MOSFET VS TRANSISTOR

[TKS]

i have 2 types in home

1:BUZ11,STP4NB80FP

2: STTIP3055

i want to use a optocoupler of type CNX83A to drive the mosfet or transistor

1) my question is how to hook this all up to be able switch fast

2) wy the ff... the Collector is connected to the cooling part of the mosfet..?? (BUZ11,TIP thing..)

ohja don't forget the gate unload part using the mosfets..

TKS

i have 12Volts and a current of lets says 12A max...

 

[TKS]

welll

ok....

i know i need a resistor then the coupler in the right direction to ground..

pin 1 tot the output of the PIC

pin 2 to ground..

then @ the other side i have different possibilities and no idea wich to use..

TKS

 

[Roff]

The BUZ11 is probably the best choice. How fast do you want it to switch? What type of load are you switching?

 

[TKS]

Welll

I have just measured it when the device (a car injector) is on it wants only 0,7 A but rising i cant measure prob it is more... then...

the ohm i measure is 16,3 ohms..

TKS

 

[Roff]

If the current is less than about 4 amps, you should be able to use the TIP3055 in the schematic below. I simulated it, but no guarantees!

 

[TKS]

....

wy u use a second 2NXXX trans..???

i have now hooked it up directly fed from the optocoupler (max =100ma..

i putted a 220 Ohm resistor in it. then another 220 Ohm then the gate

and the gate to ground whit a 10K Ohm..

the diode i know should be from a fast switching type..and that works good. (also using relais etc..)

ohja i also don't use the pin 6 (base..of the optocoupler)..

i measure a diode when the opto is on whit a needed voltage of 0,135volts..

TKS

 

[TKS]

i have taken a

look @ your circuit it seems to be a very good one

but i have 1 remark...

why not put a res of 100Ohm betweent he Gate of the 2N3055

and the output of the 2N2222..???

and when i do this can i then also use a standard Transistor..??

Like a BC547?? out of my head..

and wy the f.... always is the casing connected to the load i cant untherstand...?? that...

if they do it to the other pin @ least i was able to cool the **** whit the housing ..(GRND) ..

i now have it hooked up this way, can you tell me if it it similiar as yours or which one would be faster..// acurater..???

TKS

 

[Roff]

Re: i have taken a

look @ your circuit it seems to be a very good one

but i have 1 remark...

why not put a res of 100Ohm betweent he Gate of the 2N3055

and the output of the 2N2222..???

Go ahead, but you don't need it.

and when i do this can i then also use a standard Transistor..??

Like a BC547?? out of my head..

I should have shown the transistor as a PN2222A or 2N2222A, which is a very common transistor here in the US. The BC547 beta doesn't hold up at high currents as well, but if your injector really is 16 ohms, it should be OK.

and wy the f.... always is the casing connected to the load i cant untherstand...?? that...

if they do it to the other pin @ least i was able to cool the **** whit the housing ..(GRND) ..

Use an thermally conducting insulating pad (see this site).

i now have it hooked up this way, can you tell me if it it similiar as yours or which one would be faster..// acurater..???
TKS

I simulated your circuit. It should work fine. There is an old saying here that goes "there's more than one way to skin a cat". Do you have an equivalent one in The Netherlands?

 

[TKS]

offcourse we have,,,,

The most famous one is "there are more roads that lead to Rome..."

So if i get it right...
there is no difference in my circuit and yours..???

couldn't you really not think one advantage of yours..???

i want my system work perfectly you know..???

regards

TKS

p.s. I love this forum, i'm learning here soooowww much..!!!! maybe we should send a present to Nigel and a couple more..(they put soow much time in this forum...and i wonder if they self get info out it...)

 

[Nigel Goodwin]

Re: offcourse we have,,,,

p.s. I love this forum, i'm learning here soooowww much..!!!! maybe we should send a present to Nigel and a couple more..(they put soow much time in this forum...and i wonder if they self get info out it...)

You can learn from anyone, even total beginners can have excellent ideas, sometimes because they don't know the 'normal' way of doing things they can come up with a totally unexpected way of solving a problem.

Also, the 'discussion' process is very educational, I'm not proud - I'll steal anyones ideas :lol:

 

[Roff]

Re: offcourse we have,,,,

The most famous one is "there are more roads that lead to Rome..."

So if i get it right...
there is no difference in my circuit and yours..???

couldn't you really not think one advantage of yours..???

i want my system work perfectly you know..???

regards

TKS

p.s. I love this forum, i'm learning here soooowww much..!!!! maybe we should send a present to Nigel and a couple more..(they put soow much time in this forum...and i wonder if they self get info out it...)

Your circuit holds the injector on for about 100 microseconds (0.1 millisecs) longer than mine does. This is due to the time it takes for the 10k gate pulldown resistor to discharge the sizeable gate (and Miller) capacitance of the BUZ11. It is up to you to decide whether or not this is a problem.
BTW, you can get the injector current to decay faster after the transistor turns off by adding a 39 ohm resistor in series with the diode. If you make this value too high, the switch transistor will break down and could be destroyed. If your injector resistance is less than 16 ohms, the value of the added resistor will have to be reduced proportionally. Keep in mind that this will not speed up the turnoff of your BUZ11. It only reduces the injector current decay time after the transistor turns off.