Analog input

DDD1211

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How should protection and fault detection be performed when 0-5V analog input is used?

maychang

“How should protection and fault detection be performed when analog input is used?”

Different use environments and different devices have different "protection and fault detection". For example, a portable digital multimeter may not have any "protection and fault detection". A desktop digital multimeter may have more protection circuits.

littleshrimp

For details, please refer to the reference design of large manufacturers. Generally, resistors are connected in series with clamp diodes, transient suppression diodes are used to protect pull-up resistors, and open circuit detection is performed.

DDD1211

littleshrimp posted on 2019-8-8 17:27 For details, you can refer to the reference design of large manufacturers. Generally, a series resistor clamp diode transient suppression diode protection pull-up resistor open circuit detection

Is there any method to detect short circuit?

littleshrimp

DDD1211 posted on 2019-8-12 14:19 Is there any method to detect short circuit?

The pull-up resistor short circuit reading is close to the minimum value and the open circuit is close to the maximum value

DDD1211

littleshrimp posted on 2019-8-12 15:39 The pull-up resistor short circuit reading is close to the minimum value and the open circuit is close to the maximum value

Want to realize automatic detection of single chip microcomputer and feedback after short circuit

maychang

DDD1211 posted on 2019-8-12 16:20 I want to realize automatic detection of microcontrollers and feedback after short circuit

The microcontroller detects whether the input signal is short-circuited or open-circuited. Because your input signal is 0~5V, a short circuit is exactly the same as an input of 0V, so a short circuit cannot be detected when the input is 0V.

maychang

DDD1211 posted on 2019-8-12 16:20 I want to realize automatic detection of microcontrollers and feedback after short circuit

For non-ideal voltage sources, a signal can be sent to the input terminal to detect the internal resistance of the signal source. If the internal resistance is very, very small, it can be determined that the signal source is short-circuited.

littleshrimp

DDD1211 posted on 2019-8-12 16:20 I want to realize automatic detection of microcontrollers and feedback after short circuit

I don't understand what you mean, please be more specific.

DDD1211

maychang posted on 2019-8-12 16:25 The microcontroller detects whether the input signal is short-circuited or open-circuited. Because your input signal is 0~5V, short-circuit and input are exactly the same as 0V, so the input is 0V...

In the single-chip microcomputer system, the external load is connected to the single-chip microcomputer through the acquisition circuit. For the external input load, I want to perform short-circuit detection on it. If a short circuit occurs, the power can be cut off in time.

DDD1211

littleshrimp posted on 2019-8-12 16:29 I don't understand what you mean, please be more specific

In the single-chip microcomputer system, the external load is connected to the single-chip microcomputer through the acquisition circuit. For the external input load, I want to perform short-circuit detection on it. If a short circuit occurs, the power can be cut off in time.

littleshrimp

DDD1211 published on 2019-8-12 16:47 In a single-chip microcomputer system, the external load is connected to the single-chip microcomputer through the acquisition circuit. For the external input load, I want to perform short-circuit detection. If it is short-circuited, can...

In addition to short-circuit, are there other situations where zero volts can be output?

DDD1211

littleshrimp posted on 2019-8-12 16:50 In addition to short circuit, are there other situations where zero volts can be output?

Feedback is required for power supply, short circuit to ground, and open circuit status

maychang

DDD1211 posted on 2019-8-12 16:47 In the single-chip microcomputer system, the external load is connected to the single-chip microcomputer through the acquisition circuit. For the external input load, I want to perform short-circuit detection on it. If it is short-circuited, I can...

"In a single-chip microcomputer system, the external load is connected to the single-chip microcomputer through the acquisition circuit. For the external input load, I want to perform short-circuit detection on it. If a short circuit occurs, I can handle the power outage in time."

What is the "external input load"? Are you trying to de-energize that location?

DDD1211

maychang published on 2019-8-12 16:59 "In a single-chip microcomputer system, the external load is connected to the single-chip microcomputer through the acquisition circuit. For the external input load, I want to perform short-circuit detection. If the short circuit...

The front end of the acquisition circuit is a 0-5V analog quantity. The short-circuit detection is to allow the microcontroller to process the signal of the acquisition circuit without damaging the microcontroller.

maychang

DDD1211 posted on 2019-8-12 17:02 The front end of the acquisition circuit is a 0-5V analog quantity. The short-circuit detection is to let the microcontroller process the signal of the acquisition circuit so as not to damage the microcontroller...

"The front end of the acquisition circuit is a 0-5V analog signal. The short-circuit detection is to allow the microcontroller to process the signal of the acquisition circuit without damaging the microcontroller."

The method of “not damaging the microcontroller” is called protection.

If your "front end" is short-circuited, the microcontroller will not be damaged, but at most it will not be able to measure accurate data. I am afraid that your understanding of "short circuit" is inconsistent with that of other netizens.

DDD1211

maychang posted on 2019-8-12 17:47 "The front end of the acquisition circuit is a 0-5V analog quantity. The short-circuit detection is to let the microcontroller process the signal of the acquisition circuit so as not to damage...

It can also be said that you want the microcontroller to detect the input status (short circuit or open circuit)

DDD1211

DDD1211 posted on 2019-8-13 09:04 It can also be said that you want the microcontroller to detect the input status (short circuit or open circuit)

diagnosis

maychang

DDD1211 posted on 2019-8-13 09:04 It can also be said that you want the microcontroller to detect the input status (short circuit or open circuit)

The first post asked: "How should protection and fault detection be done when 0-5V analog input is used?"

On the 15th floor, you said: "The front end of the acquisition circuit is just a 0-5V analog quantity"

The 17th floor said again: "You can also say that you want the microcontroller to detect the input status (short circuit or open circuit)"

You never made it clear what you were going to do.

maychang

DDD1211 posted on 2019-8-13 09:04 It can also be said that you want the microcontroller to detect the input status (short circuit or open circuit)

I guess you want to measure the input 0~5V DC voltage, and require to make a judgment when the input signal is normal, open circuit or short circuit.

If the input signal source is an ideal voltage source, it is impossible to determine whether the input signal source is short-circuited, because the signal amplitude includes zero, and the result of the signal source being short-circuited is also zero.

To check whether the signal source is open circuit, refer to the method described by littleshrimp on the 5th floor. However, when using this method, the input voltage cannot be measured at the same time.