I've been building my first robot, and have been looking for a way to make it more power efficient.
When hooked up to a power supply lower than 12V 8AA, the Arduino's power LED turns dim at every once and awhile, and the servos turn on and off continually, when they're not supposed to. It works fine with 8AA.
I also measure the input current. It was about 1A, which seems like way too much.
I've looked at the robots here on LMR and their are some that can power twice as much as I have hooked up to my arduino when connected to 4AA
Here's a schematic of my robot. The yellow boxes represent everything on the list to the right, but I only drew 2 of them to save space.
I don’t much about the big green box that says “Arduino Mega”, but are you really putting 12V unregulated directly into the arduino? And why are there two 5 volt regulators in parallel ?
Sorry, that was a typo. Its fixed now. It draws 1A maximum when all servos and the ping are in use. There are two regulators so that it can regulate up to two amps instead of just one (which is when the regulators max out). Is putting 12V into the arduino bad? It says its rated for 20V
The Arduino Mega has an onboard regulator, so 12V in is fine. Suggested input voltage is 7 to 20 V.
Can you get rid of the two 5V regulators feeding the servos, and just run the servos off 6V directly? I’m not sure why; I just don’t like them being there! The servos don’t need a regulated voltage, so they seem unnecessary.
Can you measure the battery voltage feeding the Arduino board when the servos are going? Is the voltage dropping?
I looks like only 9V of power is making it to the arduino. ill try the six volt to the servos, but can the arduino run off of six volts or does it need more?
Check your connections. May be there’s a misconnection somewhere between your regulators and servos/sensors. A guess: May be there’s a short circuit. It may drive your regulators to the max or to their short circuit current (depends on what regulator you are using) and would explain the current draw. I’m not that familiar with regulators yet so I’m so sure how they act in short circuit conditions. I just noticed that ones I use have short circuit protection and short circuit current is there in the datasheet.
I can’t tell from your schematic how your ground connections are. Regulators’, Arduino’s, servos’ and Ping’s grounds are connected together but are they connected to battery pack ground? I’m just assuming they are because otherwise the whole thing wouldn’t work.
If the connections seem to be ok then I would do something like this to test the hardware:
Remove all servos and sensors.
(Test if your Arduino is ok. I haven’t used any Arduino boards so I don’t know how to do this. If you can program it it’s probably ok. At least it tells you the chip/board isn’t totally fried.)
Check if outputs are working. I’d use a led and a resistor on each output and make the led blink.
Test each servo one at a time. Make them move back and forth.
Test Ping by itself. I’d read the sensor value and send it to computer to see if it’s working.
Start adding all servos and sensors on one at a time and test if all is working before adding the next one.
Finally, I found this when I checked if regulators can be connected in parallel: “And finally, you can run several 7805s in parallel. The easiest way to do it is to make the inputs a common connection and the grounds a common connection. But don’t connect the outputs directly together. The 7805 don’t all regulate at exactly the same voltage and the one that regulates at the highest voltage will do all the work while the others loaf along and you’ll don’t have solved anything. Instead, put a small-value (e.g., 0.47 ohm, 1-watt) resistor in series with each output and THEN connect the other ends of those resistors in common as your final output. That small value of resistance will allow each regulator to work independently of the others and the current will be shared by all of the regulators fairly equally. The down side of this fix is that it makes the regulation a little bit “softer” (i.e., a higher internal resistance for the supply), but in most cases, won’t be much of a problem.” (Original post: http://www.electro-tech-online.com/general-electronics-chat/7449-multiple-regulators-parallel.html#post35998)
You NEVER want to connect the outputs of 2 regulators together and you ALWAYS want to put decoupling caps on the inputs and outputs of regulators. The reason is because the regulators will actually go into oscillation under the right conditions and will either shut down the output or self-destruct.
If you want to use 2 regulators, use each one to power several devices, (split up the load), otherwise, use a single 2-amp regulator.
If you’re running everything off 5 volts anyway, why start out with 12 and regulate everything down to 5? You waste a lot of power and generate heat. The Arduino and servos will operate just fine off 6 volts.
