View Full Version : Solved Powering the Propeller Quickstart Card P8X32A 40000 Rev A?
11-10-2011, 06:52 AM
Warning: Total microcontroller newb posting!Well, day 1 of my efforts with this, I tried compiling a linux kernel module only to find out it was already supported by my linux kernel for perhaps more than a year or two. I finally got to play with my new toy.On day 2, I tried to hook up an external power supply and I fried it. I thought that VDD and VSS were the spots for connecting a power supply. From a video in the Parallax library, it sounds like connecting directly to those is never a good idea.It seems like Vss is pin 39 and Vdd is pin 38. The combo would get me a regulated 3.3V input.It seems Vin is pin 40 and with Vss (pin 39) I would get something that I could hook up to a series of AA batteries or a 9V battery.Could people please tell me how accurate my understanding of the power options is and perhaps provide some advice on better wiring and battery selections?I may want to control motors or speakers or something later on, but I am honestly not sure yet.
11-10-2011, 09:46 AM
http://forums.parallax.com/showthread.php?133974-Powering-up-the-QuickStart should answer your questions. You should use Vin for external power supply.
11-10-2011, 11:39 AM
Yes, you want use pins 39 (ground) and 40 (Voltage In).
Currently my favorite way of powering a QuickStart board is with one these (http://www.radioshack.com/product/index.jsp?productId=2062253&filterName=Type&filterValue=AA) from Radio Shack. I solder a pair of male headers to the pins 39 and 40 (the holes in front of the 40 pin female header). I solder a match pair of female headers to the battery holder's wires. The battery holder has a built in switch.
I use four NiMH AA recharableable batteries in it. The four AA NiMHs output about 5V.
BTW, Welcome to the forums.
Edit: See the link MagIO2 gave about using a battery pack and the USB at the same time (you should use a diode). I just use one or the other.
11-10-2011, 12:01 PM
To do it really safe you can add a diode. From a 6V Battery you get then ~ 5V for Vin.
This way you have no problems if you power the Quickstart at the same time from USB and the battery is deep discharged.
11-10-2011, 12:59 PM
Thanks all for the quick reply. I hope to get my next card in the mail on Monday. I ordered it with the cheap USPS First Class postage.Anyone know what I might be able to do to salvage some/all of my current board? It did take 9v to the Vdd and I thought I smelled something on the fry. It sure doesn't get recognized as a propeller board anymore.
11-10-2011, 01:56 PM
Unfortunately, one of the reliable ways to fry an integrated circuit is to connect it (via Vdd and Vss) to either a voltage way above its maximum rated voltage (like 6V or 9V for a 3.3V part) or to connect the supply voltage backwards with the (+) terminal to Vss and the (-) terminal to Vdd. You might be lucky and one of the parts sacrificed itself and saved the others by shorting out the supply voltage before other damage could be done, but there's no easy way to tell which one (other than looking for the crispy one and replacing it, then trying the board again). You could always call Parallax's tech support people and they could have you send it in for repair.
11-16-2011, 12:50 PM
Waiting for my replacement board. Any idea if the choice of AA batteries could cause trouble for the board? I have some rechargeable ones and some pretty good ones. I don't wanna have the batteries put out too much power. I don't know if a set of overcharged AA batteries could fry it or not.
11-16-2011, 03:57 PM
As long as you are using the correct pins, four AAs wont be a problem.
11-16-2011, 11:56 PM
Chips, processors, boards, etc, generally draw what they draw. You can connect them to a 400A 5V power supply and they will draw the same current. To the power supply, your QS board looks mostly like a large value resistor between it's poles. The fun with an excessive supply starts when you, by accident, connect positive to negative in a way that provides far less resistance than the rest of the board and things start to smoke and glow. The rechargeable batteries can pump out surprising amounts of current if they get shorted so if you are wiring it up and the pretty lights go out..... disconnect the power right now.
Long story short, so long as you provide input voltage in the proper range to the correct pins, your supply's current capacity will cause no harm.
11-22-2011, 02:43 AM
Ok. I managed to get my replacement quickstart board in the mail today. I functioned normally via the usb coord and it would power up and blink the LED's via battery. The simple LED that I was using to safeguard the polarity drew enough power that it would not have the board run. It would work without the LED. Still worked after. I didn't blow it up.