# Jetson Nano restarts or will not boot on USB power: use the barrel jack

> Fix a Jetson Nano that reboots under load: use a 5 V 4 A barrel supply with the power jumper fitted, instead of micro-USB.

Canonical: https://roboticsengineering.in/fix/jetson-nano-powers-off-with-usb-power-use-barrel-jack/ | Published: 2026-11-03 | Updated: 2026-11-04

**Micro-USB power often cannot supply enough current at full load.** Use a 5 V 4 A barrel supply and fit the jumper.

## What the message means

The board can draw much more current under load than a phone charger gives. The voltage sags and the board resets.

## Fix it in this order

1. Fit the jumper at the barrel jack power select pins as the board guide says.
2. Use a 5 V supply rated at 4 A with a barrel plug of the right size.
3. Do not power motors from the same supply.
4. Use the lower power mode if you must run on USB.
5. Check the supply guide for your exact board version.

## Why it happens

Micro-USB power is meant for a lower current than the barrel jack, and the board can draw much more under load once the processor, the camera and any USB devices are all working. If the supply or its cable cannot keep up, the voltage drops and the board resets.

The barrel jack option needs a jumper to be fitted on the board, as the board guide explains. Check the guide for your board version, because figures and jumper positions can differ between versions.

## If you see this, do this

| You see | Do this |
| --- | --- |
| Restarts when the camera starts | Power too weak. |
| Works on a light load only | Move to the barrel jack. |

## Related

[Pi under-voltage](https://roboticsengineering.in/fix/raspberry-pi-undervoltage-lightning-bolt-power-supply/), [brownout resets](https://roboticsengineering.in/fix/esp32-brownout-detector-was-triggered/).

Last reviewed: November 2026. These are the usual causes and the order that finds them fastest. Test on your own board; clones and cables differ.

## Why this happens

The Jetson Nano developer kit can take 5 V either through the Micro-USB port or through the barrel jack. The USB port is meant for a supply of about 2 A. The barrel jack can supply 4 A, but only when the power select jumper (labelled J48 on the developer kit) is fitted. At full load, the module, the fan, the camera and USB devices together draw more than a USB supply or cable can deliver.

When the voltage sags the board restarts or throttles. Cable resistance makes it worse: 4 A through a cable with 0.1 ohm round trip loses 0.4 V.

## How to confirm the cause

- Check the jumper and the supply label. The label should say 5 V and about 4 A (20 W).
- Measure the voltage at the board’s power input while the board is working. A steady value near 5 V is good.
- Run sudo nvpmodel -q to see the power mode. The lower-power mode draws less current.
- Run sudo tegrastats and watch the load while you start the camera or the neural network. A restart at the moment of the load increase points to power.
- Swap the cable or the supply for another one.

## Worked example

Power arithmetic and the mode commands. Check the guide for your board version, because jumper positions and ratings differ.

```
5 V * 2 A = 10 W    (USB supply, little margin at full load)
5 V * 4 A = 20 W    (barrel supply, with margin)
cable drop at 4 A, 0.1 ohm round trip = 0.4 V

sudo nvpmodel -q        # show the current power mode
sudo nvpmodel -m 1      # 5 W mode on the Nano
sudo tegrastats         # show load while it runs
```

## Common mistakes

- Using a 12 V adapter on the barrel jack. It expects 5 V.
- Plugging into the barrel jack without fitting the jumper.
- Powering motors or servos from the same supply.
- Using a power bank with a thin cable.
- Fitting the jumper and also powering through USB.

## If this did not fix it

- A damaged SD card, which can cause restarts that look like power problems.
- Heat. Fit a heatsink and a fan.
- A USB device that draws a lot of current; use a powered hub.