Author Archives: DP

App note: How to protect mobile devices from ‘USB Kill’ threats

via Dangerous Prototypes

Great read from Bourns about USB killer devices and port protection solutions. Link here (PDF)

Researchers have long warned about the security risks of inserting other users’ USB drives into your PC, even those from whom you trust. If the threat of malware infections isn’t cause enough for concern, there have been stories of malicious USB thumb drives that have “fried” laptops. Does this seem like a far-fetched occurrence? Hearing of the threats, PC World documented the work of an electronics engineer who set out to create a prototype that could actually kill a mobile device’s USB port.

App note: Protecting USB Type-C Cable connectors featuring higher power & tighter pin spacing

via Dangerous Prototypes

Bourns’ built-in thermal cut-off devices adds extra protection from faults directly on USB Type-C cables. Link here (PDF)

The now ubiquitous Universal Serial Bus (USB) standard was initially developed in 1994 with the intent of providing a communication standard to improve and simplify communication between the PC and peripheral devices. An updated version of the USB interface standard is the USB 3.1 Superspeed+, which doubles the data rate to 10 Gbps – a 2x improvement of the previous generation USB 3.0 Superspeed. USB 3.1 Superspeed+ is backwards compatible with USB 1.1, 2.0 and 3.0 with a power delivery projected at 100 W. This gives users enhanced data encoding for more efficient data transfer offering higher throughput and improved I/O power efficiency.

In addition to the increased power capability and bandwidth achieved in this updated USB standard, the connector has been changed. The original simple 4 pin D+/ D- Power and GND format has been upgraded and now combines multiple connector functions into one. The new USB Type-C connector features 24 pins in a smaller form factor.

A downside to this combination of increased power and the extremely tight pin spacing is heightened concern about potential safety and fire hazards due to the possibility of thermal runaway at the connector. To deal with these potential threats, it is recommended that electronic equipment manufacturers and connector and cable manufacturers integrate overcurrent and overtemperature protection into the Type-C connector.

FIREO – a low power SSB/CW tranceiver with its unique speech processing

via Dangerous Prototypes

Kang.K.P.S. writes:

“FIREO” (Pronounced FIRE-O), is basically a bit of non-conventional QRP (low power) SSB/CW transceiver design in which speech compression is implemented using FM limiter circuit. This unique approach of speech processing increases the effective average transmitted power and thus it improves on the signal strength reports at the receiving end. Consequently this technique also helps to cut through any man made or natural noise, very effectively.

See the full post on Small Wonder QRP blog.

Compact Si5351 based SDR

via Dangerous Prototypes

Ray Ring has written an article detailing the build of his mini SDR radio using FV-1 Audio processor and Si5351:

This is a revised version of my FV-1 based SDR. I replaced the CS2100 clk generator with the Si5351 clk generator. The Si5351 has some advantages over the CS2100, namely you can generate quadrature clks directly. This simplifies the hardware design and improves the quadrature accuracy. The sideband rejection in LSB/USB modes is impressive..somewhere around 60 db as best I can measure.

More details at circuitsalad.com.

Check the video after the break.

An ATmega brushless sensored motor driver v02

via Dangerous Prototypes

David Gironi writes, “Brushless electric motor (BLDC motors) are synchronous motors that are powered by a DC electric source via an integrated inverter/switching power supply, which produces an AC electric signal to drive the motor. Hall sensored motors uses hall effect sensors or a rotary encoder to directly measure the rotor’s position.

See the full post on David’s blog.

Check out the video after the break.

App note: Offline non-isolated flyback converter protection

via Dangerous Prototypes

A white paper from Bourns about thermal protection PTCs on flyback converters. Link here (PDF)

This paper examines the use of resettable polymer fuses for protecting offline flyback converters. Using a thermal model of the resettable fuse surrounding solder pads and copper to optimize the trip time so that the converter is protected during overloads, there are two potential positions considered for polymer Positive Temperature Coefficient (PTC) resettable fuses in the circuit. One position is directly on the winding and the other position is beyond the control loop. Results are taken from the converter and compared with a simulation.