Tag Archives: Switch

A Heat Switch for Controlling Heat Flow Path in Electronic Systems

Schematic of the thermal switch showing the (a) ON-state with the liquid metal droplet bridging the heat source and sink and (b) OFF-state with liquid metal removed from the channel. (c) Side view image of the fabricated thermal switch device. (d) The ON and OFF thermal resistance circuits based on a 1-D heat transfer model.

A switch is a fundamental part of most electrical and mechanical devices; mechanical switches can be used to select gears in a car’s transmission or used to unlock a door; electrical switches can turn the lights in a room on and off;  semiconductor uses to route logic signals within a circuit or control bigger devices. But what about heat flows? Can we possibly control the route of heat in a device? A Thermal Switch? Well, a thermal switch is an electromechanical device which opens and closes contacts to control the flow of electrical current in response to temperature change. A Thermal switch controls the flow of current concerning the temperature change, but this doesn’t actually control the flow of heat.

Heat flow is very important to engineers, and the heat movement in a device can profoundly affect the system performance and reliability especially in an electronics system. Engineers have long desired a switch to control heat flows, but many challenges exist in the creation of such a switch. Researchers from the College of Engineering at the University of Illinois at Urbana-Champaign have developed a new technology that allows users to turn heat flows “on” or “off.” This is a great development and it’s going to impact on future electronics systems.

Heat Flow from Hot to Cool Region

“Heat flows occurs whenever you have a region on higher temperature near a region of lower temperature. In order to control the heat flow, the team engineered a specific heat flow path between the hot region and cold region and then created a way to break the heat flow path when desired” claims William King, the project co-leader and a professor at the department of mechanical science and engineering.

This technology became possible based on the principle of the “motion of a liquid metal droplet,” adds Nenad Miljkovic, assistant professor in the same department who also served as a project co-leader. “The metal droplet can be positioned to connect a heat flow path, or moved away from the heat flow path to limit the heat flow.”

The team demonstrated the technology in a system modeled after modern electronic systems, giving the potential of being deployed to our everyday devices. On one side of the switch was a heat source representing the power electronics component; on the other, liquid cooling for heat removal. When the heat switch was on, the team managed to extract heat at more than 10 W/cm2, but as soon as the heat flow was turned off, they saw a drop by nearly 100X.

According to King, the next step for the research will be to integrate the switch with power electronics on a circuit board. A working prototype will be produced later this year. The research was published in a recent edition of the journal Applied Physics Letters.

Lowest power magnetic switch uses nanoamps

Crocus Technology is introducing its CT832 Digital Magnetic Switch, in the CT83X series, a multi- function switching device with high sensitivity, reliability and new lows in power consumption, that it positions as the industry’s lowest power consuming switch.

Lowest power magnetic switch uses nanoamps – [Link]

Dual die, Hall effect, latch and switch sensor is accurate & redundant

Graham Prophet @ eedesignnewseurope.com discuss about Melexis magnetic latch and switch sensors. He writes:

Melexis (Tessenderlo, Belgium) has introduced a range of new magnetic latch and switch sensors that feature two silicon dice in the same package, yielding highly reliable devices, which are aimed at automotive applications including transmission, power steering, braking and locks/latches.

Dual die, Hall effect, latch and switch sensor is accurate & redundant – [Link]

ESPurna-H, A Compact Open Source Hardware Wireless Power Wall Switch

Controlling your AC loads using wireless power switch is not a new concept. Several commercial products from several vendors can be found on the market such as Xiaomi’s Mi Smart Socket Plug, SAMSUNG’s SmartThings Power Outlet and Sonoff Pow WiFi Switch from ITEAD.

Using ESP8266 makes the building of a customized WiFi power switch more affordable especially if you start with Sonoff Pow WiFi Switch design and you use a special Arduino C firmware called ESPurna developed by Xose (tinkerman) which is an open source firmware for ESP8266 based wireless switches such as Sonoff POW and many others.

After Xose has built the software ــ ESPurna, he decided to build his own smart switch board to meet his special needs. ESPurna-H electronic design is very similar to Sonoff POW’s one; it uses ESP12 module as a controller and as WiFi transceiver.


AC power monitoring is done using HLW8012 IC which is also present in Sonoff POW. This IC monitors both voltage and current of the AC power, and output RMS voltage, current and active power encoded as a 50% duty cycle square wave where the frequency is proportional to the magnitude. I should mention that ESPurna supports interfacing with HLW8012. In addition AC load is enabled/disabled by using a 10A relay.

ESPurna-H uses HLK-PM01 AC-DC step-down power supply module. The 100-240 VAC input range so the board can be used anywhere in the world and the good performance made Xeos select this module.

