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Hardware store robot hand

hardware-store-robot-hand

Here’s a robot hand which can be built using mostly hardware store items. It doesn’t have the strongest of grips, but it does have lifelike movement. The demonstration video shows it picking up small objects like a metal nut.

The image above shows the ring and pinky fingers of the hand beginning to flex. These are controlled by the servo motors mounted in the palm area. The skeletal structure of each digit begins with the links of a bicycle chain. The links are first separated by removing the friction fit rods. Each rod is replaced with a screw and a nut, which also allows the springs (which open the digits) to be anchored at each ‘knuckle’.

[Aaron Thomen] didn’t stop the design process once the hand was finished. He went on to build a controller which lets you pull some rings with your fingers to affect movement. This movement is measured by a set of potentiometers and translated into electrical signals to position the hand’s servo motors. The demo, as well as two how-to videos are embedded below.

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Adding Bluetooth remote control to PC speakers

adding-bluetooth-remote-control-to-pc-speakers

[Andrzej's] plain old computer speakers are ordinary no more. He pulled off a fairly complicated hack which now lets him control speakers via Bluetooth.

He had a set of Creative brand computer speakers with a volume potentiometer that needed replacing. He was having trouble finding a drop-in replacement part and decided he would just go with a rotary encoder. Obviously you can’t just drop one of those in, he would need a microcontroller to monitor the encoder and translate the change into the appropriate resistance. He figured if he was going this far he might as well make the most out of the uC.

Above you can see all the stuff he crammed into the original case. The rotary encoder is seen on the lower left. An ATmega8 is on a PCB he made himself. The white part to the left is a digital potentiometer which feeds the resistance to the original speaker PCB. On the left is the Bluetooth module which lets him control everything from his phone. You can see a demo of that after the break.

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Hi-Hat MIDI controller

midi-hi-hat-controller

Drumming hackers take note, if you’ve got an extra bass drum pedal it’s cheap and simple to use it as a MIDI controller. This rig was thrown together to supplement a DIG DRUM electric drum set. That piece of equipment has a pedal add-on that didn’t come with it. Turns out all it does is feed a resistance value to the set.

To get this up and running a frame was built from a metal base and acrylic side piece. The acrylic hosts a trimmable potentiometer which connects to an 1/4″ stereo jack right beside it. This facilitates connecting the pedal to the drum set using an audio patch cable. Interface with the pedal is accomplished with a few bits from the hardware store. The axle of the pedal sticks out one side, and is clamped between two washers. The other side of the washer grip the timpot causing it to move when the pedal does.

This hardware is a snap to use with your own MIDI device. We’d suggest giving the HIDUINO package a try.

Ask Hackaday: What’s an easy way to build a potentiometer for a soldering iron?

diy-potentiometer-2

[Lee] wrote in to share the work he’s done in building a controller for his soldering iron. The idea started when he was working with an ATX power supply. He figured if it works as a makeshift bench supply perhaps he could use it as the source for an adjustable iron. To get around the built-in short-circuit protection he needed a potentiometer to limit the current while allowing for adjustments. His first circuit used a resistor salvaged from an AT supply and a trimpot from some computer speakers. That melted rather quickly as the pot was not power rated.

This is a picture of his next attempt. He built his own potentiometer. It uses the center conductor from some coaxial cable wrapped around the plastic frame of an old cooling fan. Once the wire was in place he sanded down the insulation on top to expose the conductor. The sweeper is a piece of solid core wire which pivots to connect to the coil in different places. It works, and so far he’s managed to adjust a 5V rail between 5A and 20A.

How would you make this system more robust? Short of buying a trimpot with a higher power rating, do you think this is the easy way to build a soldering iron controller? Let us know by leaving your thoughts in the comments.

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New and improved Potentar

We like what we’re seeing and hearing with [Dorian Damon's] newest version of the Potentar. This is revision 2.0 of the instrument we saw in a December links post. He calls it the Potentar, since it uses a linear potentiometer in a way similar to how the frets on a guitar work (Potentiometer + Guitar = Potentar).

The first thing you should notice is the case upgrade. The original used what looked like unfinished scrap wood, but finished wood of this case really makes the thing look like a traditional instrument. With this design he loses the Arduino in favor of a standalone ATmega328 chip. You’ll notice knobs and a switch on the face of the body. This allows for selecting a couple different kinds of scales and turning the power off. The linear potentiometer and sewing machine button are the same as before. After the break you can catch his description and a quick performance thanks to the audio jack for patching it into an amp.

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Increasing a digital servo motor’s range of motion

Unhappy with the 120 degree range of movement for this digital servo motor [Malte] set out to expand its flexibility. He settled upon a hack that alters the feedback potentiometer in order to give the motor a wider range (translated).

The test video (embedded after the break) shows tick marks for before and after his alterations. You can see that the wider tick marks get much closer to the 180 degree range he’s interested in. The control method is no different than it was before, the internal circuitry is still listening for a control signal with pulses between 1 and 2ms to establish the position of the servo horn. [Malte] added resistors on the two outside legs of the feedback potentiometer. This is what that control circuit measures in order to judge the position of the servo horn. He’s using 1.6k Ohm resistors in this demonstration. But he didn’t just drop them in willy-nilly. His writeup discusses the calculations he used to determine the target voltage for the motor position he wants.

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Improving your flight sim experience with Hall effect sensors

hall-effect-controls

[Gene Buckle] built himself a nice custom cockpit for playing Flight Simulator, but during use he found that the gimbal he constructed for the pitch and roll controls was nearly unusable. He narrowed the problem down to the potentiometers he used to read the angle of the controls, so he set off to find a suitable and more stable replacement.

He figured that Hall effect sensors would be perfect for the job, so he picked up a pair of Allegro 1302 sensors and began fabricating his new control inputs. He mounted a small section of a pen into a bearing to use as an input shaft, attaching a small neodymium magnet to either side. Since he wanted to use these as a drop-in replacement for the pots, he had to fabricate a set of control arms to fit on the pen segments before installing them into his cockpit.

Once everything was set, he fired up his computer and started the Windows joystick calibration tool. His potentiometer-based controls used to show a constant jitter of +/- 200-400 at center, but now the utility displays a steady “0”. We consider that a pretty good result!

[Thanks, Keith]

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