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sanguino power-- what power rating?

Posted by hobi 
sanguino power-- what power rating?
December 30, 2008 01:14AM
I bought and built a sanguino just recently, but was concerned about how much power to feed it. I'm a software developer, and know very little about hardware. The documentation that I could find said '5v-24v'. I did a little experimenting:

9v 1000mA = green solid, red flashes
9v 400mA = green solid, red flashes
6v 350mA = green solid, red flickers
5v 1A = green dim but solid, red off

I know that usb is 50mA and 5v, but I did not buy the ftdi cable (accident, thought I could just cut up a usb cable. I discovered I was incorrect and ordered one). It seems odd that it would behave this way on 6v at 350mA. The 6v350mA test looked like maybe it was resetting or something. The 5v1A dim light has me completely confused.

Would someone kindly explain to me how the power works? Or perhaps I messed something up?

Also, the capacitors provided in the kit were not the ones in the schematic. I bought it from wulfden, they supplied 25v 47uF capacitors. He assured me that they would "have no noticable impact on performance" when I questioned it. This may change the results from someone using the kit as described in the schematic.

Re: sanguino power-- what power rating?
December 30, 2008 02:43PM
Just a guess, but if it's actally drawing 1 A at 9 V (and your supply isn't just set to to a max of 1A, but is supplying less), you've got a short somewhere. Follow your nose, as it'll get hot at 9 W! Don't leave it on for long, you might burn out whatever is shorted.

I haven't built my Sanguino yet, but it should draw less than 1 W I would think.

Re: sanguino power-- what power rating?
December 30, 2008 04:00PM
I may be wrong, I don't think it was drawing all of those amps, because 9v 1A and 9v 400mA were producing the same results. I purchased a multimeter today online, and will hook it up to check the draw using a 9v battery when it arrives. Thank god for that electronics course I took 4 years ago! I'll post back results.

Thank you for the reply!
Re: sanguino power-- what power rating?
December 30, 2008 07:54PM
Ah, that amperage you were quoting was the supply maximum, not the measured current draw, so it all looks good.

The DC jack on the Sanguino has a protection diode and a regulator (nice!), so you need to feed it 6 V or more to get 5 V on the chip. Thats why your 5 V test didn't work.

The Sanguino page lists the lower voltage as 6 V. You can run it off 5 if you bypass the regulator and diode, but I'd wait till you get the multimeter first. smiling smiley

I'll probably have some coding questions for you when I get mine running...

Re: sanguino power-- what power rating?
December 30, 2008 08:04PM
Thanks Wade, that explains why the green light was faded and the processor was unable to do anything. Do you have any clues as to why the red light would begin flickering at 6v 350mA? The flicker looked like it was hard resetting over and over.
Re: sanguino power-- what power rating?
January 02, 2009 01:16AM
It was most likely flickering at 6V because you were still too close to 5V at the AVR chip. Look up the voltage drop of the diode and the regulator, or just measure it, and that will tell you how low you can go.

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