Main core wire and liquid-cooled wire rod
By using the design of the first liquid-cooled tube, the first conductor, heat insulating member and insulating member in the charging gun cable, the problem of heat diffusion of the main core wire is solved, and the temperature control and stability improvement of the main core wire and other cables is achieved.
Patent Information
- Application Number
- CN202422442645.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-09
- Publication Date
- 2025-08-01
- Estimated Expiration
- 2034-10-09
AI Technical Summary
During the cooling process of existing charging gun cables, the heat generated by the main core wire will spread outward, causing it to be difficult to reduce the temperature of other cables and outer skins, increasing the risk of disconnection and affecting the service life.
The main core wire design includes a first liquid-cooled tube, a first conductor, a heat insulating member and a first insulating member is adopted. The heat is conducted through the first liquid-cooled tube to the coolant, heat is insulated with an aerogel material to prevent heat diffusion, and the contact area is increased by a copper wire braided tape to reduce contact thermal resistance.
It effectively reduces the temperature difference between the main core wire and other cables, reduces leakage, short circuit and other phenomena, extends the service life of the cable and improves performance stability.
Smart Images
Figure CN223180889U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of cables, in particular to a main core wire and a liquid-cooled wire. Background Art
[0002] The existing charging gun cables usually adopt a liquid-cooling method to cool the main core wire inside the cable.
[0003] However, the heat generated by the main core wire still diffuses outward to other cables and the outer skin of the cable inside the cable, making it difficult to reduce the temperature of other cables and the outer skin, increasing the risk of wire breakage, and thus affecting the service life of the cable. Summary of the Utility Model
[0004] Based on this, it is necessary to provide a main core wire and a liquid-cooled wire for the above problems to reduce the influence of the heat generated by the main core wire on other cables inside the liquid-cooled wire.
[0005] The utility model first provides a main core wire, including: a first liquid-cooling tube provided with a first channel for filling a coolant; a first conductor sleeved outside the first liquid-cooling tube; a heat-insulating member sleeved outside the first conductor, and the heat-insulating member is set as an aerogel member; and a first insulating member sleeved outside the heat-insulating member.
[0006] In the above main core wire, the first liquid-cooling tube can conduct the heat generated when the first conductor works to the coolant in the first channel, so as to take away the heat generated by the first conductor through the flowing coolant. The first conductor sleeved outside the first liquid-cooling tube can ensure the contact area and contact effect between the first conductor and the first liquid-cooling tube, reduce the contact thermal resistance, and thus ensure the heat dissipation effect on the first conductor; the first insulating member can prevent the main core wire from contacting other cables or structures inside the liquid-cooled wire, resulting in phenomena such as electric leakage, short circuit, electric shock, etc., and ensure that the main core wire and other cables inside the liquid-cooled wire can work normally; the heat-insulating member is arranged between the first conductor and the first insulating member, which can block the heat generated by the first conductor from diffusing outward, prevent the temperature of the first insulating member and other cables or structures inside the liquid-cooled wire from rising, thereby reducing phenomena such as thermal aging, cracking or wire breakage of the first insulating member and other cables or structures inside the liquid-cooled wire, extending the service life, improving the performance stability, and the aerogel material has high temperature resistance and good heat insulation performance, so as to ensure the heat insulation effect on the first conductor.
[0007] In one embodiment, the first conductor is set as a copper wire braid wound around the outer peripheral wall of the first liquid-cooling tube; and / or, the difference between the inner and outer radii of the first conductor satisfies 10 mm to 50 mm.
[0008] With such a setting, the copper wire braid can reduce the gap between the first conductor and the first liquid cooling tube, increase the contact surface pressure, enlarge the contact area, reduce the contact thermal resistance, improve the heat transfer efficiency, and enhance the heat dissipation effect on the first conductor; ensure that the conductor amount of the first conductor meets the specification requirements of the main core wire.
