Let's Make Robots!

Mini Machine!


Well I've started work on a new robot, with size in mind. It's setup is somewhat similar to the "start here" bot, but it's actually got a chassis and something to cover up the electronics. Hopefully the only wires we'll see on this bot is the wires from the Sharp sensor. (This info is now out of date: I can now reveal the chassis is transparent, so we can look at the guts!)

I haven't actually got the parts yet, but I've designed it and made a Cad:



Yes, the Sharp sensor DOESN'T look like that, but I couldn't be bothered to model everything exactly and make them the right colours. And yes, it's NOT going to be a dull grey, it's going to be plywood (now I can tell it's transparent acrylic). And yes, the wheels DON'T look like that, they actually have spokes (I'm too lazy), etc etc.

Well, it is quite a midget, measuring less (now a millimetre more)than 10cm long, but when I was designing it I forgot to leave space for batteries, so instead of using 4 AA batteries, I'm gonna have squish in a 9V for the motors. This is not good for two reasons:

  1. Those little 9V batteries don't last that long
  2. Those little motors are gonna go WAY too fast, and they'll sizzle, so I'll have to use PWM.

Those little motors are Solarbotic's right angle drive GM7s. Although I haven't (now I have) seen them with my own eyes, from the datasheet and technical specifications I really like them, they are really small and and their dimensions are perfect for robot building, because of the way you can simply put them against the side wall of your bot:
Of course, if your robot doesn't even have a side wall, like the "start here" bot, and many other chassisless bots, this motor is actually very bad.



General view of the bot


The guts! (without PCB as it's not made yet) sorry for the blur, my camera auto-focus get's confused by the transparent acrylic


2009/02/ 8

I've finished the Cad, now I will start building the chassis.


Now I've done a cool, transparent, orange, acrylic chassis! I know it's been almost a month since I updated this, but I was having problems with getting the chassis made, as the laser-cutter is at school. At least I've got all the parts now.

Almost all mechanical and structural details of the robot have been finished, now all I have to do is figure out how to make a printed circuit board and program the thing...

Images coming soon! (ie. once the camera's batteries have recharged)

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.

Thanks for compliments.

I got the acrylic from my school (I don't know where they get it from, sorry Electrictape!), since my school has a laser-cutter I can use for my own projects. The glue I used is a special kind of solvent designed for plastics, it basically dissolves the edges of the plastic, and then evaporates entirely, leaving nothing but the plastic it had dissolved before, so I get a almost solid seal with no residue left.

that is an amazing technic, I must research and see if I can find that glue.

You can actually make a glue like that. Take small pieces of the acrylic (shavings, broken off corners, etc...) and put them in a glass container (not plastic!). Add some acetone, probably to cover about 1/2 to 3/4 of the plastic bits and let it sit a little while. After the acrylic bits start melting, stir it up, add some more acetone if needed, stir, repeat until the resulting goo is the consistency you want.

Using homemade glue will result in less-than-pretty edges. The trick then is to get really close when gluing, then sand the edges using fine sandpaper. Afterwards, goober some toothpaste on a piece of glass and polish the acrylic part on that (kind of like lapping compound).

Otherwise, you may be able to get acrylic glue at some pet stores. Look for the stuff they use to build/repair plastic fish tanks.

Me likey.
Nice bot! Where did you get the orange plastic/acrylic from?
It looks incredibly tidy : )
amazing job.. I love the chasis design. I'm looking forward to more updates

its cute!!!  :)

what did you use to glue the acrylic pieces? hot glue?

It is possible to run the motors and the microcontroller from a single 9v battery, some power being diverted to a voltage regulator, some straght to some motors? I've got a feeling the power would go straight to the path of least resistance (whichever that is) but you know, just be sure....

My microcontroller takes 15 milliamps. I wouldn't mind working off separate batteries but at the moment my design is getting fairly wide, so of course a single battery is preferable.

If you run your robot from 9V batteries then it will be running out of power all the time. Running your processor off of 9V isn't very efficent either since the regulator will waste nearly as much power in the form of heat as what the processor will use. Read this tutorial on voltage regulation.

Another problem with the 9V batteries is that they have a reasonably high internal resisance. Running your motors from a single 9V battery will cause the voltage to drop.

If you must use 9V batteries then you will be far better off with NiMh rechargeables otherwise ditch them for 5x 1.2V NiMh (6V).