Tindie

There are people of diverse backgrounds selling on Tindie, but as far as I know, Jakub Polonský is the only one here with a PhD in electrochemistry. Though this gave him a good background in testing of electronic quantities for electrochemical systems, as far as designing electronics, he’s self taught. He graduated in 2012, but started with Arduino boards in 2010, allowing him to use this versatile tool for research purposes.

Polonský has been selling here since June of 2014, and offers test and measurement items that he’s made. I asked him to talk about the best parts of selling on Tindie.

Tindie is unique. A place that contains so much creativity and so many diverse things from people who actually designed them. It is so much different from the mass-produced generic stuff that you can buy on an auction site that begins with an “e” and ends with a “Bay”. The tight connection between the designer and customer is what I really like. I can talk with customers and if they want some feature or have a problem, I can directly solve it because I am the one who can add that feature and I know the most about my products. The conversations are very relaxed and friendly and often turn into a nice chat way past the initial issue.

As far as the worst, he notes that:

I am still not convinced that taking out pre-orders was a good idea… but I learned how to manage inventory so I am rarely out of stock.

Jakub believes the way you present information about products makes all the difference.

From what I have experienced, buyers like a good detailed documentation that can be understood even if they don’t possess such a deep knowledge of the item as the designer/seller does. So make the documentation thorough but readable. Test it on your friends/wife/grandpa 🙂

What could be considered the flagship product of his “Kaktus” store, the “MightyWatt” Arduino-controlled electronic load, was born out of his research.

I was involved in PEM fuel cell research and we had a commercial electronic load but its software was so-so and it was crashing frequently so I thought “hey, I can do this better and cheaper”. So I did and we ended up using six of MightyWatts, which costed less than one commercial load. The original application was thus PEM fuel cell testing but from my customers I know it’s being used in three main areas: solar cells, batteries and power supplies.

The device, which is now on its third revision, uses a FET as a variable resistor to maintain either a constant current load or a constant current drop. If you’re wondering, as I did, if a second resistor in series is needed to maintain the voltage drop, this is not the case:

It does not need any extra physical resistor. In the case of power supplies, they will switch to current-limited mode and in the case of batteries and fuel cells, their internal resistance will act as the second resistor so they have it “built-in.”

Pretty neat. So now you know that if you can produce something that “wastes” power in an extremely controlled and scientific manner, there’s actually a market for it. Polonský notes that, “I am really grateful that Tindie is there. I probably wouldn’t be selling MightyWatt at all if it weren’t for Tindie.”

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If you started using computers when CD-ROM drives seemed to have an amazing amount of space at around 650MB each, the fact that you can store many Gigabytes of data on a micro SD card the size of a rather small thumbnail seems amazing. At least it does to me. Though I grew up in an era when you could misplace a disk, it wasn’t going go be lost in the carpet, or even vacuumed up without some loud mechanical protest.

5 Megabytes in the 1950s; via reddit

On the other hand, even by that time things had progressed significantly, as this photo of a 5MB hard drive being loaded onto a plane shows.

So how do you actually organize these tiny devices? Cloud data storage is a great alternative for many of purposes, but if you need to keep data on portable media, you’ll need somewhere to physically store them. A baggie or jewelry box could work, but here’s something actually made for that purpose.

The picture at the top of this post is like one-organizer-to-rule-them-all and will put an end to digging through drawers looking for that microSD or low-provile thumb drive. It can hold 8 standard SD cards, 15 microSD cards, and 10 USB flash drives. As they are 3D-printed, you can customize the number of slots for each one as needed.

It looks like a clever idea. On the other hand, I wouldn’t attempt to clean it with a vacuum cleaner!

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Long before tiny OLED modules became commonplace, 7-segment displays did the job of showing users numerical data, as well as a somewhat limited alphabet. Of course, they’re still in use today and a quick and fun exercise to add to projects that need simple output. If you want to move beyond the ordinary, look into larger 7-segment displays.

Typcially one of these digits will be the size of your little fingernail. But there are other options out there. Here’s a kit that mates a larger 7-segment display with a driver backpack. It uses a transistor array to sink the current for each segment. The result is a single digit that is switches the segments serially and can be chained to more digits.

These display kits stand 45 millimeters (1.75 inches) tall when assembled. They might not make good components for a basketball display, but are quite a bit larger than standard. These are modules and it becomes more difficult to locate stock items as you get bigger than this. For instance there’s a 12″ over at Evil Mad Scientist but they’re non-stock and the price begins to add up. Foyard has a 5″ module (PDF) but trying to find a source in small quantities is an impossibility. If you really want to go big, consider building your own with an infinite amount of patience.

Digits, along with the decimal point, are changed via a shift register, which can be controlled using an Arduino. Example code and more information can be found on renewable energy innovation’s website.

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If you have an office job, chances are very high that you spend a lot of your time using a keyboard and mouse. Many of us never really think about these critical interface devices, but without them, many jobs wouldn’t be possible, or at least would be very different.

Personally, I started using a trackball a few years ago, and recently started using a relatively inexpensive mechanical keyboard. Though not that unique, they hopefully improve my efficiency somewhat.

If you’re already looking for out of the ordinary peripherals like mechanical keyboards, perhaps you’d like something absolutely unique. If that’s the case, you could make your own computer mouse, as seen in kit form here. The kit provides parts for a mouse, including a top shell and bottom base plate, as well as wiring and screws. You’ll just need to provide an Arduino board to interface between the mouse and a computer.

Alternatively, you could print your own with files for this mouse, which can be found on Thingiverse. You’d need to provide your own electronics, but the optical sensor board used in the kit can be found here, so it should work nicely.

