So, i'm trying to build an Obstacle Avoiding Robot by refering this site "Robot Obstacle Avoiding Car On the website they have provided with very poor Circuit Diagram. Please help me read the positions of capacitors. I have completed connection of all other components.

Schematic Diagram Scematic Arduino Close Capacitors Placed

Help would be appreciated

  • FYI that 9V depicted is not suitable for driving motors, those 9V bricks are made to power a low drain device for a long time. – ratchet freak Feb 7 '20 at 10:29
  • Then, should i use two of them in series? – Mutant101was_here Feb 7 '20 at 10:31
  • you are wrong, that is a very good schematic diagram ... the only very poor thing i see is the three wiring diagrams that you presented – jsotola Feb 7 '20 at 11:10
  • You need a more capable battery. Those bricks are really only capable of low-current (and/or very short lifetimes). Consider another source, supplied separately to the Arduino and to the motors. And FYI, to increase the current capability of a source, you'd need to put them in parallel, not in series. – JRobert Feb 7 '20 at 13:43

They are not poorly described.

All capacitors need to be put from the VCC to GND directly (this will not cause a shortcut).

The left 3 are related to the motor; as it uses a lot of current, it can take the current from the capacitors instead of flowing all the way to the power supply, causing problems of a voltage reduction that can cause other components to fail (temporarily).

The middle two are for the ultrasonic sensor as it also uses some current. 0.1 uF capacitors (the one for the ultrasonic sensor) is typically used for ICs and are called bypass capacitors. These needs to be placed as close as the VCC of the IC (in this case ultrasonic as possible).

And the right two for the power supply itself to remove noise/ripple.

For all capacitors, place them close to where the power is needed (for the motor/ultrasonic) and for the power supply close to the VCC input.


Below I added the capacitors for the motor, sorry for using MS paint, having no better option right now. I assume the two red wires from the L293D other than going to the breadboard are the 9V lines (VDD).

Also don't put the capacitors in the same pin as the L293D IC pins, but I didn't want to obfuscate the picture. This might destroy your breadboard or IC pins as there is too less space for both.

enter image description here

  • 1
    Would you please elaborate. I'm new to designing circuit. I've uploaded the Circuit i build. – Mutant101was_here Feb 7 '20 at 9:25
  • I edit the capacitors for the L293D, the other capacitors should be placed likewise (as close as the VCC as possible, going directly to GND). – Michel Keijzers Feb 7 '20 at 9:39
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    Thanks a lot for showing where to place motor drive capacitors, one last time just check the cirtuit. – Mutant101was_here Feb 7 '20 at 10:00
  • Personally I wouldn't put capacitors from the Arduino to the breadboard, but keep them on the breadboard (even if it's not so close to the Vin/VCC of the Arduino). But if they are close together you could. I also see a capacitor under the switch (and two from the Arduino), while only 2 in the schematics for the Arduino power. And you miss one capacitor towards the sensor (the schematics show two, you only placed one). You can place them parallel. And in principle you should have 2 capacitors PER sensor. – Michel Keijzers Feb 7 '20 at 10:09
  • Maybe it's a bit overdone with capacitors, but better a stable/reliable circuit than one that might fail in some circumstances. – Michel Keijzers Feb 7 '20 at 10:10

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