COMPACT Same brain · servos in line · short tracks
Same robot, under half the bulk.
BotTino again, folded tighter: the two servos sit one behind the other, the battery lies on top of them and the boards ride on the battery. A band of grey board instead of a box, 24 mm wheels, about 66 × 51 × 36 mm. This variant is drawn from its templates and has not been built yet. Scroll and it puts itself together.
Scroll to assemble01 Bill of materials
Fewer parts on the mat.
No distance sensor, no accelerometer, no buzzer, no shelf and no lid. Pick a line, or tap a tag on the mat, to read its sheet. Then keep scrolling: the parts leave the mat in build order.
02 Servos in line
One behind the other.
Tabs off, the servos lie on their sides in a row with the spacer O between them: 48 mm, as long as the battery. The front one drives the front-right wheel; the rear one, turned round, the rear-left. Drive wheels on a diagonal.
Before the glue
Check by hand that each servo spins freely, find its stop point, then saw the tabs off flush. Measure which end the lead leaves, how far the shaft sits from the end and the turret’s outline: the templates still use estimates for all three, and regenerating them takes one command.
M1 → GPIO6 · M2 → GPIO7 · shafts 36 mm apart
03 Cardboard band
A ring, not a box.
One strip of board wraps round the block: a tall front with the face window, low sides notched round the turrets, a back for the switch and the button. No floor: the servos are the bottom, 6 mm off the desk.
How it really goes on
Here the band folds round the block so you can see how it fits. At the bench you fold and glue the ring first, set the servos and the spacer on the table and lower the ring over them: the notches are open at the bottom and a 2 mm bridge runs above each turret. Two filler discs E inside the walls set the servos’ sideways position, and a flap closes the ring inside the rear bay.
A · 66.1 × 29.2 mm · 29 / 14.6 / 20 mm high
04 Tracks
Twenty-four millimetres.
Each idler turns on its own short pin through a side wall. The drive wheels press onto the cross horns and a band goes round each pair: 6 mm under the belly, about 8 cm/s.
Tension, then glue
Two patches outside and a filler disc inside brace each pin. Slide the pin along its slot, away from the drive wheel, until the band stops slipping while you hold the drive wheel; then a drop of hot glue on the pin, not on the wheel. Cut the 24 and 23 mm discs with tube punches if you find them, otherwise with a compass cutter. The bands are about 126–132 mm round at rest, shorter than the v1 ones. On the right the drive wheel leads, on the left it trails: the two tracks may need a trim in the firmware.
Ø 24 × 6 mm wheels · 36 / 44.8 mm
05 Rear bay
Eight millimetres of room.
Behind the rear servo a small floor closes the bay. The switch and the button stand against the back, the servo header is glued above them, and both servo leads fold up in here, uncut.
If it does not fit
The bay is the tightest spot of the variant: header, 470 µF, switch, button and about 50 cm of servo leads in 8 × 26 × 20 mm. Try it dry first. The front servo’s lead reaches the bay through the 2.4 mm gap above the servos, under the battery. If the leads will not fold in, shorten them and solder them, and lose the quick servo swap.
J1 470 µF · SW1 · SW2 → GPIO3
06 Battery and boards
A stack, not a shelf.
The battery lies lengthwise on the side walls, just above the servos. Charger and SuperMini share a plate on two rails on top of it, USB to the back. The antenna ends up over the battery: a Wi-Fi test comes first.
Wire it safely
Swap the charger’s programming resistor for 2.4 kΩ first: 500 mA instead of 1 A, half the heat right above the cell. Then solder the battery straight to B+ and B−. OUT+ goes through the switch to the header’s V+, OUT− to its GND; a 1N5819 feeds the 5V pin. Charge from a USB-A → C cable, never unattended. The chip antenna sits 4.5 mm above the pouch: if the Wi-Fi test goes badly, the boards go in a row instead.
BT1 1000 mAh · U2 500 mA · U1 ESP32-C3
07 The face
Two eyes, four wires.
The OLED goes behind its window, glass against the board. Four wires run forward over the battery from the SuperMini, the only stop on the I²C bus. Then the face wakes up.
Mark the window first
The lit area is not centred on the glass: switch the display on with a full pattern, hold it against the front, mark the lit edges and cut the window there. The module fits the band with 0.2 mm to spare on each side.
DS1 0x3C · SDA GPIO8 · SCL GPIO9
08 Assembled
Smaller hello.
A band of board, two short rubber bands, four boards and seventeen wires: the same face on a robot under half the bulk of the v1. Turn it around, look underneath, tap a part to read its sheet again.
Original design and code · compact variant, drawn from the project’s templates and not built yet; the servo turret and lead side are estimates · component data from the datasheets linked in the parts list · GPL-3.0