Hardware Crash

I just finished diagnosing an issue that’s been driving me crazy for days. I have a FEZ Raptor in the attached configuration.

The problem I was having was very specific. I had to be running with only the 12V 1500mA brick powering the device. The problem never happened if USB was connected to either a computer or a simple mobile phone charger. I could turn on the relay via the internal web server over Ethernet, but the next time a client hit the web server, the device would crash and reboot. This never happened in debug mode, and again, it never happened even if the device was being powered with a simple mobile phone charger.

I can live with having to power the device with USB, but I’m pretty sure the device isn’t supposed to be behaving like this. Ideas anyone?

things like this often end up being ground reference issues. What is the relay connected to ? Is that powering something ? And what are the specs on the 12v battery pack ? Often you can find the current draw caused by some excessive peak load drops the voltage down and the regulator might fall out of regulation or brown out sufficiently to cause a reboot. A 1500mah pack isn’t very big either…

The relay was powered from the same 110V AC that the transformer was connected to. The relay was powering a small reading lamp with less than a 40W incandescent bulb (for test purposes only…when deployed, it would control an HVAC condenser fan).

I would think that the various USB power sources I’ve tried wouldn’t be capable of providing more power than the 1500mA provided by the brick.

:think: .

the 1500mA has nothing to do with it’s ability to provide power under load.

Here’s a simple test. It requires you to have a half decent multimeter (which everyone should have). Even better if you have two of them and can watch both at once. Measure current draw from the battery while your app runs and see what happens at the point when the reset happens. See whether that is stable or increasing or decreasing. Then, do the same test measuring voltage at the terminals of the battery and see whether that stays constant at 12v or drops lower instantaneously as the load increases.

I don’t have a half decent multimeter. It’s been on the list for awhile, but the time never seems to be right.

The model number is S018EM1200150. It’s unbranded.

I find it less likely that a marked 1500mA brick is going to provide less power under load than USB 2.0 which is rated for 500mA. But hey, I’m a software engineer - not an electrical engineer. Maybe I just don’t understand the way things are.

ok, so now things might be a little clearer.

Amazon.co.uk implies the part you’re talking about is a WD power supply of some form. However who knows how it’s power regulation is. Usually, a 1500mA unit would be fine, but I’ve not seen anything that states that it is a regulated output device. An unregulated output can mean that the voltage delivered to the Gadgeteer power module can vary greatly depending on the load drawn, which then can’t be compensated for within the capabilities of the USP-DP module.

I’d look to buy a better PSU that you know is regulated - but is there any reason your phone charger option isn’t or can’t be a more permanent solution ?

The mobile phone charger is a valid solution. I intend to use it permanently. However, I would consider this issue problematic to the hobby. Many software minded people like myself would have thrown in the towel after experiencing what I did. Perhaps these modules could be sold with known good power adapters. They already come with USB cables, and I’ve had no issue with it. The increase in cost would save some people immense frustration. Alternatively, perhaps some visual indicator (such as a drop-out LED) or debug tool that could cue someone in to what’s happening might work. I just wanted to document this somewhere.

Sorry, I don’t think a drop-out indicator of anything like this is possible in a consumer device like this. Coming from Australia, an included power pack isn’t useful to me either. But I do understand the frustration you have expressed - just don’t know there’s a way to effectively address this for everyone.