[0009] In one embodiment, the first liquid cooling tube is set as a cross-linked polyolefin part or a heat-conducting silicone rubber part; and / or, the difference between the outer radius and the inner radius of the first liquid cooling tube satisfies 0.5 mm to 1.5 mm.
[0010] With such a setting, the first liquid cooling tube has good high-temperature resistance and insulation properties, a high thermal conductivity coefficient, and will not chemically react with the coolant; ensure the reliability of the first liquid cooling tube and also ensure the heat conduction efficiency of the first liquid cooling tube.
[0011] The present utility model also provides a liquid-cooled wire, including: an outer sheath provided with a second channel; and at least two main core wires as described above, which are parallelly and spacedly arranged in the second channel.
[0012] With such a setting, the heat insulation part of the main core wire can prevent the heat generated by the first conductor from diffusing outward and causing the temperature of other cables or the outer sheath in the liquid-cooled wire to rise, thereby reducing phenomena such as heat aging, cracking, or wire breakage of other cables or the outer sheath in the liquid-cooled wire, prolonging the service life, and enhancing the performance stability.
[0013] In one embodiment, the liquid-cooled wire further includes at least one second liquid cooling tube, the second liquid cooling tube is arranged in the second channel and is parallelly and spacedly arranged with the main core wire, and each second liquid cooling tube is provided with a third channel for filling the coolant.
[0014] With such a setting, the coolant flowing in the third channel can take away the heat generated by the main core wire and other cables in the second channel, and reduce the temperature of the liquid-cooled wire.
[0015] In one embodiment, the liquid-cooled wire further includes at least one cable, the cable is arranged in the second channel and is parallelly and spacedly arranged with the main core wire; the cable includes at least one of a signal wire, a control wire, and a grounding wire.
[0016] With such a setting, the signal wire is used for signal transmission, the control wire is used for controlling the operation of the device, and the liquid-cooled grounding wire is used to introduce the leakage current into the ground to ensure the safe use of the device.
[0017] In one embodiment, each of the cables includes a second conductor, a second wrapping member, and a second insulating member sleeved from the inside out in sequence, and the number of the second conductors is at least one; or, each of the cables includes a second conductor, a shielding member, a second wrapping member, and a second insulating member sleeved from the inside out in sequence, and the number of the second conductors is at least one.
[0018] With such a setting, the second wrapping member is used to tie and fix the second conductor and can isolate the cable from the external structure; the shielding member can reduce the electromagnetic interference generated by the cable to the external structure, and at the same time can also limit the influence of the external electromagnetic field on the cable, ensuring the stability and accuracy of the signal transmission of the second conductor; the second insulating member can prevent phenomena such as electric leakage, short circuit, and electric shock of the cable.
[0019] In one embodiment, the liquid-cooled wire also includes a first wrapping member attached to the inner peripheral wall of the outer sheath.
[0020] With such a setting, the first wrapping member is used to tie and fix the main core wire and the cable, and can isolate the liquid-cooled wire from the external structure, reducing the interference of the external structure on the signals of the first conductor and the second conductor, and ensuring the stability and accuracy of the signal transmission of the first conductor and the second conductor.
[0021] In one embodiment, the liquid-cooled wire also includes a tensile member filled in the second channel.
[0022] With such a setting, the tensile member can increase the strength of the liquid-cooled wire, making the liquid-cooled wire have good tensile resistance and impact resistance. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.
[0024] Figure 1 It is a cross-sectional schematic diagram of the main core wire of an embodiment of the present utility model;
[0025] Figure 2 It is a cross-sectional schematic diagram of the liquid-cooled wire of the first embodiment of the present utility model;
[0026] Figure 3 It is a cross-sectional schematic diagram of the liquid-cooled wire of the second embodiment of the present utility model;
[0027] Figure 4 It is a cross-sectional schematic diagram of the liquid-cooled wire of the third embodiment of the present utility model.
