From The MacGyver Files: Using A Stepper Motor As An Encoder

April 8, 2020 by Al Williams 27 Comments

It isn’t hard to imagine a scenario where you are stuck at home all day with nothing to do and certain items are in short supply. Sure, bathroom tissue gets all the press, but try buying some flour or a freezer and see how far you get. Plus online shopping has given up on next day delivery for the duration. Not hard to imagine at all. Now suppose your latest self-quarantine project needs a rotary shaft encoder. Not having one, what do you do? If you are [Tech Build] you go all MacGyver on an old printer and pull out a stepper motor.

How does a stepper motor turn into an encoder? Well, that’s the MacGyver part. We are not big fans of the physical circuit diagrams, but it looks like [Tech Build] borrowed (with credit) from an earlier post and that one has a proper schematic.

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Simon Says, But With Servos

April 7, 2020 by Kristina Panos 12 Comments

How much easier would life be if you could just grab hold of whatever mechanism you wanted to manipulate, move it like you want, and then have it imitate your movements exactly? What if you could give a servo MIDI-like commands that tell it to move to a certain location for a specific duration? Wonder no more, because [peterbiglab] has big-brained the idea into fruition.

With just one wire, an Arduino, and some really neat code, [peter] can get this servo to do whatever he wants. First he tells the Arduino the desired duration in frames per second. Then he grabs the horn and moves it around however he wants — it can even handle different speeds. The servo records and then mimics the movements just as they were made.

The whole operation is way simpler than you might think. As [peterbiglab] demonstrates in the video after the break, the servo knows its position thanks to an internal potentiometer on the motor’s rotor. If you locate the pot output pin on the control board and run a wire from there into an Arduino, you can use that information to calibrate and control the servo’s position pretty easily. There are a ton of possibilities for this kind of control. What would you do with it? Let us know in the comments.

If you want to try this with a bunch of servos at once, might as well build yourself a little testing console.

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Subwoofer Gets Arduino Brain Transplant

April 6, 2020 by Tom Nardi 15 Comments

The Samsung PS-WTX500 subwoofer is designed to be used as part of a 5.1 channel home theater system, but not just any system. It contains the amplifiers for all the channels, but they’ll only function when the subwoofer is connected to the matching receiver. [Alejandro Zarate] figured there must be some way to unlock the system’s full functionality without being limited to the original receiver, he just needed to reverse engineer how the subwoofer worked.

All the wires tuck underneath the Arduino

The result is a fantastically well documented write-up that covers the whole process, starting with how [Alejandro] identified and researched the Pulsus PS9829B Digital Audio Processor (DAP). Documentation for this particular chip seems hard to come by, but he was able to find a similar chip from the same manufacturer that was close enough to put him on the right track. From there, he started studying the SPI communications between the DAP and the subwoofer’s S3P70F4 microcontroller.

After analyzing the communication between the two chips, [Alejandro] pulled the S3P70F4 off the board and wired an Arduino Pro Mini 328 in its place. The Arduino was quite a bit larger than the original microcontroller, but with some careful wiring, he manged a very professional looking installation. Short of coming up with a custom PCB adapter, we don’t think it could look much better.

With some relatively straightforward code and a listing of the captured byte sequences, the Arduino was able to power up the PS-WTX500’s amplifiers and handle the incoming audio signal as a stand-alone device.

In the past we’ve seen a similar trick done with the ESP8266, which had the added benefit of enabling WiFi control of the speakers. We’re all for adding modern functionality to older hardware, even if you’ve got to hang it off the back as an external module.

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Offline Dinosaur-Jumping Becomes A Real Workout

April 6, 2020 by Kristina Panos 16 Comments

It’s great to see people are out there trying to find fun ways to exercise amid the current crisis. Although jumping up and down isn’t great for the knees, it does give decent cardio. But if you don’t have a rope or a puddle, we admit that jumping can lose its bounce pretty fast.

Quarantine has been a game-filled time for [fridaay]. Somewhere between a handful of FPS games, he decided to try to play Google’s offline dinosaur-based side scroller game by making the dinosaur spring over the saguaros whenever he physically jumps in the air. (Video, embedded below.)

Here’s how it works: [fridaay] holds a transmit circuit that consists of an Arduino UNO, an accelerometer module, and an nRF24L01 transceiver, all running on a 9 V battery. Whenever [fridaay] jumps, the accelerometer reads the change in Z and sends it to the receiving circuit, which is just another UNO and nRF. The receiving UNO is connected to a laptop and configured to press the space bar so the dinosaur canters over the cacti.

