arduino

2926 Articles

Resistors Sorter Measures Values

May 23, 2020 by 22 Comments

We’ve all been there. A big bag of resistors all mixed up. Maybe you bought them cheap. Maybe your neatly organized drawers spilled. Of course, you can excruciatingly read the color codes one by one. Or use a meter. But either way, it is a tedious job. [Ishann’s] solution was to build an automatic sorter that directly measures the value using a voltage divider, rather than rely on machine vision as is often the case in these projects. That means it could be modified to do matching for precise circuits (e.g., sort out resistors all marked 1K that are more than a half-percent away from one nominal value).

There is a funnel that admits one resistor at a time into a test area where it is measured. A plate at the bottom rotates depending on the measured value. In the current implementation, the resistor either falls to the left or the right. It wouldn’t be hard to make a rotating tray with compartments for different values of resistance. It looks like you have to feed the machine one resistor at a time, and automating that sounds like a trick considering how jumbled loose axial components can be. Still, its a fun project that you probably have all the parts to make.

An Arduino powers the thing. An LCD screen and display control the action. If you want some practice handling material robotically, this is a great use of servos and gravity and it does serve a practical purpose.

We have seen many variations on this, including ones that read the color code. If you ever wanted to know where the color code for resistors came from, we took a trip to the past to find out earlier this year.

Continue reading “Resistors Sorter Measures Values” →

An Arduino As A PLL

May 23, 2020 by 16 Comments

At the heart of many amateur radio and other projects lies the VFO, or Variable Frequency Oscillator. Decades ago this would have been a free-running LC tuned circuit, then as technology advanced it was replaced by a digital phase-locked-loop frequency synthesiser and most recently a DDS, or Direct Digital Synthesis chip in which the waveform is produced directly by a DAC. The phase-locked loop (PLL) remains a popular choice due to ICs such as the Si5351 but is rarely constructed from individual chips as it once might have been. [fvfilippetti] has revisited this classic circuit by replacing some of its complexity with an Arduino (Spanish language, Google Translate link).

The internals of a PLL frequency synthesiser
The internals of a PLL frequency synthesiser. Image by Chetvorno – CC0

A PLL is a simple circuit in which one oscillator is locked to another by controlling it with a voltage derived from comparing the phase of the two. Combining a PLL with a set of frequency dividers creates a frequency synthesiser, in which a variable frequency oscillator can be locked to a single frequency crystal with the output frequency set by the division ratios. The classic PLL chip is the CMOS 4046 which would have been combined with a pile of logic chips to make a frequency synthesiser. The Arduino version uses the Arduino’s internal peripherals to take the place of crystal oscillator, dividers, and phase comparator, resulting in an extremely simple physical circuit of little more than an Arduino and a VCO for the 40 metre amateur band. The code can be found on GitLab, should you wish to try for yourself.

It would be interesting to see how good this synthesiser is at maintaining both a steady frequency and minimal phase noise. It’s tempting to think of such things as frequency synthesisers as a done deal, so it’s always welcome to see somebody bringing something new to them. Meanwhile if PLLs are new to you, we have just the introduction for you.

Spherical Quadruped Arduino Robot

May 21, 2020 by 9 Comments

[Greg06] started learning electronics the same way most of us did: buy a few kits, read a few tutorials, and try your hardest to put a few things together. Sound familiar? After a while, you noticed your skills started increasing, and your comfort level with different projects improved as well. Eventually, you try your hand at making your own custom projects and publishing your own tutorials.

Few are lucky to have a first-project as elaborate as [Greg06’s] quadruped robot. We don’t know about you, but for some of us, we were satisfied with blinking two LEDs instead of just one.

[Greg06’s] robot has a quadruped based, housed within a 3D printed spherical body. The legs are retractable and are actuated by tiny servo motors inside the body. [Greg06] even included an ultrasonic distance sensor for the obstacle avoidance mechanism. Honestly, if it weren’t for the ultrasonic distance sensor protruding from the spherical body, you might think that the entire robot was just a little Wiffle ball. This reminds us of another design we’ve seen before.

If that weren’t enough, the spherical head can rotate, widening the range of the ultrasonic distance sensor and obstacle avoidance mechanism. This is accomplished by attaching another servo motor to the head.

Pretty neat design if you ask us. Definitely one of the coolest quadrupeds we’ve seen.

Pinball Machine Needs No Wizard

May 18, 2020 by 15 Comments

Ever since he was a young boy, [Tyler] has played the silver ball. And like us, he’s had a lifelong fascination with the intricate electromechanical beasts that surround them. In his recently-completed senior year of college, [Tyler] assembled a mechatronics dream team of [Kevin, Cody, and Omar] to help turn those visions into self-playing pinball reality.

