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Topic: l293d motor shield for Tamiya (Read 3880 times) previous topic - next topic


I am working on my second generation motor shield for my classes Sumo-bot/line following robots. I have had great success with the attached schematic, but it will only work with the L293D. no other l293 chip will work or the SN754410. I would like to modify the circuit to work with the less expensive SN754410 chip. I realize the L293D is diode protected so i think all i need to figure out is where to place the diodes in the circuit to make it work.

Thank you for all the support.
High School Engineering Teacher


Jan 30, 2011, 06:27 am Last Edit: Jan 31, 2011, 08:42 pm by nobikes Reason: 1
okay so i did some more research. Does any one see a problem with my schematic? I think i have the diodes placed properly.

High School Engineering Teacher


would be easier to comment on the schematic if we could see it! :)
there are only 10 types of people
them that understands binary
and them that doesn't


1n4004 diodes aren't ideal for motor drivers.  You should really use a schottky diode for that purpose.  Something that should be well suited to the SN754410 as an example would be a 1n5818 schottky diode.  1amp current max, 30volts max, fits fairly well with that h-bridge IC.  If you really need 36v, you could go with the 1n5819 (or if you don't need more than 20v peak, the 1n5817).


Hopefully everything can be viewed now. I will change the diodes and repost the schmatic when i get home.
High School Engineering Teacher


Okay, i fixed the diodes. see attached schematic. Could the way that i have Vcc1 connected to 6 volts through a 10k resistors be a problem? Would it be better to tie it to the arduino's V5+? and can i tie the ground from the chip to the ground on the arduino?

Thank you for all the support
High School Engineering Teacher


You want VCC1 and all your logic inputs running off the Arduino power supply.
You don't want a 10k resistor inline with VCC1.
You need to flip the ground side diodes on your motor outputs.
All grounds should be tied together. (this includes Arduino and motor supply grounds)


High School Engineering Teacher


I used this motor shield problem free with my students last semester. This semester we switched over to UNO from Duelnova and change suppliers on a few components. Now %90 of the shields produce the same error: Serial port 'COM#" already in use. try quitting any program that may be using it. If we upload before plugging in the shield everything works fine, but we cannot upload anything else without getting the error message, In order to re upload a change we have to close the Arduino ide and reopen it.

the problem occurs with both the l293d and the sn754410ne

Any ideas on a solution, or what could be causing this error?
High School Engineering Teacher


In my own project I noticed that the motors and driver IC are very noisy, noisy enough to cause false signals in the rest of my circuit. You can reduce this noise by adding decoupling capacitors to the motors and twisting the motor wires together. Might help.

My Tamiya based robot -

Duane B

Read this
then watch this



The problem occurs as soon as the board is pluged in, before the motors are even attached. The problem is something that the students are doing wrong, i just can't figure out what it is.
High School Engineering Teacher

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