[0028] Reference Numerals: 1, main core wire; 11, first liquid cooling tube; 111, first channel; 12, first conductor; 13, heat insulation member; 14, first insulating member; 2, outer sheath; 21, second channel; 3, second liquid cooling tube; 31, third channel; 4, cable; 41, second conductor; 42, shielding member; 43, second winding member; 44, second insulating member; 45, signal line; 46, control line; 47, ground wire; 48, insulating layer; 5, first winding member; 6, tensile member. Detailed Embodiment
[0029] In order to make the above objects, features, and advantages of the present application more obvious and understandable, the following will describe the detailed embodiments of the present application with reference to the accompanying drawings. Many specific details are set forth in the following description to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.
[0030] It should be noted that when a component is referred to as being "fixed to" or "disposed on" another component, it can be directly on the other component or there may also be an intermediate component. When a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be an intermediate component at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used in the specification of the present application are only for the purpose of illustration and do not represent the only implementation manner.
[0031] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined.
[0032] In the present application, unless otherwise clearly specified and limited, the first feature being "on" or "under" the second feature can be that the first feature is in direct contact with the second feature, or the first feature is indirectly in contact with the second feature through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature can be that the first feature is directly above or obliquely above the second feature, or only indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature can be that the first feature is directly below or obliquely below the second feature, or only indicates that the first feature has a lower horizontal height than the second feature.
[0033] Unless otherwise defined, all technical and scientific terms used in the specification of this application have the same meaning as commonly understood by those skilled in the technical field to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used in the specification of this application includes any and all combinations of one or more of the related listed items.
[0034] Existing charging gun cables usually use a liquid cooling method to dissipate heat from the main core wire inside the cable. However, especially when operating at high currents, the heat generated by the main core wire still spreads outward to other wires and the outer skin of the cable, making it difficult to reduce the temperature of other wires and the outer skin, increasing the risk of wire breakage, and thus affecting the service life of the cable.
[0035] To solve the above problems, as Figure 1 shown, the present utility model first provides a main core wire 1 to reduce the influence of the heat generated by the main core wire 1 on other wires inside the liquid-cooled wire.
[0036] As Figure 1 shown, specifically, the main core wire 1 includes a first liquid cooling tube 11, a first conductor 12, a heat insulation member 13, and a first insulating member 14, where: the first liquid cooling tube 11 is provided with a first channel 111 for filling a coolant, the first conductor 12 is sleeved outside the first liquid cooling tube 11, the heat insulation member 13 is sleeved outside the first conductor 12, the heat insulation member 13 is set as an aerogel member, and the first insulating member 14 is sleeved outside the heat insulation member 13.
[0037] In the main core wire 1 provided by the embodiment of the present utility model, the main core wire 1 is used to be arranged inside the liquid-cooled wire. The first liquid cooling tube 11 can conduct the heat generated when the first conductor 12 works to the coolant in the first channel 111 to take away the heat generated by the first conductor 12 through the flowing coolant. Since the first conductor 12 is sleeved outside the first liquid cooling tube 11, the contact area and contact effect between the first conductor 12 and the first liquid cooling tube 11 can be ensured, the contact thermal resistance can be reduced, and thus the heat dissipation effect on the first conductor 12 can be ensured; the first insulating member 14 can prevent the main core wire 1 from contacting other wires or structures inside the liquid-cooled wire and causing phenomena such as electric leakage, short circuit, and electric shock, ensuring that the main core wire 1 and other wires inside the liquid-cooled wire can work normally; the heat insulation member 13 is arranged between the first conductor 12 and the first insulating member 14, which can block the outward diffusion of the heat generated by the first conductor 12, prevent the temperature of the first insulating member 14 and other wires or structures inside the liquid-cooled wire from rising, thereby reducing phenomena such as thermal aging, cracking, or wire breakage of the first insulating member 14 and other wires or structures inside the liquid-cooled wire, extending the service life, improving the performance stability, and the aerogel material has good high-temperature resistance and heat insulation performance, so as to ensure the heat insulation effect on the first conductor 12.
