Let's Make Robots!

Boards & Boards (to get you bored) -- a log of homebrewed circuits coming to life...

I decided to make a blog to serve as a log for the boards I design and/or produce... well mostly because I can. So here it goes.

NOTE: Older boards at the bottom, newer at the top. So do bottom-up read if you're after a chronological perspective.

 

05 - Practice makes perfect (eventually) OR the h-bridgemania

Ok, so given that there's always room for improvement let me just keep designing boards, and I could use some more efficient ones, so I just refitted the TIP122/127 into a MJE2955/3055 one (incorporating also some physical constraints corrections) and also re-designed DanM's previously mentioned "perf-ed" schematics now into a prettier and tidier PCB design. Also, it was a good oportunity to train my double-sided PCB making skills.

At the time I'm writing this (Nov, 18th 2012) despite having improved my transfer/etching skill I'm still very bad at soldering. Most of my solder points are a mess or at most passable, in the sense that at least they allow current to pass. However, I found it way easier to make proper solder points on boardhouse made PCB... also, doing vias on DS homemade boards it's still a pain sometimes...

04 - Finally improving on (some) noticeable board design skills

Continually following the wisdom of PCB design virtuoso Bajdi I've learned on how to do design a ground plane into my board designs (while using Eagle). Also using his Bajduino328 board design as template I've designed a "simpleduino" now sporting extra features as: 3.3V vreg (my first used SMD part), nRF24l01+ header and voltage divider to gauge battery voltage levels. Since, this board is meant to be used on my hoovercraft project I'm currently calling it the "hooverduino" board. Also, this is the first Double Side board in that I actually performed a double sided transfer/etching procedure (if one does not count the silkscreen on the ATmega fusebit doctor as a DS board). In parallel, I've also designed a couple of motor drivers boards: a simple TIP120 unidirectional motor driver and a TIP122/127 H-Bridge. Alas, my ignorance regarding electronics led me build an H-bridge with a ~4V voltage drop and thus highly inefficient for my current endevour, but despite that the actual production of the PCB all went jolly fine with just some minor quirks.

03 - Refining my design skills (well... trying to) & improving on the transfer/etching technique execution

So to keep honing both my Eagle and transfer/etching skills I decided to design more boards. I've designed a board to use for the remote control of my third project. It ended up being sub-optimal in terms of design, and even had a auto-routing flaw (easily fixed with by the blue jumper) that I only picked up after populating the board with components. In parallel I've decided to also transfer/etch my first Eagle design (the mousebot board) since I had a leftover piece of copper clad board just the right size for it.

Note: On the third panel the board looks all gooey as if a caravan of slugs and snails had run across it because I'm using clear nail polish to protect the copper tracks from oxidation.

02 - Starting with designing my own boards

Given that I did not what to be locked only to freely available board designs, I decided to start learning on how to use Eagle CAD. Given that I had a breadboard setup to program my atmega328 chips with my (ebay bought) USBasp and I wanted to free up both wire jumpers and breadboard, I decided that designing a permanent board for this would be a simple project to start learning on how to use Eagle (I actually started with a mousebot PCB version design but ended up only etching it later on).

Note: The transfer/etching procedure of this board was actually done in parallel with the ATmega Fusebit Doctor board and the acquired experience led me to write up this walkthrough/tip.

01 - Moving on to homebrew PCB toner transfer + etching

Trying to move up the ladder, and using as an excuse a couple of atmega328p which were fusebit locked I decided to make try some etching a board. I got an already proved-to-work schematics and layout, the ATmega Fusebit Doctor and got to work. Perhaps I should have started with some simpler board layout, but what the heck... if I could do simple I could also do complicated.

It took me a while, and mild violence had to be applied to the board but I got it to work and thus fixed the couple of "bricked" ATmegas I had laying around.

00 - The begining

After my first fumbling with some breadboards, I needed to make things more permanent, and since I did not want to go via ready-made block (more expensive, going-through-the-paces-negating) way I started of by doing a couple of board on perf board for my first bot.

So they were a basic homemade *duino, the called "kariloyduino", but now I call it "firstduino".

Basically it sports the minimum components to make a *duino with an external xtal and has a basic 7805 vreg based supply.

And a board to house the motor driver chip (L293D) based on DanM's schematics.

For my second bot I've also used perf board for "housing" the circuit.

 

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I've noticed none of your boards are plated in the photos. This may be why you're having problems soldering. Dipping your boards in a plating solution, (available anywhere PC board supplies are sold), makes the board much easier to solder and keeps the copper from oxidizing.

I did search for such a process but got a bit disappointed with the hits I got. It seemed to me that what is typically used for plating is quite toxic. Regardless locally I haven't been able to find anything of the sort in the store I buy my PCBs. If you happen to know of one that is eco-"friendlier" then by all means recommend it, I'm still willing to try that route provided it isn't messier or more toxic than the etching itself (and of course also needs to be affordable). :)

Seems very straightfoward! Thanks.  :)

The product I use is called Tinnit. It comes as a dry powder concentrate and you disolve it in hot water. The stuff works like magic!

Here is just one source and they do ship Internationally:

http://www.parts-express.com/pe/showdetl.cfm?partnumber=340-188

 

My usual problems with soldering are a) cleanliness and b) enough heat - trying to use a low power soldering iron on a large joint is a definate no-no.

Pete

roger that!

Have you tried cleaning the copper with very fine grade 'wet and dry' sandpaper - say 800-1200 grit just prior to starting your soldering session ? It could be traces of chemicals still on the boards.

 

Pete

...actually I haven't, because in my mind since I had just used acetone to clean off the toner I thought it as clean. That was probably my mistake. I'm guessing acetone must not play nice with solder adeherence. Next time I'll be sure to "scotch brit" the hell out of the recently etched boards. :)

Have you tried using some solder flux? Looks like you are using lots of solder, I use a lot less :)