Rocket Brand Studios Little Line and Ledge Robot




The Little Line and Ledge Bot from Rocket Brand Studios is just a big bunch of wonderfullness packed in a big box of awesome.

Well, its about time... I finally got around to designing a good, solid line and ledge bot. This little guy is set up for lines, mazes and ledges (deskbot) with its 5-sensor bar in the front. Three sensors are mounted together in the center, spaced to match the width of electrical tape. Two more sensors are mounted at the far-outsides of the sensor bar. These two extra sensors are slightly wider than the wheels, and thus can detect the edge of a desk with plenty of time to stop or change direction. They are also super handy when used as a maze solving robot. --The two outside sensors are just what you need when following courses with 90 degree turns. 120:1 geared motors are not quite speed demons, but move this little bot around just fine. 

On top of all this line-follow goodness, we add a Dagu Micro Magician board. Simply an awesome board, packed full of features:
  • Atmega168 (Speaking Arduino)
  • On board USB
  • Sweet motor driver (with brakes)
  • 3 axis accelerometer  (not only a "tilt" sensor, but also can detect impacts --bump and turn with no bump switches!)
  • On board IR sensor (Control this bot with any Sony Tv remote (or universal remote)
Finally, there is even space left over (and a cut-out) if you want to add a micro servo and "head" in the future. 

                                                                     Rocket Brand Studios
                                                                      Little Line and Ledge
                                                         MicroM info, Instructions and Downloads

Step 1: Getting Started

Ok, lets get started...

First thing first, go ahead and strip off the paper backing from the plexiglass. Just use your fingernail, once you get an edge going it will just peel off. Also, if you notice a kinda funky "plastic" smell, well, that is just what the plexi smells like when it comes out of the laser cutter. The good news is that the vast majority of that smell is in the paper backing --not the plexi itself. Peel the paper and throw it away outside --the smell will go with it, I promise.

Even better, have one of your kids peel all that paper while you get some tools ready:
  • Soldering iron and solder (if you didn't get the no-solder kit)
  • Wire strippers and dykes
  • Long tweezers, needle nose pliers or a pair of hemostats 
  • Little screwdrivers
  • A little masking tape might be handy too

Step 2: Assembly 1

Organize wire and prep motors:

  • Divide up your jumpers into 3 piles:
  • (3) 6" jumpers --->   White, black, red
  • (5) 6" jumpers --> Assorted colors
  • (2) 12" jumpers --> Red and black (if you have the no-solder kit, these 12" jumpers are already on your motors)
If you are doing the no-solder kit, skip ahead now, your wires are already soldered to your motors.

If you are doing the DIY kit:
(Please follow along with the pictures --they should help a lot)
  • Locate the red and black 12" jumpers
  • Cut them exactly in 1/2. --You will end up with (4) 6" jumpers with a connector on one end, and a cut-wire on the other end)
  • Strip back the insulation about 1/2" (maybe a couple CM) from the ends of each of these (4) wires
  • Find the (2) brownish-beige capacitors. Remove them from the little paper strip
  • Bend the legs of these caps to match the width of the terminals on your motors 
  • Wrap one red wire around one leg of one cap. Wrap one black wire around the other leg
  • Repeat the above with the other (2) wires and the other cap
  • Solder the wires to the caps and clip off a bit of the excess (see pictures) 
  • Pre-solder (tin) the terminals of the motors
  • Solder your cap/jumper wire assemblies to your motors Note: It does not matter where red and black goes, but it does matter that the wires are soldered to the motors pointing the correct direction (see pictures)

Step 3: Assembly 2

Start chassis assembly:
  • Locate the big bottom plate, the (2) motor plates and the little thing that fits between the motor plates
  • Each of these pieces (with the exception of the middle piece thingy) has a right and a left. Note: If you look at the first picture included with this step, I have labeled the important parts
  • Place the two motor plates and the middle plate together in a "U" shape
  • Place this "U"-shaped assembly down on to the big base plate, lining up the "tabs and sockets"
  • Fish the nuts into their little homes, then run a screw up through the corresponding hole (There are a total of 4)
  • Just snug it up! Don't break the plexi! No need to go all red-face-tight here...
  • Set your motors in place. Route the wires through the hole in the middle piece and snug the motors into place. You will have to wiggle-ka-jiggle them a bit to get them to sit down flat. Be sure the "little extra bit" of the motor fits through the corresponding recess in the base plate. (just be sure they sit flat)
  • Secure the motors to the motor plates using the (2) 2-56 x 3/4" screws and nuts. Use the pan-head screws, NOT the long flat-head ones.

