My son and I just got our Diecimila and made a wallbot. 2 servos modded to rotate (GWS high speed 2.2 kg-cm torque, 5v) and 1 sharp GP2yoa21yk ir sensor.
Works great but I have noticed a little burning smell :-/ after running it for 3 minutes or so. And it actually paused for 1-2secs (my code has it running forward or turning all the time)
It seems like the voltage regulator is getting hot.
My power source is a gws 8.4v/730mAh battery (salvaged from an model airplane...the voltage is actually up around 10 at full charge).
I have wired the 2 servos and 1 sensor to the 5v pin and same ground pin of the Arduino.
The Voltage Reg is rated for 800mAh but I dont have anything to measure current...anyway I guess I must be overloading it.
Sooooo...is there anything I can do that would allow me to continue to use only 1 battery hooked to ext power, or will I have to go for 2 (1 for arduino, 1 for motors)
Thanks,
Ben
(PS otherwise I am totally amazed at how easy it is to get something like this up and going...60 lines of code and a breadboard...cool!)
The Diecimilia page suggests that it can take in input supply of upto 12V, so you are not exceeding that parameter.
However, the higher the input voltage, the more the regulator has to handle and if it is also handling the power for the motors it may well get hot.
(So far just echoing your thoughts).
It is common, if not usual to power motors and other power hungry devices from a different source. Partly for cost reasons - often you don't need to have such a well regulated supply for the output devices as you do for the electronics, and partly to stop the output stuff unsettling the more sensitive electronics.
There are a few things you can do -
you could pre-regulate the power to the board, say down to 7V with a biggish regulator on a biggish heatsink. This will reduce the work the on board regulator has to do.
bodge carefully attach a big heatsink to the onboard regulator.
Supply the servos from a separate battery / supply.
Well I guess I am going to order some batteries.
Soooo..I have choices but my understanding is:
My 8.4 volt battery would be fine for driving the arduino and the sensor and other little stuff that runs on 5v because the current draw is low and the waste heat will be minimal. If I end up needing to run something at 8.4 or 9 I could just pull it from the Vin of the arduino (bypassing the voltage regulator I imagine)
My servos are rated for 6v so I might as well buy 6v nimh.
Question: I see that I will be able to charge this up to 7.1 volts. Will this be a problem if i hook it straight to the servo or will I have to go thru another voltage regulator (something like a 7806)
I see 6v AAA 5packs with 700 mAh at $7 each and AA 5packs with 2300 at $11...I guess I can go with either, just a question of weight and how long I want to go between charges. Cool...thanks.