Revolar Review – How The Revolar Instinct Personal Safety Device Works?

Revolar is a multi-functional device that provides fitness tracking and safety for active individuals. Find out everything you need to know about Revolar today in our review.

What Is Revolar?

Revolar is a small tracking device that clips onto your clothing. The device uses GPS to track your location. You can send location data to family or friends to let them know you’re safe, scared, or in an emergency.

Other key features on Revolar include check-ins, step tracking, “Ring Me”, and more. The company was designed with the goal of helping everybody feel safe:

“You deserve to feel safe when you’re going out for a walk, a run, or a night on the town. That’s why we created Revolar.”

There are two versions of Revolar: the Revolar Original, and the new Revolar Instinct (which will start shipping in May 2017 after a successful Indiegogo crowdfunding campaign.

During that latest crowdfunding campaign, the company raised over $125,000 – blasting past its $50,000 goal. Revolar was founded in 2013.

In 2015, the two founders graduated from Boulder, Colorado’s Techstars 2015 program, then received $3 million in funding.

Revolar Products

Revolar now offers two products: the Revolar Original and the Revolar Instinct.

Revolar Original

The company is best-known for its Revolar Original. It’s a small, keychain-based tracking system that’s water-resistant, rings your phone, sends custom messages, and allows you to check in.

You can also send yellow alerts (if you’re scared) or red alerts (if you’re in immediate danger).

The main difference between the Revolar Original and the Revolar Instinct is that there’s no Find My Revolar feature, nor does it have step tracking.

Revolar Original is priced at $59.99 USD. You can use it for one year on a single battery. Then, once the battery runs out, it’s easy to replace.

Revolar Instinct

The Revolar Instinct is the new and improved version of Revolar. The device debuted on Kickstarter earlier this year. It’s slightly smaller than the original and comes with more features – like step tracking, tactile feedback, and a “Find My Revolar” feature.

How To Use Revolar

Whatever version of Revolar you have, there are some common features.

You start by pressing a button. Revolar lets your loved ones know where you are and if you need help through customizable messages. Each customizable message includes your live location.

You can click once for a check-in when you’re home safe, twice for a yellow alert if you’re uneasy, and then click three times for a red alert if you’re in an emergency situation.

You can select up to 5 trusted contacts using the free Revolar app. Alerts are sent through your phone to your contacts. For yellow and red alerts, contacts receive notifications by text message and email.

Revolar connects to your smartphone using Bluetooth. Other key features include:

  • Step Tracking (Only on Revolar Instinct): You can keep track of your step count, get motivated to move more, and stay safe at the same time.
  • Tactile Feedback: You can know when your alerts are sent and opened through silent vibrations from your Instinct.
  • Dating Safety: Instinct has a feature that lets you discreetly make your phone ring to get away from uncomfortable dates, meetings, and other situations.
  • Custom Messaging: Personalize your check-in and alert messages for daily use. You can change your message to say you’re on a date, going out for a run, or traveling to your hotel in a foreign city, for example.
  • Find My Revolar (Only on Revolar Instinct): This feature makes your Instinct beep so it’s easier to find.
  • No Monthly Fees: Revolar is free to use on a monthly basis, although messaging and data rates may apply (through your phone carrier).

Who Uses Revolar?

Revolar is primarily marketed as a fitness tracking, personal safety device for young women. However, the makers of Revolar claim it can be used in all sorts of different situations, including:

  • Out running
  • On campus
  • Living alone
  • Living with a condition
  • Walking at night
  • Commuting places
  • At parties
  • Walking the dog
  • Traveling abroad
  • Staying independent and safe

The makers of Revolar put a big emphasis on instinct: when you feel something is “off”, it usually means something is off. You need to trust that instinct to stay safe. Here’s what they had to say about the power of instinct:

“While designing our safety devices, we spent hundreds of hours talking with assault survivors who said time and again of their experiences, “I knew something was wrong, but I didn’t know what to do. I couldn’t call 911 based on a bad feeling.”

Revolar Pricing

Here’s how pricing breaks down for the two Revolar items available today:

  • Revolar Original: $59.99
  • Revolar Instinct: $79.99

You can purchase the Instinct for as little as $59 from Kickstarter today. The final retail MSRP will be $80. Your Kickstarter purchase comes with free shipping to the United States and Canada and a $5 flat fee for international shipping.