Step 4: Assembly 3

Battery and battery doubler:
  • Locate your battery pack, battery pack doubler and the (2) long, flat-head screws (nuts too!)
  • Place the doubler on the battery pack, noting the notch for the wires
  • Place this battery pack/ doubler assembly onto the underside of the base plate while also feeding the battery wires through the small, rectangular hole in the base plate. (At this point, you may discover you have the base plate upside-down... No worries, --just loosen the motor plates/ motors, flip it over and then put everything back on)
  • When the battery and doubler are sitting flat on the chassis, take a quick second and double check the battery wires are going cleanly through the hole, and not pinched anywhere
  • Run the (2) 2-56 x 5/8 flat-head screws through the (2) middle holes of the battery pack, through the corresponding holes in the doubler and finally through the chassis.
  • Add the nuts and just snug it a wee-tiny-bit
  • Take a second to fudge the battery pack around until it is sorta straight and square to the chassis (make it look like you knew what you were doing)
  • Tighten it down all the way

Step 5: Assembly 4

Track Ball and Stand Offs:

This one is pretty simple...
  • Unwrap your little track ball. You can also peel the paper off of the (2) spacers that come with it.
  • Feed the screws that come with the track ball through its "ears" (You may find it easier if you pop out the ball)
  • Add both spacers (The photos show only one --You should use both!)
  • Place this ball/ 2-spacer/ 2-screw assembly onto the chassis, just ahead of the battery pack.
  • Stick the nuts on --snug it down
  • While you are down there, go ahead and add the (2) 20mm brass stand offs with (2) M3 screws (see pictures)

Step 6: Assembly 5

Prep and install our top plate:
  • Go ahead and unwrap your MicroM Arduino brain and the little plastic stand-offs that come with it. Note: on some of the earlier shipments of MicroM's, the screws included with the kit were a bit long --Simply screw a nut onto a screw all the way. Then, with a pair of dykes, cut off about 1/4" (maybe 1cm) off of the screw. Now, remove the nut and as it threads off the screw, it will clean-up any threads buggered-up by the cutting process.
  • Insert the male end of the (4) stand offs into the top plate and secure with the (4) plastic nuts. Be gently with those plastic nuts (well, be gentle with all nuts, I guess) Note: the top plate has no right and left, it can go either way
  • To make a later step much easier, we are going to add a couple nuts now. If you look at the pictures, we have added (2) nuts to the "middle piece" between the motors. You can fish these nuts into place, and they will rest against the motors --they will not fall out unless you tip the whole chassis forward. Put these nuts in now, because it is a major pain to try to fish them back there later.
 With the nuts in place, we can put the top plate in place:

  • Bundle up all the wires sticking out of the bottom plate into a sorta "pony tail"
  • Feed this bundle of wires through the square hole in the top plate
  • Keep tension on these wires as you slide the top plate into place and get it aligned.
Patience now:

Now, there is no good way to do this... We need to get the (2) motor plates, the middle plate and both motors to fit in their little "spots" all at the same time. It can be a bit of a pain sometimes. Be very patient and just sorta "keep wiggling everything"... Everything will find its home eventually. Assuming all the tabs are in the sockets and the little bit of motor is fitting in its little recess:
  • Install the (2) 2-56 x 3/8 screws that correspond to the nuts you added earlier (do this now, we have made it this far without the nuts falling out --get while the gettins' good)
  • Add the (2) 2-56 x 3/8 screws and nuts that secure the motor plates to the top plate
  • Screw the top plate to the (2) 20mm stand offs with (2) M3 screws

Step 7: Assembly 6

Line Follow Sensor:

At the time of writing this Instructable, I have decided that I would rather solder together the line follow kits rather than write another Instructable. So until further notice, your line follow board will come fully assembled, populated and soldered. Ok, lets get going:
  • Locate your line follow board
  • Locate (4) 5mm stand offs, M3 nuts and M3 screws
  • Locate the little plexiglass "washers"  (These are easy to loose, I probably added extras in the kit)
  • Secure the (4) stand offs to the sensor board using (4) M3 screws and adding the (4) plexi washers (see picture) 
  • Gently "encourage" the (4) male ends of the stands offs to fit through the (4) corresponding holes on the bottom plate of the chassis. You may want to loosen the screws a little bit so you can fudge the stand offs around a bit
  • Secure everything with the (4) M3 nuts --and tighten up the screws, if you loosened them
Awesome, we got it attached. Now lets do some quick wiring. Remember those piles of jumpers you made a while ago? We need the bunch of 5 (assorted) and the bunch of 3 (Red, black, white). Note: the pins on the line follow board are in a "pack of 3" and a "pack of 5".

