Kerry Wong writes:

For simplicity, I used a single rotary encoder for controlling the attenuation. In order to prevent accidentally changing the set attenuation value, I used the built-in switch of the rotary encoder as the lock/adjust control. The idea is that the attenuation value can only be adjusted when the switch is in the “adjust” state and the attenuation value is set once the switch changes from adjust to the lock state. When the switch is in the “locked” state, adjusting the rotary encoder has no effect on the digital attenuator. The current attenuation value is displayed on a 1×16 LCD. For more details, you can find the Arduino code listing towards the end of this post along with a video demonstrating this control interface.

More details on Kerry Wong’s blog.

Check out the video after the break.

from Dangerous Prototypes https://ift.tt/2NmoSiv

KA7OEI published a new build:

One of the issues common with using a broad-band, direct-sampling SDR (software-defined radio) like the KiwiSDR is that of overload by strong, low-frequency signals, such as those on the AM (mediumwave) broadcast band – but there’s another problem that should be considered as well:  The high generally-high signal levels at lower HF frequencies.  If one looks at an spectrum analyzer connected to a broad-band receive  antenna during the evening, one will immediately note that the lower the frequency, the higher the signals seem – particularly the background noise.

See the full post on KA7OEI’s blog.

from Dangerous Prototypes https://ift.tt/2Ll5ANm

We go through a lot of prototype PCBs, and end up with lots of extras that we’ll never use. Every Sunday we give away a few PCBs from one of our past or future projects, or a related prototype. Our PCBs are made through Seeed Studio’s Fusion board service. This week two random commenters will get a coupon code for the free PCB drawer tomorrow morning. Pick your own PCB. You get unlimited free PCBs now – finish one and we’ll send you another! Don’t forget there’s free PCBs three times every week:

• Tweet-a-PCB Tuesday. Follow us and get boards in 144 characters or less
• Facebook PCB Friday. Free PCBs while you wait for the weekend
• Free PCB Sunday, right here on the blog
• Check out how we mail PCBs worldwide

Some stuff:

• Yes, we’ll mail it anywhere in the world!
• Be sure to use a real e-mail in the address field so we can contact you with the coupon.
• Limit one PCB per address per month please.
• Like everything else on this site, PCBs are offered without warranty.
• PCBs are scrap and have no value, due to limited supply it is not possible to replace a board lost in the post

Be the first to comment, subscribe to the RSS feed.

from Dangerous Prototypes https://ift.tt/2Jqm0Pe

STMicroelectronics’ solution for simplifying USB Type-C protection and filtering using transient voltage suppressors, common mode filtering and proper board layout. Link here (PDF)

The USB interface has been present on the market for nearly 2 decades and thanks to that, nowadays it is quite obvious for everybody to connect electronic devices in this manner. However, the presence of different types of connectors: type A, type B, mini USB, micro USB etc., makes difficult and complicated the choice of the right one. For this reason USB Type-C, a unique connector to drive audio and power data up to 5 or 10 Gbps, is now available.

Due to the fact that for its own nature a connector is a link to the outside world, it may be exposed to a lot of disturbances which can ruin the transceivers. Moreover, the high-speed links radiate therefore an efficient filter has to be used to solve antenna desense.

STMicroelectronics has developed some specific protection devices and common mode filters with optimized performance and layout.

from Dangerous Prototypes https://ift.tt/2NTPR5Z

SCR fundamentals discussed in this app note from STMicroelectronics. Link here (PDF)

This document provides some guidelines about how to select the right thyristor, also referred to as “SCR”, according to the different applications. Some very specific cases could require a higher level of expertise to ensure reliable and efficient operation.

from Dangerous Prototypes https://ift.tt/2mhNNYY

A how-to on making a Dual-sensor ultrasonic echo locator by lingib, project instructables here:

This instructable explains how to pinpoint the location of an object using an Arduino, two ultrasonic sensors, and Heron’s formula for triangles. There are no moving parts.
Heron’s formula allows you to calculate the area of any triangle for which all sides are known. Once you know the area of a triangle, you are then able to calculate the position of a single object (relative to a known baseline) using trigonometry and Pythagoras.
The accuracy is excellent. Large detection areas are possible using commonly available HC-SR04, or HY-SRF05, ultrasonic sensors.
Construction is simple … all you require is a sharp knife, two drills, a soldering iron, and a wood saw.

Via Arduino Blog.

Check out the video after the break.

from Dangerous Prototypes https://ift.tt/2uuqi2J

Every Friday we give away some extra PCBs via Facebook. This post was announced on Facebook, and on Monday we’ll send coupon codes to two random commenters. The coupon code usually go to Facebook ‘Other’ Messages Folder . More PCBs via Twitter on Tuesday and the blog every Sunday. Don’t forget there’s free PCBs three times every week:

• Free PCB Sunday. The classic. Every week, get free PCBs right here on the blog comments
• Tweet-a-PCB Tuesday. Follow us and get boards in 144 characters or less
• Facebook PCB Friday. Free PCBs while you wait for the weekend
• Check out our video on how we mail PCBs worldwide.

Some stuff:

• Yes, we’ll mail it anywhere in the world!
• We’ll contact you via Facebook with a coupon code for the PCB drawer.
• Limit one PCB per address per month, please.
• Like everything else on this site, PCBs are offered without warranty.

We try to stagger free PCB posts so every time zone has a chance to participate, but the best way to see it first is to subscribe to the RSS feed, follow us on Twitter, or like us on Facebook.

from Dangerous Prototypes https://ift.tt/2Jm2XFG

Anfractuosity published a new build:

“Acoustic cryptanalysis is a type of side channel attack that exploits sounds emitted by computers or other devices”

Wavecatcher is a simple PCB that makes use of a MEMS ultrasound microphone, in order to capture audio to around 80kHz, with the goal
of finding interesting ultrasound sources and playing with exfiltrating data from SMPSs etc. via ultrasound.

See the full post on Anfractuosity’s project page and the GitHub repository here.

from Dangerous Prototypes https://ift.tt/2JjNBSb

Tear down of an Electronic key  from Electronupdate:

In the mid 1980’s a company called Dallas Semiconductor was producing a wide range of small RAMs with integrated battery backup. One of the more unusual item was an early attempt at an electronic key: a user would be issued a key which could then be typically used to allow access to equipment and to keep track of usage. Not very secure by today’s standards…. but an interesting data point.
Opening it up shows that it had two major parts: a silicon die and a battery. The amount of ram on the die was very small, 256 bits!

More details on Electronupdate blog.

Check out the video after the break.

from Dangerous Prototypes https://ift.tt/2m9wo4G