What happens at low input voltages?

Autonomous Machines Jetson & Embedded Systems Jetson Nano
1

I connected the Nano to a 12V car battery through an automotive-grade 12V to 5V DC-DC converter. The car battery was very old and was producing only ~8V. The car ignition took a couple of seconds extra to turn on the car.

I tested the device in 2 ways.

  1. After the car was on, I will connect the 5V to the barrel jack and it would power up the nano. I had a raspi v2 camera recording at full resolution, a TF object detection model running and an external hard disk connected for storing the data. It worked properly. I took the car for an hours drive, I switched off the car and started it again in a few minutes. The nano kept going without any power disconnection.

  2. The next day morning, I started the car with the nano connected. The DC-DC converter failed and the board failed too. The board wouldn’t boot again with any other power supply.

My question is how the battery that had only 8V in it killed my board. What will happen if I connect the nano to a 4v(or even less) power supply? Will it harm the board?

Also, I read about brownouts happening at insufficient voltages, how to identify brownouts happening? Are there any logs that are saved about the power shortages other than tegrastats?

2

To answer your questions we’d need to know more about your DC-DC converter. I have a DC-DC converter that I’m using that takes anywhere from 5.125v to 36v and outputs 5v. The output is adjustable with a screwdriver and the only requirement is that the input voltage is 0.125v above the desired output voltage. So using my DC-DC converter, 8v would very easily produce 5v output to power the Jetson Nano.

If you killed your DC-DC converter, then it was likely killed by a voltage surge that exceeded the input tolerance of your DC-DC converter. If this is the case, then this voltage surge may have made it through your DC-DC converter to your Jetson Nano. Who knows? Is your DC-DC converter meant for automotive use? The power in a car is pretty nasty. Especially when you’re starting it.

3

Hi, there might be a huge charging voltage surge when the car is started, that might damage the converter and then damage nano board. Generally a relay for the 12V output will be helpful. 4V input won’t harm nano but board can’t turn on as it is requested to be 5V (4.75V - 5.25V).

4

I use https://www.amazon.com/Aweking-Waterproof-Converter-Regulator-Transformer/dp/B06X1DPFQQ/ref=sr_1_20?crid=R9IMR5XFCD1L&keywords=24v+to+5v+converter&qid=1581358128&sprefix=24v+to+5v%2Caps%2C344&sr=8-20

I bought a couple of these from different vendors. The one that failed was the cheapest I bought. Probably it didn’t have the over voltage protection feature.

5

We have no such recommended converter, you need to search for right one by yourself. 5.2V is in the limit and will not harm board.

6

I see this in the description:

It seems like a decent automotive grade power supply capable of producing 5V output at up to 30A with 8V to 15V input.

7

Would you suggest I get a 24V to 5.1 / 5.2V DC-DC convertor to avoid voltage sag? Will this solve my trt model not starting issue described in the following post? [url]https://devtalk.nvidia.com/default/topic/1071151/jetson-nano/gpu-initialization-failed-on-jetson-nano-powered-with-24v-to-5v-dc-convertor/post/5426729

8

Your question is answered in that topic, you can continue discussion there.

9

@Trumany, I am trying to understand if using a 5.2V supply have an advantage over a 5v supply in the brownout cases.

When you say 5.2 is in range, what can be the max voltage I can supply so that I ensure there won’t be any voltage sag.

Also, is there a way to find out if there was a brownout with logs?

I see some extra components(capacitors I guess, I am a novice on electronic components) on the 945-13450-0000-100, what are the hardware related changes being made in the new version, is there any documentation on it like release notes?

10

It is maximum 5.5V, you can find the info in module data sheet in DLC: https://developer.nvidia.com/embedded/dlc/jetson-nano-system-module-datasheet.

There is no log info for sudden power loss. The new version module is for production or development, the previous version one is only for development. No such notes needed as customer should only design product based on reference design of new version module. Also you can refer to the guide in DLC for more info of two kinds of dev kit. https://developer.nvidia.com/embedded/dlc/Jetson_Nano_Developer_Kit_User_Guide