Usb gives you 5V at 500mA (i
Usb gives you 5V at 500mA (i guess), it might not be enough to power your motors.
9v little batteries arenāt good for motors as well, you can use common RC race packs, or a couple of AAA bateries.
Take a read into the following posts:
Picking Batteries for your Robot
Once youāve decided on batteries, how do you regulate the voltage
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Capacitors?!
Iām planning to use the same H-bridge for a robot (my 1st robot and 1st H-bridge), so Iām very greatful for this istructable. Thanks 
But excuse me for asking a noob question: Are ALL those capacitors (9?) really necesary just to control to DC motors? Or is it because youāre using UNREGULATED power? Or some other specific circumstances?
required? No. suggested?
required? No. suggested? yes! They suppress noise and help with the discharge when the magnetic field collapses after the motors are shut off. (Note: In not an EE major so someone may prove me wrong but that is my understanding.)
Wellā¦
ā¦Iām quite a noob in these matters but I am aware that one should use caps to stabilize the current flow. But still 9 (!!!) thatās quite a bitā¦
Here are a few similar setups and they often do use caps, though not allways, and none of them comes close to 9:
www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1255204188
www.me.umn.edu/courses/me2011/robot/technotes/L293/L293.html
itp.nyu.edu/physcomp/Labs/DCMotorControl
akashxav.com/2009/04/18/arduino-l293d-dc-motor/
www.solarbotics.com/projects/circuits/2007/07/circuit-l293d-mini-sumo/
Just to name a few
Silly meā¦
Just noticed ā¦ the 2 large caps are for the voltage regulator. A typical setup.
So weāre down to 7 caps which is still quite a lotā¦
You can build your circuit
You can build your circuit without the caps. But as jklug80 said, they are ment to stabilize voltage spikes.
i get this circuit schematic from the ladyada motor shield. 
Wellā¦
I was planning to use a cap or two. However 7 seems like a bit of a hassle, so I think Iāll try it with less for starters and see how that goes. Did you start with 7 or is it because you had problems when using less?
I started with just the
I started with just the L293D, the motors and the microcontroller, and it works ok
I used the caps because they were on the schematic and I wanted to learn how to use them on the h-bridge. I is just a matter of getting used to, now, I canāt think in making this circuit without the caps.
Hmmmā¦error in the diagram?
It seems that the small caps (0.1uF) are depicted with the symbol for electrolytic caps, but they sure look like ceramic caps on the fotos? Correct me if Iām wrong?..
Theyāre probably Tantalum
Theyāre probably Tantalum caps, judging from the appearance, value and polarisation.
Damnit ā¦
Damnit I think youāre right. The 3rd kind I allways forget. Another noob mistake on my part. Man it isnāt easy learning electronics. A lot of incomplete or wrong information around. Guess Iāll have to find a better symbol list.
Besides these things look VERY similar to the ceramic ones 
No plus sign = ceramics
No plus sign = ceramics probably. Note the plus on the actual electrolytic. Sometimes folks use whatever symbol is handy (in graphics) for the device they have.
It does appear they have a place for caps on the LadyAda Motorshield between ground and motor outputs, but they appear to not be populated. Iād probably omit those 4 too.
Iāll keep that in mind
And the problem with the symbols is that the description I posted above (as well as many others) says the symbol with a plus sign is an ELECTROLYTIC cap. Thatās apparently incorrect. It simply means a POLARIZED cap? Furthermore the ones with no plus could mean both a tantalum or ceramic one, allthough tantalum caps are polarized too? Oh well Iāll get used to it sooner or laterā¦
Still wondering
HOW can you tell itās a tantalum cap judging from the appearance, value and polarisation?
According to the diagram theyāre NOT polarized (tantalums are). The value could be both ceramic and tantalum (or am I wrong?). And the appearences of the two types are extremely similarā¦
You can also get
You can also get non-polarised electrolytics, which naturally have no (+) sign at all =D
Damnit!!
Youāre just saying that to confuse me 
There are other
There are other non-polarised types too, such as polyester, aluminium foil, green capsā¦
At the end of the day only a few things really matter for most uses: capacitance, maximum voltage and polarity. Sometimes youāll need to know the equivalent series resistance, leakage rate, or other details but normally you donāt worry about them.
To guibot!
Now I gotta know for sure: Are the o.1uF caps tantalum OR ceramic?
DāOH!
"There are other non-polarised types too, such as polyester, aluminium foil, green capsā¦"
L293D for noobs
Just found this tutorial and thought Iād share it. It explains how the L293D works in details so even noobs (like me) canāt possibly misunderstand it.
Plus the accent is great
