Review: Transistor Tester

Amazon has been getting creepier and creepier lately with their recommendations.  Every time I log in, I’m presented with a list of new Blinky LEDs, Raspberry Pi accessories, Arduino shields, and the like. It’s as if they know me. Their customer database paid off when it recommended a $22 transistor / component tester. I’ve been seeing those testers around quite a bit lately. Curiosity got the better of me and my mouse found its way to the “Buy it now with one click” button. Two days later I had a “SainSmart Mega328 Transistor Tester Diode Triode Capacitance ESR Meter MOS/PNP/NPN L/C/R” in my hands.

I’m going to get the obvious out of the way. This thing is built cheap – as cheap as the factories can make it. My particular unit arrived with the LCD flapping in the breeze, hanging on by its flex cable. Fitting the LCD back into the acrylic backlight frame revealed a slightly worrisome twist in that same flex. Thankfully nothing was actually damaged, though I do want to give the flex cable some protection in the future. More on that later. The circuitry was open for all the world to see on the bottom of the tester. The heart of the unit is an ATmega328. Supporting it are a few transistors and a handful of passives.

I didn’t have huge expectations for the tester, but I hoped it would at least power up.  Hooking up a 9 volt battery and pressing the magic button brought the tester to life. Since I didn’t have anything in the socket, it quickly lit up and displayed its maker information – “”, and “By Efan & HaoQixin”, then it informed me that I had “No, unknown, or damaged part”.

I had a few resistors lying around the bench (doesn’t everyone?) so I put one in. The tester read it as 9881 ohms. Sure enough, it was a 10K 5% resistor.  Capacitors – ceramic disc, electrolytic, and surface mount all worked as well. The tester even provided ESR values. The real test would be a transistor. I pulled an old  2N2222 in a TO-18 metal can, and popped it in the tester. The damn thing worked – it showed the schematic symbol for an NPN transistor with Collector, Base, and Emitter connected to Pins 1,2,and 3 respectively. Flipping the pins around and re-testing worked as well. The tester showed hFe as 216, and forward voltage as 692 mV, both reasonable numbers for a 2N2222.

triacThe tester worked surprisingly well – it was able to correctly identify BJTs, FETs, even esoteric parts. The only thing it balked on was a linear voltage regulator, which showed up as two diodes. Regulators are a bit more than a simple device though, so I can’t blame the tester there.  The values returned were all reasonable as well. While I don’t have a calibrated lab to check against, the numbers lined up with my Fluke meter.

So what exactly is driving this little tester? There are about 20 versions of it on the market, all of them from China. 91make is a seller on, often referred to as “China’s ebay.” 91make’s front page features no less than 7 versions of the transistor tester, with various cases and LCDs. Some digging turned up the history on this device. It turns out the transistor tester is an open source hardware project (translated) originally created by [Markus Frejek], and built upon by [Karl-Heinz Kubbeler] and a number of others. The Subversion repository  for the project shows it is quite active, with the most recent check-in only a few hours ago. The project is also well documented. The English PDF is 103 pages, explaining theory of operation, the circuit itself, and the software. The document even explains some of the shortcomings of the Chinese versions of the tester, including using a zener diode where the original schematic calls for a precision 2.5V reference. Yes, it will work, but it won’t be as accurate as the original.

The devs also don’t officially support the clones which I can understand, considering the quality and changes in design each manufacturer is baking in to their own version. There is  a huge thread on the EEVblog forum covering these testers. Some can be modified to be closer to the official version. In fact, with an ISP tool the intrepid hacker can update the firmware to the current rev from [Karl-Heinz’s] repository.

So the final verdict on this tester is that it is a thumbs up with a small caveat. These testers are built down to a cost (and that cost is as close to zero as possible). They’re great for sorting parts, but they’re no substitute for a higher quality measuring device. I’d also love to see a version that supports the original developers.

Review: Printrbot Assembled Simple Metal

Hackaday is getting back into the swing of doing reviews, and with that comes reviews of the tool du jour, 3D printers. I have some reservations about reviewing a 3D printer; they’re a new technology, and what may be standard today could be hopelessly outdated in a few months time. Remember geared extruders? The new hotness is, apparently, direct drive extruders.

