Control your motors with L293D

Let's Make Robots Tutorials
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89

Hmmm…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 I’m wrong?..

90

They’re probably Tantalum

They’re probably Tantalum caps, judging from the appearance, value and polarisation.

91

Damnit … :slight_smile:

Damnit I think you’re right. The 3rd kind I allways forget. Another noob mistake on my part. Man it isn’t easy learning electronics. A lot of incomplete or wrong information around. Guess I’ll have to find a better symbol list.

Besides these things look VERY similar to the ceramic ones :expressionless:

92

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. I’d probably omit those 4 too.

93

I’ll 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. That’s 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 I’ll get used to it sooner or later…

94

Still wondering :expressionless:

HOW can you tell it’s a tantalum cap judging from the appearance, value and polarisation?

According to the diagram they’re 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 similar…

95

You can also get

You can also get non-polarised electrolytics, which naturally have no (+) sign at all =D

96

Damnit!!
You’re just saying that to confuse me :smiley:

97

There are other
There are other non-polarised types too, such as polyester, aluminium foil, green caps…
At the end of the day only a few things really matter for most uses: capacitance, maximum voltage and polarity. Sometimes you’ll need to know the equivalent series resistance, leakage rate, or other details but normally you don’t worry about them.

98

To guibot!
Now I gotta know for sure: Are the o.1uF caps tantalum OR ceramic?

99

D’OH!

"There are other non-polarised types too, such as polyester, aluminium foil, green caps…"

doh.jpeg

100

L293D for noobs

Just found this tutorial and thought I’d share it. It explains how the L293D works in details so even noobs (like me) can’t possibly misunderstand it.

Plus the accent is great :slight_smile:

101

hi

Hi. LMR world… . i dont have any PICAXE or arduino or any other development board… Is there any alternative way of checking it out?? 

102

First - thank you for this

First - thank you for this tutirial. Now the question. On the first foto you have 2 big caps before and after the voltage regulator. But then you have 2 smaller but not 0.1uF caps on the Vss and enable pin of the L293. On the schematic later you only have 2 “big” caps, but on the first foto 4! Why is that, and do I need additional “big” 100uF caps on the L293. Thank you

103

Caps

The two caps on the first foto are, as you can see here very advisable.
The other caps on the drawing are meant to supress electric noise and voltage spikes… you can try all the circuit without the caps and it will work, but remember it is always a good practive to use them. I am no EE though and I apologize for not being able to explain this in greater details.

104

Problems when using it with a Tamiya Twin Motor Gearbox

Hey, Guibot!

Obrigado pelo bom tutorial! :wink:

I have been experimenting with this same IC and I am having unidentified problems. Mainly when using it in conjunction with the Tamiya Gearbox. The problem is that those motors use only 3VDC.This is below the minimum specified voltage for the IC VCC. I was wondering if there are any limitations to VCC2 or pin 8. Can I simply apply 3VDC to pin 8 and get them out of either output pin (if enable and control pins are high)?

Or do I need to use 5VDC for everything (including pin 8) and drop them down to 3 VDC after the output pins with some diodes?

Thanks for your help,

AndrĂŠs

105

The L293D drops about 1.5V

The L293D drops about 1.5V from the supply you give it to what the motors actually see. So if you supply 5V the motors will actually see about 3.5V, which should be fine.

106

Thanks, Ignoblegnome. I will

Thanks, Ignoblegnome. I will do that then.

Cheers!

AndrĂŠs

107

Same problem

Hi Andres,

I kinda have the same problem. I bought a Tamiya double gear box (double gear) and i am using a Arduino Mega ADK board. I understand that the motors are rated @3VDC.  Did u get them to run now? Also I am using a L293DNE motor driver. My circuits are according to this example and the code too. But my motors/motor doesn’t respond. Any suggestions?

 

Gokul

108

Try this…

Hey Gokul,

Yep. I got them running. If yours don´t spin AT ALL, make sure the following is happening:

  • Pin 16 is getting between 4.5 and 36VDC.
  • Either or both pins 2 and 15 or 6 and 11 get a logic high.
  • That the enable pins (1 and 9) are high at the same time of the ones in the previous point.
  • That the GND is common between the L293D power supply and the mcu power supply.
  • Pin 8 gets at least 4.5VDC.

Here is what I´ve learnt: pin 8 (motor V+) will not accept anything below it´s minimum rating: 4.5 VDC. In my own research, the IC will drop between 0.5 and 0.8 VDC. That means you will be supplying between 4 and 3.7 VDC to the motors. In my case, that was still too hot for my motors. I solved it doing something that should not have solved it. I hooked a bicolour LED (common cathode) in parallel to the IC´s motor output. So, if the motor spins CW, the green half of the LED lights up. If it spins CCW, I get a red.

Hope this helps.

AndrĂŠs