CPX Drone Claw

In this project we’ll show you how to build a DIY Drone Claw.

We designed and 3D Printed a claw attachment for the DJI Mavic Pro. This doesn’t obstruct the vision sensors so we can fly safely with obstacle avoidance.

This build can be used for educational projects like the classic egg drop or even delivering small objects.

You can also use this to pick up the trash, carry objects to research sites or even camping grounds. There’s a lot of tasks that you can do with a claw attachment.

The Claw

The claw is actuated using a micro servo and remotely triggered using the remote controller.

We’re using the Light Sensor on the Adafruit Circuit Playground to detect when the LEDs are on.

Trigger with Light Pipes

A light pipe tunnels the LEDs on the Drone into the 3D printed enclosure.

So the servo opens and closes when the LEDs are remotely turned on and off.

WebUSB

Makecode can also pair with your Circuit Playground Express through the Google Chrome web browser by visiting this guide page.

Visit the project here: https://makecode.com/_WgrDeHKLf0RH

This means code edit will upload directly to the Circuit Playground Express without the need to drag and drop file onto it!

Follow the instruction to set up your board and you'll be able to quickly send code to Circuit Playground Express! 

NinjaFlex Port Coverts

The JST, USB and Reset Button Extension is printed with NinjaFlex material. The covers require them the bend around the cylinder shape of the enclosure to help block out any lights that may enter in those areas.

Prep Wires

We'll start by stripping our Female/Male 'Extension' Jumper to about 110mm long.

We can optionally tin the wires to keep them from fraying or just twist them. Next we'll mold them into a hook shape. 

Connect wires to CPX

Instead of soldering, we can use three M3x6mm + nuts to connect the wires to VOUT, A1 and  GND.

Insert the screw from the top of the board and them attach the nut from the bottom of the board. Use your finger or a screw driver to hold the screw in place while attaching the nut.

Give the nut a turn or two, this way we'll have enough room to insert each wire.

Hook each wire to its pin and them use pliers to securely fasten each nut. 

Position the wires as shown in the picture, this will make threading wires through the enclosure easier later!

CPX case

Now we can move on to assembling the case. The case holds the Circuit Playground Express board and the 500mah battery.

The standoffs have enough clearance to allow the battery to sandwich in between the case and the CPX board. 

Lipo

First we'll lay the battery inside the case positioned as shown, with the connections near the opening on the case. Pass the wires through the opening and then insert the battery. 

The CPX board lays over the battery. Align the board so the bigger cutaways can align with the USB port. 

Cover + Leg

The cover is attached to the Left Leg part using two M2x5mm screws. Insert the screws from inside between the standoffs. Fasten the two screws half in to help create the threads for the screws.

Next we can align the protruding screws to the holes on the side of the Left Leg part. Check that the mounting position is so that it leaves enough clearance on the bottom of the leg.

Reset Button Extension

We designed a rest button part, so we could still access it while the CPX is inside the enclosure. Insert the Reset Button between the standoffs, next to the light pipe hole.

Align case

Position the case and cover over each other so the bigger port cutaway aligns with USB port. Press fit the two parts and rotate them so both the JST and USB port opening align.

Use tweezers to ensure the holes on the CPX board align with the standoffs on both the case and cover. 

With all of the holes aligned we can use a small drill to fasten the cover and case. To reach through the enclosure and CPX board, we'll need two or four M3x16mm screws. 

Leg Claw 

Now we can move on to assembling the leg claw! First we'll prepare the Left Claw part.

This part is driven by the rotation of the Right Claw. To stop the claw from getting loose, we'll need to add a lock nut or a threaded insert to keep the screws from unfastening itself.

Use tweezers to help position the the threaded insert inside the Leg Claw part. 

The Left Claw will use one M3x6mm + threaded insert. Insert the screws until it sits inside the grove above the gear teeth.

Align the Left Claw to the threaded insert. We used flat pliers to hold the threaded insert in place while fastening the M3 screw. Don't tighten it all the way, leave a bit slack so the claw can freely rotate.

Right Claw - Servo Horn

The servo horn tightly press fits into Right Claw part, and is then secured with the included M2.5x5mm screw.

First, we'll want to align the gears of the claws so they are both at the close position as shown in the picture. 

Carefully rotate the horn until you feel where the gear teeth insert into the servo and then press fit the horn into the servo. 

Test the close position by connecting the CPX to verify both claws align when opened and closed. Modify by moving the claw until the gears both align to the closed position.

Prep Light Pipe

To prevent light leaking into the sensor, we'll need to cover the sides of the PETT filament by painting, plastic dipping or using a sheathing like a heat shrink tube.

We measured a heat shrink tube 130mm long and inserted it over the PETT filament.

Leg Install 

With the CPX case and leg claw parts assembled, we can move on to installing the components. 

Front Legs

Rotate the leg parts so they align with shape of the Mavic legs. Make sure to clean and remove any overhangs left over after printing, as it could block the legs from fully seating into the parts.

Wire clip

The wires are held in place with the Wire clip part. The clip secures the servo wires to the side of the Mavics body, away from the sensors and propellers. 

Attach wire clip 

Route the wires as shown in the picture. The Leg Claw part has a bit of slack to allow the cable to sit underneath the LED on the back of the Mavics body.

Pull the wire taut against the Mavics body to ensure the wires are away from the propellers and the sensors. 

Connect Jumper wires 

Now we can go ahead and connect the servo wires to the Circuit Playground Express. Align the jumper wires and press them together until they are full connected.

Wire Slack Tuck

You can insert any wire slack into the wire port opening on the enclosure.

LED Cover Clip

To attach the PETT light pipe, we'll snap fit the LED Cover part onto the LED on the Mavics front propeller mount. Make sure you clean any retraction bits around the part and test fit inserting the light pipe into the clip before mounting.

Make sure the heat shrink completely covers the light pipe. If any light sources hit the light pipe it could trigger the sensor on the Circuit Playground.