All purchases come with a case and battery.

Customers also get a 45 day money back guarantee and a 1 year limited warranty.

The first 10,000 Revolar Instinct units are shipping in May 2017.

There are no ongoing monthly fees for using Revolar. That’s different from other personal safety devices – which can cost between $10 and $15 per month to use.

The reason Revolar doesn’t have monthly fees is because it uses data from your cell phone (including GPS and messaging).

You also don’t have access to a 24/7 call center – you’re just messaging trusted friends and family, who can then choose whether or not to alert emergency services.

About Revolar

Revolar was founded by CEO Jacqueline Ros and CPO Andrea Perdomo in 2013. They created the company with the goal of building “empowering technology that helps people keep themselves and their loved ones safe”.

By 2015, they had raised over $80,000 on Kickstarter and graduated from Techstars 2015 in Boulder. They also received $3 million in funding from Foundry Group. Later, they took part in Techstars Retail 2016 in Minneapolis.

You can contact the company by email contact form.

Revolar Summary

Revolar is an innovative personal safety device used by thousands of people on a daily basis. Some people buy it for themselves, while others buy it for a loved one – like a daughter going away to college alone.

With Revolar, you can alert friends and family of a potentially problematic situation. You can’t call 911 because you have a “bad feeling”. Revolar lets you tap once for safety, tap twice for uneasiness, and tap three times for an emergency.

Alerts are sent to friends and family, who can then send emergency services to your location. Friends and family know your location because Revolar sends location data with every message.

Whether you’re buying it for yourself or a loved one, you can get peace of mind with Revolar. It’s available today for between $60 and $80 online.

Static Analysis? We Don’t Need No Stinkin’ Static Analysis

Of course, the original quote is from the 1948 movie, The Treasure of Sierra Madre, and has been famously parodied over the years, memorably in the comedy classic Blazing Saddles. But we are not here to talk about badges. We are here to talk about static analysis and C and C++ programmers.

I am talking specifically to C and C++ programmers because they tend to be in the majority when it comes to embedded applications but the discussion is equally applicable to most other programming languages in common use including Java.

C programmers are really the target for this article because C lacks almost any static analysis short of enough for the compiler to turn the source code into object code. C has been touted as a high level macro assembler and that is not too far from the truth. Its advantage is how close it allows a developer to get to the hardware. The downside is that the developer must create an application that is error free based on their expertise. Most programmers want to think they are good and conscientious but expertise varies widely. The problem is that even the best programmers make mistakes and these can be hard to find and correct.

C++ has many of the problems of C but significant improvements in other areas including a better type and template system that does significantly more static analysis that can help catch errors early. The problem is that C++ essentially allows the same issues to arise that occur in C. For example,

            if ( i == 10 ) {}

does not do the same thing as

            if ( i = 10 ) {}

The latter is an assignment that is always results in a true condition. Some C and C++ compilers do a little more static analysis and will flag this as an error or warning even though it is a valid statement.

Coding standards typically catch this class of error, especially those that implement all or part of the standards using static analysis tools. In the simplest case it is a matter of enabling this checking by the compiler. Even using this minimal static analysis support can be very beneficial.

So why do programmers forego static analysis?

In our recent Embedded Revolution survey, we did ask about the importance and use of coding standards and static analysis (see figure below), but not why. Less than half of those in the survey even had a standard to follow let alone using a static analysis tool that enforced the process.

Not all companies are employing coding standards in their development process. Multiple responses were possible so only some of the 43 percent employed MISRA C/C++ (from Electronic Design’s 2017 Embedded Revolution survey).


At this point I have to theorize why this is the case and I think it comes back to the “We don’t need no stinkin’ badges” quote. Programmers and managers like to think they are better at preventing bugs from creeping into their code and that any limitations or tools that would “get in the way” are bad. Never mind that these tools or procedures would catch or eliminate a significant number of bugs in the long run that gives more time to find those other bugs that are in the code or to spend time improving and application, or getting the application done sooner, or …

Another issue is availability of open-source tools. The LLVM Clang Static Analyzer is one option. It works with C, C++, and Objective-C as a standalone application. CPPcheck is another open-source option. It is integrated with a number of development tools including Eclipse, Visual Studio, and there is even a Git-plugin for catching errors in files as they are committed. There is a list of CPPcheck checks available.

