Let's Make Robots! | RobotShop

Etching PC Boards and Speed Control

Well, my 28x board is on its way and I have a good chassis to work with, so I will be building my first really cool robot soon. The problem I have is that the motors and wheels I going to use are just too darn fast! I was thinking it would be cool to add a speed control... Maybe as it gets closer to an obsticle it can slow down and in the open it can go all-out. I do know that when I wire it into the 28 project board I am going to have to hack a little -I only want the varied voltage to goto the motors. Since I don't want slow servos, I guess I'll have to invent a V3!

In addition to instructions on the variable voltage regulator, I also include some info on etching your own pc board -it is wicked easy... Lets go. (Yeah, and I have no macro on my camera)

The etch kit is from good ol' Radio Shack. It comes with some blank board, etching stuff and some cleaner. As for the speed control, the main chip is also from R.S. and is super simple to hook up.

PCB_Speed_control_001.jpg Here is the sheet of pc material that came with the kit. I have cut-in the servo and installed the 5K pot. I used a dremel tool with a cut-off wheel to cut.

PCB_Speed_control_007.jpg Now cut down to size, I have laid out the circut I want to etch. Just use a sharpie! -One is included in the kit. Be sure you let the ink dry and then go over it again with the marker, you want all the lines good and dark. I usually make little circles where the componant legs will be soldered and where wires will go. You can also note + or - or what ever you want. I suggest drawing the lay-out first on paper and REMEMBER the back is reversed (or upside down) to the other side... Just double check your pin layouts -I have reversed a ton of stuff making these. Obviously, don't cross streams and... ...Aww for cryin' out loud I am rambling... Just draw the damn thing.

PCB_Speed_control_011.jpg Next, pour etching crap into a little tray and stick the pc board into it. Wait. I suggest you enjoy a fine, domestic lager. 20 or 30 minutes later you got a board. Just keep checking it and swirl the tray every once and a while. I don't think you should touch the liquid crap but really I don't know how nasty-a-stuff it is. Rinse the board off with water and, I don't know if you should but, I reuse the etchant and pour it back in the bottle.

PCB_Speed_control_019.jpgDone. The sharpie is wiped off with the solvent. Judging by the smell it is just rubbing alcohol. At the top you can see some flames and a cool rocket! The red letters are part of the board. Now I just have to drill some holes and start soldering. (A 1/16" bit is actually a bit big -see if you can something smaller at the hobby store)


PCB_Speed_control_028.jpg Here is everything soldered together. Oh yeah, the circut! Well, you can use the one on the back of the LM317 package (it is a super simple circut to make) or go here: http://www.wikihow.com/Add-Variable-Voltage-to-Your-ATX-Based-Bench-Power-Supply


PCB_Speed_control.jpg This little voltage regulator is actually pretty handy. Here is one I made and put in a nifty little project box. Simple terminals for input allows me to use just about input power I have as long as it is dc and under about 30v. I have used 9v's and old cell phone chargers, what ever I have got. I suppose you could add a guage, but I really don't mind just checking it with a multi-tester as I adjust it. As for the output, I can stick a bare wire into the terminal, a banana jack or aligator clips.


PCB_Speed_control_029.jpg And she's all done! I used a drill bit collar and welded a little "horn" to it. The copper wire linkage is actually welding wire -not an electrode but the kind you use with a TIG or a torch. If you go to a welding store ask for 1/16" copper-clap mild steel welding rods. The rods come 3' long and get get about 50 in a cool plastic tube for about $10. These little pieces of wire are good for everything and bend better than piano wire or a coathanger.


So that's it -Go watch the video.


Chris the Carpenter






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Very nice. I'd always wondered just how much of a pain it'd be to etch circuit boards, nice to finally see an example. Need bigger pictures though! It's hard to make out the detail on those tiny pics :)


I read this just before I got to bed.. and started laughing when I should sleep.

I thought hey, what is happening to this website? Instead of "Let's make robots" we should start calling it "Wacky stuff that nerds makes"; A mechanical speed control :D

Also I think you are in a state I can see many of us end up in; "I ordered something, and I just want to build. NOW!" - I think I wil make a section for that in the forum :)

And.. Then.. Nice with a walkthrough for PC-etching! What would a robot-builder's site be without it? I will have to try it some day!

Inspiring, thanks,

/ Fritsl

I was toying with the idea several times - and stood in staring at the etchant in radioshack for an eternity before convincing myself that it was too caustic, messy, and hard for me.  Your tutorial and the picture of the PBR has convinced me otherwise !

cheers :)


Apart from the fact that it is always cool and fun to see wacky stuff made by you, I do believe that the true value of this post is the "How to etch-part".

For motor controller - controlled by servo-puls, i'd go for this, in comparison:



(I am not negative here, just honest! - I still love you!) 

/ Fritsl