A fuel-powered engine rotational speed detection circuit

Abstract

The utility model provides a kind of fuel power engine rotating speed detection circuit, it is related to engine rotating speed detection field, including wiring terminal (1), operational amplifier (2), first capacitor (3), second capacitor (4) and multiple resistance, wiring terminal (1) is two pin designs, the 2nd pin is connected in order first resistance (5) and second resistance (6) after, with the opposite input end connection of operational amplifier (2), the 1st pin is connected in order third resistance (7) and fourth resistance (8) after, with the same phase input end connection of operational amplifier (2), the positive power supply end of operational amplifier (2) is connected with 5V power supply;The output end of operational amplifier (2) is connected with rotating speed detection IO mouth (16) after through multiple resistance and second capacitor (4).The detection circuit can sample two kinds of signals, with the advantages of high detection precision, safe and reliable, strong practicality etc.

Description

Technical Field

[0001] This utility model relates to the field of engine speed detection technology, specifically to a fuel-powered engine speed detection circuit. Background Technology

[0002] Currently, engine speed is determined by measuring crankshaft speed, which is typically obtained using a signal disc mounted on the crankshaft. Measurement methods include electromagnetic pulse, Hall effect, and photoelectric. The electromagnetic pulse sensor works by rotating the signal disc, causing the disc teeth to cut the magnetic field formed by the sensor's magnetic core, generating a magnetic field that induces an alternating voltage in the sensor's coil, outputting a pulse signal. The frequency of the pulse signal is proportional to the rotational speed of the signal disc. By calculating the frequency of the pulse signal and the number of teeth on the signal disc, the engine speed is obtained. The Hall effect sensor, by placing a Hall element in a magnetic field and passing a current perpendicular to the magnetic field through both sides (e.g., the top and bottom) of the Hall element, generates a Hall voltage on the other two sides (left and right). When the signal disc rotates, the impeller of the signal disc interrupts the magnetic field, the Hall voltage disappears, and the sensor outputs a rectangular pulse signal. The number of signals output by the sensor for each revolution of the signal wheel equals the number of notches (or blades) on the signal wheel, thus obtaining the engine speed. The photoelectric type utilizes the principle that the working characteristics of a photosensitive element change when it is exposed to light. A light-transmitting hole is machined into a signal disk, and a light-emitting diode (LED) and a photosensitive element are installed in front of and behind the signal disk, respectively. As the signal disk rotates, when the light emitted by the LED is blocked by the signal disk, the photosensitive element outputs a low voltage; when the light emitted by the LED passes through the light-transmitting hole and shines on the photosensitive element, the photosensitive element outputs a high voltage. This change causes the sensor to output a rectangular wave, and the rotational speed is obtained based on the frequency of the wave.

[0003] Currently, fuel-powered products include single-power and end-power products. End-power products use a dedicated digital igniter to generate a positive high-voltage pulse signal. Single-power products ignite by having the engine rotor drive a magnet to generate periodic excitation; a conventional igniter then senses this excitation and generates a negative high-voltage pulse signal. The waveforms of the negative high-voltage pulse signal generated by a mechanical igniter and the positive high-voltage pulse signal generated by a digital igniter are similar, but the average amplitude of the positive high-voltage pulse signal is above 400V, while the average amplitude of the negative high-voltage pulse signal is above 200V. Furthermore, the positive half-axis of the negative high-voltage pulse contains a low-pulse wave with a relatively small amplitude, but the waveform of the positive half-axis contains a lot of noise, making it unsuitable as a speed sampling point. The waveform of the positive half-axis of the positive high-voltage pulse signal has an amplitude above 400V, and the waveform of the negative half-axis signal is similar to that of the positive half-axis of the negative high-voltage pulse signal. Therefore, there is currently a lack of a speed detection circuit that can be used for both positive and negative high-voltage pulse detection, thereby avoiding the inability to use detection noise as a detection point and improving detection accuracy and efficiency. Utility Model Content

[0004] To address the problems existing in the prior art, the purpose of this utility model is to provide a fuel-powered engine speed detection circuit. This detection circuit can detect two different waveforms, positive high-voltage pulse signal and negative high-voltage pulse signal, and sample the two signals. It has high detection accuracy, safety and reliability, and strong practicality.

