CN203337592U

CN203337592U - Circuit for detecting soil moisture with time domain method

Info

Publication number: CN203337592U
Application number: CN2013203613569U
Authority: CN
Inventors: 高扬; 孙学宏; 徐高松
Original assignee: Jiangsu IoT Research and Development Center
Current assignee: Jiangsu IoT Research and Development Center
Priority date: 2013-06-21
Filing date: 2013-06-21
Publication date: 2013-12-11
Anticipated expiration: 2023-06-21

Abstract

The utility model provides a circuit for detecting soil moisture with a time domain method. The circuit comprises an NPN (Negative-Positive-Negative) triode and a 555 timer, wherein a base electrode of the NPN triode is connected with an input square wave signal by a first resistor, an emitting electrode of the NPN triode is grounded, and a collecting electrode of the NPN triode is connected with one end of a third resistor, one end of a fourth resistor and a first probe through a second resistor; the other end of the third resistor is connected with a power supply; the other end of the fourth resistor is connected with a second pin and a sixth pin of the 555 timer and a second probe; the sixth pin of the 555 timer is grounded through a first capacitor, a fifth pin of the 555 timer is grounded through a second capacitor, and a first pin of the 555 timer is directly grounded; a seventh pin of the 555 timer is suspended, a fourth pin and an eighth pin of the 555 timer are connected with the power supply, and a third pin of the 555 timer is connected with the power supply through a fifth resistor; the third pin of the 555 timer generates an output voltage. According to the circuit, the time (namely time difference Ts) for the first probe to descend to 1/3 VCC (Voltage to Current Converter) from the highest voltage point can be accurately obtained so that the Ts is conveniently analyzed by an upper computer.

Description

Adopt time domain approach to detect the circuit of soil moisture

Technical field

The utility model relates to a kind of testing circuit, especially a kind of circuit that detects soil moisture.

Background technology

In current family's planting technique, usually according to people's experience, to water, this mode is only limited to plantation experience people, and for majority, this method is also inapplicable, and especially new hand often not too easily holds soil moisture.The required soil moisture of different classes of green plants is also different, even if water according to experience, usually also can't know quantitatively that whether too much or very little watered water.And the equipment of the soil moisture of specialty detection now is very expensive, can't be popular, be difficult to spread to common people's family.Therefore, be necessary to invent a kind of low cost, be applicable to most crowds' soil moisture detection device.

Summary of the invention

For the deficiencies in the prior art, the utility model provides a kind of circuit that adopts time domain approach to detect soil moisture, can survey exactly soil moisture, further combined with host computer, is analyzed, and can obtain the humidity situation of soil.The technical solution adopted in the utility model is:

The technical scheme provided according to the utility model, described employing time domain approach detects the circuit of soil moisture, comprising: comprise a NPN triode and one 555 timers;

The base stage of NPN triode connects the input square-wave signal by the first resistance, grounded emitter, and collector connects an end of the 3rd resistance, an end and first probe of the 4th resistance by the second resistance; Another termination power of the 3rd resistance; The other end of the 4th resistance connects crus secunda and the 6th pin of 555 timers, and the second probe;

The 6th pin of 555 timers is by the first capacity earth, and the 5th pin is by the second capacity earth, the direct ground connection of the first pin; The 7th pin of 555 timers is unsettled, and the 4th pin and octal connect power supply, and tripod connects power supply by the 5th resistance; The tripod of 555 timers produces output voltage.

Above-mentioned NPN triode also can be replaced with a NMOS pipe.

Advantage of the present utility model: this circuit can obtain exactly the first probe place and drop to the time (being mistiming Ts) of 1/3VCC from the voltage peak, this mistiming, Ts reacted the difference of soil moisture, further combined with host computer, to this, mistiming Ts is analyzed, and just can obtain soil moisture situation accurately.Circuit has adopted low-cost 555 timers, has reduced cost.

The accompanying drawing explanation

Fig. 1 is circuit diagram of the present utility model.

Fig. 2 is signal schematic representation of the present utility model.

Embodiment

Below in conjunction with concrete drawings and Examples, the utility model is described in further detail.

