hi im controlling a couple of motors using my uno and the NTD5867N module. works exceptionally well im very happy, only thing being is after a about 15 seconds of operation the PC makes that "USB unplugged" sound alert for the uno, the uno itself does not lose power and it works fine SO FAR, but im worried that the motors are producing a back EMF and its going to kill the micro controller after a while when i put the circuit in the main system im building.. I have put diodes parallel to the load as well as one from the button output to the gate of the FET.
basically i want to know if im being over overcautious or it will be a problem,
(also note the uno im using will be replaced with an AT mega 328 thats been preprogrammed in the project its going into pending me becoming less of a noob)
only thing being is after a about 15 seconds of operation the PC makes that "USB unplugged" sound alert for the uno, the uno itself does not lose power and it works fine SO FAR,
Sounds like you are trying to pull too much current from the USB connector.
I would add a 150 ohm gate resistor myself, but that circuit is OK (assuming the free-wheel
diode). The MOSFET is logic level.
However you haven't said what the motors are, their supply voltage, stall current etc.
That MOSFET has 0.05 ohm on-resistance which means a heatsink may be needed
if the current is more than a few amps - if it overheats it could fail and damage the low-voltage stuff.
Since you have to common the motor supply ground and Arduino ground you
may be getting ground currents if neither supply is floating.
If the motors are on a relatively high voltage (more than 12?) use a MOSFET driver to drive
the gate, otherwise you risk back-driving the Arduino pin from the large
dV/dt swing via the gate-drain capacitance. Such back-driving could cause
latch-up of the microcontroller and explain the symptoms.
yea i mean and USB hardware as a collective seems to have a pretty quick redundancy i had the motors powered by a 15 VDC from a 240 VAC wall adapter. So there is nothing in the fuse department + another separate IC or maybe array of cmos that are actuated by that dV/dt swing? or maybe i mean rectifier
ok, its not possible to exist a circuit breaker triggered by an if statement orientated around the occurance of the dV/dt swing between gate and source
Maybe, but irrelevant. You don't have high voltages though so dV/dt isn't likely to
be an issue. In general the more power you switch the more important a good
solid gate-drive circuit with protection becomes.
A circuit breaker that can respond in a few nanoseconds would be something
BTW!