[0005] The objective of this utility model is achieved through the following technical solution: A combustion engine speed detection circuit includes terminals, an operational amplifier, a first capacitor, a second capacitor, and multiple resistors. The terminals have two pins. Pin 2 is connected to the first and second resistors in sequence and then to the inverting input ("-") of the operational amplifier. Pin 1 is connected to the third and fourth resistors in sequence and then to the non-inverting input ("+") of the operational amplifier. The positive power supply of the operational amplifier is connected to a 5V power supply. The two ends of the first capacitor are connected to the 5V power supply and ground, respectively. One end of the fifth resistor is connected between the second resistor and the inverting input, and the other end is connected between the 5V power supply and the positive power supply. The positive power supply of the operational amplifier is connected to the output. One end of the sixth resistor is connected between the fourth resistor and the non-inverting input, and the other end is grounded together with the negative power supply of the operational amplifier. The output of the operational amplifier is connected to the speed detection I / O port through the multiple resistors and the second capacitor.

[0006] Based on further optimization of the above scheme, the output terminal of the operational amplifier is connected to the seventh resistor and the eighth resistor in sequence, and then connected to the speed detection IO port. The second capacitor and the ninth resistor are connected in parallel across the eighth resistor, and the second capacitor and the ninth resistor are grounded. One point between the second capacitor and the speed detection IO port is connected to the positive terminal of the diode and the bidirectional TVS diode, respectively. The negative terminal of the diode is connected to the 3.3V power supply, and the other end of the bidirectional TVS diode is grounded.

[0007] Based on further optimization of the above scheme, the terminal block model is HX42002-2A, the resistance of the first resistor is 1MΩ, the resistance of the second resistor is 5.1kΩ, the resistance of the third resistor is 1MΩ, and the resistance of the fourth resistor is 5.1kΩ.

[0008] Based on further optimization of the above scheme, the operational amplifier is designated as TP10-2-SR.

[0009] Based on further optimization of the above scheme, the capacitance of the first capacitor is 0.1uF and the withstand voltage is 50V; the resistance values ​​of the fifth resistor and the sixth resistor are both 51 kΩ.

[0010] Based on further optimization of the above scheme, the capacitance of the second capacitor is 0.1uF and the withstand voltage is 50V; the resistance of the seventh resistor is 6.8 kΩ, the resistance of the eighth resistor is 1 kΩ, and the resistance of the ninth resistor is 13.2 kΩ.

[0011] Based on further optimization of the above scheme, the diode is model 1N4148W and the bidirectional TVS diode is model PESD3V3L1BA115.

[0012] The following are the technical effects of this utility model: The detection circuit of this application connects the high-voltage transformer pulse signal to the terminal block. After being stepped down by multiple resistors, it is differentially amplified by an operational amplifier. The negative half-wave of the signal is shielded by the single power supply of the operational amplifier. Only the positive half-wave high-voltage pulse signal is output by the operational amplifier and enters the speed detection IO port, thereby realizing the speed detection. Even when using a digital igniter, the high-voltage pulse signal is primarily a positive pulse signal with an amplitude of 400V relative to the chassis ground (with a small negative signal present), while using a mechanical igniter, the high-voltage pulse signal is primarily a negative pulse signal relative to the chassis ground (with a small positive signal present). When the operational amplifier is powered by a single power supply, it can only output a positive signal and has no negative power supply; all its negative output signals become the common ground terminal. Therefore, if the input high-voltage pulse signal is a positive pulse signal, then pin 1 of the terminal block is connected to the positive pulse signal and pin 2 is connected to the common ground, and the operational amplifier output is positive. If the input high-voltage pulse signal is a negative pulse signal, then pin 1 of the terminal block is connected to the common ground and pin 2 is connected to the negative pulse signal, and the operational amplifier output is positive. This effectively solves the problem of different high-voltage pulse signals generated by digital or mechanical igniters, ensuring that the operational amplifier always outputs a positive signal to the speed detection I / O port.

[0013] Meanwhile, by setting the amplification factor of the operational amplifier, this application amplifies both the positive pulse signal of the high-voltage transformer above 400V and the negative pulse signal of the high-voltage transformer around -200V to the power supply output voltage, that is, the output value of both pulse signals is close to 5V, effectively protecting the speed detection IO port, avoiding overvoltage damage to the device, and ensuring the long-term stable operation of the circuit. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the speed detection circuit in an embodiment of the present invention.

[0015] Figure 2 This is a waveform diagram of the negative pulse signal from the high-voltage transformer.

[0016] Figure 3 This is a waveform diagram of the amplified negative pulse signal from the high-voltage transformer.

[0017] Figure 4 The output waveform diagram is shown in the embodiment of this utility model after the positive pulse signal of the high voltage transformer passes through the operational amplifier.