As shown in Figure 1 and Figure 2:

A kind of circuit that adopts time domain approach to detect soil moisture, comprise a NPN triode Q1 and one 555 timers;

The base stage of NPN triode Q1 connects input square-wave signal IN by the first resistance R 1, grounded emitter, and collector connects an end of the 3rd resistance R 3, an end and the first probe A of the 4th resistance R 4 by the second resistance R 2; Another termination power VCC of the 3rd resistance R 3; The other end of the 4th resistance R 4 connects crus secunda and the 6th pin of 555 timers, and the second probe B;

The 6th pin of 555 timers is by the first capacitor C 1 ground connection, and the 5th pin is by the second capacitor C 2 ground connection, the direct ground connection of the first pin; The 7th pin of 555 timers is unsettled, and the 4th pin and octal meet power supply VCC, and tripod connects power supply VCC by the 5th resistance R 5; The tripod of 555 timers produces output voltage V out.

Each pin definitions of 555 timers is:

The 1-GND earth terminal; The 2-TRIGGER trigger end; The 3-Output output terminal; The 4-RESET reset terminal; 5-CONTROL VOLTAGE controls voltage end; 6-THRESHOLD threshold value end; The 7-DISCHARGE discharge end; The 8-Vcc power end.

NPN triode Q1 plays Isolation input square-wave signal IN and will input square-wave signal IN acting in opposition.NPN triode Q1 can replace with a NMOS pipe.When the first probe A and the second probe B insert in soil simultaneously, can form simulated capacitance C, form Schmidt triggers with 555 timers.

As shown in Figure 2, oscillogram during for the utility model specific works, IN is input square-wave signal waveform, take T2 as the time zero description, when IN inputs by low uprising, NPN triode Q1 conducting, the first probe A ground connection, the simulated capacitance C that the first probe A and the second probe B form is discharged, now the output voltage V out of 555 timers is still low level, when reaching T3 constantly, during the first probe A place voltage<1/3VCC, the output voltage V out of 555 timers becomes high level.

At T4 constantly, when IN becomes low level by high level, NPN triode Q1 cut-off, the first probe A place is linked into high level (by the 3rd resistance, being connected to power supply VCC), formed simulated capacitance C due to the first probe A and the second probe B equally, from T4 constantly, the voltage at the first probe A place starts to raise gradually, when the first probe A place voltage reaches T5 constantly, i.e. the first probe A place voltage > during 2/3VCC, the output voltage V out of 555 timers becomes low level, completes thus the detection of one-period.

Wherein the mistiming Ts of T2 and T3 is the time signal of wanting host computer to be detected.When the humidity of soil is different, between the first probe A and the second probe B, the simulated capacitance C that soil forms is also different, and to discharge and recharge the time also different for simulated capacitance C, thus also difference of the time (being Ts) that the first probe A place drops to 1/3VCC from the voltage peak.By host computer, mistiming Ts is carried out to analyzing and processing, and calibrated with accurate instrument, just can obtain according to mistiming Ts the humidity situation of soil.

This circuit structure is simple, and highly versatile is easily implemented.

Claims

1. a circuit that adopts time domain approach to detect soil moisture, is characterized in that: comprise NPN triode (Q1) and one 555 timers;

The base stage of NPN triode (Q1) connects input square-wave signal (IN) by the first resistance (R1), grounded emitter, collector connects an end of the 3rd resistance (R3), an end and first probe (A) of the 4th resistance (R4) by the second resistance (R2); Another termination power (VCC) of the 3rd resistance (R3); The other end of the 4th resistance (R4) connects crus secunda and the 6th pin of 555 timers, and the second probe (B);

The 6th pin of 555 timers is by the first electric capacity (C1) ground connection, and the 5th pin is by the second electric capacity (C2) ground connection, the direct ground connection of the first pin; The 7th pin of 555 timers is unsettled, and the 4th pin and octal connect power supply (VCC), and tripod connects power supply (VCC) by the 5th resistance (R5); The tripod of 555 timers produces output voltage (Vout).

2. employing time domain approach as claimed in claim 1 detects the circuit of soil moisture, it is characterized in that: described NPN triode (Q1) can be replaced with a NMOS pipe.