Adorable Desktop Disc Sander Warms Our Hearts and Our Parts

Casually browsing YouTube for “shop improvements” yields a veritable river of project ideas, objects for cat amusement, and 12 INCREDIBLE SHOP HACKS YOU WON’T BELIEVE, though some of these are of predictably dubious value. So you might imagine that when we found [Henrique]’s adorable disc sander we dismissed it out of hand, how useful could such a tiny tool be? But then we remembered the jumbo tub o’ motors on the shelf and reconsidered, maybe a palm sized sander has a place in the tiny shop.

Electrically the build is a simple as can be. It’s just a brushed DC motor plugged into a wall wart with a barrel jack and a toggle switch. But what else does it need? This isn’t a precision machine tool, so applying the “make it out of whatever scrap” mindset seems like a much better fit than figuring out PWM control with a MOSFET and a microcontroller.

There are a couple of neat tricks in the build here. The most obvious is the classic laser-cut living hinge that we love so much. [Henrique] mentions that he buys MDF in 3 mm sheets for easy storage, so each section of the frame is built from layers that he laminates with glue himself. This trades precision and adds steps, but also give him a little flexibility. It’s certainly easier to add layers of thin stock together than it would be to carve out thicker pieces. Using the laser to precisely cut holes which are then match drilled through into the rest of the frame is a nice build acceleration too. The only improvement we can imagine would be using a shaft with a small finger chuck (like a Dremel) so it could use standard rotary tool bits to avoid making sanding disks by hand.

What could a tool like this be used for? There are lots of parts with small enough features to be cleaned up by such a small tool. Perhaps those nasty burrs after cutting off a bolt? Or trimming down mousebites on the edges of PCBs? (Though make sure to use proper respiration for cutting fiberglass!)

If you want to make one of these tools for your own desk, the files are here on Thingiverse. And check out the video overview after the break.

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3D Printed Brushed Motor is Easy to Visualize

A motor — or a generator — requires some normal magnets and some electromagnets. The usual arrangement is to have a brushed commutator that both powers the electromagnets and switches their polarity as the motor spins. Permanent magnets don’t rotate and attract or repel the electromagnets as they swing by. That can be a little hard to visualize, but if you 3D Print [Miller’s Planet’s] working model — or just watch the video below — you can see how it all works.

We imagine the hardest part of this is winding the large electromagnets. Getting the axle — a nail — centered is hard too, but from the video, it looks like it isn’t that critical. There was a problem with the link to the 3D model files, but it looks like this one works.

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Adding Smarts To Dumb Brushed Motors

A big part of the Hackaday Prize this year is robotics modules, and already we’ve seen a lot of projects adding intelligence to motors. Whether that’s current sensing, RPM feedback, PID control, or adding an encoder, motors are getting smart. Usually, though, we’re talking about fancy brushless motors or steppers. The humble DC brushed motor is again left out in the cold.

This project is aiming to fix that. It’s a smart motor driver for dumb DC brushed motors. You know, the motors you can buy for pennies. The motors that are the cheapest way to add movement to any project. Those motors.

The Smart Motor Driver for Robotics allows a DC brushed motor to be controlled by a host microcontroller over I2C, and sends back the speed and direction of the motor. PID is implemented, and the motor can maintain its own speed, independently of a lot of difficult control on the host system.

The guts of this motor controller are made of a PIC 12F microcontroller, a H-bridge motor driver, a Hall-effect sensor, and a neat magnetic encoder disc. Ultimately, this project will simply bolt onto the back of a cheap brushed motor and give it the same capabilities as a fancy servo or stepper. It’s never going to have the same torque or power handling as a beefy NEMA 17 stepper, but sometimes you don’t need that, and a simple brushed motor will do. A great project, and an excellent entry for the Hackaday Prize.

Zip Tie Quadcopter Frame is as Cheap as They Come

We’ve seen some cheap quadcopter builds over the years, but this one takes the cake. After seeing somebody post a joke about building a quadcopter frame out of zip ties and hot glue, [IronMew] decided to try it for real. The final result is a micro quadcopter that actually flies half-way decently and seems to be fairly resistant to crash damage thanks to the flexible structure.

The first attempts at building the frame failed, as the zip ties (unsurprisingly) were too flexible and couldn’t support the weight of the motors. Eventually, [IronMew] realized that trying to replicate the traditional quadcopter frame design just wasn’t going to work. Rather than a body with arms radiating out to hold the motors, the layout he eventually came up with is essentially the reverse of a normal quadcopter frame.

Zip ties reinforced with a healthy coating of hot glue are arranged into a square, with a motor at each corner. Then four zip ties are used to support the central “pod” which holds the battery and electronics. No attempt is made to strengthen this part of the frame, and as such the heavy central pod hangs down a bit in flight. [IronMew] theorizes that this might actually be beneficial in the end, as he believes it could have a stabilizing effect when it comes time to record FPV video.

He mentions that he’s still struggling to get the PID values setup properly in the flight computer, but in the video after the break you can see that it’s flying fairly well for a first attempt. We wouldn’t recommend you tear into a bag of zip ties when it comes time to build your first quadcopter, but it does go to show that there’s plenty of room for experimentation.

We’ve covered a number of unique quadcopter frames if you’re looking for something to set your next build apart from the rest. If you’ve got a big enough bed you can 3D print a very nice frame, but if you’ve got more time than equipment, you could always cut one out of a piece of plywood.

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Hacked Sea Scooter Lives Another Day

The Seadoo GTI Sea Scooter is a simple conveyance, consisting of a DC motor and a big prop in a waterproof casing. By grabbing on and firing the motor, it can be used to propel oneself underwater. However, [ReSearchITEng] had problems with their unit, and did what hackers do best – cracked it open to solve the problem.

Investigation seemed to suggest there were issues with the logic of the motor controller. The original circuit had a single FET, potentially controlled through PWM.  The user interfaced with the controller through a reed switch, which operates magnetically. Using reed switches is very common in these applications as it is a cheap, effective way to make a waterproof switch.

It was decided to simplify things – the original FET was replaced with a higher-rated replacement, and it was switched hard on and off directly by the original reed switch. The logic circuitry was bypassed by cutting traces on the original board. [ReSearchITEng] also goes to the trouble of highlighting potential pitfalls of the repair – if the proper care isn’t taken during the reassembly, the water seals may leak and damage the electronics inside.

Overall it’s a solid repair that could be tackled by any experienced wielder of a soldering iron, and it keeps good hardware out of the landfill. For another take on a modified DC motor controller, check out the scooter project of yours truly.