Design Products That Meet Their Intended Requirements

Practical steps in design verification using a DAQ data logger



Design verification plays a crucial role in the product development life cycle. Ensuring products are designed as intended is a rigorous and disciplined design process control.

Find out how to perform product characterisation using a data acquisition (DAQ)system to improve test efficiency and effectiveness. View the white paper to learn key practical steps to help you achieve your goals in design verification.

5-146281-2 – Pin Headers for Arduinos and Breadboards

Small companies usually lack the dedicated engineering…

Small companies usually lack the dedicated engineering facilities required for prototyping parts with extremely fine pitch – getting BGA soldered at home is tremendously difficult and almost impossible. A nice way to get small companies interested in your product involves offering evaluation boards. These usually end up in a breadboard or a socket, where the pitch of 2.54 millimeters has established itself as a quasi-standard. This odd pitch, quite incidentially, dates back to imperial units – it is equal to 0.1 inch.

When designing such breakout boards, cost should not be the primary factor. Saving money on the headers is stupid – if they corrode, precision parts get problems. Due to that, using high-quality mechanicals from an established company such as TE Connectivity makes perfect sense.

The 5-146281-* family can be considered the standard offering for the 2.54mm standard. They are series of pins attached to one another, which can be broken down with scissors if smaller dimensions are needed. Acquiring them is not particularly difficult. TE Connectivity offer them in a range from 1 to 40 pins in a single row, the individual part numbers can be taken from the table.

…the part number contains information about the number of pins found in the header

The parts at hand should not be limited to Arduino shields and similar interfaces. They can also be used to create test points where an advanced debugging peripheral can be attached. The scope ranges from in certain in-circuit debuggers such as Microchip’s ICD family to custom testing rigs used for product development.

Interestingly, pricing can be an issue. The two-pin variant starts out at like 50 cents, while the 40 pin variant sets you back like 3.6€ – if you have time on hand, breaking parts down in-house is a neat way to reduce costs.

TT Electronics ULW3-100RJA1 – A Resistor Which Doubles as a Fuse

In many cases, a resistor is found in series with a fuse. If an assembly is intended to be factory-maintained only, fusible resistors let you eliminate one of the components.

Fusible resistors usually come in device families. We will focus our attention on the ULW3-100RJA1 – it is a 100 Ohm through-hole resistor with a rated power of 3 watts. A variety of lead options are offered, as is shown in figure one.

…TT Electronics offer their fusible resistors in various lead configurations

Through-hole parts may increase assembly costs, but are beneficial for repair – if your technicians are instructed to cut the leads before desoldering the part, minimal amount of heat stress is to be expected inside of the PCB. Due to the high levels of heat reached during “shutdown”, PCBs should be of high quality – if the PCB catches fire, the fuse failed its function.


Fusible resistors, generally, are slower than dedicated fuses. In the case of our part, a five second overload of 15 watts is considered allowed – the circuit needs to be able to withstand significant overcurrent if a fusible is to be the only protective element used.

Finally, keep in mind that ambient temperature directly affects the switching voltage levels. Figure two, taken from the datasheet, shows that the rated power starts to fall at about 25 degrees celsius.

Ambient temperature has significant impact on current levels…

TT Electronics obeys the UL1412 standard, which can be considered the go-to set of rules for fusible resistors – visit https://standardscatalog.ul.com/standards/en/standard_1412_5 to find additional information not found in the datasheet.

LM2653MTC-ADJ from Texas Instruments

Texas Instruments offers engineers a set of switching regulator evergreens which combine high efficiency with simple PCB layouts. The highly efficient LM2653, first introduced in 1999, usually stands in the shadow of his SimpleSwitch-branded brothers.

While the letter are expensive and don’t deliver high efficiency, the LM2653 performs efficiently and affordably over a wide range of output currents.

…the part at hand is efficient at both low and high currents.



From a technical point of view, there is not much to say about the part. It is a switching regulator which boasts a working frequency of 300kHz, and uses a coil and an inductor to perform a bucking operation. An example schematic presents itself like figure two.

