Hi,

I have a Motor being controlled by a Programmable controller and I need to reduce the voltage to it.
The output of the controller is 4.8v and the motor is a 3v motor. So i need a voltage drop of 1.8volts before the motor.
I know this is simple but I'm really stuck can anyone help?

Thanks in advance.

 

Hello...

This is not simple since PWM (Pulse Width Modulation) -- is really the only way to control motors.

 

two standard diodes in series will drop about the amount you desire.

 

I think that, though PLC is an industrial computer control system that continuously monitors the state of input devices and make decisions based on the custom programs to control the state of output devices.
figure shown below illustrates the control circuit and wiring diagram of a 65% tapped, autotransformer, reduced-voltage-start motor control circuit. This reduced voltage startminimizes the inrush current at the start of the motor (locked rotor current) to 42% of that at full speed.

In this example, the timer must be set to 5.3 seconds. Also, the instantaneous contacts from the timer in lines 2 and 3 must be trapped.

 

annanya, that is a nice reduced voltage starter method, but this post is about a small dc motor, not a 3 phase a c motor.

 

Unless you are speed controlling it where the higher voltage would not matter, I agree with Kermit, two diodes in series.
Max.

 

Unless you are speed controlling it where the higher voltage would not matter, I agree with Kermit, two diodes in series.
Max.

Unless the OP is reversing the motor.

If the controller uses PWM for speed control, and if you rarely run the motor wide open, I wouldn't even worry about it...

If the controller is programmable, why not restrict the top speed to only ~75% of what it would normally be. The startup, inrush current to initially start the motor will still apply 4.8V for a second, but then as the motor comes up to speed, the controller will reduce the effective voltage across the motor to more like 3V.

 

Unless the OP is reversing the motor.

.

Another couple in reverse parallel.
'Programmable controller' often refers to PLC? No PWM.
Max.