The Un-Digital Robotic Arm

556When you think of a robotic arm, you’re probably thinking about digital control, microcontrollers, motor drivers, and possibly a feedback loop. Anyone who was lucky enough to have an Armatron knows this isn’t the case, but you’d still be surprised at how minimal a robotic arm can be.

[viswesh713] built a servo-powered robotic arm without a microcontroller, and with some interpretations, no digital control at all. Servos are controlled by PWM signals, with a 1 ms pulse rotating the shaft one way and a 2 ms pulse rotating the shaft the other way. What’s a cheap, popular chip that can easily be configured as a timer? Yep, the venerable 555.

The robotic arm is actually configured more like a Waldo with a master slave configuration. [viswesh] built a second arm with pots at the hinges, with the resistance of the pots controlling the signal output from a 556 dual timer chip. It’s extremely clever, at least until you realize this is how very early robotic actuators were controlled. Still, an impressive display of what can be done with a simple 555. Videos below.

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Solar-Powered Mosquito Birth Control Is Making Waves

Mosquitoes really suck. Joking aside, they spread dangerous and deadly diseases like Malaria, Dengue and West Nile. They like to breed in pools of stagnant water which can be difficult to keep up with. From egg-laying to larval development, still water is vital for breeding mosquitoes. Instructables user [Gallactronics] hypothesized that disrupting the surface tension of potential nurseries was the key to discouraging breeding, and he built a solar-powered device for under $10 that proves his theory.

There are a few standard ways of dealing with standing water. Someone can keep it drained or it can be sprayed with pesticides. By aerating the water, mosquito mothers are far less likely to successfully arrange their eggs on the surface. Even if the eggs take, the turbulent water surface will suffocate the larvae.

This bubbler ticks all the boxes. It starts as soon as it comes in contact with water and sounds a piezo alarm when the pool has dried or when someone removes it. It runs for 10 minutes at 10-minute intervals using a 555 timer and some transistors. The water probes are stainless steel bolts, and it runs on a 6V 450mA solar cell. Be sure to watch the demonstration below.

We love to see this kind of ingenuity and elegance in problem solving. Then again, we also like the idea of killing them with lasers.

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DIY Bell For Your Trains of Lionel

[Peter]’s dad recently rekindled his love for Lionel trains and wanted a bell to keep the crossings safe for O gauge drivers and pedestrians. Using parts he had lying around and a doorbell from the hardware store, [Peter] concocted this DIY train crossing bell at his dad’s request.

The idea was to make the bell chime about once per second. To achieve this, [Peter] used a non-repeating electro-mechanical doorbell that emits a single note on continuous press. You could also roll your own bell with a spring-loaded solenoid and something bell-like for it to strike.

[Peter]’s three-stage design uses a full-wave bridge rectifier to convert the AC from the train transformer to DC. He drops it to 5V and sends it through a 555 and some resistors to set the frequency and duty cycle. His output section translates the voltage back up to match the input desired by the doorbell.  [Peter] included a 1N4002 as a back EMF snubber to keep feedback from damaging the power MOSFET. Stick around for his demonstration video after the jump.

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A 555-Based, Two-Channel Remote Control Circuit

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[fahadshihab], a young tinkerer, shared his circuit design for a simple remote control using 555 timers.  Using a 555 calculator, he designed a clock circuit that would run at 11.99 Hz. Two transistors are connected to inputs (presumably button switches). One sends the plain clock signal, and one sends the inverted clock signal. A matching circuit at the other end will separate the channels. All it requires is connecting the two circuits in order to synchronize them. It would be easy enough to interface this with an oscillator, an IR LED, or a laser for long-range control.

The great thing about this circuit is its simplicity. It’s often so easy to throw a microcontroller into the mix, that we forget how effective a setup like this can be. It could also be a great starter circuit for a kid’s workshop, demonstrating basic circuits, timers, and even a NOT gate. Of course, it would be a good refresher for those without a lot of circuit knowledge too. Once you’ve mastered this, perhaps an AM transmitter is next?

What’s inside a 555?

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The 555 timer chip is a ubiquitous piece of technology that is oft-considered the hardcore way of doing things. Of course, the old timers out there will remind us that discrete transistors are the badass way of doing things, and tubes even more so. It’s not quite at the level of triodes and transformers, but Evil Mad Scientist’s discrete 555 kit is still an amazing piece of kit.

Instead of transistors and resistors etched into silicon as in the OG 555, [Windell] over at EMS turned the basic circuit inside a 555 into a mega-sized version using discrete components. Your parts bins need new scale if you’re going to work with this and other up-scaled hobby electronic components.

Although the integrated stand that makes the whole package look like an overgrown DIP doesn’t break out the signals on the board, it does include some neat screw terminals for alligator clips and bits of wire so this kit can be used in a circuit. Because it uses discrete components, you can also take a meter or scope to check out how a 555 chip works from the inside.

The easy or hard way to build a PWM dimmer

From what you would gather from Hackaday’s immense library of builds and projects over several years, the only way to do PWM is with a microcontroller, some code, a full-blown IDE, or even a real-time operating system. To some readers, we’re sure, this comes naturally and with an awesome toolchain it can be as easy as screwing in a light bulb. There is, of course, an easier way.

[Jestin] needed to vary the current on a small 12 Volt load. Instead of digging out an in system programmer, he turned to the classic 555 chip. With a single pot, it’s easy to vary the duty cycle of the 555 and connect that to a MOSFET. Put a load in there, and you have a very easy circuit that’s a fully functioning PWM dimmer.

If all you have are a few scraps in your part drawers, this is a very, very easy way to set up a dimmer switch. We’re also loving [Jestin]’s improv aluminum tube enclosure, as seen in the video below.

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Hacking McDonald’s Minion toy to be an electric slidewhistle

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This is a look at the brain surgery which [Tim] performed on a Happy Meal Toy. The McDonald’s package meal perk comes with one of several different Despicable Me 2 characters. But [Tim] wasn’t a fan of this one since you had to blow in it to make noise. He grabbed a 555 timer and added his own circuit to the toy which turns it up to 11 (seriously, turn your volume down before playing the video).

Disassembly includes removing a screw which needs a 3-sided screwdriver (protip: use a bench grinder and a cheap screw driver to make your own). There’s also some prying to get into the skull and then its time to work on the slide whistle. The blue tube is a regular slide whistle which you blow into from the back and pull on the red goo to change the pitch. [Tim] added a photoresistor to the mouthpiece and an LED on the slide. Moving the light source changes the intensity which is one of the adjustments to make 555 circuit howl.

We love the Happy Meal toy hacks because they seem so visceral. A couple years ago it was parts harvesting from Avatar toys. which in turn inspired a tripwire hack with a Penguin toy.

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