inspect it carefully with my loupe. Occasionally there'll be a solder bridge or a pin that doesn't solder down. Either takes just a moment to solve with your soldering iron. Sometimes the copper will discolor while cooling. If this is annoying, I hit it with my number 2500 sandpaper and shine it back up.

 

The thermostat in my skillet quit working and it would turn off too cold. So I took it apart and added a wire inside, so now I just plug it in, and unplug it to let it cool down.

The largest known prime number: 282589933-1

Without adult supervision.

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Jamison
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Posted by Jamison: Tue. Oct 6, 2015 - 04:09 AM
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@Ross

Wow, this is fantastic information. I will be sure to utilize one these methods when building my next project. Thanks!

 

@Torby

That's awesome! I never thought reflow could be done with an electric skillet. The idea of doing that almost makes surface mount seem less daunting to me. I will definitely put those items on my shopping list when I buy my next batch of electronics (hopefully soon!).

 

Again, I want to thank all of you awesome folks for the fantastic information.

My digital portfolio: www.jamisonjerving.com

My game company: www.polygonbyte.com

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Jamison
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Posted by Jamison: Wed. Oct 7, 2015 - 07:10 PM
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@Torby

I can get a 450° Fahrenheit (about 232° Celsius) electric skillet at my local electronics store for cheap ($30). Do you think this temperature would work for reflowing boards? The bit of a looking and videos I've seen of solder reflow, most people talk about 200° to 250° C (granted, those are for dedicated reflow machines or toaster ovens). So I do believe this should work. What do you think?

 

The idea of doing it this way actually fascinates me and I am really anxious to try it out now! But I don't want to rush into it.

My digital portfolio: www.jamisonjerving.com

My game company: www.polygonbyte.com

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Torby
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Posted by Torby: Wed. Oct 7, 2015 - 07:42 PM
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Mine (used to) go to 400F. I fiddled the thermostat a little -- that is -- I bent the bimetalic strip a little so it would go higher. After a few years of use, it started turning off too low to reflow. So I added a wire across the thermostat. Now it just gets hotter and hotter till I unplug it and let it cool down.

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valusoft
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Posted by valusoft: Wed. Oct 7, 2015 - 11:11 PM (Reply to #14)
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Torby wrote:

 Now it just gets hotter and hotter till I unplug it and let it cool down.

Argh... so it is the barefoot brat that is causing global warming...

 

Ross McKenzie ValuSoft Melbourne Australia

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Kartman
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Posted by Kartman: Thu. Oct 8, 2015 - 07:04 AM
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If the skillet has a teflon (non stick) coating you don't want it getting too hot as the teflon will outgas and poison you. Hot air tools from China are pretty cheap, so I've not needed to do the skillet trick. The hot air also works for removing the parts as well.

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Torby
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Posted by Torby: Thu. Oct 8, 2015 - 12:59 PM
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That's why I unplug it as soon as the reflow is finished. That's how it cools down.

The largest known prime number: 282589933-1

Without adult supervision.

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Jamison
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Posted by Jamison: Thu. Oct 8, 2015 - 09:10 PM (Reply to #16)
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Kartman wrote:

If the skillet has a teflon (non stick) coating you don't want it getting too hot as the teflon will outgas and poison you. Hot air tools from China are pretty cheap, so I've not needed to do the skillet trick. The hot air also works for removing the parts as well.

Thanks for the tip on the teflon non-stick coating (that's a scary thought!). If I do decide to go with a skillet, I will be sure to find one that doesn't have a coating or make sure to utilize proper safety protection. What do you personally use for hot air?

My digital portfolio: www.jamisonjerving.com

My game company: www.polygonbyte.com

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