New circuit on-off detector design
1. Working principle Such a phenomenon is often found in electronic production. When we touch one of the input terminals of the power amplifier circuit with our hands, the speaker will produce noise due to human clutter. If so, why can't we use this phenomenon to detect the continuity of the circuit? First, we input an audio signal at one end of the line under test. {It can only be low frequency, not high frequency. If the frequency is too high, it will affect the accuracy of detection.) If the circuit has no open circuit failure, this audio signal will be transmitted to the other end of the wire through the wire. We will use an audio amplifier to detect this When the audio amplifier will sound to indicate that the circuit is normal. Conversely, there will be no sound when the circuit is broken. This is how the circuit continuity detector works. Second, the circuit diagram The circuit on-off detector consists of two parts, an audio signal generator and an audio signal amplifier. 1. Audio signal generator The audio signal generator is mainly composed of KD-9300, KD-9300 series music integrated circuit is a large-scale CMOS integrated circuit, which stores a world famous song or popular song, such as happy birthday, Honghu water, etc., the typical operating voltage is 1.5 V-3V, trigger a memory loop once. The audio signal generating circuit made by this chip is shown in the following figure: The audio signal generator has few peripheral components, only one transistor and a switch. When welding, the transistor can be directly welded to the hole reserved for the music chip, and then a line is drawn from the collector of the transistor to connect the crocodile. Clamp, the power supply uses a 7th battery, usually the circuit current is very small, so there is no power switch. When the switch K is pressed, the circuit is triggered, and the triode collector generates an audio signal, which is output through the alligator clip. 2. Audio signal amplifier output The circuit principle is shown in the figure, the audio signal is sent to the power integration block TD2822 through the probe, and the weak audio signal is amplified. After the amplification, it is output through pins 1 and 3 to drive the speaker to sound. The speaker volume is very small here. So it is recommended to use buzzer instead. The disadvantage is that the sound quality of the circuit after the replacement is poor, and the sound distortion is serious, but our circuit has no requirements for sound quality. 3. Selection and installation of components This circuit on-off detector does not have high requirements for components, and the required components can be purchased from the local electronics market. The printed board provided by me is for reference only, the only principle is to make the continuity detector into a pen type, which is easy to carry. If there is no condition, the component can be directly soldered to the multi-purpose board, and the effect is the same. This circuit on-off detector is not only simple in principle but also very simple to make, as long as the welding is correct, it can be successful without debugging. Finally, the audio signal amplifier of the circuit continuity detector is installed in a used whiteboard pen and fixed, and the probe is drawn from the pen core. The audio signal generator can be placed in an 80mmx25mm self-made small box, leading out the alligator clip from one end of the small box. Insert the battery, and the whole production is completed. Four, use method and matters needing attention Before using, press the switch K to give a trigger signal to the audio signal generator so that it can send out an audio signal, then clamp one end of the line with an alligator clip, and finally touch the other end of the line with the probe of the audio amplifier. If the circuit is not broken, the music audio signal generated by the audio signal generator will be transmitted to the other end of the line through the line, and the audio amplifier will send out a wonderful piece of music when it receives this signal. Conversely, if the circuit has a broken circuit, the audio signal amplifier will not emit music, or only a small noise. In particular, this detector is suitable for detecting 100m The line within is very effective, and the correct rate can reach 100% when the operation is correct. However, if the line under test exceeds this range, or the line bypass is particularly complicated, its accuracy will be reduced, so it should be noted in actual use. When making an audio signal amplifier, the ground terminal of the circuit should be led out and made on the casing, and it should be in contact with human hands during use. This can increase the volume of the speaker and increase the sensitivity of the detector.
OEM and ODM designs are welcome.
MOQ: normally 5000set/design, or we can further discuss.
Sampling: if we have samples available, we're glad to send you free sample as long as you can offer us your courier number.
Certificate: our art sets are able to pass EN71 part 1 to part 3, Phthalate free, ASTM D-4236, CPSIA HR4040...etc.
Delivery: usually 35-40 days after approval of pre-production sample.
Payment terms: 30% TT deposit prepaid, 70% TT balance against BL copy.
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