Hi Benjamin!

Any new control methods for the tank you've found? I'm looking for some simple beginner friendly Logo turtle-like programming environment for such an ESP robot, not bumped into a decent one yet. The idea would be to make it follow simple programs like "L30 F50" (left 30 degrees, forward 50 units) to accomplish missions, like the ones kids nowadays have in their schoolbooks, to transfer these on-paper excercises to the physical world.

BTW, been a while since the conversation about battery terminals, but these are good for printed battery cases. Also these strips I have used, with bumps printed in the minus end under the strip.

Hey Turo! Thanks for the battery holder suggestions (cheap 18650 packs are great for robotics)! I haven't messed with the ESPtank too much since I got it working (I've been teaching programming for my school robotics club and building a reprap in the meantime), and in my most recent attempt to program it, I managed to brick the ESP8266 on it (though I'm not quite sure how).

I've been pretty excited for micropython [https://micropython.org/] on the ESP systems lately, and have put a bit of thought into using it for the tank. When I get a replacement for the '8266 on the bot, I can definitely look into implementing a simple wireless serial command system like you're suggesting. The major limitation to using it in an educational environment like you suggest is that my particular design is pretty bare-bones, and doesn't include encoders on the motor shafts. This just means that unless you add some kind of rotation sensor on the motors, the commands would be based more around motor direction, motor power, and time than accurate unit movements and degree turns.

Regarding the mechanical design, the tank was easy to build and is pretty great for traversing obstacles, but a 3d printed "can bot" [https://www.thingiverse.com/thing:2104214] or other 3d printable tank might be cheaper. The electronics would remain essentially the same.

Hi, i am interested in how you did the battery tabs? For my project (https://hackaday.io/project/9900-rian-simple-and-easy-built-robot-for-education), i printed the box and got the tabs from a commercial battery box, but i'm looking for other ways to do it. Could you give me more details about it?

Hi Audrey! It took me a while to figure out how to mount 18650s in a convenient, reliable way, and I still haven't quite figured out a clean solution. I've used 3 methods so far (all with varying improvisation based on what I had): 

1. Right-angle wood channel with glued-on perfboard end caps & metal strapping fashioned into "springs." Worked well, but took time to assemble and was too easy to remove the battery.

2. The 3D-printed design I referenced above by [enif], which has awesome integrated springs (but requires you to wrap wire through tiny slots - very time consuming and tedious, and melted the PLA a bit when soldered). This is the version currently on the robot.

3. The same 3D-printed design with thin metal strips cut from the strapping (any thin sheet metal would work the same) instead of wire. This is quite a bit easier to get through the slots (more so on the flat side than the spring side), and is what I'm currently using in my parallel battery charging setup (external).

Sorry that these are so difficult to replicate (your method seems almost better in this regard), they were just easy to make with materials I had on hand. Pictures to come.

Hi, thanks for the insights. As you mentioned, i'm looking for a method to produce this easily at low cost, so ideally i wish i could find just the battery tabs alone... however i still have to buy the battery boxes and get the tabs out of it (and i am left with the plastic boxes afterwards, maybe i can turn those in battery storages?)

Anyway, thanks for the answers, and keep on hacking, this one is a really neat project!