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I'm following this tutorial to control a DC motor with an Arduino.

I have the same problem as this stackexchange post arduino.stackexchange.com/questions/10049/problems-with-l293d where the motor is not rotating.

  • The chip is heading to the right. (5v pins are on the right)
  • Connecting directly the motor to the battery works.
  • Current (5V on the bottom & 2*1.5V) is flowing everywhere expected EXCEPT on the yellow & green wires of the motor (the red wire of the battery pack is connected to the second line of the breadboard).
  • Connecting directly the motor to the battery works.
  • I copied the code of the above tutorial which is basically : "digitalWrite(4,HIGH);", there is current on the cable.

Am I wrong into thinking that a L293D chip can output sufficient current ? Is the chip malfunctioning ?

My montage

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Your picture shows a holder for two AA cells, yielding something in the neighbourhood of 3v. That is far too little for an L293D. (This isn't really your fault, as it appears you got this erroneous idea from following a bad tutorial, but it does demonstrate that not everything you read on the Internet is sensible. Using a 9v "transistor" battery is also a bad idea). 3 cells would be about the minimum, but even there it would not work well, as that chip has two bipolar transistors in the path yielding a voltage drop of over a volt.

To use a an L293D you really want at least a 5 or 6 volt system, and a motor wound for low to moderate current at that voltage.

If you want to use a lower voltage, look at a more modern MOS-based H bridge chip - the TB6612FNG is an often used example. You will however still want to choose motors wound for moderate current at a 3- or 4- cell voltage - those intended for 2-cell usage typically draw more current than is ideal for an IC driver chip.

It is entirely possible that there are additional issues with your attempt as well. Normally, a question such as this would require a complete and accurate schematic diagram, which you have not provided.

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  • I think you're right even though i've seen demonstration videos using 2 AA batteries and 2 DC motors working fine. The goal of my project is to use a smaller DC motor than this and a small 3.7v rechargeable battery. So switching to a smarter motor contoler might be a better idea. I'll try the reference you gave me, thanks ! – Théo Naciri Dec 14 '15 at 9:27
  • So I used a 4x1.5v battery pack. The L293D chip was faulty, I changed it. Still, the motor is running way slower than directly connected to the batteries. The TB6612FNG chip is not to be used for a small DC motor like this, it is meant for bigger scale projects. – Théo Naciri Dec 19 '15 at 15:12
  • Whoever told you the TB6612FNG is only for larger projects has no idea what they are talking about. The L293D has a large voltage drop - effectively one of the cells in your battery is only to offset that loss, and part of a second too - which is why you should not be using it. In contrast the TB6612FNG and similar MOSFET bridges are much more efficient - a far greater fraction of your battery voltage actually shows up across the motor, and less is wasted as heat. – Chris Stratton Dec 19 '15 at 15:57
  • I ordered the TB6612FNG chip and will soon experiment on it. Thank you for your clear explanations and the reference of the chip. – Théo Naciri Dec 20 '15 at 16:20
  • Make sure you get or have plans to make a carrier PCB - the pins are about twice the density of your breadboard, so it won't be fun to hand-wire to. It wouldn't make a bad introduction to toner-transfer PCB fabrication though, and it shouldn't be too hard to hand solder to a PCB as long as you approach it carefully: solder one corner, check alignment, solder the opposite, check alignment, and only then solder everything else. Ultimately it is surface tension and flux which get the solder in the right place. Have some of the finest size solder braid on hand to fix any accidental bridges. – Chris Stratton Dec 20 '15 at 16:33

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