Controlling 12/24V DC motor - mosfet circuit

Other Hardware General Electronics
141

when apply voltage to the optocoupler pin 1, I'm reading 11.72V on pin3 of the opto with respect to GND2

142

Hi,
The current through the opto LED is.

( 5 - 1.4 ) / 470 = 7mA

The 817 specs are at 20mA, you are not driving the opto hard enough I believe.

( 5 - 1.4 ) / 0.02 = 180R would be better.

Tom... :smiley: :+1: :coffee: :australia:

143

What about on the gate of the MOSFET?
What about the Drain of the MOSFET?
What about the Source of the MOSFET?

Tom... :smiley: :+1: :coffee: :australia:

144

I have either a 330R resistors available. Shall I add it in parallel to the 470R resistor I have between opts pin 2 and GND1(arduino GND) ?

Is this will make the most be fully on ?

145

Hi,
330 // 470 = 193R

Should give you more current, yes.

Tom... :smiley: :+1: :coffee: :australia:

146

11.72V in respect to GND2

0V in respect to GND2

0V in respect to GND2

147

why you subtract 5 by 1.4? is it 0.7V for the voltage drop across the Opto diode and another 0.7 across the led itself?

148

Read the spec for the opto, 1.2 to 1.4 V LED Vdrop.
There is only a LED in the opto, no extra diode.

If the drain goes to 0V, does the solenoid activate?
What is the value of VCC1 when you turn the opto on and off?

Tom... :smiley: :+1: :coffee: :australia:

149

Yes

When off the value of VCC1 in respect to GND2 is 13.84V
When on the value of VCC1 in respect to GND2 is 11.83V

150

Hi,
So what is the problem?
Do the solenoids release when you remove volts to pin1 of the opto?

Tom.. :smiley: :+1: :coffee: :australia:

151

Is this good reading of voltage?

Yes they are when I'm doing it manually.
But when I've run the code with all 9 solenoids some of them were stuck and won't release until I either touch them or when they strick against an object they release without an issue.

Does adding the 330R in parallel to the 470R resistor will help that?

152

Hi,
Have you got any 0.1uF caps and say 10uF or 100uF capacitors?
You may need to add bypass capacitors to the power supply line on your two boards.

Tom... :smiley: :+1: :coffee: :australia:
PS, Its after midnight here, and got to work in the morning, so will check back much later to see how you have got on.

153

It may, but having a higher level of LED current that is closer to the optos spec, will ensure reliable operation.

Tom... :smiley: :+1: :coffee: :australia:

154

Yes I have all those value. Which value should I add? placing it in parallel between VCC2 and GND2 and VCC1 and GND2?

Thanks for your help!

155

Will do so then!

156

Hi,
Put 10uF and 0.1uF in parallel across the supply lines, VCC1 and GND2 as well as VCC2 and GND2.

Tom.... :smiley: :+1: :coffee: :australia:

157

Actually I don't have 10uf. Can I put 4.7uF instead?

it is a polarized cap right?

158

So I've added the 330R resistor in parallel with the 470R resistor. I've added 100nf cap between VCC1 and GND2 and between VCC2 and GND2.
Still some of the solenoids are stuck in their position and not turning off... :frowning:

159

image
image1920×2560 544 KB

If your solenoids fully energizes then does not retract:

  • the MOSFET is not fully turning OFF.
  • the spring isn’t strong enough.
  • there is a miss wiring.
  • the barrel of the solenoid is rough and the armature gets caught on something.
160

So I have made some more trouble shooting.
I could confidently say that the issue I'm facing is at mosfet driver of solenoid 1 and 5. The rest seems to work fine. What shall I look for at those drivers?