Tag Archives: Current

Low-side I/V sensing IC, with internal power calculation

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Maxim Integrated has posted details of the MAX44299, a low-side current, voltage, and power monitoring circuit that provides an analogue output current proportional to the measured current, voltage, and the internally calculated instantaneous power. The power monitor offers high precision and integration in tiny size.

Instantaneous power is calculated internally by multiplying the load current and a fraction of the load voltage set by an external resistive divider. All three outputs are scaled to a full-scale current of 100 µA. An additional output current of 100 µA is available at the reference (REF) output; this current can be used to create a reference voltage for the ADC that is being used to measure the power, voltage, and current signals.

Low-side I/V sensing IC, with internal power calculation – [Link]

USB Power Meter

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Daniel Grießhaber @ hackaday.io has published his build of a USB power meter. His device is based on ATTiny 85 mcu and 0.96″ OLED Display and is able to measure voltage, current and power output from USB port.

Since USB has become more and more a power delivery standard, it would be nice to have a convenient way to measure the power consumption these devices need. Of course there are already power meters out there, but they are just boring or don’t have all the features I like.

USB Power Meter – [Link]

Over Current Protection Switch

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Current Sensing Switch is designed to operate a Relay Contact when there is a DC current through the sense resistor exceeds the set point, Set point adjustable from 1A to 3Amp using on board potentiometer. This circuit can offer over current protection to your project.

Specifications

  • Input: 12 VDC
  • Range: 1 to 3 A selectable with onboard preset
  • Output: SPDT Relay (Normally Open & Normally Closed)
  • Power Battery Terminal (PBT) and Terminal Pins for easy connection
  • Four mounting holes of 3.2 mm each
  • PCB dimensions 52 mm x 47 mm

Over Current Protection Switch – [Link]

Protecting the USB from over voltage and overcurrent threats

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An application note from Littelfuse about USB protection.

This application note addresses the various requirements for protecting the Universal Serial Bus (USB) from overcurrent and overvoltage environmental threats. The solutions presented cover both USB 1.1 and the higher speed USB 2.0 circuitry. Specific emphasis is placed on USB 2.0 with information directed at hot connection over current conditions and electrostatic discharge (ESD) induced in the USB system.

Protecting the USB from over voltage and overcurrent threats – [Link]

Measure small currents without adding resistive insertion loss

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by Maciej Kokot @ edn.com:

In most cases, you measure current by converting it into a proportional voltage and then measuring the voltage. Figure 1 shows two typical methods of making the conversion. In one method, you insert a probing resistor, RP, in series with the current path and use differential amplifier IC1 to measure the resulting voltage drop (Figure 1a). A second method is a widely known operational amplifier current-to-voltage converter in which inverted IC1’s output sinks the incoming current through the feedback resistor (Figure 1b).

Measure small currents without adding resistive insertion loss – [Link]

USB power supply active load tester

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Sasa Karanovic has designed and built a DIY USB power Supply active load tester, that is available at GitHub:

USB Power supply Active Load Tester or short PAL Tester is unit designed for testing the quality of the power supplies.
Idea was to create low-cost, precise device for simultaneous measurement of Voltage and Current drawn from the device under test.

USB power supply active load tester – [Link]

Current monitor uses Hall sensor

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by Paul Galluzzi @ edn.com:

The Fig 1 circuit uses a Hall-effect sensor, consisting of an IC that resides in a small gap in a flux-collector toroid, to measure dc current in the range of 0 to 40A. You wrap the current-carrying wire through the toroid; the Hall voltage VH is then linearly proportional to the current (I). The current drain from VB is less than 30 mA.

To monitor an automobile alternator’s output current, for example, connect the car’s battery between the circuit’s VB terminal and ground, and wrap one turn of wire through the toroid. (Or, you could wrap 10 turns—if they’d fit—to measure 1A full scale.) When I=0V, the current sensor’s (CS1’s) VH output equals one-half of its 10V bias voltage. Because regulators IC1 and IC2 provide a bipolar bias voltage, VH and VOUT are zero when I is zero; you can then adjust the output gain and offset to scale VOUT at 1V per 10A.

Current monitor uses Hall sensor – [Link]

Using the cirrus logic CS5464 for AC current measurement

Using the cirrus logic CS5464 for AC current measurement by Corgi-Tronics:

Continuing the series on examining devices to measure AC current, this time we’ll try out the CS5464 from Cirrus Logic. I initially built it up on a breadboard, but I’ll skip writing up this test and instead build up a prototype and run AC line power through it.

This is a Three-channel, Single-phase Power/Energy monitoring chip, and also can use current shunts and is intended for power meters.
This device provides no direct isolation, instead the entire device (input and output) directly coupled to the AC power line. Any isolation must be provided separately.

[via]

Using the cirrus logic CS5464 for AC current measurement – [Link]

A simple current-sense technique eliminating a sense resistor

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An old but interesting app note (PDF) from Microsemi on resistorless current-sensing technique. [via]

This application note introduces a simple current-sense technique that eliminates that sense resistor, resulting in system-cost reduction, PCB space saving, and power efficiency improvement. Furthermore, the new current sensing mechanism allows higher dynamic tripping current than the static one (built-in low-pass filtering) to improve current-sense noise immunity.

A simple current-sense technique eliminating a sense resistor – [Link]