Back-Pinning Probe

A test instrument includes a set of probes. Here we will look at back-pinning probes!

In a back-pinning probe, also know as back probe, its needle is made to push into some type of connectors from the back, making it possible to measure while the connector is connected. 

These probes are essential for probing today’s small, fragile connectors. Since a back-pinning probe is very sharp, it slides past connector seals with ease.

Thus these nifty little needle probes are the perfect electronic accessory when a quick and easy test connection needs to be made without piercing the wire insulation.

Another probe in this category is the Piercing Probe (see below).

The trick is that a tin needle can cut through the isolation and contact the conductor inside. When the probe is removed the hole will basically close itself. This makes it possible to measure on wires without stripping or cutting it and without locating the ends of the wire.

The small diameter and extra sharp pin of a piercing probe (insulation piercing probe) makes it ideal for piercing the insulation on small gauge wires where traditional piercing tools might cause damage.

Generally, a piercing probe has a needle or multiple needles that pierce the wires outer insulation jacket to access the wires internal conductor for testing. By activating the needle(s) upon wire contact, diagnostic testing is able to occur as an instant connection is created to the test and measurement instrument.

Below you can see the image of Pico Technology's Back-Pinning Probe Set ⪫

Note that back-pinning probes and piercing probes are mostly for automotive electric/electronic system diagnosis.

These special probes obviously make non-invasive testing perfect for hard to reach wires and also eliminates the time consuming and destructive nature of strip or cutting wire to access the conductor for testing.

Further Info ⪫ https://e-z-hook.com/blog-guide-to-back-probe-connectors/

More on this later. Thanks for reading!

I3C Bus Introduction

I3C Bus is a serial communication bus. It is in fact a migration from the legacy I²C Bus, initially intended for mobile applications as a single interface that could be used for all digitally interfaced sensors.

In principle, I3C is a serial communication interface implemented using a complementary metal oxide semiconductor (CMOS) I/O, which uses a two-wire interface to minimize pin counts and number of signal paths between components.

The I3C specification takes its name from, uses the same electrical connections as, and allows some backward compatibility with, the I²C bus, a de facto standard for inter-chip communication, widely used for low-speed peripherals and sensors in computer systems.

The I3C standard is designed to retain some backward compatibility with the I²C system, notably allowing designs where existing I²C devices can be connected to an I3C bus but still have the bus able to switch to a higher data rate for communication at higher speeds between compliant I3C devices. 

That is, I3C is a specification to enable communication between computer chips by defining the electrical connection between the chips and signaling patterns to be used.

Short for Improved Inter Integrated Circuit, the standard defines the electrical connection between the chips to be a two wire, shared (multidrop), serial data bus, one wire (SCL) being used as a clock to define the sampling times, the other wire (SDA) being used as a data line whose voltage can be sampled.

The standard defines a signaling protocol in which multiple chips can control communication and thereby act as the bus controller.  Source Wikipedia ⇱

As said before, MIPI I3C is a follow on to I²C but it has major improvements in use and power and performance, and it is an optional alternative to SPI for mid-speed (equivalent to 30 Mbps).

Obviously, it is an evolutionary specification that builds upon the legacy I²C standard. The aim is to reduce the number of physical pins used in sensor system integration and supports low-power, high-speed digital communication typically associated with UART and SPI  interfaces so that I3C becomes a single interface combining all the capabilities of the legacy interfaces.

The I3C Protocol has a multi-drop bus which, at 12.5 MHz, is over 12 times faster than what I²C supports while using significantly less power. The key features include backward compatibility with legacy I2C, multi-master and multi-drop capabilities, dynamic addressing, in-band interrupts, hot-join support, etc.

Note at this point that the MIPI I3C interface uses an I²C-like interface with an open drain data line (SDA) and a push-pull clock line (SCL).

The open drain SDA line allows for slaves to take control of the data bus and initiate interrupts. The push-pull SCL line is used by the master to clock the communication bus up to 12.5 MHz.

I3C and I3C Basic FAQs https://www.mipi.org/resources/i3c-frequently-asked-questions ↗

The first I3C interfaced sensor we saw in practice was the BMP581 absolute barometric pressure sensor. 

The BMP581 Sensor offers outstanding design flexibility, providing a single package solution that we can easily integrate into a multitude of existing and upcoming devices such as GPS modules, wearables, hearables, smart home, IoT and industrial products. Here's the Datasheet PDF ↗

More information will follow shortly...

RS232 LCD Modules

Obviously, RS232 and I2C liquid crystal display drivers provide easy operation of standard 20x4 or 16x2 LCD text displays. Usually such a serial LCD module demands only a 5V power supply and just two data connections, thus freeing up I/O pins on your microprocessor.

Character type LCD module with RS232 interface would be another perfect display solution for industrial control and PC's auxiliary display applications.

Lumex Inc. currently offers three types of character LCD modules with RS232 interface. Their 20x2 characters LCD module with white LED backlight is shown above.

