Open Hardware Board For Robust USB Power Monitoring

We’ve all seen the little USB power meters that have become popular since nearly every portable device has adopted some variation of USB for charging. Placed between the power source and the device under test, they allow you to see voltage and current in real time. Perfect for determining how long you’ll be able to run a USB powered device on batteries, or finding out if a USB power supply has enough current to do the business.

[Jonas Persson] liked the idea of these cheap little gadgets, but wanted something a bit more scientific. His design, which he refers to as UPM, is essentially a “smart” version of those ubiquitous USB gadgets. Instead of just showing the data on a little LCD screen, it can now be viewed on the computer and analyzed. His little gadget even allows you to cut power to the device under test, potentially allowing for automated testing of things such as inrush current.

Essentially the UPM works in much the same way as the simple USB meters: one side of the device goes towards the upstream power source, and the device under test plugs into the other side. Between the two devices is a 16 bit ADC and differential amplifier which measures the voltage and current. There’s a header on the board which connects to the ADC if you wanted to connect the UPM to an external microcontroller or other data logging device.

But most likely you would be using the internal microcontroller to analyze the output of the ADC over I2C, which [Jonas] very cleverly connected to the upstream port with an integrated USB hub. One side of the hub goes off to the device being tested, and the other to the microcontroller. So the host device will see both the UPM’s integrated microcontroller and the target device at the same time. From there, you can use the ncurses user interface to monitor and control the device in real-time.

While the hardware looks more or less finished, [Jonas] has some more plans for the software side of UPM, including support for remote control and monitoring over TCP/IP as well as robust logging capabilities. This is definitely a very interesting project, and we’re excited to see it develop further.

In the past we’ve seen homebrew USB power meter builds, and even commercial offerings which boasted computer-based logging and analysis, so it was only a matter of time before somebody combined them into one.

The Crystal (Testing) Method

It used to be any good electronics experimenter had a bag full of crystals because you never knew what frequency you might need. These days, you are likely to have far fewer because you usually just need one reference frequency and derive all the other frequencies from it. But how can you test a crystal? As [Mousa] points out in a recent video, you can’t test it with a multimeter.

His approach is simple: Monitor a function generator with an oscilloscope, but put the crystal under test in series. Then you move the frequency along until you see the voltage on the oscilloscope peak. That frequency should match the crystal’s operating frequency.

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Arduino Powered Portable Function Generator

It’s probably not much of a stretch to say that many of us have taken on a project or two that were little more than thinly veiled excuses to add a new tool or piece of gear to our arsenal. There’s something to be said for a bench full of button-festooned test equipment blinking away, it’s like bling for nerds. But just like getting your name written out in diamonds, it can get expensive quick.

Luckily, the hacker has enough technology at their disposal these days that DIY test equipment can help fill your bench without emptying your wallet. [Faransky] has created a very impressive Arduino function generator that doesn’t skimp on the features. Capable of generating sine, triangle, and square waves up to 10MHz with its all-digital circuitry, it’s a piece of gear that’s well worth the $30 USD or so it should cost to build your own version.

For those worrying that [Faransky] is relying on the PWM functionality of the Arduino Nano to generate waveforms, have no fear. At the heart of the device is a AD9833 waveform generator; with the Arduino, rotary encoder, and 16×2 LCD providing an interface to control it over SPI.

Unfortunately, the AD9833 doesn’t have a way to control amplitude, something which is pretty important in a function generator. So [Faransky] uses a X9C104P 100KOhm 8-bit digital potentiometer as a voltage divider on the chip’s output.

To wrap up the build, he added a 2000mAh 3.7V Li-Ion battery and TP4056 charger, with a DC-DC boost converter to get 5V for the Arduino. Though if you wanted to create a benchtop version of this device, you could delete those components in favor of a 5V AC/DC adapter.

We’ve seen our fair share of DIY function generators, ranging from minimalist builds to hardware that could pass for a commercial offering. We’ve even seen some cheap turn-key function generators, though the usual warnings about getting what you pay for apply.

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Review: SMD Tweezer Meter or Tweezer Probes For Your Multimeter?

It’s remarkable how tiny electronics have become. Heaven knows what an old-timer whose experience started with tubes must think, to go from solder tags to SMD in a lifetime is some journey. Even  the generation that started with discrete transistors has lived through an incredible shift. But it’s true, SMD components are tiny, and that presents a challenge aside from the one you’ll face when soldering them. Identifying and measuring the value of a chip component too small to have any writing upon it becomes almost impossible with a pair of standard test probes.