There have also been a number of projects to add annotations to address programming issues, although none tend to be as integrated or exhaustive as SPARK. One example is the Clang thread safety annotation. The following example shows some of the annotations and where an error would occur.



In this case the function foo uses variables a and b. The first is protected by mutex mu1 and the other by mu2. Unfortunately on the mu1, mutex is locked.

Often these tools cover certain aspects of static analysis such as looking for style issues or particular types of bugs. Using multiple tools can be more cumbersome but they provide better coverage of potential problems. Many commercial tools address a wider range of issues and often have better reporting features.

As many would say, “There Ain’t No Such Thing as A Free Lunch” (TANSTAFL). Developing coding standards, implementing them, using static analysis or using programming languages like Rust and SPARK/Ada is not free from costs. The real question is whether the cost of using these techniques or tools provides a sufficient payback. In general, they do pay and usually quite well, although your mileage may vary.

It is always hard to get workers of any sort to switch to different techniques when the current ones have been working, to a degree. It is also a hard sell for those delivering the tools because of this. The losers when these tools and techniques are not used are across the board though as applications get shipped with bugs and security holes that come back to haunt not only the consumer but the company and its employees.

Temperature Matters… Even When Using DC Sources

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During my engineering career, I’ve had the fortune of working in a comfortable, room-temperature environment. I’ve visited tropical factories where test equipment was being used in 90°F temperatures with 99% humidity, and I could imagine that same equipment being used on a mountaintop laboratory or in a military vehicle where it could get quite cold. While human operators may find these extreme temperatures uncomfortable, we must also consider the effects of these temperatures on the test equipment—and on the device under test.

Temperature Effects on Lithium-Ion Cells

Let’s start with an example of a device under test. In January 2016 (that means winter here in New Jersey), I was involved in some delicate testing work with lithium-ion cells. Our test goal was to very accurately measure the open circuit voltage (OCV) of the cells over a few days. So, we started making measurements in our comfortable laboratory environment.

We were actually quite surprised to find the voltage of the cells drifting up as time progressed. Now, we expected the cell voltage might drop over a few days as the cells slowly self-discharged (the subject for a future article), but we hadn’t considered that they might rise in voltage.

Figure 1 shows our test data. As you can see, the OCV of the cell varied inversely with room temperature. Because it was winter, the building temperature would experience a 2°C swing as the building cooled down during the cold overnight and warmed up during the day when the heating system turned on. The data shows that the cell had a temperature coefficient of voltage of approximately ‒110 μV/°C.

1. This plot reveals the temperature sensitivity of a lithium-ion cell.

Temperature Effects on DMMs and Other Instruments

To run these OCV measurements, we employed a very-high-accuracy Keysight 3458A 8.5-digit digital multimeter (DMM). Like the cell we were measuring, this instrument also has a temperature sensitivity, which means its accuracy varies with temperature. To achieve its high-end specifications, the 3458A combats temperature fluctuations in its environment through use of an auto-calibration (ACAL) function. The 3458A’s ACAL capability corrects for measurement errors resulting from the temperature drift of critical components following ambient temperature changes of less than ±1°C since the last ACAL.

Alternatively, some instruments counteract the effects of environmental temperature swings by keeping their own internal temperature constant with a reference circuit inside an “oven” that’s inside the instrument. The principle is simple: If you can keep the critical internal components at a constant temperature via an internal temperature-regulated oven, there’s no need to add in a temperature coefficient because the critical components’ temperatures are changing.  For example, this technique is used to stabilize the temperature of oscillators in various time-measuring and signal-sourcing instruments. 

Temperature Effects on DC Sources

Temperature sensitivity also applies to dc sources. Let’s look carefully at the specifications of a high-performance power supply, such as the Keysight N7970A Advanced Power System, rated at 9 V, 200 A, 1800 W (Fig. 2).

