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MOSFET is working even if I connect ground on gate.

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tayY

New Member
Hi, I'm trying to make a switch with a MOSFET.

I connected battery(11v) on drain side with motor connected,

gate is connected to ARTIK which is a control voltage 0v to 5v

and source is connected to ground.

I used 2n7000 MOSFET.

when I don't connect anything on the gate, motor doesn't work but

whenever I connect something(0v or 5v or ground) motor works. it supposed to only work when the gate voltage is 5v..

I have no idea what is going on.

I also connected 10K resistor gate to source to make pull down.

Please help..
 

ericgibbs

Well-Known Member
Most Helpful Member
hi tay,
Check the pin orientation of the 2N7000.
Can you post a photo shot.?
E
 

GromTag

Active Member
What is the motors current rating?

thoughts are that is the 2n7000 has failed being it is an 200mAnominal / 500mA pulse max current device, then the 2N7000 Gate could be allowing the 11V supply through the motor to either the 0v or the 5V logic, at 5V on the 2n7000 gate the motor would be weaker in operation overall.
 

dr pepper

Well-Known Member
Most Helpful Member
The above would be proven if you connect the gate to ground through a 10k, if the motor then either dosent turn or turns very slow then it looks like that is the case.
A 2n7000 is a little small for a motor, an irf540 or whatever similar is in fashion at the moment might be better.
 

Willen

Well-Known Member
Posting a schematic and a photo would make clear.
 

tayY

New Member
I just tested with a voltage supplier as a gate voltage (set it as 5v)

whenever I connect to the gate, the voltage supplier reads 11v (which is battery voltage) and motor doesn't turn on

when I connect ground from voltage supplier to the gate, it doesn't work.

but ARTIK board ground as a gate turns motor on.
 

jpanhalt

Well-Known Member
Most Helpful Member
You appear to have the mosfet leads identified correctly.

You can easily test a mosfet with a multi-meter set to ohms: https://www.utm.edu/staff/leeb/mostest.htm Frankly, I always found it kind of neat that you can discharge the gate with your body and watch the conductance decrease.

John
 
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