Happily the test equipment manufacturers have risen to the challenge, and produced all sorts of meters designed for SMD work that have a pair of tweezers instead of test prods. When I was looking for one I did my usual thing when it comes to Hackaday reviews. I looked at the budget end of the market, and bought an inexpensive Chinese model for about £16($21). And since I was browsing tweezers I couldn’t resist adding another purchase to my order. I found a pair of tweezer test probes for my multimeter which cost me just over a pound ($1.30) and would provide a useful comparison. For working with SMD components in situ, do you even need the special meter?

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Analog Discovery 2 as a Vector Network Analyzer

A while back, I posted a review of the Analog Discovery 2, which is one of those USB “do everything” instruments. You might recall I generally liked it, although I wasn’t crazy about the price and the fact that the BNC connectors were an extra item. However, in that same post, I mentioned I’d look at the device’s capabilities as a network analyzer (NA) sometime in the future. The future, as they say, is now.

What’s an NA?

In its simplest form, there’s not much to an NA. You sweep a frequency generator across some range of frequencies. You feed that into some component or network of components and then you measure the power you get out compared to the power you put in. Fancy instruments can do some other measurements, but that’s really the heart of it.

The output is usually in two parts. You see a scope-like graph that has the frequency as the X-axis and some sort of magnitude as the Y-axis. Often the magnitude will be the ratio of the output power to the input power as a decibel. In addition, another scope-like output will show the phase shift through the network (Y-axis) vs frequency (X-axis). The Discovery 2 has these outputs and you can add custom displays, too.

Why do you care? An NA can help you understand tuned circuits, antennas, or anything else that has a frequency response, even an active filter or the feedback network of an oscillator. Could you do the same measurements manually? Of course you could. But taking hundreds of measurements per octave would be tedious and error-prone.

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Function Generator Gets DIY Frequency Standard

For those of us who like to wrangle electrons from time to time, there are some exceptional deals out there for low (or at least lower) cost imported test equipment. If you’re willing to part with a few hundred dollars US, you can get some serious hardware that a decade ago would have been effectively outside the reach of the hobbyist. Right now you can order a four channel oscilloscope for less than what a new Xbox costs; but which one you’ll rack up more hours staring at slack-jawed is up to you.

10 MHz output from DIY frequency standard

Of course, these “cheap” pieces of equipment aren’t always perfect. [Paul Lutus] was pretty happy with his relatively affordable Siglent SDG 1025 Arbitrary Function Generator, but found its accuracy to be a bit lacking. Fortunately, the function generator accepts an external clock which can be used to increase its accuracy, so he decided to build one.

[Paul] starts off by going over the different options he considered for this project, essentially boiling down to whether or not he wanted to jump through the extra hoops required for an oven-controlled crystal oscillator (OCXO). But the decision was effectively made for him when his first attempt at using a more simplistic temperature controlled oscillator failed due to an unfortunate misjudgment in terms of package size.

In the end, he decided to spring for the OCXO, and was able to use the USB port on the front panel of the SDG 1025 to provide the power necessary for the crystal to warm up and remain at operating temperature. After he got the oscillator powered, he just needed to put it in a suitable metal enclosure (to cut down external interference) and calibrate it. [Paul] cleverly used the NIST WWV broadcast and his ears to find when his frequency standard overlapped that of the source, therefore verifying it was at 10 MHz.

Hackers love accuracy, and accordingly, we’ve seen a number of frequency standard builds ranging from extremely cheap to luxuriously overkill.

Handy Continuity Tester Packs Multiple Modes into a Tiny Package

From Leatherman multitools to oscilloscopes with built-in signal generators and protocol analyzers, there seems no end to tools with multiple personalities. Everybody loves multitaskers because they make it feel like you’re getting more bang for your buck, and in most cases that’s true. But a jack of all trades is seldom master of any, and there are times when even the humble multimeter isn’t the best tool for the job.

With that in mind, [sidsingh] has developed what we think is a very nice dedicated continuity tester. With a goal of using only parts on hand, he had to think small to fit everything into the case he had. So he started with a PIC10LF322 to support all the flavors of continuity testing he wanted to support. In addition to straight continuity, the tester can handle diode testing, detecting shorted or open diodes and even differentiating between regular and Schottky diodes. It also has an LED test mode and an interesting “discontinuity” testing mode — it only sounds its buzzer when continuity is broken. The video below shows that mode in action for finding intermittent cable faults, along with all the other modes.

For an ostensibly single-purpose tool, this tester still manages to pack a lot of tests into one very compact package. Simpler continuity testers are good, too — check out this cheap dollar store build, or this slightly more complicated unit based on an ATtiny85.

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