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If you like to browse around on Tindie to see what is available, you’ll find sections full of interesting and unusual items. For me at least, that’s part of the fun of writing for this site.

The Sound section, which as of this writing has six pages of acoustic goodness, seems especially popular listing-wise. And why not? Making music is all about creativity, and if you can build your own instrument and/or accessory, what could be more creative?

On the other hand, after getting a DSLR and gradually getting better and better (less worse?) at controlling my camera for good and/or experimental effects, I have to report that there is only one page of Camera Equipment listings. What’s there looks really neat, much of it involving using a GoPro camera at extreme depths, but certainly it would be a great place for lighting, custom intervlometers, or even a light painting robot, like the one seen in the video below:

The great thing about this from a seller’s perspective, is that if you do want to list your camera hack, it won’t have as much competition as some other items!

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Polar plotters, AKA polargraphs, are devices that print on a vertical surface, based on the length of two strings holding a drawing instrument. Unlike a traditional CNC setup, where there are independent X and Y axes, polar plotters use a combination of the length of these lines and trigonometric relationships to determine a point on a whiteboard or other surface.

Thinking about this more, when I, and other students were in high school or middle school, it was hard to see why we needed to take algebra, or trigonometry. After graduating from engineering school and getting a job in the “real world” however, the need to know these concepts really well became obvious when designing certain parts and figuring out control schemes.

A polar plotter is a great way to show students that this kind of relatively complex math is actually quite useful in certain situations. I featured the Makelangelo plotter here in February, but another exciting solution, that almost seems specifically made for a classroom setting, is the gocupi, seen in the video below. It uses two suction cups to anchor the pulling motors, and attaches directly to a Raspberry Pi for control.

Now, if you’d like to illustrate to kids and/or college students why calculus is necessary, you might find that a little more challenging!

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Do you like soldering PCBs? Personally, I’d choose a terminal connector any time over having to deal with soldering (check out Wednesday’s post about ESP8266 screw terminals). This may be due in part to my equipment though, including a cheap helping hand device which doesn’t hold PCBs too well.

If you have to deal with soldering PCBs quite a bit, or if you even enjoy it, then this PCB Rax circuit board holder by Bench Werx looks like it would make the job much, much easier. It can hold rectangular boards up to 9-1/4″ x 8″, and if you need to build/repair something even bigger, the connecting rods can be replaced.

Where it really shines though is that it has extension brackets that are designed to hold oddly shaped boards, like the Christmas tree seen above. Once you have things roughly fastened together with the extension brackets, the threaded rods that connect the two halves of this device can be tightened further without hand tools. Additionally, the device can be set in a vertical or horizontal position, allowing you to work on projects in ergonomic comfort to your heart’s content!

Check it out in the video below. It looks much better than the tools I normally use; perhaps it could even convert solder-haters into solder-tolerants!

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If you want to build a CNC router, laser cutter, or other setup, you’ll generally need some sort of gantry system, stepper motors, a control board, and… wait for it… a computer with a parallel port. Yes, that’s right, many of the CNC controllers used today (including my own actually) still use a parallel port for control. And if you’re thinking you can just use a USB to parallel port adapter, I’ve found from personal experience that that doesn’t really work (though a PCI parallel port does).

The other popular option is a grbl-based solution, which runs on an Arduino and needs to be assembled from a variety of components. Tindie seller “Class B Project” thought there needed to be a better way to do this, and created an all-in-one solution with his motionPro 3+1 axis CNC controller.

This device can control up to four stepper motors, giving you the ability for X, Y, Z, and even a fourth axis if your setup is that advanced. Alternatively, you can clone one of these axes in order to control two motors, which can be useful in some situations. The board communicates via USB and a Bluetooth module can even be added for wireless control!

You can see this setup controlling a CNC laser cutter/engraver in the video below:

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If you’re going to work with electronics, you may have accepted the fact that you’ll need to solder components together. On the other hand, I can’t be the only one that finds this to be more of an annoyance than anything. Not only do you have to wait for your iron to heat up and make sure to unplug it afterwards so as not to cause a fire, you also need to get and keep wires in the proper position so they can be bonded together.

The good news is that there are alternatives. If you have the wherewithal, much of the work can be done using robots, and there are “helping hands” products that make the job easier. In certain situations, I’m a big fan of screw terminals, or even spring terminals, where you simply have to open them up, insert a wire, and release it so that its firmly held. Admittedly, it helps if you’ve applied ferrules or tinned the wires, but let’s not get ahead of ourselves.

These connections are common in industrial applications, but we’re seeing this method filter into maker applications more and more. I wrote about an Arduino screw terminal shield previously, and now there is one that can add these connections to the ESP8266 WiFi module. Given my previous rant, perhaps there is some irony in the fact that it can be had fully assembled or as a kit/just a PCB, meaning in those cases that you’ll need to solder it together. On the other hand, something like that would allow it to be ready to go when needed, perhaps in an application where you don’t have power for an iron available.

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Randomness is an interesting concept. If you were to flip a coin or roll dice, you’d expect random results. However, there is some nearly undetectable bias based on the construction of these objects and the person doing the flipping/rolling. The same concept applies to computer systems, which need to create random numbers for encryption and other functions.

In order to obtain random values, computers can keep a “pool” of random values to use as needed. In the Linux operating system this pool is only 4 kiloBytes in size, and is replenished using external sources such as keyboard timings and mouse movements. When used, this pool has to be replenished, which can take time.

If you need more randomness in your computing, the TrueRNG V3 USB number generator produces more than 400 kilobits per second of true random numbers. This can fill up the Linux entropy pool extremely quickly, allowing you to run applications for security, gaming, or simulations without delay.

A Random Pattern Generated with TrueRNG

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