Can the microcontroller detect negative values if it is powered by a single power supply?

QWE4562009

Can the microcontroller detect negative values if it is powered by a single power supply? [Copy link]

 

Can the microcontroller detect negative values if it is powered by a single power supply?

dcexpert

It should be a documentation error

QWE4562009

dcexpert posted on 2021-1-15 16:24 It should be a document error

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w494143467

I feel that most single-chip microcomputers do not have the function of detecting negative values, and basically require an external chip.

dcexpert

QWE4562009 posted on 2021-1-15 16:36 How to say moderator

Ordinary circuits cannot detect negative pressure, and general single-chip microcomputers will not add complex circuits to detect negative pressure for cost reasons.

QWE4562009

dcexpert published on 2021-1-15 21:38 Ordinary circuits cannot detect negative pressure. Generally, single-chip microcomputers will not add complex circuits to detect negative pressure for the sake of cost.

Is the documentation wrong?

dcexpert

QWE4562009 posted on 2021-1-19 09:03 So the document is wrong?

I guess there is an extra minus sign.

LuJianchang

The charging current and discharging current have opposite circuits.

QWE4562009

LuJianchang published on 2021-1-19 14:25 The charging current and discharging current loops are exactly opposite

Do you know the process of negative pressure treatment? For example, the reverse stall current is -10A and the sampling resistance is 0.001 ohm. How is the sampling and AD conversion completed?

LuJianchang

QWE4562009 posted on 2021-1-19 15:49 LuJianchang posted on 2021-1-19 14:25 The circuits of charging current and discharging current are just opposite. Do you know the process of negative pressure treatment? ...

First, the differential is amplified 300 times to get a voltage of about 3V, and then converted through the MCU ADC.

LuJianchang

LuJianchang published on 2021-1-19 16:59 First, the differential is amplified by 300 times to get a voltage of about 3V, and then converted by MCU ADC.

If one end of the sampling resistor is grounded, an inverting amplifier can be used to amplify it.

仙猫

1. From this information, it cannot be seen that VCD must be positive, that is, "-VCD" must be negative;

2. If you really want to measure negative values, it is not impossible to do so. You can use the built-in inverting op amp as the input.

QWE4562009

LuJianchang published on 2021-1-19 16:59 First, the differential is amplified by 300 times to get a voltage of about 3V, and then converted by MCU ADC.

http://www.szssyx.com/plan2-13-9.html

This is the chip specification. I don't see any differential circuit inside. If it is as stated in the specification, it can detect negative pressure.

QWE4562009

LuJianchang published on 2021-1-19 17:01 If one end of the sampling resistor is grounded, an inverting amplifier can be used to amplify it.

The sampling resistor is not grounded. One RS1 and one RS2 are connected to the SH36730X chip in a differential form.

QWE4562009

Xianmao published on 2021-1-19 17:30 1. From this information, it cannot be seen that VCD must be a positive value, that is, "-VCD" must be a negative value; 2. If you really want to measure negative values, it is not impossible to do it, ...

http://www.szssyx.com/plan2-13-9.html Don't know about negative values with signs? This is a specific number, not a vector. In addition to indicating the direction, it also indicates positive and negative.

kirk

Differential signal input can be used to detect the AD value between the negative voltage and the ground, and the negative voltage can be calculated.

LuJianchang

QWE4562009 Published on 2021-1-20 11:55 The sampling resistor is not grounded. One RS1 and one RS2 are differentially connected to the chip SH36730X

This is the direction of the charging current. At this time, VRS2-VRS1 is a negative value. In addition, one end of the sampling resistor is connected to the negative end of the battery pack, which is the reference ground of this circuit.

LuJianchang

LuJianchang published on 2021-1-20 13:53 This is the direction of the charging current. At this time, VRS2-VRS1 is a negative value. In addition, one end of the sampling resistor is connected to the negative end of the battery pack, which is the reference ground of this circuit...

This is the discharge current direction, at this time VRS2-VRS1 is positive.

LuJianchang

LuJianchang posted on 2021-1-20 13:57 This is the direction of the discharge current. At this time, VRS2-VRS1 is positive.

-VCD should be the charging status detection voltage

QWE4562009

LuJianchang posted on 2021-1-20 14:03 -VCD should be the charging status detection voltage

When charging, it is still negative.