Let's Make Robots!

Trial and Error...lots of error



The parts finally arrived on Monday from PICAXE.  Over the weekend I also traveled to a local electronics store (Alphatronics, near the South-Center mall in Seattle) to purchase a soldering pencil ($18), some 330 ohm resistors ($1.25), some additional pins to solder into the circuit board ($0.50), and some terminal casings for wires ($0.75).  

-- note that I'm making up all of this terminology.  I doubt "terminal casings" means anything.  I'm referring to those thin black plastic thingies that go on the end of wires and fit onto the pins.  "Terminal casings" just sounds better.

Soldering Pencil

Finally, I purchased a spool of solder, a soldering sponge, and some double-sided tape at ACE Hardware for another $10.  For those like me who have never soldered before, I recommend taking a gander at some of these youtube videos. They make for a sufficient crash-course in the art of soldering.

Another note for beginners: you may want to purchase some kind of mini-vise.  Trying to hold the the soldering pencil, the solder, and the two pieces your trying to solder together - all at once - can be quite difficult.

Using Frits' model as a template, I was able to quickly put together the wheels to the gears, the servo, and mount all of those components just as it is shown on the "start here" page.

The next step was putting together the components on the circuit-board.  Though all the steps are fairly straight forward, it took about 20 minutes of me dumbly staring at the board to figure out its logic.  The first step was to figure out which direction to insert the micro and motor-controllers, which is actually quite obvious once you get it.  Simply place the board so that its text ("www.picaxe.co.uk") is going left to right, then insert the chips so that their text (the letters are small and hard to read) read from top to bottom.  Duh, you say.  Indeed, but it take me a few minutes to get that straight.


Inserting the ohm resistor was also straightforward.  But there are a few things to be aware of that gave me some pause.  When you go to the electronics store, you'll notice several different Watt values for the resistors, ranging from 1/8w - 2w.  I was told that anything between 1/4 - 1 would suffice, so don't kill yourself trying to find exactly the right resistor.  Also, when you're inserting the resistor into the board, you'll need to give it a little shove before it sticks.  However, the resistor's legs are flimsy, so don't shove too hard.

After inserting the resistor, the next step was to solder in some pins.  By my count, there were 6 pins that needed to go in the board. One at "0" on the edge row of the digital output - for the ground wire of the servo.  1 on the inside row of the analog input - for the G wire of the sensor.  And 2 each for the four "A" and "B" holes - for the gear-motors.  (In Frits' model, he solders the wires directly to the board, but I think it'll probably be easier for me to fiddle with the motors if they're attached by pins and sockets.)  


-- note that the pins come in rows of anywhere from 10 - 40.  This confused the hell out of me at first.  I'd find out that it's actually really easy to detach individual pins.  Duh, again.


The soldering itself turned out to be a tough learning experience.  My hands were shaky and I faired poorly on my attempt to solder the four pins into the "A" and "B" holes.  I think I got the board a little too hot, as the black pad began to get shiny, and the soldering on two of the pins actually fused together to make one giant pool (It's pretty obvious on the picture to the left). I may have to go back and try those again at some point.  

After that, I went out and got some alligator clips to hold the board in place while I soldered. This proved to be a much better strategy going forward.

After the soldering was complete (which included soldering the other end of the wires to the motor) I crimped some "terminal casings" onto the end of the sensor's wires and placed them on their pins.  I also placed three additional wires on the unused "left floating" analog inputs as Frits does in his model (he calls it "short-cutting").  However, I'm not sure I did that correctly.  You can see in one of the images above and to the left that I used three green wires and connected them, one each, to a pair of V and input pins.  I wonder if this is what is meant by "short cut" in Frits tutorial.  -- ? --

 In any event, after all of that work, here is what the robot currently looks like:


 I know it looks remarkably similar to Frits' model, but for my first attempt here, I'm not trying to win any design awards.  The goal is to simply get this thing up and running.

This weekend I'm gonna try to get everything connected to my computer and throw some commands at this guy and see if he responds.  I already know there will be some trouble, as my computer (a Mac running OS X on a Power PC) will not recognize PICAXE's USB cable.  I am also having some curious things happen when I try to open PICAXE's AXEPAD program editor.  So there is still much work to be done.

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Hi MrLomez, nice walkthrough of your build!

With practice you will get soldering down easy. That joint has WAAAY too much solder on it though despite the obvious bridge. A good joint should make a kind of small cone shape up the wire lead, if the sides start to look convex it`s too much solder. I`m no expert at soldering, but my joints improved 10x once I made myself some helping hands to hold things for me.

My helping hands.. cheap flexible camera tripod:$1 + crocodile clips:$1.



Or check this out for info a good looking/larger one.

YES!  A camera tripod.  Why didn't I think of that?  Perfect idea.  And thanks for your pointers.

 As far as the joint with too much solder...should I desolder that and do it again?  Or will it still function properly as is?


Based on the picture, I would say desolder. It looks like your A and B pins are shorted together. Too much solder on a joint won't hurt, but it looks like the joints are soldered together, which is no bueno.
Also, be careful with the desoldering. I did the same thing you did, and I ended up putting too much heat for too long on the joint. The curcuit uses a tiny tiny tiny little copper ring around the A and B holes. I accidentally burned mine off and had to make my own add-on circuit for the motor driver.

I'm worried that I may have done the same. In general, if the black base of the circuit board gets that shiny look, does that mean you've burned it?  Or is that just a cosmetic effect of any soldering job? 

How did you add on another motor circuit? That sounds like some serious work.

the heat of the solder will make the board a little shiny, but that's not a problem. when i did it, i saw the little copper rings pop out. and it was after a lot of rooting around with the iron. But if you can desolder just enough so that none of the pins are touching each other, you're good to go. The board's made to be soldered.

To make my own, I made the circuit described in this post. (which is what is built into the project board already). I've also taken the l239 and just bent the "motor" pins out, soldered wires to them, and plugged it into the board.

The shiny stuff is just flux which shouldn`t hurt it too much. It is slightly acidic so can slowly corrode the joint but that usually takes years I think.. I`ve never bothered about it anyways :D Rubbing alcohol can get it off easy though.

Yeah I would get the excess solder off that joint. I bought a cheap solder sucker and also some desoldering wick a while back and both are incredibly handy when I fudge up.

Thanks, Calc.  Tha's some good info.

 You said you bent the "motor pins out."  Do you mean you literally bent the legs of the motor-chip and soldered wires directly to the chip's legs? It makes sense intuitively, but I didn't realize you could go directly to the chip like that.  I'm not gonna try it myself, but that's good to know.

Practise soldering some more. Make sure it's a wam-bam-thank-you-m'am action that does the job. Overheating does happen when you apply your heat source for too long. Not when it is "too hot".

When soldering onto a chip leg, remember this. The board may hold out long enough for your slow "solder pasting technique", an integrated circuit certainly will not. That's one of the reasons to put them in sockets.