[0038] Among them, the aerogel component can be wrapped around the outer peripheral wall of the first conductor 12 by a winding process, and the production and processing method is simple.
[0039] In one embodiment, the first liquid cooling pipe 11 is provided as a cross-linked polyolefin component or a thermally conductive silicone rubber component. Specifically, the first liquid cooling pipe 11 can be processed and formed by an extrusion process, and the production and processing method is simple. Moreover, both the cross-linked polyolefin material and the thermally conductive silicone rubber material have good high-temperature resistance and insulation properties, high thermal conductivity, and will not chemically react with the coolant. Of course, in other embodiments, the first liquid cooling pipe 11 can also be made of other materials such as polytetrafluoroethylene, as long as it can conduct the heat generated by the first conductor 12 to the coolant in the first liquid cooling pipe 11 and ensure that the main core wire 1 can work normally. The embodiments of the present invention do not make specific limitations here.
[0040] As Figure 1 shown, the inner and outer radius difference b of the first liquid cooling pipe 11 satisfies 0.5 mm to 1.5 mm. That is, the wall thickness of the first liquid cooling pipe 11 satisfies 0.5 mm to 1.5 mm. In this way, the reliability of the first liquid cooling pipe 11 can be ensured, and at the same time, the heat conduction efficiency of the first liquid cooling pipe 11 can be ensured.
[0041] In one embodiment, the first conductor 12 is provided as a copper wire braid wound around the outer peripheral wall of the first liquid cooling pipe 11. Specifically, the copper wire braid can be formed by braiding multiple fine pure copper wires with a diameter less than or equal to 0.1 mm, and the braiding density is greater than or equal to 85%. The copper wire braid can be evenly wrapped around the outer peripheral wall of the first liquid cooling pipe 11 by a multi-layer tight winding process. The copper wire braid can reduce the gap between the first conductor 12 and the first liquid cooling pipe 11, increase the contact surface pressure, and increase the contact area, thereby further reducing the contact thermal resistance, improving the heat transfer efficiency, and enhancing the heat dissipation effect on the first conductor 12. Moreover, since the copper wire braid is formed by braiding soft fine pure copper wires, only the innermost layer of the wound copper wire braid contacts the first liquid cooling pipe 11. Therefore, the probability of the copper wire breaking and piercing the first liquid cooling pipe 11 can also be reduced, and the reliability of the main core wire 1 can be improved.
[0042] Of course, in other embodiments, the first conductor 12 can also be made of other materials such as a thick conductor or a stranded conductor, as long as it can ensure that the main core wire 1 can work normally. The embodiments of the present invention do not make specific limitations here.
[0043] As Figure 1 shown, the inner and outer radius difference a of the first conductor 12 satisfies 10 mm to 50 mm. That is, the thickness of the multi-layer copper wire braid satisfies 10 mm to 50 mm. In this way, it is ensured that the conductor amount of the first conductor 12 meets the specification requirements of the main core wire 1.
[0044] Moreover, the first insulating member 14 can be made of resin, plastic, silicone rubber, PVC, etc. to ensure the insulation effect of the first insulating member 14. Specifically, the first insulating member 14 can be wrapped around the outer peripheral wall of the heat insulating member 13 by an extrusion process, and the production and processing method is simple.
[0045] As Figures 2 to 4 shown, an embodiment of the present invention further provides a liquid-cooled wire, including an outer sheath 2 and at least two of the above-mentioned main core wires 1. The outer sheath 2 is provided with a second channel 21, and at least two main core wires 1 are arranged in parallel and spaced apart in the second channel 21. The first conductors 12 of two of the main core wires 1 are respectively used as DC+ and DC- power supply wires. The heat insulating members 13 of the main core wires 1 can prevent the heat generated by the first conductors 12 from diffusing outward, resulting in an increase in the temperature of other cables or the outer sheath 2 inside the liquid-cooled wire. Thereby, it reduces the occurrence of phenomena such as heat aging, cracking, or wire breakage of other cables or the outer sheath 2 inside the liquid-cooled wire, extends the service life, and improves the performance stability.
