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| introduction [2020/05/14 11:11] – adminz | introduction [2020/05/14 11:11] (current) – adminz |
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| It was originally conceived as a way to protect arcade boards connected to an Atari AR-II power supply, since they can still experience failures that cause them to put dangerously high voltages (at least for 5v TTL) down the +5v line. There are also lots of pages that talk about "bulletproofing" an AR-II power supply, but no one ever actually bulletproofs it - they just talk about performing the Sense Mod and replacing parts. | It was originally conceived as a way to protect arcade boards connected to an Atari AR-II power supply, since they can still experience failures that cause them to put dangerously high voltages (at least for 5v TTL) down the +5v line. There are also lots of pages that talk about "bulletproofing" an AR-II power supply, but no one ever actually bulletproofs it - they just talk about performing the Sense Mod and replacing parts. |
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| Even after all that, the danger of 6+ volts going up the +5v line still exists (e.g. if the 2n3055 shorts). So despite what the page says, //you really did **not** bulletproof anything!// Since the change of overvoltage conditions still existed, something more was needed. Although that was the genesis of the device many years ago, it has applications other that with an AR-II. | Even after all that, the danger of 6+ volts going up the +5v line still exists (e.g. if the 2n3055 shorts). So despite what these pages say, //you really did **not** bulletproof anything!// Since the change of overvoltage conditions still existed, something more was needed. Although that was the genesis of the device many years ago, it has applications other that with an AR-II. |
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| It can be used anywhere you want overvoltage protection in low voltage circuits. The trigger voltage (//vTrigger//) is set via two resistors **R1** and **R2**. When the device is in operation, exceeding //vTrigger// will cause the SCR to quickly bridge the **GND** and **Protected 5v**((Note that even though this PCB has "+5" and "Protected +5" written on it, other voltages can be used. Just consider that to be read as **VCC** and **Protected VCC** instead)) circuits, and will illuminate the Activated LED. If the available current is high enough, and the fuse being used was chosen well, the fuse will blow quickly and will open up the protected side of the circuit. If not, the fuse may take longer to blow, additional heat will be dissipated by the SCR, and a voltage drop will occur. | It can be used anywhere you want overvoltage protection in low voltage circuits. The trigger voltage (//vTrigger//) is set via two resistors **R1** and **R2**. When the device is in operation, exceeding //vTrigger// will cause the SCR to quickly bridge the **GND** and **Protected 5v**((Note that even though this PCB has "+5" and "Protected +5" written on it, other voltages can be used. Just consider that to be read as **VCC** and **Protected VCC** instead)) circuits, and will illuminate the Activated LED. If the available current is high enough, and the fuse being used was chosen well, the fuse will blow quickly and will open up the protected side of the circuit. If not, the fuse may take longer to blow, additional heat will be dissipated by the SCR, and a voltage drop will occur. |
