Can you please put pin numbers on you Fet's pins? 1=Gate, 2=Source & 3 = Drain...
I'm more used to working with Pin numbers rather than signs since apparently not quite standardized in the industry.

 

Please confirm the Ground here belongs to the 5V Logic side?
thanks

 

Can you please put pin numbers on you Fet's pins? 1=Gate, 2=Source & 3 = Drain...
I'm more used to working with Pin numbers rather than signs since apparently not quite standardized in the industry.

I don't know what N-ch and P-ch MOSFETs you are going to use.

I don't know if you are actually going to build this thing or not.

However, if you are actually going to build it, you might look at:
FDS4897C - Logic level N-ch P-ch MOSFET (Vdss=40,Rdson=29m,46m,Id=6.2,-4.4)
http://www.fairchildsemi.com/pf/FD/FDS4897C.html

But using P-ch and N-ch MOSFETs in the same package could make for quite a messy board layout.

 

Please confirm the Ground here belongs to the 5V Logic side?
thanks

The IR emitter side ground (left) belongs to the logic side.
The output switch (emitter) ground belongs to the 24v side.

 

The IR emitter side ground (left) belongs to the logic side.
The output switch (emitter) ground belongs to the 24v side.

Does that then mean the IR emitter side ground is connected to the 24v side Ground?
If so, then doesn't that break the voltage Isolation concept by making a common ground?

 

I don't know what N-ch and P-ch MOSFETs you are going to use.

I don't know if you are actually going to build this thing or not.

However, if you are actually going to build it, you might look at:
FDS4897C - Logic level N-ch P-ch MOSFET (Vdss=40,Rdson=29m,46m,Id=6.2,-4.4)
http://www.fairchildsemi.com/pf/FD/FDS4897C.html

But using P-ch and N-ch MOSFETs in the same package could make for quite a messy board layout.

Yes, I will be building this and I did initially meant to utilize Logic Level Fets but, they may not be available to me here for now which is why the Zener Diodes and the IRF's...
Please explain the problem associated with P&N Ch. Fets on the same board.

Thank you

 

Does that then mean the IR emitter side ground is connected to the 24v side Ground?
If so, then doesn't that break the voltage Isolation concept by making a common ground?

Sorry - I worded that in what could be a confusing way.

On the left side of the optocoupler/optoisolator is an infrared LED. It emits light. In datasheets, you'll see the infrared LED referred to as "the IR emitter", as in it emits light.

On the right side of the optocoupler/optoisolator is a transistor. The transistor as supplied normally has no connections made to the collector or emitter terminals. Some optocouplers/optoisolators also have a base terminal available.

So, the cathode leg of the IR emitter gets connected to the logic side ground.

The output transistor emitter gets connected to the 24v return, or power side ground.

Does that make more sense now?

 

Yes, I will be building this and I did initially meant to utilize Logic Level Fets but, they may not be available to me here for now

Where are you? You should at least put your country in your profile, as otherwise we have no idea as to what kinds of parts might be available to you.

Logic level FETs might help for the lower side (N-ch) MOSFETs, but if you are using optocouplers/optoisolators anyway, there is no reason you have to use logic level MOSFETs.

which is why the Zener Diodes and the IRF's...

You're going to have to reference the gate voltage to the individual MOSFET's source terminal anyway. Might as well just use Zener diodes.

Please explain the problem associated with P&N Ch. Fets on the same board.

No problem with using P & N channel MOSFETs on the same board.

However, using N-ch and P-ch MOSFETs that are in the same package would make for a very spaghetti-like board layout. I was just thinking about board space, but you will really need to use P-ch and N-ch MOSFETs that can be separated from each other by a good distance.

 

Sorry - I worded that in what could be a confusing way.

On the left side of the optocoupler/optoisolator is an infrared LED. It emits light. In datasheets, you'll see the infrared LED referred to as "the IR emitter", as in it emits light.

On the right side of the optocoupler/optoisolator is a transistor. The transistor as supplied normally has no connections made to the collector or emitter terminals. Some optocouplers/optoisolators also have a base terminal available.

So, the cathode leg of the IR emitter gets connected to the logic side ground.

The output transistor emitter gets connected to the 24v return, or power side ground.

Does that make more sense now?

