# Jetson Nano dc Barrel jack

I am making a project for jetson nano where i will be using battery as a source, I want to use the dc barrel jack, knowing that the performance is faster. But I am worrying cause I do not know much about electronics. Does supplying jetson nano dc jack 5v with more than 4a is unsafe. Example 5v 6a total of 30w. I just want to know if it’s safe.

If you pick the correct voltage (and if you look closely something like 5.1 V may be better), and regulate that voltage quite well, then having more current available is good, not bad. At a given voltage you only draw a certain amount of current if the load (the Jetson) decides to consume it. You could have a 5 V source capable of 999999 A, and it would draw the same 1 A for any power source capable of 1 A or more if and only if the load is exactly 5 ohms resistance. Jetsons are variable load. Whether they draw 1 A or 2 A or 4 A depends on what they are doing at the moment.

So having more current available is good. Jetsons are rather picky though about the quality of voltage regulation. All power sources will drop in voltage by some tiny amount when the load goes up (higher resistance), and conversely, they tend to raise voltage by some tiny amount when the load goes down (lower resistance). How much the voltage changes when the load change is what you can call the quality of regulation. High quality means the Jetson can consume its lowest amount or its highest amount of current and you won’t be able to tell the voltage changed. Or at least it won’t change by an amount the Jetson cares about.

Now if something went wrong, e.g., there is a storm and a power line breaks and shorts, then consequences of the short for a power supply capable of 2 A is less than the consequences of a 4 A supply at the same voltage. In both cases the voltage will go to near zero, the current will go to max, and something will fry. The shorted 2 A will fry less than the shorted 4 A supply. This is more or less how an arc welder works, and they don’t have particularly high voltage, but they supply a lot of current. They don’t supply any current until the welding rods short and they start melting. A 5 V supply with a 4 A output isn’t going to be particularly hazardous even when shorted, but it could destroy a Jetson if applied to the wrong place (so could a 2 A supply if connected wrong).

Because a Jetson needs high quality regulation it also implies that if you power something else which varies in load with the same supply it can be a problem. A common example is some sort of rover or drone with powerful motors. The motors change load depending on terrain, weight, speed, so on. Turning a motor on draws extra current for a moment. Turning the motor off might cause a short voltage spike. Powering both with the same battery, and without separate and independent regulators, cause cause the Jetson to shut down or reboot every time the motors are engaged or disabled. A big enough spike in voltage from an inductive load (like a motor) can destroy a computer. The surge protectors you can buy at the store for your computer protect against inductive spikes and to some extent lightning strikes. If you get an UPS (uninterruptible power supply) capable of avoiding “brownouts” (when voltage drops too much), then you also protect against outside loads (such as an air conditioner kicking on) which drop voltage too much.

When powering both the Jetson and motors with one battery, one solution is to use a high quality regulator which powers only the Jetson, and if needed, add a second regulator for the motors or other current sinks (anything supplying current is a current source; anything drawing power is a current sink).

Another issue is that the wires supplying the power have resistance. Double the length, and the resistance doubles. This degrades the quality of regulation since the voltage drop on those wires goes up based on current load. Shorter wires, and wires which are thicker (a heavier gauge is a lower gauge number; lower gauge is a larger diameter) help. There are other things which help with regulation, but most of the time you won’t need more. An example is that if the regulation is still not stable enough you could put a large electrolytic capacitor right next to the Jetson’s power connector (capacitors are like batteries, but they store power in an electric field instead of storing in a chemical reaction).

Definitely go for more current. Going for higher regulation quality is hard to judge without trying it because most of the supplies you buy from Amazon won’t tell you how good regulation is. When you go to more expensive lab supplies they will probably come with charts and specs related to quality of regulation.

I just bought this 11.1v battery and step down converter to 5.25v with 5a from an online store. I think 5.25v may be too much foe jetson nano

I don’t recall the exact spec, but the provided power from a USB 2 source is “listed” as 5V, and yet it has an actual range of tolerance. Quite often I see this at 5.2V, and 5.2V is actually a good voltage to use. I don’t know if 5.25V is too much, but it is so close to the common 5.2V that I suspect it is fine at that voltage. I just can’t guarantee it. The real trick though is that if the Jetson goes to and from a high load, does it shut down? If it does not shut down, then you’re probably in luck and all should be good.

Someone else might be able to verify if 5.25V is in tolerance.

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