These power supplies are calibrated at a specific temperature, which is normally 23°C. However, the specific information about calibration temperature is listed on the calibration certificate that’s available for the power supply. As stated in the power supply’s specifications table, if the calibration temperature is 23°C, then the specifications are valid from 23°C ±5°C. This valid temperature range is usually documented in a footnote or in a paragraph at the top of the specification table. In the case of the N7970A, the temperature range for valid specifications is found in a footnote stating “At 23°C ±5°C after a 30-minute warm-up.”

2. The Keysight Advanced Power System (APS) is a family of dc power supplies that comprises 24 models at 1000 W (top) and 2000 W (bottom). These power supplies are carefully characterized with temperature coefficient specifications that allow users to source with very high accuracy at any temperature.

To apply this temperature coefficient, or tempco, specification, you must treat this like an error term. If you’re operating the power supply at 33°C, you need to factor in this tempco as follows:

  • You want to set the voltage to 5.0000 V.
  • The temperature is 33°C or 10°C above the calibration temperature of 23°C.
  • Voltage programming tempco is ± (0.0022% + 30 μV) per °C.
  • To correct for the 10°C temperature difference from calibration temperature: ± ((0.0022%/°C * 10°C * 5.0000 V) + 30 μV) = ± (110 μV + 30 μV) = ± 140 μV of temperature induced error at 10°C away from 23°C.

Note that this temperature-induced error must be added to the normal programming error, which is ± (0.03% +1.5 mV) as shown in the table. Calculating this programming error:  ± ((0.03% * 5.0000 V) + 1.5 mV) = ± (0.0015 V + 1.5 mV) = ± 0.0030 V.

Therefore, the total error, including accounting for temperature, will be ± (0.00014 V + 0.003 V) = ± 0.00314 V. That means your output voltage will be somewhere between 4.99686 V and 5.00314 V when attempting to set the voltage to 5.0000 V in an ambient temperature of 33°C.

Since the 140-μV part of this error is temperature-induced, as the temperature changes, this component of the error will change, and the output of the power supply will drift. This drift with temperature is the direct effect of the power supply’s tempco.


Temperature matters. That’s why calibration labs carefully maintain and record their temperature. The devices that you’re testing will vary with temperature. The instruments that you use to make measurements on those devices will vary with temperature. The sources used to apply power to those devices will vary with temperature. By understanding temperature coefficients and how and when to apply them, you can improve your measurements and get good measurements down into the microvolt range.

An Open-Source Project for Internet of Things Gateways

The field of edge computing has scored its latest endorsement: The industry group behind the Linux operating system announced that it would release an open-source standard for building gateways that sit between sensors inside factories, office buildings, city infrastructure – and the cloud. The standard, which is still under development, is supported by fifty companies right out of the gate.

Called EdgeX Foundry, the project debuted this week at the Hannover Messe trade show in Germany. It aims to lower the cost and complexity of installing gateways at the edge of the Internet of Things, allowing data analysis and device control to happen much closer to sensor nodes. Gateways will not always need to communicate with the cloud, where the most intense data-crunching takes place.

Developing gateways with EdgeX requires little more than snippets of standard code, which will be freely available. The code organizes the transfer of information from sensors in manufacturing robots, office lighting systems, shipping trucks, and wind turbines – to gateways or servers on the edge. That helps companies save money by allowing them to choose any operating system, hardware, and software.

Making the code open-source is hardly surprising for the Linux Foundation, which is supervising the EdgeX project. But endorsements for EdgeX also came from fifty companies, including Dell and Canonical, which produces Ubuntu. The code originated in a Dell project codenamed Fuse, which was revealed last year to rally support for edge computing, which would likely drive sales of Dell’s gateway boxes.

The concept behind EdgeX is not exactly new. A rival project called Kura is aiming to standardize code for internet gateways used in fog computing, a term coined by Cisco for shifting basic cloud functions to edge of a business’s network. Kura would create standards for how gateways sift through feedback from sensors, sending only the most vital information or worst failure alerts to the cloud.

With EdgeX, the gateways will contain around 125,000 lines of standardized code, which erect a software layer between different messaging protocols. The code will enable gateways to send automatic commands, provision devices, and clean up metadata so that it can be organized faster and more accurately. With these services standardized, businesses will have less work to do when updating an IoT system.

