What’s the maximum ratings for the USB port on the AR300M? 2.0 maximum value of 500mA?
I ask because I think the Novatel U620L may be drawing enough to cause a brown-out on the port because of the way it acts when I try to run with it instead of the WiFi as WAN I’m limping along with right now.
Is there any current limit explicitly set on the routers? Is it the same for all the models?
With my AR150 I had to switch from Huawei E3276 to E3372 which is known to be less power hungry. With E3276 connected I experienced frequent disconnects. At the same time E3276 works fine with the old similar size router TP-Link MR3020, so I suspect some current limiting enforced in AR150.
@RangerZ yes, they are. Mine is a simple one, it cannot display V and A simultaneously, so I see only one value in a given moment. As I recall with E3276 I was able to see spikes like 600-700 mA. Potentially those meters may introduce some voltage drop between in and out, that could create a problem for the attached USB device.
Voltage dips come from loading of the device, pulling the supply rails down.
@alzhao so I’m presuming that while it can source up to an amp, it doesn’t hold regulated as well as it could (or at all) unless it’s got some really solid clean power. I had a lot less issues with this (almost none) with a Pi3 power supply, which holds the USB power rails a bit higher voltage and sources like 2.4 A of current at 5.25v. But running it off of a stock 2.4A supply…it wasn’t as happy. Running it off of a USB battery pack, same story… Worse, the device ran warmish at the port on my laptop’s USB3 port. That’s indicative of higher loads than one would expect, going to the 500 mA range or spiking for times hotter.
Guess I need to break down and re-aquire one of the good USB meter units and monitor the device(S). I can tell you that the U620L got “warmish” under use on the laptop which means it means it’s likely to be causing occasional brown-outs on the rails. Annoying. I’ll start qualifying it- I’m more than happy to help add to the knowledge base on this score…I know I’m pushing the envelope in a few ways…
I’ll try get back to everyone a bit quicker to update on the subject- because people WILL need to know. Was busy on my end the last couple of weeks…(sigh…)
Nod. Well, there’s a bit of a drop across the whole of the system from the USB power to the USB jack. .1-.3 V average below 5v with the occasional sag below that.
I’m thinking the U620L is touchy about the power it’s getting.
@alzhao, I’m not seeing enough current to be causing a sag of this nature. while it’s mostly within the USB spec, there’s a couple of times it dips below thresholds allowed for voltage, being as much as .5 v below nominal voltages…enough to brown out the advanced device that the U620L is. Are you sourcing the rails off of the USB power rails powering everything or through some other means that might be causing a voltage drop. It’s not a problem, per se, because it obviously works for most of your customers- but they don’t have an ARM v7 core in their dongle… X-D
@AndrewZ, it’s not enough to matter much. I’ve measured with a precision meter and taps before. They end up being roughly within the domain of the resolution of the device- hundredths of a volt. For most things, these devices do rather well for sniffing out problems. I don’t have a current problem, per se, but a voltage one. Need to see if I can get a unit that has a USB jack that can properly power the Pi3 to see voltages on the USB port of the router.