Introduction
The seed planter attachment lets your Rover dig small holes and plant seeds. Seeds go in the seed tank at the top of the planter frame. One servo turns the seed barrel inside the frame, which picks up seeds and drops them down a spout into the planting cone. A second servo swings the cone down to push the seeds into the soil. It clips onto the front of the Rover via the rover shell.
Before you start:
- You need two micro servos, and they do different jobs. The cone servo (left port) moves to set positions, so use a standard 180° positional servo. The seed planter activity spins the barrel servo (right port) one way, then stops it with 0, so use a continuous rotation servo for the barrel.
- Keep track of which servo is which. The barrel servo goes on the servo plate in Step 4. The cone servo goes in the shell in Step 7.
- Calibrate the cone servo before its horn goes on (Step 8). If the horn goes on at the wrong angle, the cone won't line up with the seed spout.
Drag to rotate, scroll to zoom
Interactive 3D BuildOverview
The Finished Seed Planter
The planter clips onto the front of the Rover. The right servo turns the seed barrel to drop seeds down the spout into the cone; the left servo swings the cone down to the ground. Drag to look around, then step through the build.
What You'll Need
Parts:
- 6x M3 x 10mm Screws (Countersunk)
- 2x M3 Nut
- 1x M2.5 x 8mm Screw (Countersunk)
- 2x Servo Horn (single-arm)
- 4x Servo Mounting Screws
- 1x Servo Horn Screw
- 2x Micro Servo (one positional, one continuous rotation)
Tools:
- 3mm Allen Key
- 2.5mm Allen Key
- Phillips Head Screwdriver
Thingiverse
Printables
Makerworld13D Print Your Parts
- 1x Robot Shell
- 1x Planting Cone
- 1x Seed Barrel
- 1x Servo Plate
- 1x Planter Frame
2Insert the Nuts
- Find the servo box on top of the rover shell. Its outer side has two small slots, one under each hole in the top of the box.
- Lay an M3 nut flat and push it into each slot, with a corner pointing in, until it stops at the shaped end of the slot.
- Check the fit: look down each hole in the top of the box. You should see the nut's thread centred under it. If it isn't, push the nut in further.
3Attach the Planter Frame
- Sit the planter frame's flat foot on top of the servo box, so its two countersunk holes line up with the two holes over the nuts.
- The frame's arm should rise up and out in front of the shell, with the round barrel housing at the top.
- Screw the foot down with two M3 x 10mm countersunk screws into the nuts. The heads should sit flush in the foot.
4Mount the Servo to the Servo Plate
- Use the continuous rotation servo here. It turns the seed barrel.
- Sit the servo between the two blocks on the servo plate, with its output shaft through the large keyhole-shaped hole. The servo's tabs rest on the blocks.
- Fix it with two servo mounting screws, through the tabs and into the blocks from the servo's side.
5Attach the Servo Horn
- Turn the plate over to its flat side, where the servo's shaft pokes through the keyhole.
- Push a single-arm servo horn onto the shaft and fix it with the servo horn screw.
6Assemble the Seed Barrel
- Slide the seed barrel into the round housing on the planter frame, from the open side with the four screw lugs. The barrel's small round boss goes in first, into the hole in the back of the housing.
- Fit the servo plate over the housing, horn side towards the barrel. Turn the barrel until the horn drops into the slot in the barrel's face. Make sure that the horn fits into the slot correctly, or the barrel won't turn.
- Line up the plate's four corner holes with the four lugs on the frame and secure it with four M3 x 10mm countersunk screws. They screw straight into the plastic lugs, so stop as soon as they're snug.
- Check the fit: the plate should sit flat against the frame with no gap.
7Mount the Second Servo
- Use the positional servo here. It swings the planting cone.
- Drop the servo into the servo box on the shell, under the frame's foot. Its output shaft faces the middle of the Rover, at the end of the box away from the curved clip.
- Secure it with two servo mounting screws through the tabs into the box.
- Leave the horn off for now. Calibrate the servo first (next step).
8Calibrate the Servo
- Before attaching a servo horn to a servo, you need to make sure that the servo moves in the correct range.
- Plug the servo into the left servo port and run the calibration code.
- Upload the code and attach the servo horn to the servo so it is in the correct position when the servo is at 0: a single-arm horn, pointing forward along the shell towards the curved clip and level with the top of the shell, as in the picture.
9Attach the Planting Cone
- Fit the slot on the end of the cone's arm over the servo horn, so the cone hangs under the frame's seed spout.
- Screw the M2.5 x 8mm countersunk screw through the hole in the arm into the middle of the horn and servo shaft.
- Check the fit: the horn should be hidden inside the arm's slot, and the cone should swing freely without rubbing on the shell.
Fit and Test It
- Clip the shell onto the front of the Rover.
- Plug the cone servo (in the shell) into the left servo port and the barrel servo (on the servo plate) into the right port. Match the brown wire to the - on the port icon.
- In the Code Editor, set the left servo to -90 to swing the cone down. It should stand upright with its tip at the ground, right under the seed spout. Then set it to -60 to lift it. These are the
CONE_DOWNandCONE_UPvalues the seed planter activity uses. - Put a few seeds in the seed tank at the top of the frame. With the cone down, set the right servo to 90 for half a second, then 0 to stop it. The barrel turns and drops seeds down the spout into the cone, the same order the activity uses.
Because the barrel servo is a continuous servo, its value sets speed and direction rather than position, and 0 stops it. The activity below spins it the other way (-90) on every second seed to stop seeds jamming.
The height of the planting cone may need to be adjusted depending on how high the Rover is from the soil.
Troubleshooting
- The barrel servo runs but no seeds come out: the horn isn't in the slot in the barrel. Take the servo plate off and refit it with the horn in the slot.
- The barrel servo only turns a little, then stops: you've used a 180° positional servo for the barrel. Swap it for a continuous rotation servo.
- The cone doesn't line up with the seed spout: the horn went on at the wrong angle. Take the cone off, calibrate the servo again and refit the horn.
- The cone servo buzzes when the cone is up: the cone is pressing against the frame. Use a value a little closer to -90 for the up position, such as -65.
