Prop Chip overheating
fstanovich
Posts: 14
I have a Boe Bot self made chassis aluminum with Propeller Proto Board. My main use is to tinker with sensors. The board has too XBee's one for data transfer and the other programming. I was testing a program and pushed the reset button while pressing the button the prop chip felt very hot. So, I turned off Proto board to investigate. Turned it back on and everything working except data XBee. Moved Tx Rx pins to other pin location and it worked. Tested the original pins with LED and it appears the P7 pin has burned out it don't work.
Has this happened to anyone else? It's strange that the Prop chip didn't fry.
Frank
Has this happened to anyone else? It's strange that the Prop chip didn't fry.
Frank
Comments
The reset button is not in a good place. Could my finger in some way caused the problem?
The Prop chip now run cool and the Boe Bot preforms all actions.
In order to help determine why something may have been overheating it would be helpful to know EXACTLY how you have everything connected.
- Do you have a schematic?
- What pins are the XBee modules connected to and powered?
- What other devices are connected to the Propeller? Is everything running at 3.3V
- Do you have any resistors between the Propeller I/O pins and the devices they are connected to? Can be important for 5V devices.
- Do you have a listing of your code? Do you have all the I/O configured properly? If one is accidentally set as an output when it should really be an input then that can cause problems.
The more details you can provide, the easier it will be to identify the issue.
Robert
You are correct in all the above issues. I just got started in Robotics and trying to get up to speed as fast as i can.
This stuff is very fascinating and addictive and up to this point i have not been very careful and systematic.
And i should know better considering i have a electronics and programming background. But, this stuff is so much fun that i want to try everything.
That said i probable caused some of my own problems. I will use your comments as a guide and start to check my work over.
One note the Xbee's are 3.3V powered should i still have resistors on in/out pins?
Thanks for responce
Frank
I have been working with the Xbee quite a bit, and when I am connecting to the prop data pins I always think "Din, Dout, relative to who?" It has occurred to me that it would be very easy to reverse connect the Rx and Tx, which could lead to problems if the prop was trying to drive a line at the same time the Xbee was. The Xbee may have built in protection (but I have not read it in the manual), or the baud rate may be high enough that the issue would be momentary and not a problem, it it still always concerns me. I have considered going to pull-ups/open-drain on the bus lines, but I will probably wait until I fry a component before I make the effort.....
For the type of prototyping you are doing, it's not at all a bad idea to just start putting in 1K to 10K current limiting resistors whenever you hook the prop up to another device unless the schematic shows exact values.
I also have a pre-power check that I remember most of the time. Make sure the board is not sitting on anything metal including bits of wire or solder. Make sure test leads are cleanly and securely fastened. Make sure your power supply polarity is correct. If you can, set your power supply to a very low cut-off current limit.
Good luck!
Jim-
In regards to the resistors there are some places you definitely should add them. Each one of the LED's directly connected to the Propeller pins should have a current limiting resistor. At least 220ohm if not larger. There are plenty of examples of connecting LED's to the prop which show good values to use. Also, since the servos are probably running at 5V (or higher) you need to add a 1K or larger (2.2K or 2.7K) resistor on the prop pin going to the servo. This will help protect the Propeller pin. Chris Savage just had an excellent article in the Nuts'N'Volts about interfacing 3.3V and 5V devices that you may find useful.
Robert
I am using one for LoadProp program to load programs into Bot (i got tired of plugging and unplugging the USB cable) and another for data from sensors.
The 3 XBee's are set to default setting for now while i learn the best way to configure. When I am programming the Bot i have to select none for comm port on Parallax Serial Terminal and i unplug the ground from the data XBee. That is where maybe my problem happened because i would unplug and plug in ground while Prop was still on.
What i think i will have to do is write a program for PC to change the host XBee address to the remote XBee i want to use.
Well anyway still learning.
I race cars as another past time and would like to use XBee for telemetry to monitor G-force true turns and the such. So i will be having a lot of question for you good people.
Code is attached.