【 Weak current College 】 car audio conversion problems with ground noise

Car audio is a converted in grounding is extremely important, very important theoretical knowledge, otherwise encounter failures do not know how to exclude.
With electricity (signal), this is a pair of inseparable twins. Grounding, commonly referred to with conductor and the Earth. Available in electronic technology, probably had nothing to do with the Earth, it is just a circuit equipotential surface. Such as radio, TV set, it is only a receiver circuit in potential reference point. Grounding, electronics, both simple and complex, but also essential. The role of the ground, can be divided into work grounding and protection earthing, overvoltage protection, earthing, anti-static grounding and shielding and grounding, signals etc. In radio technology, several grounding type above will encounter. Now with actual technical problems for some grounding for a description.
1. protective grounding
Protective earth is to prevent the power polarity reversed causing damage to the equipment of the protective device, the simple way is the power supply input to ground plus reverse diode, car audio equipment is particularly common in the circuit.
II. over-voltage protection earthing
This is set to high voltage power and grounding protection device. -Point the spark for the most widely used is the pressure-sensitive diodes and is a bubble. Adopted-grounding absorption and limiting. If the tuner is damaged many high voltage cuanru and striking receiver.
Equipment power supply input voltage circuits are also equipped with overvoltage protection circuit and overcurrent protection circuit, and thermal protection circuit.
III. shielding and
To prevent electromagnetic induction and Visual and audio cable shielded metal jacketing, electronic equipment, metal shell, shielding enclosures, buildings of metal shielding network (such as measuring sensitivity, selectivity and other indicators of shielding room) for the grounding of a protective measure. In all the Earth, the shield and the most complex, say, road unknown feeling. Because the screen itself can prevent outside interference, they may pass it on to outside interference, and the components in the device has to be between anti-electromagnetic interference, such as the familiar shell and tube in week shielding enclosures are examples. Signal cable shielding and grounding is important.
Shielding, grounding incorrectly can cause interference, such interference:
1. the exchange of interference, this caused primarily by AC power. Protection against AC interference, usually on the power supply for filtering or signal cable with shielding and grounding. In large stray electromagnetic field, electromagnetic interference shielding to prevent grounding necessary. For example, the generator will produce electromagnetic interference, also through wire transfers to interior equipment, filter and shielding ground, a solution to this problem.
2. the high-frequency interference. This kind of interference from various wireless transmitter frequency or hyper-frequency signals, they are channeling into electronic device in the machine to get non-normal demodulation and audio interference forming. If the spark plug ignition, relay contact spark.
The higher the frequency, body skin effect, equipment for metal mesh eyelet is smaller, the signal cable shielding braid it should more dense, shielding effect will be lost. To frequently swap signal cable, should prevent the shield in plug loose and falling off. Because sometimes instrument and equipment of the shield is shielded by the signal line into the ground (they join via plug socket) if shielded falls off, you can easily cause interference. If the signal line placement and interference, sometimes hand touch signal cable shield without interference, the description is high frequency signal interference caused by a distributed capacitance coupling.
IV. signal ground
A variety of electronic circuit, there is a benchmark potential points of this benchmark potential point, is the signal. Its role is to ensure that the circuit has a unified benchmark potential, not floating, signal errors.
Signal connections are: same device signal input-and output-end cannot join together and separately; the former level (equipment) to only output after the class (device) is connected to the input field. Otherwise, the signal may be formed through the ground, causing signal feedback. This equipment tests, signal connection with particular attention. For example, the signal cable jacketing break ground noise. The original is to give back by signal so that the results are not consistent. There's power amplifier Shell cannot directly grounding, put all this grounding point to not grounded, there is no noise phenomenon.
5. car audio special grounding
Number of vehicles installed power amplifier, play loud bass (no more than normal electricity consumption), instrument lights flashing with music, this is because only the amplifier of cathode ray bold and ignore the negative cable circuit formation from positive to negative, it is necessary to maintain a loop of anode cathode and coarse, fine is unable to increase the current, as water-weight does not have water flow flow only in fine. So you want to increase the negative electrode of current, specific practices: 1, engine to batteries a (engine and body is insulation). 2, engine-to-body a (to increase generating capacity). Line thickness is at least as to the positive electrode cable.