EveryCircuit - Reverse Polarity Protection Circuit

7 years ago

Can anyone tell me why the first voltmeter is only showing 35.3mv? I expected it to show 12v. Is it the forward voltage required by the Fet?

hurz

7 years ago

What is you are protecting? MOTOR or LED?

hurz

7 years ago

You try to protect

emanjackson

7 years ago

The led is simply to show the circuit is on. It is to protect a 12v circuit. the motor is just to represent a load

kiani

7 years ago

There is only 0.4 v across the motor.. over voltage protextion, over current protection, two different things.

hurz

7 years ago

@emanjackson, better start with the example section. This is to simple for you

jose1979

7 years ago

No es el procedimiento correcto de protección de un motor cc.

jose1979

7 years ago

En el arranque el motor cc intenta mover la carga , tanto es así que demanda mucha intensidad , sería una negligencia amplificar esa corriente ,. Generalmente se limita la intensidad que demanda rm el arranque en tres pasos , jamás se utilizan bjt.

jose1979

7 years ago

No sería más sencillo no enchufarlo incorrectamente 💥💥💥💥💥💥💥💥💥💥💥💥💥💥💥💥💥💥💥💥💥💥💥 hay que tener un poco de cuidado... No conectar una puerta lógica en AC , inventa una protección...

emanjackson

7 years ago

I have installed the trans. as protection against reversing the polarity by accident, but I was curious to know why the voltmeter only has 35.3mV running through it. A little help would be appreciated instead of "TOO SIMPLE FOR YOU"

hurz

7 years ago

You put things in series which suppose to be in parallel. This is what newbies do and you are a noob, right? So you ask questions to circuits which are far to complicated for you. Again, you better start with examples and even much more “simple“ circuits then this. Or do you know what a body diode of a Mosfet transistor is and what impact it does in this circuit? No, you do not know.

emanjackson

7 years ago

You are correct, i do NOT know what I am doing, which is the whole point of this program is it not? to get help and guidance from others?? You dont have to be so "mean" in what you say. I will go back to watching videos and stuff and see if I can learn more.

hurz

7 years ago

We can only help you, if things are not overcomplex for you. It doesn't make sense. What is your background? We might find a better start point.

hurz

7 years ago

So what was your initial idea to put a 2A motor in series with a 20mA LED plus a current limiting resistor?

emanjackson

7 years ago

I need a circuit that has a 12v motor, a latching led switch (for motor power), that is protected from reverse poliarity. I watched a youtube vdeo that said the best and most efficient way to protect from reverse polarity is to use a npn trans.

hurz

7 years ago

But this here is a PMOSFET transistor

hurz

7 years ago

I think a mosfet is the better choice for such a protection circuit. Check this http://everycircuit.com/circuit/5749006310572032

emanjackson

7 years ago

Thanks Hurtz, I did a little modification, you can now see the model working

hurz

7 years ago

@emanjagson, but im still missing the body diode!

hurz

7 years ago

Put a body as they are in any MOSFET and see if your circuit is still working. Im afraid it does not, and we are at the beginning of this thread, here your circuit with mosfet body diode http://everycircuit.com/circuit/6553200953131008 think about!

hurz

7 years ago

Are you still there or are you finished? I dont see a “simple“ working circuit! There is at least one step missing.

hurz

7 years ago

Ok, for anybody else who is still interessted, you put the mosfet wrong. Drain and Source must be swapped to have the body diode into the right direction. This is against the normal conventions how mosfets are used but is a must to get a functioning reverse voltage protection. You still think this is a simple topic for you as you still say in headline?

emanjackson

7 years ago

Sorry hurz, have been really busy with work. I am back now, and ready to learn more. I have swapped around the D+S. Also added a diode

emanjackson

7 years ago

P.S I have not changed any characteristics of the diode, just installed as packaged in the program.

emanjackson

7 years ago

The lamp is to simply represent a load on the system. Could be anything that uses between 5v and 12v

hurz

7 years ago

Now its what is working in real life. The voltmeter in the gate wire doesn't make sense cuz you have short circuit it anyway. Remove it. The full functioning version needs an resistor and if you go higher in supply the 20 V you need a gate protecting zener diode. Cuz most mosfet are easy kill with voltages higher the Vgs=20V. Check this http://everycircuit.com/circuit/5253788125626368

emanjackson

7 years ago

Hi Hurtz, Thanks for the updated circuit, I see now. Much appreciated.