Linear Actuator Speed Control Using Transistors

[jayjayd_123]

I am using some linear actuators to build a stand up desk and they have a large starting current which I want to avoid for numerous reasons.

I've decided to use relays for direction control and transistors or mosfets for speed control and right now I am using the IRFZ44N mosfet (one on each motor) as the logic level should make it easier to work with Arduino.

I have the speed slowly ramping up and for one of them it seems to have control over speed but the max speed doesn't seem to be the full speed of the actuators and the other one just runs at full speed no matter what I do to it, even with the identical mosfet.

If I switch the mosfets, then the motors switch behaviors as from above.

I tried a lot of different types of logic level mosfets and also TIP-120 and TO-220 transistors.

the TIP-120 transistor didn't have any effect on the motors and voltage passed through at full no matter the base voltage.

the TO-220 transistor seems to work great, just with either a lot of resistance or inability to supply enough current and the motors never reach full speed before they heat up too much.

Is there something I am doing wrong? is there a better solution to control a 36v and roughly 2-4 amp motor speed? Schematic is attached.

 

[KlausST]

Hi,

this is no schematic. It uses no standard schematic symbols and the wiring is more than confusing.
If you want useful feedback I recommend to provide useful informations first.
A hand drawn schematic may be more useful than this artwork.

A breadboard isn´t suitable for high current.

Klaus

 

[betwixt]

...and from what I can see, the MOSFETs are directly across the supply and the Arduino drives the motors directly. Isn't going to work!
The whole concept of speed control using relays doesn't sound right.

Brian.