The Lumex RS232 LCD module uses UART and AT command as protocol to communicate with various devices. Also, users can use the same firmware when there is need to switch from character type display to graphic type display or the other way around.

Usually the Serial mode (RS232) operates over a link with a baud rate of 9600 bps and 5V signals. However, do not connect RS232 directly to a generic RS232 LCD module as you will destroy it in most cases. Note that often you need to use a MAX232 (or equivalent) IC to convert the RS232 levels to 5V (TTL).

Here you will find the technical documentation for LCD05 I2C/Serial LCD https://www.robot-electronics.co.uk/htm/Lcd05tech.htm

Next is the system block diagram of the CFA632 customizable LCD Modules (Crystalfontz America, Inc.). 

Note that you can use any of six interfaces on any of the LCD modules in the series by simply changing the interface selection in a command and using the appropriate jumper configurations.

Now download and read the PDF Datasheet below to understand more about CFA632 series smart LCD modules ↓

https://www.crystalfontz.com/products/document/3392/CFA632_Series_Data_Sheet_Release_Date_2015-03-30.pdf

OK, see you next week!

Zero Threshold MOSFET

When choosing a MOSFET, parameters that are focused on by most design engineers intuitively are VDS, VGS, RDS(on), ID, and VGS(th).

• VDS represents the absolute maximum voltage between drain and source
• VGS represents operating driver voltage between gate and source
• RDS(on) represents drain-source on-state resistance
• ID represents the continuous conduction current
• VGS(th) represents the gate threshold voltage

Anyway, note that the current that flows into the Drain (ID) of a MOSFET is related to the Gate-Source Voltage (VGS), the threshold voltage (VTH) and a property called the transconductance(gM) that describes how well it conducts.

Back to the MOSFET parameters, the MOSFET VGS(th) or Gate Threshold Voltage is the voltage between the Gate and Source that is needed to turn on the MOSFET. In other words, if VGS is at least as high as the threshold voltage, the MOSFET turns on.

That's fine! Then what is a Zero Threshold MOSFET?

Advanced Linear Devices Inc (ALD) created an industry breakthrough Zero Threshold MOSFET device introducing a new level of precision in analog design that makes 0.1-Volt circuits possible for the first time.

With this new analog component, the shackle of “threshold turn-on voltage” placed on the circuit design engineer has just been broken.

The operating voltage of a circuit will no longer be limited by the gate threshold voltage or the bipolar turn-on voltage.

Now a simple circuit using this new device can be constructed to operate on as little as a 20mV supply. On more complicated circuits, consisting of many stages stacked on top of each other, a system operating voltage of just 0.2V to 0.45V becomes a reality.

Providing zero threshold MOSFETs for the first time will support the design of analog circuits that operate on less than one microwatt, giving designers the flexibility to extend the maximum signal range of low voltage systems.

Such versatility supports the operation of countless applications from ultra-sensitive, remote sensor arrays to implantable medical devices.

This new device can be classified as both an enhancement mode device when operated above the threshold voltage and a depletion mode MOSFET device when operated at or below threshold voltage.

Now see a sample datasheet https://www.aldinc.com/pdf/ALD110800.pdf

Current Limiting Diode

A current limiting diode (CLD) or current regulating diode (CRD) is a diode that regulates and limits current over a specified voltage range. These devices allow the passage of current, rise to a certain value, and then level off at a specific value. 

Contrary to Zener diodes, which keep voltage constant, CLDs keep the current constant. A CLD can also be considered a current source as it is an electronic circuit that delivers or absorbs an electric current, independent of the voltage across it. See its circuit symbol below.

CLDs start with a JFET process where the gate (G) and source (S) are connected. This interconnect is part of the diffusion process. Additionally, the diffusion process for each type is carefully controlled in order to provide the specific regulation current required.

Simply put, these devices regulate current over a broad voltage range as a counter part offering to zener diodes that regulates voltage over a broad current range.

Creating a constant current circuit generally involves multiple components, but with a CLD or CRD only one component is required to accomplish the same function!

Here is a PDF from Central Semiconductor Corp. https://www.centralsemi.com/pdfs/selection/leaded/what_is_a_cld.pdf

See also the J500 Series CRD Datasheet https://www.mouser.com/datasheet/2/1442/J500SeriesDSRevA10-3180164.pdf

AC Input Photocoupler/Optocoupler

It is very common these days to see a logic circuit with an AC input photocoupler (optocoupler).

Such a bidirectional input device enables the circuit to operate safely at dangerous AC line voltages.

The most common AC input photocouplers widely used are PC814 and LTV814.

This is the internal connection of the SHARP PC814 AC Input Photocoupler:

There are two LEDs connected back-to-back on the input side so that the first LED lights and a signal is transferred when current is applied in the direction of Pin 1 to Pin 2, and the second LED lights and a signal is transferred when current is applied in the reverse direction of Pin 2 to Pin 1.

