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[Reply #15 on:]

 The L293D has inbuilt diodes. I'm still trying to figure out how he got the motor to work with just the logic hooked up but if the logic supply was also supplying the motor then that and the voltage drop thru the regulator would make it a little toasty. I like to put weak pulldowns on the enables and also run a ground wire (like a servo) with the wires for the control signals so as to form the common ground.

About the only reason to have the 7805 would be to use the motor voltage for the logic without having to supply another voltage that needs to be regulated. The arduino should easily supply the +5 for the L293D.

[Reply #16 on:]

The L293 datasheet says external clamp diodes are required for inductive loads...

Datasheet states that it has internal clamp diodes.

I have tested the voltage levels on the pins today and I seems to me there is something wrong with the regulator. Because for a 5V regulator its output is about 6.11V without any loads. I have to replace it with a new one and I will let you know about the progress,




update: I just did a voltage test on IC pins and found out that VCC2 has 2.8V across its terminals with 5V logic supply signal inputs connected to the board. I am clueless...

[Reply #17 on:]

The L293D is plugged in backwards.  Look at the notch orientation on the board file (to the right) and look at it on your board (to the left).

[Reply #18 on:]

The L293D has inbuilt diodes. I'm still trying to figure out how he got the motor to work with just the logic hooked up but if the logic supply was also supplying the motor then that and the voltage drop thru the regulator would make it a little toasty. I like to put weak pulldowns on the enables and also run a ground wire (like a servo) with the wires for the control signals so as to form the common ground.

About the only reason to have the 7805 would be to use the motor voltage for the logic without having to supply another voltage that needs to be regulated. The arduino should easily supply the +5 for the L293D.

Ah, I think I was looking at a datasheet for both the L293 and the L293D - its text wasn't careful to explain the difference!

[Reply #19 on:]

The L293D is plugged in backwards.  Look at the notch orientation on the board file (to the right) and look at it on your board (to the left).

How can be so blind   , I would like to apologize from all the forum members who has contributed to this topic. I think I finally know what happened. I did the layout for this board and gave it to one of my good friends to develop it, he said he has altered the design a bit and I really thought that the IC was is in its original position. Well, really sorry guys, and thank you all for your valuable contribution.