Basic MOSFET install

[DeadShot_1987]

Hi everyone,

Looking for some mosfet related help, I have tried searching but not had any luck.

I have just aquired a basic mosfet switch but im struggling to find an installation guide to suite the type of mosfet I have. it does not have active breaking and it has only three wires.

all the guides I can find show mosfets with two wires going to the battery and three to the gearbox (two thick and one thin wire) but mine only has three wires total (two thik one thin wire)

Can someone please point me in the right dirrection?

Thanks in advance,
DS.

[Genista]

Re: Basic MOSFET install

A pic would help, but you need to end up with the two thick wires running between the -ve battery connection and -ve motor.

The thin wire goes to one side of the trigger switch.

You also need a wire from the +ve battery connection to the motor AND to the remaining trigger switch contact.

NB you need to get the -ve wires the right way round or the switch won't work. The wire from the centre pin (drain) should go to the motor.

[DeadShot_1987]

Re: Basic MOSFET install

Sorry the picture isnt great I only had my phone to hand. Does this help?

IMG_0754.jpg

[Genista]

Re: Basic MOSFET install

Well, I've not come across that particular design before. Is it home made?

I don't think it is possible to work out which way round the source and drain quite are frim that pic. Unless the person who made it can tell you, you may need open up the heat shrink.

(you could also test it with a battery and multimeter but I wouldn't recommend it unless you know what your doing).

[No1_sonuk]

Re: Basic MOSFET install

(you could also test it with a battery and multimeter but I wouldn't recommend it unless you know what your doing).

A diode test might work - find out which way round the internal diode is connected.
On an N-type MOSFET, the diode's anode will be the Source of the MOSFET, and should be connected to the -ve of the battery.

The small wire is the Gate.
If you can work out which side of the MOSFET that's connected to (probably through a resistor), the middle pin will be the Drain, and the other side pin will be the Source.

So:
Drain goes to motor -ve (Thick wire)
Source goes to battery -ve (Thick wire)
Gate goes to trigger contact A (Thin wire)

Battery +ve goes to motor +ve (Thick wire)
Battery +ve goes to trigger contact B (can be thin wire, like the MOSFET Gate wire).

If you get the Drain and Source the wrong way around, it may run the motor as soon as you plug it in, and it more than likely will damage the MOSFET.

I would suggest initial testing with the motor electrically connected, but not mechanically linked to the gearbox. Just in case...

[DeadShot_1987]

Re: Basic MOSFET install

Thanks for the help guys learnt more here reading your replies than all the time i spent tralling the web.
I will see if I can identify which wire is which and go from there.

Genista, no its not a home made job, I bought it from a major uk based online store.

Thanks again,
DS

[Genista]

Re: Basic MOSFET install

Which is good news. It means you should be able to get some support, info as to which was round it's wired.

[Genista]

Re: Basic MOSFET install

I've found it. Is there a piece of black tape/heatshrink on one of the thicker wires?

[DeadShot_1987]

Re: Basic MOSFET install

Genista, sorry for the delay iv just got back to this, yes one wire is marked with some heatshrink.

[Genista]

Re: Basic MOSFET install

Good! So when they tell you which way round it should go you can tell which wire is which!

(Maybe update on here?)

How much was it, if you don't mind me asking?