Thanks for the explanation, yes I understand the IR and the Transmitter side and if we again number the pins as in attached then pin #2 being the IR Ground and #4 being the Transmitter Ground, then you are connecting the 2 together and that breaks the Isolation or not?

thanks

 

Where are you? You should at least put your country in your profile, as otherwise we have no idea as to what kinds of parts might be available to you.

Logic level FETs might help for the lower side (N-ch) MOSFETs, but if you are using optocouplers/optoisolators anyway, there is no reason you have to use logic level MOSFETs.

You're going to have to reference the gate voltage to the individual MOSFET's source terminal anyway. Might as well just use Zener diodes.


No problem with using P & N channel MOSFETs on the same board.

However, using N-ch and P-ch MOSFETs that are in the same package would make for a very spaghetti-like board layout. I was just thinking about board space, but you will really need to use P-ch and N-ch MOSFETs that can be separated from each other by a good distance.

I'm presently working in the UAE region.
Thanks for lots of useful info in this post. I'm glad that the correct rout is the separate Fets and the Zenners. BTW, someone had mentioned before due the same Zeners controlling the voltage the R's at the Gate won't be necessary hence the 10k R at Transmitter side of the Optos. Also, I will be using Opto's, feel more comfortable with them not damaging the Arduinos on the logic side(already burnt one but all be it due soldering shorting).

 

Thanks for the explanation, yes I understand the IR and the Transmitter side and if we again number the pins as in attached then pin #2 being the IR Ground and #4 being the Transmitter Ground, then you are connecting the 2 together and that breaks the Isolation or not?

Yes.
Pin 1 gets the 620 Ohm resistor connected to it.
Pin 2 gets connected to logic-side ground.

Pins 4 & 5 get connected to their respective 24v-side items; the 2k resistor and the gate of the MOSFET and either +24v or the return for 24v.

But unless your schematic package provides for separate grounds between the two sides, you may not be able to keep them separate when you are routing the PCB.

 

Yes.
Pin 1 gets the 620 Ohm resistor connected to it.
Pin 2 gets connected to logic-side ground.

Pins 4 & 5 get connected to their respective 24v-side items; the 2k resistor and the gate of the MOSFET and either +24v or the return for 24v.

But unless your schematic package provides for separate grounds between the two sides, you may not be able to keep them separate when you are routing the PCB.

So, pin 2& 4 should not be connected, right?
thanks for the clarification.

 

I'm presently working in the UAE region.

Dubai? That looks like a beautiful area.

I have absolutely no idea what kind of semiconductors you might be able to obtain there; I have never visited that part of the world.

Thanks for lots of useful info in this post. I'm glad that the correct route is the separate Fets and the Zeners.

I was trying to save some space and individual parts count. You will have a LOT of soldering and assembly to do on this project.

BTW, someone had mentioned before due the same Zeners controlling the voltage the R's at the Gate won't be necessary hence the 10k R at Transmitter side of the Optos.

This needs to be discussed.

Also, I will be using Opto's, feel more comfortable with them not damaging the Arduinos on the logic side(already burnt one but all be it due soldering shorting).

That's fine. You will need them for isolation on the high side MOSFETs.

I'm starting to re-think some of this at the moment.

 

............

I'm starting to re-think some of this at the moment.

You have been a great help in this and I sure appreciate your sharing your knowledge and knowhow with us all in this forum.

thanks

 

BTW, The Sols. will be up to a couple of yards away from the MBD, will that be a problem?
Do the EMF Diodes need to be close to the Sols., go where they are located or they can stay at the PCB location obviously maintaining the circuit integrity at all times.

 

BTW, The Sols. will be up to a couple of yards away from the MBD, will that be a problem?

OK, what exactly IS your application? Why do you need 1,000 solenoids in an array? What are you trying to accomplish?

It would help quite a bit if you would tell us what the application is. There may be a much less complex way to approach it.

Do the EMF Diodes need to be close to the Sols., go where they are located or they can stay at the PCB location obviously maintaining the circuit integrity at all times.

There would be less electrical noise if they were at the solenoids.

 

If your schematic editor doesn't provide different symbols for different GND types, as shown in Fig 2, you can use a Jumper (J1) symbol as I've used it in Fig 1. It more clearly helps indicate that your Micro & Solenoid GNDs are isolated from each other.

Edit: The GND symbol labeled GND_PWR, by one of my Cad editors, is more commonly accepted as Chassis GND or Board GND and even Circuit GND. Earth GND however is very definitive.