[0018] Figure 5 The output waveform diagram is shown in the embodiment of this utility model after the negative pulse signal of the high voltage transformer passes through the operational amplifier.

[0019] Among them, 1. Terminal block; 2. Operational amplifier; 3. First capacitor; 4. Second capacitor; 5. First resistor; 6. Second resistor; 7. Third resistor; 8. Fourth resistor; 9. Fifth resistor; 10. Sixth resistor; 11. Seventh resistor; 12. Eighth resistor; 13. Ninth resistor; 14. Diode; 15. Bidirectional TVS diode; 16. Speed ​​detection I / O port. Detailed Implementation

[0020] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments.

[0021] Example 1: A combustion engine speed detection circuit includes a terminal block 1, an operational amplifier 2, a first capacitor 3, a second capacitor 4, and multiple resistors, such as... Figure 1 As shown, terminal 1 is a two-pin design (terminal 1 is the connector between the high-voltage transformer pulse signal and the common terminal). Terminal 1 is model HX42002-2A. The second pin is connected in sequence to a first resistor 5 with a resistance of 1MΩ and a second resistor 6 with a resistance of 5.1kΩ, and then connected to the inverting input terminal (i.e., the "-" terminal) of operational amplifier 2. Figure 1 Connect pin 2 (as shown). Operational amplifier 2 is model TP10-2-SR. Pin 1 is connected in sequence to a third resistor 7 with a resistance of 1MΩ and a fourth resistor 8 with a resistance of 5.1kΩ, and then connected to the non-inverting input terminal (i.e., the "+" terminal) of operational amplifier 2. Figure 1 Connect pin 3 as shown.

[0022] The positive power supply terminal of operational amplifier 2 (i.e. Figure 1 Pin 8 (as shown) is connected to the 5V power supply. The first capacitor 3, with a capacitance of 0.1uF and a withstand voltage of 50V, is connected to the 5V power supply and ground respectively. The fifth resistor 9, with a resistance of 51 kΩ, is connected at one end between the second resistor 6 and the inverting input terminal, and at the other end between the 5V and positive power supply terminals. The positive power supply terminal and the output terminal of operational amplifier 2 (i.e.,...) are also connected. Figure 1 Pin 1 (as shown) is connected, with one end of the sixth resistor 10 (51 kΩ) connected between the fourth resistor 8 and the non-inverting input, and the other end connected to the negative power supply terminal of operational amplifier 2 (i.e., pin 1). Figure 1 Pin 4 (as shown) is grounded together.

[0023] The output of operational amplifier 2 (i.e. Figure 1Pin 1 (as shown) is connected to the speed detection I / O port 16 of the MCU (microcontroller) via multiple resistors and a second capacitor 4. The MCU measures the signal frequency using its built-in timer to obtain the speed. Specifically: the output of operational amplifier 2 is connected to a seventh resistor 11 (6.8 kΩ) and an eighth resistor 12 (1 kΩ) in sequence, and then to the speed detection I / O port 16. A second capacitor 4 (0.1uF, 50V) and a ninth resistor 13 (13.2 kΩ) are connected in parallel across the eighth resistor 12, and the second capacitor 4 and the ninth resistor 13 are grounded. A point between the second capacitor 4 and the speed detection I / O port 16 is connected to the positive terminal of diode 14 and the bidirectional TVS diode 15, respectively. Diode 14 is a 1N4148W, and the bidirectional TVS diode 15 is a PESD3V3L1BA115. The negative terminal of diode 14 is connected to a 3.3V power supply, and the other end of the bidirectional TVS diode 15 is grounded.

[0024] Working principle: Since the positive pulse signal from the high-voltage transformer is above 400V and the negative pulse signal is around -200V, by adjusting the amplification factor of operational amplifier 2, both types of signals can be amplified to the power supply output voltage simultaneously. Because operational amplifier 2 has a limited input voltage range, high-voltage signals like the high-voltage pulse signal need to be stepped down before being input to the op-amp's input stage. This technique uses a resistor divider to step down the high-voltage pulse signal. The differential voltage across the second resistor 6 and the fourth resistor 8 is: In the formula: V 1 This indicates the voltage at pin 1 of the terminal block. V 2 This indicates the voltage at pin 2 of the wiring forging process. V + , V - These represent the voltages to the left of the fourth resistor and the second resistor, respectively. For a pulse signal with a positive pulse value of 400V: V + and V - The differential voltage is 2.02V. For a pulse signal with a negative pulse of -200V: V + and V - The differential voltage is 1.01V; according to the calculation formula for differential op-amps, it is not difficult to deduce that: In the formula: R 2This indicates the resistance value of the second resistor. R 5 This indicates the resistance value of the fifth resistor; Therefore, the theoretical output voltage for a 400V positive pulse signal should be 10.1V, and for a -200V negative pulse signal, it should be 5.05V. Since the pulse width of the high-voltage pulse signal is 5µs, to ensure undistorted signal output using a 5V power supply, an operational amplifier with a slew rate of at least 1V / µs must be selected. This application selects a rail-to-rail operational amplifier with a slew rate of 4.5V / µs and uses a 5V power supply. Therefore, the theoretical output value for both pulse signals exceeds 5V, but because the power supply is 5V, the output values ​​for both pulse signals are close to 5V.