…setting up the advanced features requires a set of capacitors and resistors


The relative complexity of the example can be explained by looking at the block diagram. In addition to the thermal and overcurrent protection available in almost all switching regulators, the part contains a set of delay circuits which perform additional safety checks.

Hot feature number one is the soft start capacitor, which usually gets connected to pin SS. The IC charges it with the current of about 2 µA, and watches the voltage level until it reaches 2V. That way, the system starts up slowly, which can be helpful when charging capacitors and other elements.

Secondarily, the system has undervoltage and overvoltage protection. Should the load be able to sink the voltage to less than 80% of the desired value, a delay capacitor is charged slowly but surely – when it reaches a voltage level of 2V, the part switches off the supply to prevent short circuit and similar damages.

From a technical point of view, the part at hand is relatively docile. The datasheet contains detailed information on capacitor and diode selection, and comes with a few precalculated examples. The IC itself is available in TSSOP housing with sixteen pins.

M24xxx Series – Cheap Memory for Microcontrollers

Cheap memory for microcontrollers

No matter how large your microcontroller’s memory might be – in practice, you will always need just a little bit more. In that case, STMicroelectronics’s SPI EEPROM provides a nice alternative to more established players.

Obviously, the biggest advantage of SPI involves the simplicity in connecting the part – you don’t need to worry about limited I2C address ranges or other problems. If your application has a free SPI controller, you are ready to go.

…if multiple CS pins are available, adding SPI EEPROMs becomes really simple

Alternatively, an SPI MUX can be driven from the GPIO port bank in a fashion similar to the bank switching implemented in Solomon Systech’s display controllers. Either way, the maximum permitted clock frequency is set at relatively speedy 5MhZ.

STM simplifies the design of such boxes by providing a dedicated hold output input. If hold is activated, the serial data output line becomes high independence, while inputs and clock inputs are discarded silently.

A question of complications

ST‘s part differs from its colleagues in that it’s memory is organized in a set of banks. The total amount of spacious 2Mbit is divided into a groups of pages made up of 256 bytes each, one of which can be designated as a read only identification page intended to store serial numbers and similar information.

Actually interacting with the SPI flash then is accomplished via a set of dedicated instructions shown in the figure.

Eight bit instructions set the operational mode of the chip


Finally, keep in mind that ST also goes after the extremely lucrative I2C EEPROM market. Their offering for this market is called M24xxx. Both chip families are automotive certified, thereby permitting their usage in challenging environments.

BlueNRG-1 bluetooth without hassle

Designing and impendance matching RF-related circuitry is an art of its own. STMicroelectronics’s SPBTLE-1S combines a Bluetooth 4.2 radio module with a Cortex-M0 processor intended to handle RF communications.

A look at the block diagram confirms that the module is, by and large, an SoC in a box. Thanks to STM pre-soldering it all onto a planar, certification hassles are avoided (in the USA) or mitigated (in Europe).

The SPBTLE-1S contains all an IoT developer dreams of at night…

Interaction with external hardware can be accomplished via a full complement of GPIO ports, two ADC channels, one SPI and two I2C interfaces. The module, furthermore, has the capability to work as a dedicated Bluetooth 4.2 radio chip being controlled by a seperate microcontroller.

ST Microelectronics prides itself on the module being able to run from a single coin cell or a pair of AAA batteries – any input power ranging from 1-.7V to 3.6V is acceptable. This, sadly, is a problem for hosted mode – interfacing the module with a run of the mill 5V microcontroller requires level switching hardware. Power consumption in active mode is 1.9mA, with a 0.9 Microampere sleep mode also available.

Integrating the module is relatively simple: STMicroelectronics picked a form factor similar to the one used by the various ESP32 modules. This means that even non-sophisticated pick and place houses should not have trouble handling the part – if land geometry is suitable, hand soldering also is possible due to the pads being exposed from both sides.

…the SPBTLE-1S can be soldered by hand

Unlike some other products from STM, the SPBTLE-1S does not stand alone. It, instead, can use almost all example code provided for the BlueNRG platform – getting started with it is as easy as selecting a C program’s skeleton which fits your needs.