This is a review of the Printrbot Assembled Simple Metal. If you need any evidence that reviews of 3D printers have a shelf life, you only need to look at the Getting Started guides for this printer. When I bought my Simple Metal, the Printrbot recommended software stack was Slic3r and Repetier-Host. Barely three months later, Cura is now the Printrbot recommended software stack. If you think a simple change in software is inconsequential, check out these prints:

prusa parts
Prusa i3 X-carriages. Left sliced by Slic3r, right sliced by Cura

The print on the left was sliced with Slic3r. The print on the right was sliced with Cura. Notice the small teeth that grip the timing belt on each of these prints. With the Cura-sliced print, everything is fine. The Slic3r-sliced print is a complete failure, not of the machine, but the recommended software for the machine.

Therefore, if the goal of writing a review is to have a definitive opinion of a piece of equipment, a number of questions must be addressed. Since most 3D printing software is open source, should software be included in the review? Is the value proposition of a 3D printer simply a function of price to build volume (this seems to be the standard metric now), or are there intangibles? Should the review cover the quality of prints out of the box, or should the review only focus on print quality after dozens of hours of tweaking? I simply don’t know the answers to these questions, and I suspect you couldn’t get any two people to agree on the answers to these questions.

With that said, I feel I have used this printer enough to make a judgment call as to if this printer was a good buy.

Continue reading “Review: Printrbot Assembled Simple Metal”

Review: Re:load Pro

About a year ago, [Nick Johnson] over at Arachnid Labs sent a tip in about Re:load Pro, his digital constant current load design. [Nick] was running a crowdfunding campaign, which always makes me think twice about posting. However in this case, I had no qualms writing a feature here on the blog (and backing the campaign with my own cash). Re:load Pro is actually [Nick’s] third generation current load. Having purchased and used the original Re:load, I knew [Nick] was capable of fulfilling all the promises in the campaign. Turns out I was right – [Nick] and the Arachnid Labs team had a very successful crowdfunding campaign. All the kickstarter backers have been enjoying their units for months now. When it came time to stock up the Hackaday Store, the Re:load Pro was a no-brainer.

What does one need a digital constant current load for? Plenty of jobs could benefit from it! From testing batteries to verifying power supplies, to tests of many driver circuits, a digital load is a great tool to have in your arsenal.

Like many electronic devices, our first step with the Re:load Pro was to upgrade the firmware. Since the Re:load Pro is operated by a Cypress Semiconductor PSOC 4,  firmware updates are handled by the cyflash python package. For now this means heading to the command line and installing pip and cyflash. Those who aren’t familiar with a command line prompt will find a step by step guide on the firmware update page.

I should note that the Re:load Pro is powered by the USB input. I connected it up to my lab PC, which had no problem supplying the necessary power.


The next step is calibrating the Re:load Pro. This requires an adjustable power supply capable of supplying at least 10 volts at 2amps, a decent multimeter, and of course some test leads. If you don’t have a reliable adjustable supply ask around; it should be easy to find someone who does.

The calibration is performed in three steps – first with nothing connected to the Re:load Pro. Then a power supply set to approximately 9.99 volts is connected. The voltage displayed on the Re:load Pro is tweaked with the rotary encoder to display the same value as that of the power supply. My power supply has a rather cheap internal voltmeter, so I used a multimeter in parallel with the setup. With voltage done, the Re:load Pro will draw 2 amps from the power supply. You need to adjust the current displayed on the Re:load Pro such that it matches the voltage displayed on your power supply current meter. Again, since my supply doesn’t have the most accurate meter, I used a multimeter – this time in series with the Re:load and the power supply.

Taking Measurements

reload-pro-review-thumbWith all the preliminary work done, it’s time to make some measurements! Re:load pro has a simple user interface. everything is accessed with the rotary encoder on the front panel. Turn the dial to your desired value, and press to select. In my case, I wanted to check the voltage drop of a LiPo battery under various loads. I simply hooked up the battery and dialed 350ma on the encoder. The Re:load Pro showed me that the battery was holding at 12.1 volts, and a display on the lower left side showed me how many milli amp hours I had pulled from the battery.