[0046] As Figures 3 to 4 shown, the liquid-cooled wire further includes at least one second liquid-cooling tube 3. The second liquid-cooling tube 3 is arranged in the second channel 21 and is arranged in parallel and spaced apart from the main core wire 1. Each second liquid-cooling tube 3 is provided with a third channel 31 for filling a coolant. Specifically, the second liquid-cooling tube 3 can also be set as a cross-linked polyolefin member or a heat-conducting silicone rubber member, and can be processed and formed by an extrusion process. The coolant flowing in the third channel 31 can take away the heat generated by the main core wire 1 and other cables in the second channel 21, further reducing the temperature of the liquid-cooled wire, preventing phenomena such as heat aging, cracking, or wire breakage of the liquid-cooled wire, extending the service life, and improving the performance stability. Among them, the number of the second liquid-cooling tubes 3 can be Figure 3 [[ID=1Z]]shown as one, Figure 4 shown as two or more. The specific number and size of the second liquid-cooling tubes 3 can be adjusted according to the number of circuits, power, size, etc. inside the liquid-cooled wire, and the embodiments of the present invention do not make specific limitations here.
[0047] As Figures 2 to 4 shown, the liquid-cooled wire further includes at least one cable 4. The cable 4 is arranged in the second channel 21 and is arranged in parallel and spaced apart from the main core wire 1. The cable 4 includes at least one of a signal wire 45, a control wire = 46, and a ground wire 47. The signal wire 45 is used for signal transmission, the control wire 46 is used for controlling the operation of the device, and the ground wire 47 is used for introducing the leakage current into the ground to ensure the safe use of the device.
[0048] As Figures 2 to 4As shown, in one embodiment, each cable 4 includes a second conductor 41, a second wrapping member 43, and a second insulating member 44 that are sequentially sleeved from the inside to the outside, and the number of second conductors 41 is at least one. Among them, each cable 4 may include only one second conductor 41, or may include two or more second conductors 41. When each cable 4 includes more than two second conductors 41, an insulating layer 48 is wrapped around each second conductor 41 to prevent short circuits or signal transmission interference caused by contact between adjacent second conductors 41.
[0049] Specifically, the second conductor 41 can be made of materials such as copper wire braid, thick conductor, or stranded conductor to ensure the normal operation of the cable 4. The second wrapping member 43 can be made of materials such as polytetrafluoroethylene, polyester tape, etc., and can be wrapped around the second conductor 41 or the outer insulating layer 48 of the second conductor 41 by a winding process. The second wrapping member 43 is used to tie and fix the second conductor 41, and can isolate the cable 4 from the external structure, reducing the interference of the external structure on the signal of the second conductor 41 and ensuring the stability and accuracy of the signal transmission of the second conductor 41. The second insulating member 44 can be made of materials such as resin, plastic, silicone rubber, PVC, etc. to ensure the insulating effect of the second insulating member 44 and prevent leakage, short circuit, electric shock, etc. from occurring due to contact between the cable 4 and other cables or structures in the second channel 21.
[0050] As Figures 2 to 3 shown, in another embodiment, each cable 4 includes a second conductor 41, a shielding member 42, a second wrapping member 43, and a second insulating member 44 that are sequentially sleeved from the inside to the outside, and the number of second conductors 41 is at least one. Specifically, the shielding member 42 can be made of materials such as metal, and can be wrapped around the outer insulating layer 48 of the second conductor 41 by processes such as wire drawing, winding, or braiding. The shielding member 42 can shield the electromagnetic field generated when the second conductor 41 is energized inside the cable 4, reducing the electromagnetic interference generated by the cable 4 on the external structure, and at the same time can also limit the influence of the external electromagnetic field on the cable 4, further ensuring the stability and accuracy of the signal transmission of the second conductor 41.
