Don’t Trust Connectors, Solder, or Wires (EE Tip #138)

Engineer Robert Lacoste is one of our go-to resources for engineering tips and tricks. When we asked him for a few bits of general engineering advice, he responded with a list of more than 20 invaluable electrical engineering-related insights. One our team’s favorite “Lacoste tips” is this: don’t trust connectors, solder, or wires. Read on to learn more.

One of my colleagues used to say that 90% of design problems are linked either to power supplies or to connector-related issues. It’s often the case. Never trust a wire or a connector. If you don’t understand what’s going on, use your ohmmeter to check if the connections are as planned. (Do this even if you are sure they are.) A connector might have a broken pin, a wire might have an internal cut, a solder joint might be dry and not conductive, or you might simply have a faulty wiring scheme. (See the nearby photo.)

Using the wrong pinout for a connector is a common error, especially on RS-232 ports where it’s approximately 50% probable that you’ll have the wrong RX/TX mapping. Swapping the rows of a connector (as you see here) is also quite common.

Using the wrong pinout for a connector is a common error, especially on RS-232 ports where it’s approximately 50% probable that you’ll have the wrong RX/TX mapping. Swapping the rows of a connector (as you see here) is also quite common.

Another common error is to spend time on a nonworking prototype only to discover after a few hours that the prototype was working like a charm but the test cable was faulty. This should not be a surprise: test cables are used and stressed daily, so they’re bound to be damaged over time. This can be even more problematic with RF cables, which might seem perfect when checked with an ohmmeter but have degraded RF performance. As a general rule, if you find that a test cable shows signs of fatigue (e.g., it exhibits intermittent problems), just toss it out and buy a new one!—Robert Lacoste, CC25, 2013

 

Low-Power Remote-Control Transceivers

LinxThe TT Series remote-control transceiver is designed for bidirectional, long-range, remote-control applications. The module includes an optimized frequency-hopping spread spectrum (FHSS) RF transceiver and an integrated remote-control transcoder.

The FHSS is capable of reaching more than 2 miles in typical line-of-sight environments with 0-dB gain antennas. An amplified version increases the output power from 12.5 to 23.5 dBm, boosting the range to more than 8 miles in line-of-sight environments with 0-dB antennas.

The TT Series transceiver features best-in-class receive sensitivity (up to −111 dBm) and low power consumption (only 19.2 mA in receive mode and 36 mA in transmit mode at 12.5 dBm). The initial version operates in the 902-to-928-Hz frequency band for North and South America.

The transceiver is housed in a compact reflow-compatible surface-mount technology (SMT) package. It doesn’t require any external RF components except an antenna, which simplifies integration and reduces assembly costs.

Programming is not required for basic operation. The transceiver’s primary settings are hardware-selectable, which eliminates the need for an external microcontroller or other digital interface. Eight status lines can be set up in any combination of inputs and outputs to transfer button or contact states. A selectable acknowledgement indicates that the transmission was successfully received. For advanced features, a UART interface provides optional software configuration.

A simple pairing operation configures two modules to operate together. A single button press on each side causes the modules to automatically swap their 32-bit addresses and store them in nonvolatile memory. It can be configured to automatically send an acknowledgement to the transmitting unit either after receiving a command or with external circuitry when an action has taken place. An optional external processor can send two data bytes with the acknowledgement.

The TT Series transceiver module is available as part of Linx Technologies’s master development system that comes with two development boards for benchmarking and prototyping. Each board is populated with a transceiver, two remote-control development boards, and programming boards. The system also includes antennas, a daughterboard with a USB interface, demonstration software, extra modules, and connectors.

Contact Linx Technologies for pricing.

Linx Technologies
www.linxtechnologies.com