EdgeX is a “modular architecture is designed to help anyone easily build edge computing solutions with preferred hardware, software, standards and services while minimizing reinvention,” said Jason Shepherd, Dell’s director of Internet of Things strategy and partnerships, who supervised the company’s Fuse project, in a statement.

10X Oversampling Scopes Make Accurate Measurement “Insanely” Easy

It’s not every day I see the words “insanely easy” when it comes to advanced signal and power measurements, so I had to take a second look at Teledyne LeCroy’s updated line of HDO4000A, HDO6000A, HDO8000A, and MDA800A analog and mixed-signal oscilloscopes.

Popular for power-line, automotive, and embedded debug, the four lines each have eight channels, and a bandwidth range from 200 MHz to 1 GHz. The MDA800A is built on the HDO8000A platform, but also performs three-phase electrical and mechanical power calculations with unique static and dynamic power views, as well as complete control system validation.

All use the company’s 12-bit HD4096 display technology. First introduced in 2012, the 4096 refers to its high-definition display for crystal-clear signal viewing. The 12.1-inch WXGA display is capable of Ultra HD in extended-desktop mode.

It turns out that the insanely easy part simply refers to Teledyne LeCroy’s MAUI OneTouch user interface. Of course, making things seem simple requires a lot of complex thinking as to how users would actually use the scope, as well as sensitive touch technology to make it quick and responsive, without being overly so. Teledyne LeCroy accomplished this, making the MAUI OneTouch smart enough to enable access to common operations with a single touch of the display (see figure).

Users of Teledyne LeCroy scopes series scope will already be familiar with MAUI OneTouch, including its touch-to-zoom, drag-and-drop actions to copy and set up channels, math and analysis functions, shortcuts, and dialog boxes. All help to make measurement and analysis of complex power and analog-mixed signals a lot more efficient. The “Add New” button, for example, quickly enables a new channel, math, or measurement, while traces and parameters turn off with a flick of a finger.

The “insanely easy” to use HDO-A and MDA800A 1-GHz, 10X oversampling analog and mixed-signal scopes combine accuracy and ease of use in cost-scalable models. (Source: Teledyne LeCroy)

Enhanced Sample Rate

However, what’s actually new with the HDO-A/MDA800A lineup isn’t the interface, or the display, it’s the Enhanced Sample Rate mode with 10X oversampling. This lets you acquire as much of the signal as possible in order to digitize, interpolate, filter, and view the signal as accurately as possible. The sampling rate works in conjunction with the low-noise inputs and architecture, as well the brick-wall frequency response that’s limited to 1 GHz.

While 10X oversampling enables a more accurate representation of the acquired signals, it also adds flexibility with respect to digital filtering: The more information the system has, the better. The tradeoff is more memory to store the oversampled data, as well as the processing horsepower to deal with analyzing and filtering it.

To that end, the HDO-A has 250 Mpoints/channel of acquisition memory as well as a 250-GB removable solid-state drive. The back-end processing was also upgraded, as was local CPU memory.

Serial Data Tools

Like any high-function scope, the line comes with a suite of optional software packages, in this case for all serial-data test requirements, ranging from automated standards compliance packages to flexible debugging toolkits. A suite of protocol-specific measurement and eye-diagram packages specifically provides insight into serial data anomalies.

These packages complement the scopes’ powerful trigger/decode software that can extract decoded data and plot over time, perform bus timing measurements, and create eye diagrams for testing against standard or custom masks. The 16 digital lines in mixed-signal models can be used for trigger, decode, and measurements for analyzing timing irregularities or for general-purpose debug of digital designs. As a result, analog channels can be reserved for observing physical-layer defects.

Priced for Value

At a list price between $10,100 and $19,600, the HDO4000A’s eight models give the most bang for the buck. For comparison, the Keysight DSOX3104T, 1-GHz, 4-channel scope is priced at $14,483. Moving upscale, the HDO6000A comes in six models ranging from $15,500 to $23,500; the HDO8000A’s three models cost between $25,850 and $31,850; and the MDA800A ranges between $30,850 and $36,850 across three models.