Share some design schemes and experiences of MCU hardware circuits

“Scale back the affect of the facility provide of the rear stage on the entrance stage, stop the constructive and adverse connections of the facility provide from burning out the rear stage circuit, and stop the present from flowing backward when the facility provide is turned off. Nonetheless, there's a voltage drop of about 0.4V by means of the diode. It is going to be decrease than the conventional working voltage of the next circuit.

“

Writer: Fish and Feather

1. Button circuit

R1 pull-up resistor:

The indeterminate sign is clamped at a excessive stage by means of a resistor, maintained in a non-triggered state or returned to the unique state after being triggered. (Private suggestion so as to add)

C1 capacitor:

Scale back key jitter and high-frequency sign interference. (Private suggestion so as to add)

R2 present limiting resistor:

Shield the IO port, stop the IO port from being burned out by overcurrent and excessive voltage, and take in static electrical energy or some high-voltage pulses. (Private suggestion so as to add)

The worth of R2 ranges from 100 ohms to 10k. If an inner pull-up is ready, the worth shouldn't be too giant, in any other case the present is not going to be sufficient to drag down the IO port.

D1 ESD diode:

Electrostatic safety diode to stop electrostatic interference or harm to the IO port. (That is primarily based on the associated fee and safety stage necessities of the PCB to determine whether or not so as to add or not)

2. Exterior sign enter

R3 pull-up resistor:

The indeterminate sign is clamped at a excessive stage by means of a resistor, maintained in a non-triggered state or returned to the unique state after being triggered. (If the exterior connection line is comparatively lengthy and the inner pull-up functionality of the chip is comparatively weak, it is suggested so as to add it. Normally the communication distance just isn't lengthy, and it may be omitted if there may be an inner pull-up)

C2 Capacitor:

Stop excessive frequency sign interference. (Notice that if the enter frequency sign is comparatively giant, the capacitance worth of C2 must be correspondingly decreased, or C2 must be omitted instantly)

R4 present limiting resistor:

Shield the IO port, stop the IO port from being burned out by overcurrent and excessive voltage, and take in static electrical energy or some high-voltage pulses. (Private suggestion so as to add)

D2 ESD diode:

Electrostatic safety diode to stop electrostatic interference or harm to the IO port. (That is primarily based on the associated fee and safety stage necessities of the PCB to determine whether or not so as to add or not)

3. Output circuit relay

U1 optocoupler:

Separate excessive and low voltage, stop excessive voltage interference, and obtain electrical isolation.

D5 1N4148:

The freewheeling diode, which protects the aspect from being damaged down or burned out by the induced voltage, is related in parallel to each ends of the aspect that generates the induced electromotive pressure, and types a loop with it, in order that the generated excessive electromotive pressure is consumed by the freewheeling present within the loop. In order to play the function of defending the components within the circuit from being broken.

4. Darlington transistor

Darlington transistors are typically utilized in stepper motor drives. Actually, they can be utilized for motor velocity regulation, high-power switching circuits, driving relays, driving LED gentle sources with comparatively excessive energy, and utilizing PWM to regulate the brightness.

R6, R7, R8 resistors:

It's used for present limiting to stop harm to the ULN2001, ensuing within the excessive voltage being instantly enter to the IO of the MCU. (As a result of the ULN2001D itself comes with a 2.7K resistor, R6, R7, and R8 will be omitted right here; if some driver chips do not need resistors, it's best so as to add them by your self. For particulars, you possibly can verify the information sheet of the chosen chip to decide)

COM terminated energy provide:

When the output terminal is related to an inductive load, the load doesn't want so as to add a freewheeling diode. The chip is designed with a diode, and solely the COM port must be related to the load energy provide. When different hundreds are related, the COM port will be left unconnected.

When utilizing the RC step-down circuit to produce energy to ULN2001D, for the reason that RC step-down voltage can not stop the transient excessive voltage fluctuations on the grid, a 104 capacitor should be related to the COM terminal and the bottom terminal of the ULN2001D. cannot be added.

5. Operational amplifier

Utilizing the op amp to gather the present present of the load ingeniously, you possibly can precisely know the present operation of the load and whether or not it's working usually, which could be very straightforward to make use of.

GND2 is the bottom terminal of the load. It's related to the frequent floor by means of the R16 resistor (R16 must be chosen in accordance with the dimensions of the load present), and there will likely be a small voltage distinction.

This circuit is a proportional operation circuit in the identical section, so the voltage of the sampling terminal = the voltage of the enter terminal * (1+R9/R11) = 69 occasions the enter voltage. You may modify R9 to regulate the magnification in accordance with the measurement vary.

6. MOS tube

Management energy output on and off

7. Enter energy

If the circuit value is comparatively tight, parts will be appropriately deleted as wanted.

F1 resettable fuse:

Overcurrent safety, the edge worth will be adjusted in accordance with the precise load present.

D10 Schottky Diode:

Scale back the affect of the facility provide of the rear stage on the entrance stage, stop the constructive and adverse connections of the facility provide from burning out the rear stage circuit, and stop the present from flowing backward when the facility provide is turned off. Nonetheless, there's a voltage drop of about 0.4V by means of the diode. It is going to be decrease than the conventional working voltage of the next circuit.

TVS Tube:

The enter voltage is just too excessive safety, typically 1.4 occasions the conventional enter voltage.