I am new to LMR and new to robotics, so i am slowly learning.
I have created an Autonomous Robot using the motor driver L293D, arduino duemilanove & Sharp IR Sensor.
Everything seems to be working fine when hooked up to the usb cable, does exactly what it should do.
When i try to run everything off batteries it does not work. I made the first mistake in trying to run 2 motors using a 9v battery, and after reading the post on here about which battery to use, i went and purchased some NiMH rechargeable batteries.
I tried lastnight to hook up a 9v battery to the arduino and 6 AA batteries to the 2 motors. It smoked and i quickly pulled the plug. Luckily it didnt fry anything, just seems as though there was too much energy passing from the battery to the motors, as it was the battery wires that were over heating.
My question is - Is this too many AA batteries to power 2 motors?
The only reason I can think that your wires would have smoked would be that you were trying to pull too much current through them. If you have seen RC battery packs, you will notice that they have something along the lines of 10 or 12 gauge wire that plugs directly into the speed controller. The reason for that is so when the motor pulls current the wire is sized large enough to handle it. The motors on your robot shouldn’t be pulling more than 2A at startup. I say that because the L293D isn’t rated for more than about 1A peak and 0.6A nominal(regularly). According to this chart, 22 gauge wire can supply 5A for up to 6 feet and 10A for up to 3 feet. Working backwards, I would guess 22 gauge wire could supply 2A for about 12 feet, 6 feet to and 6 feet from.
Putting all of this information another way. Is it possible you had a short somewhere rather than a battery issue?
One other thought, you say you purchased some NiMh batteries. You didn’t mix and match with alkaline batteries did you?
I bought all the batteries together, all NiMH same brand. It was the actual wire from the battery pack that smoked as it heated so much the plastic on the wires melted together a little bit.
I have added more capacitors to the circuit and a 5v regulator, but i havent had chance to test it as when it smoked it drained my batteries. Would the capacitors stabalize the current flowing through the circuit, or is this just to protect the chips and components on the circuit?
One of the major questions I asked, you didn’t answer.
Is it possible you had a short in your circuit that connected the battery pack?
You shouldn’t have had enough of a current pull to smoke/melt the wires from the batter pack unless the pack was all the way across the room. Like I mentioned in my previous post, your motor driver can only handle a couple Amps peak, as in only a couple Amps for maybe a second or less.
So is the reason why it is working fine on a usb connection is because the arduino has a 5v regulator included on its board, as i am using the usb to power everything?
So when i use external power this should then be run through a v regulator?
There is no need for a regulator if you run it off the USB. USB supplies a pure 5V so there’s no need to tinker with it. The regulator onboard the duemilanove regulates power from the battery jack.
I was going to say something about your post and the replies but I realised there aren’t too many positive things I had to say…
so I’ll just say this:
The answer to your question is NO
I have checked it very thoroughly, and that quite definitely is the answer. I think the problem, to be quite honest with you is that you’ve never actually known what the question was.
Wasnt able to get onto the internet the weekend to post a reply, but it does seem as though i had a short in the circuit. I have now re-wired the L293D and it seems to be working fine now. Thanks for all the help.
