Controlling 12v power with 5v logic

Other Hardware General Electronics
1

Hi

I tried to use a IRFZ44N with 5v logiv on gate to control 12v power source, but it somewhat failed :

  • Putting 5v to the gate won't let 12v go through
  • I can't use the mosfet on the 12v ground because in this case the motor will use another ground (stepper driver)

This is what I tought I'd do :

975×621 21.4 KB

I need to run the stepper motors until they have reached a stop switch BUT this switch can't simply cut the 12v because the motors needs to be able to run counterclockwise after that. This is intended to synchronize 3 steppers controlled by one single µC, in case of one having too much load it can keep going while the 2 others are waiting at the end of course...

I decided to use 3 drivers but only one µC to prevent other sync problems between them.

Any design ideas ?

I got a PM regarding IRFZ44N's Vgs beign too low, here is what I found in the datasheet :

1123×805 117 KB

2

  1. The IRFZ44N is not a logic level fet, so can't be used with 5volt logic.
    It needs 10volt at the gate to fully saturate.
    Same for the IRF530.

  2. The gate needs to be 10volt higher than the source for the fet to fully turn on.
    The source, when the fet is switched on is 12volt, so the gate must be 12+10= 22volt.
    How are you going to do that with a 5volt pin...

  3. Are these high impedance steppers. Low impedance steppers most likely need to be current driven (not voltage driven). Post a link to the stepper datasheet.
    Leo..

3

Would a 30N06L fit ?

17HS4401 are driven by A4988.

4

High-side switching (in the + line) is usually done with a p-channel fet.
Try to understand the mosfet circuits on this page, especially diagram 3.

Not sure why you want to switch power to the A4988, since it has an enable pin.
Leo..

5

Wawa:
High-side switching (in the + line) is usually done with a p-channel fet.
Try to understand the mosfet circuits on this page, especially diagram 3.

Not sure why you want to switch power to the A4988, since it has an enable pin.
Leo..

There's only one enable pin for two conditions so..
I should use and/or/not gates but I don't have them.

6

I guess I'll wait for the 74HCXX to be delivered

I created this circuit to enable/disable 4988 when the direction (clockwise/counterclockwise) and safety limit switch are triggered

1195×576 13.8 KB

7

I created this circuit to enable/disable 4988 when the direction (clockwise/counterclockwise) and safety limit switch are triggered

I don't see where this circuit connects to the A4988.

8

I actually don't understand the whole story.
End switches should be connected to the Arduino, with proper debouncing.
And the program should decide of it's safe to run the stepper(s) in both directions or not.
None of the above should be needed.
Seems like a classic XY problem.
Leo..