Simply put, a signal can be transferred even if the polarity between the input pins 1 and 2 is switched from positive to negative and vice versa.

The figure below shows a basic circuit connection example when AC 100V is input to an AC input photocoupler via a current-limiting resistor.

In general, the final output signal is used after smoothing by a buffer capacitor, etc.

And the next figure shows the relationship between the input and output signals of an AC input photocoupler.

In this case, the output signal obtained from the ac input photocoupler is in the form of a full-wave rectified AC input signal.

OK, if you have applications in your projects where you need to know the status of a fatal line voltage circuitry perhaps an ac input photocoupler can be of use to you too. Give it a try!

Thanks RENESAS ⨶

Photomultiplier Tube (PMT)

Photomultiplier tube (PMT) is among the most sensitive of all light sensors and are used to detect faint light.

In other words, a photomultiplier tube, useful for light detection of very weak signals, is a photo emissive device in which the absorption of a photon results in the emission of an electron. These detectors work by amplifying the electrons generated by a photocathode exposed to a photon flux.

Note at this point that tubes without a multiplication function are called phototubes (PT).

Photomultiplier tubes are mainly used as secondary electron detectors in scanning electron microscopes (SEM).

Photomultipliers acquire light through a glass or quartz window that covers a photosensitive surface (photocathode0 which then releases electrons that are multiplied by electrodes known as metal channel dynodes.

Most photomultiplier tubes have 9 to 12 dynodes and amplify to the 5th to 8th power of 10, and finally output as a current.

At the end of the dynode chain is an anode or collection electrode. Over a very large range, the current flowing from the anode to ground is directly proportional to the photo electron flux generated by the photocathode.

Further Reading: https://hamamatsu.magnet.fsu.edu/articles/photomultipliers.html ↗

There are two types of photomultiplier tubes - head-on type with a photosensitive area at the tip and side-on type with a photosensitive area at the side. And, there are numerous types of photocathodes with different photosensitive surface sizes and wavelength sensitivities.

Most photomultiplier tubes operate at voltages ranging from 500 V to 2000 V. Below you can see a high-voltage power supply module for PMTs (Hamamatsu HVPS Module).

In order to generate high internal gain, the electrons initially generated at the PMT's photocathode needs to be accelerated by a high-voltage (kV) potential, so that the potential causes the electrons to strike several dynodes that generate secondary electrons. The photocurrent that has accumulated after the final dynode stage represents the amplified signal and is collected by an anode.

So, Photomultiplier tubes are used to detect faint optical signals from weakly emitting sources. 

Compared to Avalanche Photodetectors (APDs), they offer significantly larger active areas, making them ideal for capturing signals that may be diverging due to scatter or nonlinear optical effects.

Since the first commercial photomultiplier tube was developed in the early 1940s, it has remained the detector of choice for experiments requiring fast response times and high sensitivity.

Today, the PMT is a staple for research in many fields including analytical chemistry, particle physics, medical imaging, industrial process control, astronomy, and atomic and molecular physics.

This PMT Tutorial (Thorlabs, Inc.) provides introductory material for the principle of operation and key specifications to consider when choosing a PMT for a given application. 

⫸ Finally here is the Wikipedia Article https://en.wikipedia.org/wiki/Photomultiplier_tube  

Zero Ohm Resistor (ZOR)

 Zero Ohm Resistor (ZOR) is simply a zero-ohm (0Ω) jumper!

It is a single resistor that is manufactured to have zero ohm of resistance when measured. A through-hole resistor with zero ohm is often marked with a single black band, which indicates the value of the resistance whereas a surface mount ceramic resistor will have a single or a multiple number of zeros to represent the zero ohm resistance.

A few reasons to use a zero-ohm resistor:

• It simplifies PCB routing and traces
• It helps to easily enable or disable a signal
• It isolates inputs or outputs between different circuit sections during development, servicing, or repairing circuits (just by unsoldering them)

Basically, a zero ohm resistor functions like a wire. Since most large batches of printed circuit boards are automatically populated by machines, the machines can easily place these standardized resistors when a jumper is needed instead of cutting and stripping a custom wire or jumper wire resistor.

There is also a less obvious rationale for zero-ohm resistors. It can complicate and conceal a circuit’s function and confuse someone trying to trace out and thus reverse-engineer the design.

These are at least some reasons where this apparently mystic component makes sense.

Note that the resistance of a zero ohm resistor is only approximately zero, that is, only a maximum is specified, which is typically in the range of 10–50 mΩ.

Here is the datasheet of a zero ohm chip resistor in PDF  https://www.resistor.com/assets/pdf/RCZ1206CPX.pdf

So, zero-ohm resistor is an odd component whose function seems useless at first. However, it is quite useful for masters who are aware of it and empathize how it can help solve circuit design and layout problems at very low cost with no or minimal complexities.

Thanks for reading!