We’ve never been able to stay alive long enough in the game to see this happen, but apparently you need to crouch at some point in the game. [fridaay] has yet to implement a control for that, but we’re sure he’ll think of something. Jump past the break to see the video, and hit him up if you need the code.

If you have a lot of parts at your disposal, why not make a physical version?

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NeoPixel Matrix Simulation Lets You Virtually Groove To The Lights

April 4, 2020 by Al Williams 5 Comments

You are stuck at home quarantined and you want to do some Arduino projects. The problem is you don’t have all the cool devices you want to use. Sure, you can order them, but the stores are slow shipping things that aren’t essential these days. If you want to get a headstart while you are waiting for the postman, check out Wokwi’s Playground. For example, you can write code to drive a virtual NeoPixel 16×16 matrix. There’s even example code to get you started.

There are quite a few other choices in the playground including Charlieplexed LEDs, a keypad, and an LCD. There are also challenges. For example, in the traffic light challenge, you are given code that uses a task scheduler library to implement a traffic light. You have to add a turn signal to the code.

In addition to LEDs in various configurations, the site has some serial bus components, an LCD, a keypad, and a NeoPixel strip. There are also a few tools including an EasyEDA to KiCad converter and a way to share sourcecode similar to Pastebin.

Of course, simulations only get you so far, but the site is a fun way to play with some different I/O devices. It would be very nice if you could compose for the different components together, but you could work your code in sections, if necessary. You can do similar things with TinkerCad circuits. If you want to install software, there’s a simulator for you, too.

Minimalist Magnetic Minute Minder Mesmerizes

April 3, 2020 by Kristina Panos 26 Comments

Timepieces are cool no matter how simplistic or granular they are. Sometimes its nice not to know exactly what time it is down to the second, and most of the really beautiful clocks are simple as can be. If you didn’t know this was a clock, it would still be fascinating to watch the bearings race around the face.

This clock takes design cues from the Story clock, a visual revolution in counting down time which uses magnetic levitation to move a single bearing around the face exactly once over a duration of any length as set by the user. As a clock, it’s not very useful, so there’s a digital readout that still doesn’t justify the $800 price tag.

[tomatoskins] designed a DIY version that’s far more elegant. It has two ball bearings that move around the surface against hidden magnets — an hour ball and a minute ball. Inside there’s a pair of 3D-printed ring gears that are each driven by a stepper motor and controlled with an Arduino Nano and a real-time clock module. The body is made of plywood reclaimed from a bed frame, and [tomatoskins] added a walnut veneer for timeless class.

In addition to the code, STLs, and CAD files that birthed the STLs, [tomatoskins] has a juicy 3D-printing tip to offer. The gears had to be printed in interlocked pieces, but these seams can be sealed with a solution of acetone and plastic from supports and failed prints.

If you dig minimalism but think this clock is a bit too vague to read, here’s a huge digital clock made from small analog clocks.

Using A Vending Machine Bill Acceptor With Arduino

March 31, 2020 by Tom Nardi 9 Comments

We’ve all seen, and occasionally wrestled with, bill acceptors like the one [Another Maker] recently liberated from an arcade machine. But have you ever had one apart to see how it works? If not, the video after the break is an interesting peak into how this ubiquitous piece of hardware tells the difference between a real bill and a piece of paper.

But [Another Maker] goes a bit farther than just showing the internals of the device. He also went through the trouble of figuring out how to talk to it with an Arduino, which makes all sorts of money-grabbing projects possible. Even if collecting paper money isn’t your kind of thing, it’s still interesting to see how this gadget works on a hardware and software level.

As explained in the video, a set of belts are used to pull the bill past an array of IR LEDs. The hardware uses these to scan the bill and perform some dark magic to determine if it’s a genuine piece of currency. [Another Maker] notes that these readers actually need to receive occasional firmware updates to take into account new bill designs. In fact, the particular unit he has is so out of date that it won’t accept modern $5 bills; which may explain how he got it for free in the first place.

Years ago we saw one of these bill acceptors used to make a DIY Bitcoin ATM. Of course back then, a few bucks would get you a semi-reasonable amount of BTC. These days you would skip the paper currency and do it all digitally.

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