You can indeed play the machine manually, and the Arduino Mega will keep track of your score just like a regular cabinet. If you need to scratch an itch, ignore a phone call, or just plain want to watch a pinball machine play itself, it can switch back and forth on the fly. The USB camera mounted over the playfield tracks the ball as it speeds around. Whenever it enters the flipper vectors, the appropriate flipper will engage automatically to bat the ball away.

Our favorite part of this build (aside from the fact that it can play itself) is the pachinko multi-ball feature that manages to squeeze in a second game and a second level. This project is wide open, and even if you’re not interested in replicating it, [Tyler] sprinkled a ton of good info and links to more throughout the build logs. Take a tour after the break while we have it set on free play.

[Tyler]’s machine uses actual pinball machine parts, which could quickly ramp up the cost. If you roll your own targets and get creative with solenoid sourcing, building a pinball machine doesn’t have to be a drain on your wallet.

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Building D-O, The Cone Face Droid

May 17, 2020 by 10 Comments

For many of us, movies are a great source of inspiration for projects, and the Star Wars films are a gift that just keeps giving. The D-O droid featured and the Rise of Skywalker is the equivalent of an abandoned puppy, and with the help of 3D printing, [Matt Denton] has brought it to life. (Video, embedded below.)

D-O is effectively a two-wheeled self-balancing robot, with two thin drive wheels on the outer edges of the main body. A wide flexible tire covers the space between the two wheels, where the electronics are housed, without actually forming part of the drive mechanism. The main drive motors are a pair of geared DC motors with encoders to allow closed-loop control down to very slow speeds. The brains of the operation is an Arduino MKR-W1010 GET on a stack that consists of a motor driver, shield, IMU shields, and prototyping shield. [Matt] did discover a design error on the motor driver board, which caused the main power switching MOSFET to burst into flames from excessive gate voltage. Fortunately he was able to work around this by simply removing the blown MOSFET and bridging the connection with a wire.

The head-on D-O is very expressive and [Matt] used four servos to control its motion, with another three to animate the three antennas on the back of its head. Getting all the mechanics to move smoothly without any slop took a few iterations to get right, and the end result looks and moves very well. Continue reading “Building D-O, The Cone Face Droid” →

Piston-Powered Pellet Pusher For Peckish Pets

May 14, 2020 by 2 Comments

We all have our new and interesting challenges in lockdown life. If you’ve had to relocate to ride it out, the chances are good that even your challenges have challenges. Lockdown left [Kanoah]’s sister in the lurch when it came to feeding her recently-adopted pet rat, so he came up with a temporary solution to ensure that the rat never misses a meal.

Most of the automated pet feeders we see around here use an auger to move the food. That’s all fine and good, but if you just need to move a singular mass, the screw seems like overkill. [Kanoah]’s feeder is more akin to a pellet-pushing piston. It runs on a Metro Mini, but an Arduino Nano or anything with enough I/O pins would work just fine. The microcontroller starts counting the hours as soon as it has power, and delivers pellets four times a day with a servo-driven piston arm. [Kanoah] has all the files up on Thingiverse if you need a similar solution.

There many ways of solving the problem of dry pet food delivery. Wet food is a completely different animal, but as it turns out, not impossible to automate.

Passing The Time By Reading The Time

May 14, 2020 by 4 Comments

Binary clocks are a great way to confuse your non-technical peers when they ask the time from you — not that knowing about the binary system would magically give you quick reading skills of one yourself. In that case, they’re quite a nice little puzzle, and even a good alternative to the quarantine clocks we’ve come across a lot recently, since you can simply choose not to bother trying to figure out the exact time. But with enough training, you’ll eventually get the hang of it, and you might be in need for a new temporal challenge. Well, time to level up then, and the Cryptic Wall Clock built by [tomatoskins] will definitely keep you busy with that.

Example of the clock showing 08:44:47
Diagram of the clock showing 08:44:47

If you happen to be familiar with the Mengenlehreuhr in Berlin, this one here uses the same concept, but is built in a circular shape, giving it more of a natural clock look. And if you’re not familiar with the Mengenlehreuhr (a word so nice, we had to write it twice), the way [tomatoskins]’ clock works is to construct the time in 24-hour format by lighting up several sections in the five LED rings surrounding a center dot.

Starting from the innermost ring, each section of the rings represent intervals of 5h, 1h, 5m, 1m, and 2s, with 4, 4, 11, 4, and 29 sections per ring respectively. The center dot simply adds an additional second. The idea is to multiply each lit up section by the interval it represents, and add the time together that way. So if each ring has exactly one section lit up, the time is 06:06:02 without the dot, and 06:06:03 with the dot — but you will find some more elaborate examples in his detailed write-up.

This straightforward and yet delightfully unintuitive concept will definitely keep you scratching your head a bit, though you can always go weirder with the Roman numerals palm tree clock for example. But don’t worry, [tomatoskins] has also a more classic, nonetheless fascinating approach in his repertoire.