BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coaster, and more particularly to a light-emitting diode pad that senses pressure and drives the light-emitting diode to emit light and change the color light according to different pressures. [Prior Art] In the summer, people often like to drink cold drinks. When the ice drink is placed on the tabletop, the water will be condensed on the outer surface of the cup, so people will use the coaster to place the cup and the table. In addition, it can avoid the trouble of desktop water collapse and prevent the cup from slipping. In order to make the cup can have more added value, take Taiwan's new patent. M240938 "Cover structure with entertainment and lighting effects" as an example, that is, a circuit device and a light-emitting element are arranged inside the coaster, so that the coaster has light. In this way, even with the visual effect of flashing lights, the artistic beauty of the coaster is added.馨 However, these illuminating functions are mostly cyclical changes of the system, or even only—the constant single-color light continues to illuminate, making the creation of the cup 塾 combined with the illuminating function seem dull and boring. SUMMARY OF THE INVENTION It can be seen from the above description that although the conventional coaster incorporates a light-emitting function, it is mostly a system change, which is dull and uninteresting. In view of the above, the main object of the present invention is to provide a light-emitting diode coaster system capable of sensing the weight of the cup placed on the cup and displaying different colors of 1351264 light, so that the light-emitting display of the coaster reaches the perception. The effect of environmental stress. The main technical means for achieving the above purpose is that the light-emitting diode coaster comprises: a light-transmitting pad body; a pressure sensor is disposed in the light-transmitting pad body to sense the light transmission The surface pressure of the pad body 'and outputs different pressure value signals according to different pressures; a control circuit board' is located in the light-transmitting pad body and is provided with a plurality of light-emitting ones, and the control circuit board is connected to the pressure sensor Receiving the pressure value signal transmitted by the LED, and controlling the illumination of the LED according to different pressure values. When a cup containing the beverage is placed on the above-mentioned light-emitting diode coaster, the control circuit board senses the weight change of the surface of the coaster by the pressure sensor to control the lighting of the light-emitting diode according to the weight change. [Embodiment] Referring to the first embodiment, a preferred embodiment of the present invention includes a light-transmitting pad body (10), a pressure sensor (2 〇), and a control circuit board (30). ). The light-transmitting body (10) may be a circular, square or other shape, and the material may be a light-transmitting material such as plastic or glass; in the embodiment, the light-transmissive body (10) is a square shape. a transparent plastic pad body, and at least one light guide plate (1 1 ) is vertically disposed at a peripheral edge thereof. The light guide plate (1 1 ) can be further engraved, laser processed, etc. to further form a texture (1 2 ), when the color light is transmitted through This texture (12) produces a better visual effect due to refraction. [S3 1351264] The pressure sensor (2 ◦) is disposed in the light-transmitting pad body (1 〇), can sense the surface pressure of the light-transmitting pad body (1 〇), and output different pressure values according to different pressures. Signal 'In this embodiment, the pressure sensor (20) is a piezoresistive type flexible pressure sensor. The control circuit board (30) is disposed in the light-transmitting pad body and is provided with a plurality of light-emitting diodes (3 1 ). In the embodiment, the light-emitting diodes (3 1 ) are respectively disposed on the control circuit board. The periphery of (3 〇) corresponds to the position of each light guide plate (1 1 ), and may include three colors of red, blue and green. As shown in the second figure, each of the light emitting diodes (3 1 ) may further correspond to the light guide plate (1 1 ) ) The texture (1 2) 'The resulting color light is refracted through the grain (1 2) to produce a better visual effect; the control circuit board (3 〇) is connected to the pressure sensor (20) and contains a stored The memory of the driver is turned on, and the control circuit board (30) controls the light-emitting diode (3i) to emit light according to the received pressure value signal by executing the lighting driver. When a cup is placed on the light-transmitting pad body (i 〇), the pressure sensor (2 〇) senses the pressure value and transmits it to the control circuit board (3 〇) for lighting control. . The aforementioned texture (12) can be designed in a variety of shapes to achieve different visual effects. As shown in the third figure, the texture is large (丄2) and can be designed to exhibit a wide and narrow column shape. Please refer to the fourth figure. The foregoing lighting driver includes the following steps in this embodiment: Obtaining the pressure value (100) 'Getting the pressure value through the pressure sensor (2 〇)' The pressure sensor ( 2 0 ) It can transmit 1351264 every other time interval. · The weight change controls the lighting of the LEDs. 'For example, different weight segments display different colors' and the coaster itself can achieve light scattering refraction by engraving or the like. The effect of 'equal effect' makes the color light display of the light-emitting diode more dazzling. [Schematic description] The first figure: a perspective view of a preferred embodiment of the present invention. Second Figure: Side view of a preferred embodiment of the invention. 2 is a side view of another preferred embodiment of the present invention. Fourth: Flow chart for determining the pressure value according to a preferred embodiment of the present invention. [Main component symbol description] (1 ◦) Light-transmitting pad body (1 1 ) Light guide plate (1 2 ) Grain (2 0) Pressure sensor (30) Control circuit board (31) Light-emitting diode [S1 8