unfiltered 5V power - any concerns?

[wjsx]

Hi.

Just curious if anyone has considered possible side-effects of using 5V unfiltered power on this project. I haven't experienced any, but was just wondering if it could be an issue at some point.
Thanks.

[mightyohm]

I don't think there is any regulation between the 5V input and the USB port, so using unfiltered or unregulated power is probably a bad idea.

[wjsx]

Thanks for the reply, Jeff.

Your comment matched my concern about a power source.

I was looking at the pictures you posted of your radio once installed within the custom cabinet. I concluded that your were using the 5V output of the dual-voltage power supply. Do I have that right? If so, does that PS provide filtered/regulated voltages?

-- Bill (wjsx)

[mightyohm]

Yes, it provides a very well regulated 5 and 12V supply.

[wjsx]

Glad I asked.

To program the AVR, I used the USBTiny kit for Ladyada.com, and I'm pretty sure that didn't have any filtering the power from a USB port.

Would you know what others have done about power? I'm not sure how hard it would be to try and use power off the router mainboard. I'd prefer not to have two power supplies, so perhaps I have to construct my own regulator and backfeed 5V to the router.

Any thoughts would be welcome.

Thanks, Jeff.

[mightyohm]

USB ports provide a regulated 5V supply that is spec'd to be within 10% of the nominal voltage, if I remember correctly.

What are you trying to do? I'm not sure I understand what you need a power supply for, the router comes with a 5V wall wart you can use to power it.

[wjsx]

I may be confusing some issues, Jeff.

My understanding is that the average wall-wart does not supply what's regarded as filtered power and that the advertised voltage can vary quite a lot. Sparkfun's tutorial on building a voltage regulator really stresses that point. It is also my understanding (or misunderstanding) that the USB power is also unfiltered.

But from your response I'm thinking that perhaps I'm assuming an issue when there isn't any. I've certainly not had problems with power through the AVR programmer, so maybe I've answered my own question.

Thanks for the help and any other thoughts.

[mightyohm]

The wall wart that comes with the WL-520gU contains a DC-DC converter and outputs a regulated 5V.

How well regulated is a good question. My experience has shown that it is completely fine for powering any USB device I have ever connected to the router. It is certainly as good or better than the power supplies for cheap USB hubs.

[wjsx]

Thanks.

I was just checking on standard USB specs and I learned that the voltage to a device is regulated, as you've suggested. So perhaps I can draw upon the USB power to run the AVR assembly.

I've certainly learned a lot through this project.

[wjsx]

As a follow-up to everything in this thread, closer examination of the Asus wall-wart reveals that it seems to be a switching power supply, given that it can operate from 120 to 240 volts and 50 or 60 Hz. From everything I've read, a switching power supply provides "clean enough" power so my previous questions/concerns seem unnecessary.