Mosfet controlled Motor activates randomly

[fax8]

Hello guys, I'm designing a little project and I'm using a small Mosfet 2N7002P to drive on/off a vibration motor from an ATMEGA 32u4.

This is the relevant schematics and associate board layout:



The problem I'm having is that, as long as the micro actively drives the gate to low or high, well.. everything work as expected.. instead when the micro is not driving the gate actively (high impedance) or when it's shut down (motor connected directly to the battery), the motor randomly activates.. sometimes just a simple vibration or touching with hands activate it.

Battery is 1S Lypo 110mAh 3.7V nominal and the micro is running at 3.3V after an LDO.

Is there anything I can do to prevent such effect? Maybe changing the gate resistor or adding one from the battery to the gate?

Thanks for your help,

Fabio

[firewalker]

You should not have the gate floating at any time.

Notice the 100k resistor.


Alexander.

[fax8]

Thanks Alex. That makes perfect sense.. I wander what I was thinking...