The Re:load Pro’s USB connector isn’t just for power. It will show up on your PC as a serial device. Just open your favorite terminal emulator, set the port to 115200 baud 8/N/1, and you’re good to go. The Re:load Pro uses a simple text based command/response protocol, all the commands are outlined on the Arachnid labs page.


Re:load Pro is one of the first of new breed of open source tools. Like the closed source Rigol Oscilloscope, it replaces tools which cost several times more. [Nick] and Arachnid Labs aren’t just resting on their success though – they’ve just finished up a kickstarter for their latest open source tool. Tsunami is an open source signal generator based upon the Arduino platform. Tools enable projects, and open source tools are the best way to push the entire ecosystem forward.

Editor’s Note: We are reviving the concept of “Reviews” on Hackaday. These were pioneered long long ago by Hackaday Alum [Ian Lesnet] with his post on smart tweezers but little has been done since. We see a lot of tools, parts, raw materials, and equipment flow through our inbox. We plan to post reviews as a new Hackaday Column. These reviews are not paid placement, they are chosen by editors and writers based on our own interest. This particular example is available in the Hackaday Store and we started with it because we already have the hardware in-hand. However, we will be reviewing items we do not sell and have already put out requests for review units. If you know of something you think worthy of a review, please let us know by submitting it to the tips line. Thanks!

-Mike Szczys, Managing Editor

Hands-On Othermill Review Grinds Out Sparkling Results

We’ve been on the lookout for alternatives to chemically etching circuit boards for years. The problem has been that we don’t particularly want to devote months of or lives learning how to build precision CNC mills. Off in the distance there may be an answer for that quandary if you don’t mind parting with twenty-two Benjamins. Sure, it’s a heck of a lot more expensive than toner transfer and cupric chloride, but the Othermill can be purchased right now (in your hands a few months later) and after reading this in-depth review we are a bit less hesitant about opening our wallets for it.

othermill-review-thumbIt’s a tome of a review, but that means there’s something for everybody. We especially enjoyed seeing the 10 mil board shown here which took about 1-hour to mill. Considering it has also been through-hole drilled we’d put that on part with the time it takes to etch a board. There are obvious places where the traces are not perfectly smooth (not sure if that’s burring or over-milling) but they are not broken and the board’s ready to be populated.

Alignment is something of an issue, but the Othermill isn’t limited to PCBs so we’d recommend designing and milling your own alignment bracket system as an early project.

Who isn’t envious of custom-builds that can get down to 10-mils, like this beauty from 2013. Our hopes had been sparked when Carbide 3D came onto the scene. We’re still optimistic that they will make a big splash when they start shipping preorders in a few months.

As this review proves, Othermill is already out in the wild with a 6-8 week wait before shipping. We saw it in action milling multiple materials at the Hackaday Omnibus Lauch Party and were duly impressed. Price or waiting-period aside we’re going to hold off until the software options expand beyond Mac-only; either Othermill will add support or someone will come up with a hack to use traditional CNC software. But if you count yourself as a subscriber to the cult of Apple the software, called Otherplan, does get a favorable prognosis along with the hardware.

Already have an Othermill sitting on your bench? Let us know your what you think about it in the comments below.

Bonus content: [Mike Estee], CTO of Othermill just gave a talk last night about how he got into making mills and the challenges of building something with super-high-precision. Sound isn’t good but the talk is solid. Hackaday’s [Joshua Vasquez] also gives a talk on the video about building an SPI core for FPGA. These talks are one of the Hardware Developer’s Didactic Galactic series which you really should check out if you’re ever in the San Francisco area.

Continue reading “Hands-On Othermill Review Grinds Out Sparkling Results”

Arduino vs. Phidgets vs. Gadgeteer

A few days ago, we saw a dev time trial between the Arduino and Phidgets, a somewhat proprietary dev board that is many times more expensive than an Arduino. The time trial was a simple experiment to see which platform was faster to prototype simple circuits. As always in Hackaday comments, there was a ton of comments questioning the validity and bias of the test. Not wanting to let a good controversy go to waste, [Ian Lee] tossed his hat into the ring with the same dev trial with the Gadgeteer.

