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I want to install a Siriusxm radio receiver in an antique car with a 6 volt system. The Sirius receiver 12 volt power adaptor states that the output is 5 volts. If I wire the receiver directly into the 6 volt system, will that extra volt burn out the receiver over time? If so, what device can be wired in to drop the voltage to 5 volts? I have read here about diodes and SEPIC to do this, but not being savvy in electronics, I don't understand which way to go. Could someone advise me on how specifically to do this? Any recommendations on what I should buy, to include source if known, would be appreciated.

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    \$\begingroup\$ Automobile voltage is highly unstable. You would need to stabilize it even if it was 5V. \$\endgroup\$
    – Eugene Sh.
    Feb 5 '18 at 17:45
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    \$\begingroup\$ Use a low drop out voltage regulator. It's drop out should be 0.5V or lower if you can. \$\endgroup\$
    – Passerby
    Feb 5 '18 at 21:27
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    \$\begingroup\$ Thanks Passerby. The description of the LDO 7805 states "This regulator has a ~2V linear drop-out. That means you must give it at least 7V to get a clean 5V out". My car output is 6 volts (6.4). Is there another that will work? \$\endgroup\$
    – Opie
    Feb 5 '18 at 22:09
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    \$\begingroup\$ @Opie 7805 is not an LDO \$\endgroup\$ Feb 5 '18 at 22:33
  • \$\begingroup\$ Proof that I don't know what I am doing! I really need some guidance when it comes to electronics. \$\endgroup\$
    – Opie
    Feb 5 '18 at 23:01
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First, you have to know, what current your device will draw. I'd personally use a DC-DC with low voltage drop or a simple LDO if the current isn't too high. There's also an option, to use diodes.

option A: Buy over the internet or create your own low drop DC-DC buck converter, which will hold the power dissipation for current across your device.

enter image description here

option B: Use LM1117 5.0V if your current won't exceed 1A and you can have 6.3V on the input.

enter image description here

option C: Use 1N4007 and 1N4148 diodes in series (same direction), where the 1N4007 will cause ~0.7V drop and 1N4148 will cause ~0.3V drop.

enter image description here

option D: if the current is small, you can use just a simple voltage resistor with proper ratio!

enter image description here

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  • \$\begingroup\$ Thanks Jakey. The Sirius receiver requires 5 volts/1.5 Amps, so option B is out. You said "if the current isn't too high" for the other options. What options will work at 1.5 Amps? \$\endgroup\$
    – Opie
    Feb 5 '18 at 22:43
  • \$\begingroup\$ Please define "isn't too high". Thanks. \$\endgroup\$
    – Opie
    Feb 6 '18 at 23:18
  • \$\begingroup\$ The 1N4148 can only carry 50mA current. You need a power Schottky diode if you wanted 0.3V drop at ~1A. But two 1N4007 will also match here. \$\endgroup\$
    – Janka
    Oct 29 '18 at 9:09
  • \$\begingroup\$ Keep in mind that the voltage drop of a Diode is dependent on the current flowing through it. Low currents will see less of a voltage drop. So make sure if you do this to add some capacitors and maybe a load resistor if your circuit uses little current. There are pretty straight forward graphs in diodes datasheets to show voltage drop vs. current. \$\endgroup\$
    – Meozaa
    Nov 29 '18 at 0:19
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The easiest and cheapest way to drop a small amount of voltage would be too use a diode , there forward voltage drop is around 0.7v so is perfect for reducing small amounts of voltage, I hope this helps, also it shouldn’t burn out with the 1 extra volt there should be a 20% tolerance , but if your wanting to get it exact I would recommend using diodes. EDIT ( When using a diode remember to always check the data sheet for the voltage drop as this can vary)

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    \$\begingroup\$ This is a duplicate of part of @jakey's answer above. \$\endgroup\$
    – Hearth
    Nov 28 '18 at 23:54

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