![]() When used in conjunction with isolated power supplies, these devices block high voltages, isolate grounds, and prevent noise currents from entering the local ground and interfering with or damaging sensitive circuitry. These devices have their logic input and output buffers separated by TI’s capacitive isolation technology using a silicon dioxide (SiO2) barrier. To make efficient use of one technology supporting the other, external circuitry is required that separates the bidirectional bus into two unidirectional signal paths without introducing significant propagation delay. The I2C bus operates in bidirectional, half-duplex mode, while standard digital isolators are unidirectional devices. The most common speeds are the standard and fast modes. This data can be transferred in four speeds: standard mode (0 to 100 kbps), fast mode (0 to 400 kbps), fast-mode plus (0 to 1 Mbps), and high-speed mode (0 to 3.4 Mbps). Data is transferred between the master and slave through a serial data (SDA) line. The master, or processor, controls the bus, specifically the serial clock (SCL) line. The bus consists of a two-wire communication bus that supports bidirectional data transfer between a master device and several slave devices. The I2C bus is used in a wide range of applications because it is simple to use. Open-drain outputs with 3.5-mA Side 1 and 35- mA Side 2 sink current capability.3-V to 5.5-V supply range, Side 1 Connected to Arduino Uno 5V Supply.Isolated bidirectional, I2C compatible, communication. ![]() This board requires two separate supplies, side one powered from Arduino UNO 5V, side 2 require separate 3.3V to 5V. LED D1 is the power indicator for side two. For applications where clock stretching by the slave is possible. The project is suitable for multi-master applications. The ISO1540 has two isolated bidirectional channels for clock and data lines. ![]() When used with isolated power supplies, these devices block high voltages, isolate grounds, and prevent noise currents from entering the local ground and interfering with or damaging the Arduino board. These devices have logic input and output buffers that are separated by Texas Instruments Capacitive Isolation technology using a silicon dioxide (SiO2) barrier. This series of products are UL1577-qualified for safety, support a variety of dielectric strengths (3kVrms, 3.75kVrms, 5kVrms, 5.7kVrms), and feature low power consumption, high electromagnetic. ![]() The NSi824x is a high-reliability four-channel digital isolator. I have used the ISO1540 Low-Power Bidirectional I2C Isolator IC from Texas Instruments to build this project, and the device is compatible with I2C interfaces. Isolated RS485 Tranceiver with Integrated Isolated Power. For the TVS diodes you could use these, for instance.Optically isolator Arduino Shield has been designed to provide optically isolated I2C communication between Arduino and any other device or sensors that works with I2C protocols. That resistor's value shouldn't be too high for two reasons: it will form a divider with the pull-ups and so lift up your low level, and also it will deteriorate the falling edges of your signal. If you want to protect your RPi against spikes there may be a more simple solution: use TVS (Transient Voltage Suppression) diodes, possibly in combination with a small series resistor. If you think you do need isolation this document may help to get you started. For a proper PSRR (Power Supply Rejection Ratio) you can have a separate LDO close to each sensor. Make sure the sensors' power supplies are properly decoupled. If it's the power supply you worry about then isolating the bus doesn't make much sense. So noise may not be a too big problem there. Are you sure you need isolation? The I2C bus carries digital signals, and is relatively low impedance you can go as low as 2 kΩ. ![]()
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