[0051] Of course, in other embodiments, each cable 4 may also include only the second conductor 41 and the second insulating member 44 sleeved outside the second conductor 41, and the number of second conductors 41 is at least one.
[0052] As Figures 2 to 4As shown, the liquid-cooled wire also includes a first wrapping member 5 attached to the inner peripheral wall of the outer sheath 2. Specifically, the first wrapping member 5 can be made of materials such as polytetrafluoroethylene and polyester tape, and can be wrapped around the outer sides of the main core wire 1 and the cable 4 by means of a winding process. The first wrapping member 5 is used to tie and fix the main core wire 1 and the cable 4, and can isolate the liquid-cooled wire from the external structure, reducing the interference of the external structure on the signals of the first conductor 12 and the second conductor 41, and ensuring the stability and accuracy of the signal transmission of the first conductor 12 and the second conductor 41.
[0053] As Figures 2 to 4 shown, the liquid-cooled wire also includes a tensile member 6 filled in the second channel 21. Specifically, the tensile member 6 can be made of materials such as Kevlar filling ropes, glass fibers, and silica gel. The tensile member 6 can increase the strength of the liquid-cooled wire, making the liquid-cooled wire have better tensile resistance and impact resistance, further extending the service life, and improving the performance stability.
[0054] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.
[0055] The above-described embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the patent protection scope of the present application shall be subject to the appended claims.
Claims
1. A main core wire, characterized in that, Comprising: A first liquid cooling tube (11) provided with a first channel (111) for filling a coolant; A first conductor (12) sleeved outside the first liquid cooling tube (11); A heat insulation member (13) sleeved outside the first conductor (12), and the heat insulation member (13) is arranged as an aerogel member; and, A first insulating member (14) sleeved outside the heat insulation member (13).
2. The main core wire according to claim 1, characterized in that, The first conductor (12) is arranged as a copper wire braided tape wound around the outer peripheral wall of the first liquid cooling tube (11).
3. The main core wire according to claim 1, characterized in that, The difference between the inner and outer radii of the first conductor (12) satisfies 10 mm to 50 mm.
4. The main core wire according to claim 1, characterized in that, The first liquid cooling tube (11) is arranged as a cross-linked polyolefin member or a heat-conducting silicone rubber member; and / or, The difference between the inner and outer radii of the first liquid cooling tube (11) satisfies 0.5 mm to 1.5 mm.
5. A liquid-cooled wire, characterized in that, Comprising: An outer sheath (2) provided with a second channel (21); and, At least two main core wires as described in any one of claims 1 to 4, parallelly and spacedly inserted into the second channel (21).
6. The liquid-cooled wire according to claim 5, wherein, The liquid cooling wire further comprises at least one second liquid cooling tube (3), the second liquid cooling tube (3) is inserted into the second channel (21) and arranged parallelly and spacedly with the main core wire, and each second liquid cooling tube (3) is provided with a third channel (31) for filling a coolant.
7. The liquid-cooled wire according to claim 5, wherein, The liquid cooling wire further comprises at least one cable (4), the cable (4) is inserted into the second channel (21) and arranged parallelly and spacedly with the main core wire; The cable (4) comprises at least one of a signal wire (45), a control wire (46) and a ground wire (47).
8. The liquid-cooled wire according to claim 7, wherein Each cable (4) comprises a second conductor (41), a second wrapping member (43) and a second insulating member (44) sleeved in sequence from inside to outside, and the number of the second conductors (41) is at least one; or, Each cable (4) comprises a second conductor (41), a shielding member (42), a second wrapping member (43) and a second insulating member (44) sleeved in sequence from inside to outside, and the number of the second conductors (41) is at least one.
9. The liquid-cooled wire according to claim 5, wherein The liquid cooling wire further comprises a first wrapping member (5) attached to the inner peripheral wall of the outer sheath (2).
10. The liquid-cooled wire according to claim 5, wherein, The liquid cooling wire further comprises a tensile member (6) filled in the second channel (21).