[0025] The output waveforms of the two signals are as follows Figure 4 , Figure 5 As shown in Figure 4, the period between the two square waves is approximately 17ms, and the frequency is 58Hz, which translates to a rotational speed of 3529 r / min, consistent with the speed obtained using a tachometer. It should be noted that... Figure 5 The high-level width of the square wave is about 500µs, while the high-level width of the high-voltage pulse from the high-voltage transformer is 5µs. The duration of the two levels differs by more than a hundred times. This is because... Figure 5 The operational amplifier output level, due to the high slew rate performance of the selected op-amp, includes a certain rise time, fall time, and level hold time of the high-voltage pulse signal, resulting in a 500µs level hold time, which does not affect the accuracy of the speed measurement. After the operational amplifier outputs a 5V level, the signal is transmitted to the speed detection I / O port of the MCU for level frequency measurement. However, since not all MCUs support 5V signals, the signal is divided. The divided signal then passes through diode 14 (clamping diode) to the MCU, thus protecting the MCU and ensuring safety and reliability.

Claims

1. A speed detection circuit for a fuel-powered engine, characterized in that: It includes terminal blocks, operational amplifier, first capacitor, second capacitor, and multiple resistors; The terminal block has a two-pin design. Pin 2 is connected to the first and second resistors in sequence and then to the inverting input of the operational amplifier. Pin 1 is connected to the third and fourth resistors in sequence and then to the non-inverting input of the operational amplifier. The positive power supply of the operational amplifier is connected to the 5V power supply. The two ends of the first capacitor are connected to the 5V power supply and ground respectively. One end of the fifth resistor is connected between the second resistor and the inverting input, and the other end is connected between the 5V power supply and the positive power supply. The positive power supply of the operational amplifier is connected to the output. One end of the sixth resistor is connected between the fourth resistor and the non-inverting input, and the other end is grounded together with the negative power supply of the operational amplifier. The output of the operational amplifier is connected to the speed detection I / O port through multiple resistors and the second capacitor.

2. The engine speed detection circuit for a fuel-powered engine according to claim 1, characterized in that: The output of the operational amplifier is connected to the seventh and eighth resistors in sequence, and then connected to the speed detection I / O port. The second capacitor and the ninth resistor are connected in parallel across the eighth resistor, and the second capacitor and the ninth resistor are grounded. One point between the second capacitor and the speed detection I / O port is connected to the positive terminal of the diode and the bidirectional TVS diode, respectively. The negative terminal of the diode is connected to the 3.3V power supply, and the other end of the bidirectional TVS diode is grounded.

3. The engine speed detection circuit for a fuel-powered engine according to claim 2, characterized in that: The terminal block is model HX42002-2A. The first resistor has a resistance of 1MΩ, the second resistor has a resistance of 5.1kΩ, the third resistor has a resistance of 1MΩ, and the fourth resistor has a resistance of 5.1kΩ.

4. The engine speed detection circuit for a fuel-powered engine according to claim 2, characterized in that: The operational amplifier is model TP10-2-SR.

5. The speed detection circuit for a fuel-powered engine according to claim 2, characterized in that: The first capacitor has a capacitance of 0.1uF and a voltage rating of 50V; the fifth and sixth resistors both have a resistance of 51 kΩ.

6. The engine speed detection circuit for a fuel-powered engine according to claim 2, characterized in that: The second capacitor has a capacitance of 0.1uF and a voltage rating of 50V; the seventh resistor has a resistance of 6.8 kΩ, the eighth resistor has a resistance of 1 kΩ, and the ninth resistor has a resistance of 13.2 kΩ.

7. The engine speed detection circuit for a fuel-powered engine according to claim 2, characterized in that: The diode is model 1N4148W, and the bidirectional TVS diode is model PESD3V3L1BA115.

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