Don't the Source and/or the Drain need Resistors?

 

Here's a new Schem. included another Resistor to the MOSFET, only was not sure about it's capacity.
Please advice if this looks good or needs more changes?

thanks

 

Hello,

The gate of the fet will not be opened as there is no voltage going there.
Here is a schematic I posted some time ago.
It uses a relays, but the solenoid will fit too.

Greetings,
Bertus

 

Here's a new Schem. included another Resistor to the MOSFET, only was not sure about it's capacity.
Please advice if this looks good or needs more changes?

thanks

R4 should connect between the collector of the optocoupler to the +24V source, then R3, should connect to pin 4 of the optocoupler along with the gate of the MOSFET. R4 will supply the voltage to the optocoupler transistor, which then drives the gate on the MOSFET. R3 keeps the Gate of the MOSFET near ground when no signal is present.

 

Sorry, was away buying the Mosfets and will get working on both suggestions right

away.

As usual, greatly appreciate the help and support provided gentlemen.

cheers...

 

Well, I must be getting close...after all the help I got and considering this being my very first circuit and NOT a simple one!

 

Hello,

You will still not have the voltage on the gate of the FET.
I made some changes in your schematic to have about 10 Volts at the gate when activated.

Greetings,
Bertus

 

Thank you, here's the modified one.
p.s.
R4 should read 15k!

 

Hello,

R4 should be 15K as I have drawn.
The resistor for the led in the optocoupler can also be changed, lower it to 270 Ohms.

Greetings,
Bertus

 

Please confirm if R4 should be 15 or 100k???
I have doubts now due different opinions.

thanks

 

thanks, here. Please verify.

 

Hello,

Yes, I think it will work now.

Greetings,
Bertus

 

Thanks everybody for all the help and support provided. I'll try it out next.

 

As shown in last schematic, it should work.

How often will the solenoid be switched on and off?

Stop back and let us know how it works out either way!

 

As shown in last schematic, it should work.

How often will the solenoid be switched on and off?

Stop back and let us know how it works out either way!

Hi,
So far on a proto board it's more or less...!

1-The voltage from the Arduino is about 5V but as soon as the Opto is plugged into the circuit, it drops to about 1.5v! Why?

2- However, the Opto is still working fine since on the other side of it utilizing a 12v for now, it shows about 12 with Opto inactive and when the Opto kicks in it drops to 12(source) - (1.5 from Arduino with Opto active) = 10.5!!! Why is the Arduino voltage being deducted from the 12v source?
3- The Mosfet is also functionin but sending just 1V to the solenoids!!!???

What am I doing wrong?

Each solenoid after Muliplexing will get to be on for just a couple of seconds every 15 minutes or so, but like every couple of seconds, a solenoid will get activated.

thanks

p.s.
the led doesn't function or maybe at .8v it just not showing? The solenoid does function with .8v but with no strength obviously.

 

What is the part number of the optocoupler?

With the 220Ω Current limiting resistor between the uC and optocoupler LED, that will allow a 22mA drain from the UC, which may be a bit on the high side, causing the votlage sag. Try a 1k resistor in place of the 220Ω for less current draw on the uC.

Please measure the voltage at:

A) Mosfet Gate
B) Mosfet Source
C) Mosfet Drain
D) uC side of R2
E) Optocoupler side of R2

Both with +5V to the Optocoupler and without. i.e. Those 5 measurements (referenced to ground) while it is "on" and while it is "off".

It may just be some resistors changing. Are you using the 24V supply, or just the 9V supply?

 

What is the part number of the optocoupler?

With the 220Ω Current limiting resistor between the uC and optocoupler LED, that will allow a 22mA drain from the UC, which may be a bit on the high side, causing the votlage sag. Try a 1k resistor in place of the 220Ω for less current draw on the uC.

Please measure the voltage at:

A) Mosfet Gate
B) Mosfet Source
C) Mosfet Drain
D) uC side of R2
E) Optocoupler side of R2

Both with +5V to the Optocoupler and without. i.e. Those 5 measurements (referenced to ground) while it is "on" and while it is "off".

It may just be some resistors changing. Are you using the 24V supply, or just the 9V supply?

Thank you so much for taking the time:

1- VOltage directly off of Arduino pins with or without 1k R when NOT connected to OC = 4.85
2- OC connected = 1.12! Please note, the other DC supply NOT connected. So the OC alone causes the V drop?!
- without the 1kR with OC then V is 1.32.
Disconnecting the + line to OC the V shows -.85

thnks

 

Is the Arduino running and holding that pin high?

What is the part number of the optocoupler, or the datasheet, if you have it.

Have you tried a different optocoupler?

--ETA: Is this the same output that burnt out several transistors? If so, it may have dimiinished capacity. The above schematic won't allow damaging current to be sourced from the uC, so if it is possible, try a different output line.

 

What is the part number of the optocoupler?

With the 220Ω Current limiting resistor between the uC and optocoupler LED, that will allow a 22mA drain from the UC, which may be a bit on the high side, causing the votlage sag. Try a 1k resistor in place of the 220Ω for less current draw on the uC.

Please measure the voltage at:

A) Mosfet Gate
B) Mosfet Source
C) Mosfet Drain
D) uC side of R2
E) Optocoupler side of R2

Both with +5V to the Optocoupler and without. i.e. Those 5 measurements (referenced to ground) while it is "on" and while it is "off".

It may just be some resistors changing. Are you using the 24V supply, or just the 9V supply?

Hi,
Thank you for taking the time.
Here's what I think is happening:
!- Voltage drop at the OC is probably because of the OC's LED usage which seems to consume over 3V?! In any case that does not seem to cause a problem because when 12v DC power connected to the Transistor part of the OC it seems OK except without the 5v power supplied to OC it's pins show the 12v DC and with 5v switched on the OC Tr. kicks in and the 12v DC on the OC's Tr. side drops to Zero as it should. So far so good, I will next check the rest of the circuit. The OC is a PC817. Is this OC good for 24V? So I could check it out with my 24v which is a cleaner powe supply than the 12 V I have.

thanks again

 

Measuring the voltage at polls of the Solenoid is 1V but taking just 1 pol against the ground shows v going from about 12 to about 9 as the Arduino switches the 5v on and off????!!!! So the problem is the v at the solenoid against the ground not dropping to Zero! Does this make sense?
Anyone has the parts to simulate the situation quickly on a bread board maybe?

thanks