HLK-PM01 Inside (Image Source ــ lygte-info.dk )
HLK-PM01 Inside (Image Source ــ lygte-info.dk )
HLK-PM01 Inside (Image Source ــ lygte-info.dk )
HLK-PM01 Inside (Image Source ــ lygte-info.dk )

ESPurna-H has another option to enable/disable the relay using a capacitive touch switch using TTP223 module.

Xose designed the board with Eagle CAD and released the schematics, PCB layout and other hardware design files on Github.

Source: cnx-software

Reliable molecular switch

by Eric Bogers @ elektormagazine.com:

Nanotechnology repeatedly breaks new records in the area of miniaturization. However, there are physical limits when reducing the size of electronic components and these will be reached in the near future. This means that new materials and components will be required – and it is here where molecular electronics will play a role. Researchers from the Karlsruher Institut für Technologie (KIT) have succeeded in developing a molecular toggle switch, which will not only remain in the selected position, but can also be switched as often as desired without any deformation taking place.

Reliable molecular switch – [Link]

Simple Pressure Sensor Amplifier & Over Pressure Switch

The pressure sensor amplifier built using LM358 op-amp and MPXM2051GS pressure sensor from NXP semiconductor.  The circuit provides 4V output for full scale pressure input 0-7.5PSI.  One op-amp is used as amplifier and 2nd op-amp is used as comparator to provide an output at set value that can be used as over pressure switch to control a pump or solenoid.  This is a low cost general-purpose circuit for those applications where +/-3% performance is acceptable. Multi turn potentiometers are provided for Offset, span adjust & over/under Pressure set point to control output devices like solid state relay, Pump, and solenoid.


  • Supply 12V DC
  • Pressure Sensor range 0-7.5PSI
  • Output 0-4V (Approx.)
  • PR1 Multi-Turn Potentiometer Offset
  • PR2 Multi-Turn Potentiometer Span Set
  • PR3 Multi-Turn Potentiometer Comparator (Switch) output Set
  • D1 Power LED
  • CN1 4 Header Connector Outputs & Supply Input

Simple Pressure Sensor Amplifier & Over Pressure Switch – [Link]

Wafer-scale-packaged integrated FET switches handle 1 – 4A

by Graham Prophet @ edn-europe.com:

Silego Technology has developed a series of integrated power switches for use in mobile and battery powered products, to carry out power gating of functional blocks within a design; the devices come in sub-mm-size chip scale packages, handle currents from 1 to 4 A, and integrate functions such as in-rush current limiting and over-current or thermal protection.

Wafer-scale-packaged integrated FET switches handle 1 – 4A – [Link]

LTM9100 – Anyside™ High Voltage Isolated Switch Controller with I²C

The LTM9100 μModule is an all-in-one solution for controlling, protecting, and monitoring high voltage power supplies up to 1000VDC. A 5kVRMS galvanic isolation barrier separates the digital interface from the switch controller, driving an external N-channel MOSFET or IGBT switch. Isolated digital measurements of load current, bus voltage, and temperature are accessed via the I2C/SMBus interface, enabling power and energy monitoring of the high voltage bus. The LTM9100 saves design time, certification effort, and board area by wrapping all the needed functionality, including digital telemetry and isolated power, in a compact BGA package.

LTM9100 – Anyside™ High Voltage Isolated Switch Controller with I²C – [Link]

Dual-Channel Quadrature Hall-Effect Bipolar Switch Module for Magnetic Encoder

The A1230 is a dual-channel, bipolar switch with two Hall-effect sensing elements, each providing a separate digital output for speed and direction signal processing capability. The Hall elements are photo lithographically aligned to better than 1 µm. maintaining accurate mechanical location between the two active Hall elements eliminates the major manufacturing hurdle encountered in fine-pitch detection applications. The A1230 is a highly sensitive, temperature stable magnetic sensing device ideal for use in ring magnet based, speed and direction systems located in harsh automotive and industrial environments.

The A1230 monolithic integrated circuit (IC) contains two independent Hall-effect bipolar switches located 1 mm apart. The digital outputs are out of phase so that the outputs are in quadrature when interfaced with the proper ring magnet design. This allows easy processing of speed and direction signals. Extremely low-drift amplifiers guarantee symmetry between the switches to maintain signal quadrature. The Allegro patented, high-frequency chopper-stabilization technique cancels offsets in each channel providing stable operation over the full specified temperature and voltage ranges.

Dual-Channel Quadrature Hall-Effect Bipolar Switch Module for Magnetic Encoder – [Link]

Load switch with self-resetting circuit breaker


has designed a simple load switch using two transistors and some resistors.

The simple current-limiting load switch shown in Figure 1 will be familiar to most readers. In this circuit, a high level signal applied to the input switches on MOSFET Q2, which energizes the load. The load current is limited by negative feedback applied via Q1.

Load switch with self-resetting circuit breaker – [Link]