PIC controlable linear actuator circuit help

I need to build a circuit for a linear actuator. I would appreciate any feedback on the circuit Ive put together and let me know what needs to be changed if anything. The actuator draws 4 amps at full load and Im not sure if the MOSFET Ive chosen is suitable or not. The relay will allow the polarity to be switched at the actuator for forward and reverse and the actual movement signal will come from the MOSFET. Any help appreciated!

EDIT: I would actually like to know of a good SMD MOSFET that would be suitable.

Hi strokedmaro,

I guess you can't reverse a drive with a single relay (also using a stop function). Your double transistor circuit looks somewhat funny to me.

Simplicity is the name of the game not requiring a super high current MosFet transistor.

Everything can be accomplished using small signal transistors and two I/O port pins of your MCU. Using two SPDT relays the relay activation does not matter. There is no way to create a short circuit when connecting the relays as shown.

Since the current of the acutator will have to be supplied by the relays take care of double current switching capabiltity of the relays for long relay life.

Assuming a current flow of 4A in the actuator 8A relays should work over a long period without malfunction.

Boncuk

The OP's circuit would make sense if they wanted PWM control of actuator speed and direction, not just on/off and direction.

Ken

I was trying to use what I have in my spare parts bin. Is there a way to do this without relays?

Are you telling you don't have a relay in your spare part bin, although you used it for your design?

A way around relays is using a full H-bridge (LM298) which requires three inputs from the controlling MCU.

I only have DPDT's at the moment. I would love to try and use your H-bridge idea but definitely need help with that circuit. I would really appreciate a quick schematic if you can help me out. Thanks!