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I know DEAD HORSE.. but if you feel like it,.. Help me with Class A/B vs Class D.
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<blockquote data-quote="bbeljefe" data-source="post: 8222463" data-attributes="member: 655960"><p>I'll try to explain it in the simplest terms but please don't mistake it as condescension. I may cover something you already understand but that doesn't mean I don't think you know it. ;-)</p><p></p><p>Relays are electric switches. There is only one fundamental difference between a relay and the light switch in your office and that's the means by which it is moved. The switch in your office is moved by your hand and the switch on a relay is moved by electrical current exiting the coil and creating magnetism that pulls the switch from its normal position. In this case, the coil is pins 85 &amp; 86. Those pins are not polarity conscious, meaning that neither is positive or negative but obviously, one needs a positive connection and the other, a negative, in order for it to work.</p><p></p><p>Moving on to the switch portion of the relay... the only difference between 4 &amp; 5 pin relays is that 4 pin automotive relays are normally open and 5 pin automotive relays are normally open or normally closed. Normal = the rest position of the switch or, the position it reverts to when the coil is not energized. The 5 pin relays we're discussing designate the N.O. (normally open) terminal as pin 87 and the N.C. (normally closed) terminal as pin 87a. And again, they are not to be confused as being the same. They are opposites and they serve the opposing functions of closing a circuit or opening a circuit, respectively.</p><p></p><p>For what you're doing, you need pins 30 &amp; 87 (N.O.) and you do not need pin 87a. I mentioned 5 pin relays because they're quite common and obviously for me as a dealer, more versatile as they can serve to switch multiple applications... thereby allowing me to stock fewer parts but still be able to accomplish multiple goals. But for your goal, a 4 or 5 pin relay will work and for the sake of this conversation, forget about pin 87a altogether... you don't need it and it does not exist. <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" /></p><p></p><p>Also, to reinforce the explanation, pins 85 &amp; 86 work together and are completely (electrically) isolated from pins 30 &amp; 87. 85 can be ground and 86 can be positive from the head unit or vice versa... it doesn't matter. 30 &amp; 87 are the two connections on a single pole, single throw switch and for your application, it doesn't matter which is used for power and which is used to send that power to the amp and fan. 30 is usually used as the power input but again, it doesn't matter. All that matters is that you have a switch (pins 30 &amp; 87) between the power feed and the devices you wish to send power to.</p><p></p><p>In summary, the only reason we're even using a relay is so that you can switch high current devices with a low current signal and that's the single most common application for automotive relays. If your head unit provided 1 amp of current to the remote wire, we wouldn't need a relay but since it doesn't and we still need to use the head unit to switch on a higher current circuit, a relay does that while also isolating (protecting) the head unit's remote wire from the high current draw of the amp + the fan.</p><p></p><p>I hope that makes some sense, lol.</p></blockquote><p></p>
[QUOTE="bbeljefe, post: 8222463, member: 655960"] I'll try to explain it in the simplest terms but please don't mistake it as condescension. I may cover something you already understand but that doesn't mean I don't think you know it. ;-) Relays are electric switches. There is only one fundamental difference between a relay and the light switch in your office and that's the means by which it is moved. The switch in your office is moved by your hand and the switch on a relay is moved by electrical current exiting the coil and creating magnetism that pulls the switch from its normal position. In this case, the coil is pins 85 & 86. Those pins are not polarity conscious, meaning that neither is positive or negative but obviously, one needs a positive connection and the other, a negative, in order for it to work. Moving on to the switch portion of the relay... the only difference between 4 & 5 pin relays is that 4 pin automotive relays are normally open and 5 pin automotive relays are normally open or normally closed. Normal = the rest position of the switch or, the position it reverts to when the coil is not energized. The 5 pin relays we're discussing designate the N.O. (normally open) terminal as pin 87 and the N.C. (normally closed) terminal as pin 87a. And again, they are not to be confused as being the same. They are opposites and they serve the opposing functions of closing a circuit or opening a circuit, respectively. For what you're doing, you need pins 30 & 87 (N.O.) and you do not need pin 87a. I mentioned 5 pin relays because they're quite common and obviously for me as a dealer, more versatile as they can serve to switch multiple applications... thereby allowing me to stock fewer parts but still be able to accomplish multiple goals. But for your goal, a 4 or 5 pin relay will work and for the sake of this conversation, forget about pin 87a altogether... you don't need it and it does not exist. :-) Also, to reinforce the explanation, pins 85 & 86 work together and are completely (electrically) isolated from pins 30 & 87. 85 can be ground and 86 can be positive from the head unit or vice versa... it doesn't matter. 30 & 87 are the two connections on a single pole, single throw switch and for your application, it doesn't matter which is used for power and which is used to send that power to the amp and fan. 30 is usually used as the power input but again, it doesn't matter. All that matters is that you have a switch (pins 30 & 87) between the power feed and the devices you wish to send power to. In summary, the only reason we're even using a relay is so that you can switch high current devices with a low current signal and that's the single most common application for automotive relays. If your head unit provided 1 amp of current to the remote wire, we wouldn't need a relay but since it doesn't and we still need to use the head unit to switch on a higher current circuit, a relay does that while also isolating (protecting) the head unit's remote wire from the high current draw of the amp + the fan. I hope that makes some sense, lol. [/QUOTE]
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I know DEAD HORSE.. but if you feel like it,.. Help me with Class A/B vs Class D.
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