The Gadgeteer has the same design philosophy as Phidgets: modular components and a unique software system -the Gadgeteer is based on .NET Micro Framework – that allows you to get up and running quickly. Unlike Phidgets, the Gadgeteer is priced competitively with the Arduino, and the mainboard is priced within an order of magnitude of a single ATMega chip.

[Ian] pulled off three projects with the three development platforms: blinking a LED, moving a servo, and building a pedometer with an accelerometer. For each trial, the time taken and the price of all components were added up. Here’s the relevant graph:

Continue reading “Arduino vs. Phidgets vs. Gadgeteer”

Repairing and Reviewing a 1976 PONG Clone

Hackaday alum [Todd] has been searching for an old PONG clone for the last two years. This variant is called, “The Name of the Game”. [Todd] has fond memories of playing this game with his sister when they were young. Unfortunately, being the hacker that he is, [Todd] tore the game apart when he was just 14 to build his own Commodore 64 peripherals. He’s been wanting to make it up to his sister ever since, and he finally found a copy of this game to give to his sister last Christmas.

After opening up the box, [Todd] quickly noticed something strange with the power connector. It looked a bit charred and was wiggling inside of the enclosure. This is indicative of a bad solder joint. [Todd] decided he’d better open it up and have a look before applying power to the device.

It was a good thing he did, because the power connector was barely connected at all. A simple soldering job fixed the problem. While the case was still opened, [Todd] did some sleuthing and noticed that someone else had likely made repairs to several other solder joints. He also looked for any possible short circuits, but everything else looked fine. The system ended up working perfectly the first time it was started.

The end of the video shows that even after all this time, simple games like this can still capture our attention and be fun to play for hours at a time. [Todd] is working on part 2 of this series, where he’ll do a much more in-depth review of the system. You can watch part 1 below. Continue reading “Repairing and Reviewing a 1976 PONG Clone”

Arduino vs. Phidgets – Dev Time Trials

Is developing on an Arduino too slow? Are Phidgets too expensive? When might you use one or the other? Hackaday regular [Ken] breaks down what he learned from three experimental time trials.

The main development differences between Arduino and Phidgets are a mix of flavor preferences and some hard facts. The Arduino is open source, Phidgets are proprietary. Arduino requires a mix of hard- and software where Phidgets only needs (and only allows) a connection to a full computer but enables high level languages – it is expected to get the job done sooner and easier. And finally, Arduinos are cheap, Phidgets are 3-5x the cost.

The three time trials were common tasks: 1. Blink an LED. 2. Use a pot to turn a servo. 3. Build a pedometer. For [Ken], the Phidgets won in each of the three experiments, but not significantly: 37%, 45%, and 25% respectively. The difference is only minutes. Even considering time value, for most hackers it is not worth the cost.

HAD - Phidgets3In context, the advantages of a mildly more rapid development on the simplest projects are wasted away by needing to rebuild a permanent solution. Chained to a PC, Phidgets are only useful for temporary or fixed projects. For many of our readers that puts them dead in the water. Arduinos may technically be dev kits but are cheap enough to be disposed of in the project as the permanent solution – probably the norm for most of us.

[Ken] points out that for the software crowd that abhor electronics, Phidgets plays to their preferences. Phidgets clips together their pricey peripherals and the rest is all done in code using familiar modern languages and libraries. We wonder just how large this group could still be; Phidgets might have been an interesting kit years ago when the gulf between disciplines was broader but the trend these days is towards everyone knowing a little about everything. Hackaday readers probably represent that trend more than most, but let us know if that seems off.

[Ken]’s article has much more and much better detailed explanations of the experiments and the tradeoffs between the platforms.

If you enjoy watching parallel engineering, see the time-lapse video below for a split screen of the time trials.

Continue reading “Arduino vs. Phidgets – Dev Time Trials”