Product details

How to use digital I/O to protect relays

1. Brief introduction

In the case of a short circuit or open circuit in a switching system, the relay is often overloaded due to the presence of additional current or voltage. All relays have a maximum load current and heat transfer power, if beyond this range, will increase the risk of relays welded together, resulting in failure to release, or release time is too long.

The reason is that there are capacitive devices in this part of the power supply, which may release a large current, resulting in heat that makes the connection part melt, and it is possible to connect together after cooling.

Adding an additional current limiter can reduce this part of the problem, but it needs to be clear that adding a current limiter in the power supply part can not avoid the impact of capacitive current, and because the current limiter is connected to the power control system, it takes a certain time to respond when working, and the desired result is not achieved.

Module cards like 40-411, 40-412 and 40-413 can be used to reduce the occurrence of welding failures, especially when accessing the test target of failure. To explain how the above digital IO module can reduce this aspect of damage, let's take the fault injection module as an example to illustrate.

2. Digital I/O module

The outputs of 40-411, 40-412, and 40-413 have limited-current drivers that use MOSFET outputs and include limiters that allow current to flow smoothly. After the drive enters current limiting mode, the voltage drop will pass through the MOSFET, and this voltage drop will make the MOSFET hot. The drive also includes a temperature sensor that can turn the MOSFET off by protecting the current. When the MOSFET cools, it can start working again. This powerful device protects the device from damage - before a sustained high voltage burns it out. The temperature sensor and current limiter are very close to the MOSFET, so the response time is very short, which can effectively protect the MOSFET.

In a digital I/O card that includes a pull current and a fill current drive, both drives can be turned off, either by connecting one drive to a power source or by grounding it.

Where the high level is applied, it should be noted that it contains a bias diode, which, when the switch is on, means that there will be a voltage drop through the drive, which results in a higher impedance than expected.

Electromagnetic counter is mainly used to record the cumulative number of electrical pulse signals. Can be composed with secondary instrument digital display instrument, widely used in petroleum, chemical, textile, machinery, mining, national defense, agriculture, food, printing and other industries of various electrical pulse counting. After the electrical signal is input to the counter, the suction force is generated in the electromagnet, so that the armature drives the escapement and drives the digital wheel to rotate for decimal counting.

With the development of electronic counters, the current trend of electromagnetic counters to be replaced, but in some complex environments, voltage instability conditions, electromagnetic counters have a living space

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