From the pack of 3:
  • Connect black to -
  • Connect red to +
  • Connect white to S
From the pack of 5:
  • Connect one each to the 5 remaining pins. It does not matter what color goes where. 

Bundle up these wires and get ready to start feeding them through the chassis. In fact, one of the pictures below shows the wires tucked under and fed through the chassis. Actually, it would be better to go ahead and take a look at the next step before running them through. Certain wires need to go certain directions --In the next step there is a clear picture on how to do this.

Step 8: Assembly 7

Continuing from the last step...   ...Feeding wires:

Take a quick minute and look at the first picture included with this step. We need to sorta pre-route all of our wires so they are pointing in the general direction of where they will eventually be plugged in. The picture below shows all these positions well. Take a minute and see if you can get all your wires to match what is shown in the picture. Double-triple check that you have not mixed up the battery wires and the motor wires (they are both red and black).
  • Left and right motors stick out the front
  • Battery power stick out the right side
  • All (5) line sensor wires stick out the left side
  • From the "bundle of 3" wires (from the line sensor) -- The white signal wire goes off to the right and the red/ black wires go off to the left
  • Smush all the wires down or tape them as shown in the picture
  • Place the MicroM Arduino board on top of the (4) white plastic stand offs. Be sure the USB connector is closest to the edge of the chassis, NOT to the middle.
  • Tighten it down with the (4) plastic screws (be wicked gentle when tightening the screws)
Let's connect stuff:
  • Battery Wires: These will connect to (2) of the (4) pins right next to the switch. These (4) pins probably (and should) have a small jumper block connecting the (2) center pins. Connect the black battery wire to the pin labeled "GND". Connect the red battery wire to the pin labeled "VIN". Leave the small jumper block in place.
  • Motor Wires: The motor wires will connect to the (2) sets of (2) pins at the very end of the board (the end opposite the USB connector). It does not matter what color goes where, but be SURE that (2) wires from one motor go to one set of pins and the wires from the other motor go to the other set of pins.
  • Line Follow Wires: We will be connecting these wires (one each) to the ADC inputs of the board. If you look closely, you will see them labeled A3-A7. Ok, back to the line follow board for a sec. --Take a look at the (5) jumpers plugged into the line follow board  --Look at the very front of the robot (head-on). Note the color pattern of these (5) wires, but note the order going from right to left. The first color (the one on the far right when looking at the front of the robot) will plug into A3. Continue to plug in wires, following your color pattern until you finish with the far left wire of the line sensor being plugged into A7. (see picture)
  • While we are here at the ADC inputs, we might as well steal some power for the line follow board. Connect the red and black wire to any of the unused power pins of the ADC's. Red will go to a center pin. Black will go to a pin nearest the edge of the board. (see picture)
  • Line follow signal wire:  Lastly, we need to connect the signal wire (from the line follow sensor) to a digital output pin. This signal wire is used to turn the line follow board on and off. I have decided output 2 is as good as any, so you can plug the remaining white wire into D2.
Holy wow, that was a lot of stuff to connect.

Ok, I think we are done with the hard stuff. Take a minute, and for fun, stick your wheels on. The flat part of the hub of the wheel goes to the outside, the side with the bump in the middle goes to the motor.

How 'bout that, kinda looks like a robot now.

Step 9: Assembly 8

How 'bout that! You did it! Good Job.

It is time now to go ahead and start programming this guy. We will focus on the MicroM board first. You will need to download and install the driver for the USB cable and it probably would not hurt to do a quick read-through of the manual. You can find all that information here:

MicroM Info, Instructions and Downloads

 Next, we should move on to a little test code, and maybe a tutorial video or two. All this and more can be found here:

Little Line and Ledge at Rocket Brand Studios

Have fun, and remember --it is always a good idea to remove your batteries when not playing with your bot.

Happy coding!



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    5 Discussions


    7 years ago on Introduction

    Nice job Chris, good detailed instructions. I am very happy to see a Micro Magician robot on Instructables.

    1 reply

    Reply 7 years ago on Introduction

    Finally. And yes, I agree. I really like the micro magician board, mostly because it has the IR controller built in!


    7 years ago on Introduction

    epic. i absolutely love your robots. but i think the tiny tanks chassis is a bit too low slung...