Back in the late 80’s I loved the “Stomper” toys. They were the first all wheel drive little electric car toys, no remote control, just forwards and with a 2 speed gearbox, crawl and quick-ish! I loved the ruggedness and the fact they could crawl up steep angles.

StoRPer is definitely influenced by them.

StoRPer aims to be a cheap way to get into robots and robotics. It’s essentially an add on printed circuit board for the very affordable raspberry pi pico. The PCB forms the chassis of StoRPer and on the PCB are 4 motor driver circuits built around the affordable but perfectly usable L9110S drive IC. Why 4 motor drivers.. well this means we have options! We can build this up as a straight 4 wheel drive machine but it also means it’s trivial to add mecanum wheel for exploring some very fancy movements and motions.

To mount motors I’ve added 2 holes per motor area which can be used in different ways. The basic approach is for you to find some N20 style motors and then use a 3D printed motor mount to bolt them into place and then solder them to the motor drive connector pads. Why did I chose to use a custom motor mount rather than those nifty (and excellent) commercial N20 mounts that people like Pimoroni sell. Well.. the idea is with a little more space in the motor mount hole we can actually design numerous different motor mounts for different purposes, for example we could design a mount for a different motor, or, on my StoRPer to do list, is to design and make a tracked robot assembly that would bolt into these holes. For that I plan to only use 2 motors, one each side, so then we have the nice idea that we can use the other motor drivers for none drive things… think small rotating turrets or pan and tilt ideas!

Also on the PCB are some breakouts for the remaining pins from the Pico (all the pins are broken out apart from the pins attached to the motor drivers). The main connector at the front of the PCB is designed so that we can create add on devices for the StoRPer board easily using only standard 2.54mm pitch pin headers and sockets for addons that can mount above or below the chassis PCB. Note that it’s also designed so that the power pins are arranged that if you are using a 2 row header that plugs into all the pins/sockets then you can’t accidentally short the add on if you accidentally reverse the connector.

For power, there are numerous options. You can drive the Pico and 4 N20 motors perfectly well directly from the Pico’s USB socket, finding a small USB power bank is therefore a great way to get going. For more compact options you can use the power connector pads. Note that you can drive this only up to 5.5V, if you go beyond that you’ll damage the Pico voltage regulator. However you can directly connect something like an 18650 cell (or the smaller 14500) cell directly to these pins and it will run the Pico and the motors well. If you prefer to run the motors at 5V you can of course use any type of boost module to boost your cell, obviously MAKE SURE YOU CHECK YOUR BOOSTED VOLTAGE DOESN'T EXCEED 5.5V.

If you opt for N20 motors there are loads of wheels and tyres out there for sale that will fit. Make sure you are buying N20 motors that are designed to run at up to 6V. If you have access to a 3D printer that can print PLA and TPU you can keep cost lower by printing your own wheels. There is a starter design for printable wheels up on the repository that have worked well. For tyres the softer the TPU the better but I’m also planning to do a quick design of wheel that uses super sticky off the shelf o-rings as tyres.

There are also a couple of drawings for different mountable plates or “decks” you can add to your StoRPer using the standoff screw holes. In the options I’m selling some lasercut versions of these, with options for cutouts to reveal the various breakout connectors, power connections and also the “Really Useful Hole” which allows wires to be routed from the underside of the chassis board if needed and through the stack. I've managed to find some 100% recycled acrylic to laser cut the decks out of. If you use header sockets on your Pico then using 15mm standoffs on the PCB board will mean that your deck will sit just clear of the inserted Pico. Of course you can stack multiple decks and or make your own!

As for code, at the moment there are some example micropython sketches up on the repo, one for just getting the stoRPer running in stomper mode (just go forward!) but also a sketch for testing mecanum wheels and manoeuvres. I look forward to people hopefully sharing their own code. Certainly on the roadmap is to use a wireless Pico and create some kind of remote control system.

Check out all the purchase options on the listing, I’m trying to make these affordable for people so if you have access to a laser cutter and a 3D printer you can just buy the board (which includes unsoldered header sockets for the Pico) and make the other parts yourself. For others I’m selling 3D printed N20 motor mounts (with the nuts and bolts) and the decks and standoffs. Oh.. and everyone gets a StoRPer sticker! Check out the video below to see and hear a bit more about stoRPer and check out the repository linked below.

edit: as of August 6th 2024 I've added an extra add on option which is the "kludge deck and Bumper" add on kit. This is a collection of 2 PCB boards, one a electronic and mechanical prototyping deck and the other a PCB bumper that adds the option to add ultrasonic range finding sensors and bump switches. They are available separately as well for those who already have a stoRPer so you can read more and see a video about these over on this page.

Finally, just to clarify as a couple of people have enquired. The basic "stoRPer" option offered here is just the yellow PCB and 2 x 20 pin headers you can solder in. The Pico and motors aren't included. You can add the 3D printed motor mounts and/or lasercut decks the mounts and decks come with the required nuts bolts or standoffs. The add on Kludge deck and Bumper kit come just as bare boards with no other components. Thanks.