I'm trying to replace the brain of my neato vacuum which is broken.

I've already repair a cleaning MOP but with this one I have a problem with the brushless motor which is throwing some party fun in the circuit. First I was Using the onbord 5v regulator from the l298n module like this: enter image description here But when the brushless FAN motor start turning quickly, the Atmega start to hang. I've tred to use a powerbank to power the IC and it was going well.

I've start to plug a regulator LM7805 on the battery power source, It was really better, but one time or two I have notice a little hang.

here is a video to explain:

How could I filter more the current for my IC? Put others capcitors?

Maybe starting the wheels once the brushless motor speed is stabilized could be an idea? Could use some delay inside the IC before starting?

enter image description here

  • \$\begingroup\$ Don't use a linear regulator to feed a motor. Use the full supply voltage is modulate it appropriately in the drive electronics. Also the L298 is a horrible part and almost certainly a mistake, as documented in many related questions here. \$\endgroup\$ – Chris Stratton Jun 21 '19 at 13:04
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    \$\begingroup\$ You have some serious contradictions between the text of your post and your comment ("First I was Using the onbord 5v regulator for the l298n module.") No one is going to be able to help you unless you stop contradicting yourself. Regardless of that, the L298 remains a horrible choice. \$\endgroup\$ – Chris Stratton Jun 21 '19 at 13:56
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    \$\begingroup\$ Like most people who come to that mistaken conclusion, you are neglecting the absurd losses in the L298. Again, this has been covered here many times before, read the related questions. \$\endgroup\$ – Chris Stratton Jun 21 '19 at 14:15
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    \$\begingroup\$ You show Brushed DC motors in your diagrams …..where are the Brushless motors you reference in the question? The L298 is just fine at 15V, BUT it does not have enough capability for your 3.5A motors. You appear to be driving the L298 incorrectly. In your schematic one motor is directly across 15V!!! the other is driven across A and B outputs ...why?? \$\endgroup\$ – Jack Creasey Jun 21 '19 at 15:02
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    \$\begingroup\$ In your schematic the LM78L's ground is not connected to circuit ground. Please correct this mistake. Motors draw high current at startup, which can upset sensitive parts of the circuit if the ground wires are not run separately. Please show us a photo of your setup with all wiring clearly visible. \$\endgroup\$ – Bruce Abbott Jun 22 '19 at 0:47

Conducted ground/supply noise and radiated EMI make your signals look noisy.

Research on this site or web to consider how to shield, suppress, filters and isolate your offending motor noise cables away from the sensitive ones or any high impedance.

Also avoid inductive loops, with low ESR supply caps then using MOSFET Half Bridge drivers instead. (BJT style for < =15V are inefficient and outdated).

Expect surge currents to motors are up to 10X rated current or V/DCR when changing directions or starting.

I hope the large skinny loops on your schematic will teach you these are loop antenna and your fun isn’t over until you stop broadcasting noise with BW up to 0.35/Rise time of current or voltage spikes.


U1 needs a low ESR e-cap directly across it and low Inductance power lines.

All Motors need a BLDC drivers with small area power loops to minimize crosstalk back to battery or PS. The AC voltage noise may be measured with balanced twin probes in A-B mode or AC coupled to a 50 Ohm cable and 50 Ohm termination to DSO.

  • \$\begingroup\$ hey Jack ?...... pls comment \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jun 21 '19 at 21:24
  • \$\begingroup\$ why negative vote? \$\endgroup\$ – bodtx Jun 22 '19 at 10:40
  • \$\begingroup\$ Negative attitudes without comments cause negative votes \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jun 22 '19 at 14:14
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    \$\begingroup\$ You can call it obtuse, but it's a very common term in microcontrollers to indicate a DC supply sag serious enough to stop operation of the processor. I can find that term in datasheets if you would like. \$\endgroup\$ – W5VO Jun 22 '19 at 15:22
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    \$\begingroup\$ Finally what seems to work for now is to wait that the brushless fan's speed is stabilized before driving the motors wheels. Once the fan is at full speed I can start. I have also to drive the brush (to clean not brushed) motor, I will also rampup this motor slowly and wait before starting the wheels. I've twisted all the cables as the original design was done like this, it helps to get ride of EMI. Thx! \$\endgroup\$ – bodtx Jun 26 '19 at 7:50

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