Let's Make Robots!

Juice Box Robot Plan, Needs review

***UPDATE MARCH 11: After reading the comments here I have made a couple of changes to my plans. I have replaced the PICAXE 18 with the PICAXE 28 and appropriate board. I have switched to 3 AAA cells as a power source and I have changed to servos to power the "arms". When I wrote the original post used the word "arms" as a placeholder, but while I always intended to have actuation it was never actually going to be a set of arms. One servo will power a number of separate actions that allow the robot components to fold out of the box (for example the gearboxes descend so the wheels stick through slots in the bottom of the box). The other servo will be used to actuate the tabs of the juice box like "ears". I also have a few new questions with my updated plan. Wil the projecct board have the correct outputs to run the motors forward/backwards and also the servos? Or what else do I need? And if anybody has experience with this board will it be able to fit in the 4"x2"x1" space of a juice box (the website doesn't list a size).***

I want to create a mobile robot project that hides inside of a juice box. While I have done robotics before in the FIRST robotics competition but never somethiing working with smaller components like those I will need here. I have talked to some people from a local robot shop in Calgary, AB, Canada "Solarbotics" and together we have come up with a list of compenents to make this project a reality:

PICAXE 18 Projecct Board: https://solarbotics.com/product/28460/

***PICAXE 28x1 Chip: https://solarbotics.com/product/28480/

***PICAXE 28 Project Board: https://solarbotics.com/product/28510/

PICaxe Programming Cable: https://solarbotics.com/product/28405/

A Remote Control IR Receiver: https://solarbotics.com/product/TSOP4038/

GM3 Motors for Drivetrain: https://solarbotics.com/product/gm3/

***Tiny Gear Motor Mounts for Wheels: https://solarbotics.com/product/gmw/

Pager motors to actuate arms: https://solarbotics.com/product/gm15a/https://solarbotics.com/product/gm15/

***Micro servos for actuating features: https://solarbotics.com/product/25500/

Lithium Ion Batery: https://solarbotics.com/product/battr15/

Li-ion Charger: https://solarbotics.com/product/50834/

***3 AAA Cell Holders for power: https://solarbotics.com/product/bholdaaa_1_cell/

I will CAD and 3d print the chassis itself. Does this seem like a set of components that will work effectively together or do you have some suggestions how to improve it. Also, where can I find a good tutorial on how to program the IR receiver. 

Thanks in Advance, Alex

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a motor driver. Actually, you will need a pair of motor drivers since you are planning on using 4 motors. Second, you won't need to "learn" how to interact with the IR receiver. PICAXE chips come preprogrammed being able to understand the Sony protocol. You just need to use the proper command, which I believe is irin or infrain. I don't rightly recall. The geared pager motors say they only have .5 oz/in of torque, but, their speed is 920rpm or just over 15 rev/sec. I am not sure, without seeing your plans for an arm, they will really do what you are after.

PS: I just recalled that the PICAXE 18 board you are looking at has a darlington bridge(?) onboard. I am guessing that is what is being planned for use to drive the motors.

Based on your BOM, you have just about rebuilt the Start Here robot with a few additions and of course, a juice box.

If you are looking at making a robot in general, it might not be worth reinventing the wheel here. Not to mention, you could get a better selection of parts (ones that would work for this application) for less money.

  • 28x board instead of the 18x --The 18 does not have a motor driver, the 28x does
  • IR reciever --If the 28x board is used, it has provisions (and an available kit) for the addition of IR
  • Pretty much all of the GMx motors would be fine, a little math is needed on gear ratios, wheel dia, etc.
  • If you go with a li-ion battery, you will need 2. Each is a little over 3v, with 2 of them adding up to 7.2v or so. This would need to be then regulated down to 5v for the picaxe. Option 2 is to use the M2 versions of the Picaxe chips that allow for 3.3v operation. 

***NOTE*** You are NOT showing Li-Ion battery in your BOM. You are showing a Li-po battery (lithium polymer). There is a substantial difference between the two and no newbie should ever play with Li-po's until they have a firm understanding of the proper handling, discharge and charging. As an example, in the above text, I told you to use 2 of these to get 7.2v. This is just fine with a Li-ion, but li-po's on the other hand, need to be "balanced" and "matched" before being assembeled into a pack. Simply wiring 2 of these together is a really bad idea. Heck, the pack you show does not even seem to have under/over volt protection.

**I don't mean to harp on you here about these batteries, but this is sorta a big one. You just can't screw around with Li-po batteries. If you short them, they explode. If you try to suck too much current, they explode. If you charge them improperly, they explode. Its just not something to play around with until one knows what they are doing. 

Thanks for all your advice! I have updated the original post with the updated plan, take a look.

I can tell its a good one because you have successfully re-invented the Start Here Robot.

I would order the Start Here kit (and save yourself a few bucks over buying everything stand-alone) then add the few extra parts you show (extra servos and the like).