# How can I delay the voltage up and down in this circuit?

Discussion in 'Homework Help' started by rigerman, Aug 24, 2015.

Apr 25, 2014
40
0
2. ### MikeML AAC Fanatic!

Oct 2, 2009
5,450
1,066
That supply is an adjustable constant-voltage DC supply, with rudimentary current-limiting. The intrinsic current limiting is set too high to accelerate the motor smoothly. Making the 0.33Ω larger in steps of 2X would help that. There is nothing in this circuit to control the braking of the motor.

To do this right would require implementing a ramp-up, ramp-down using PWM, which would likely be done most easily using an Arduino.

3. ### MaxHeadRoom Expert

Jul 18, 2013
10,832
2,502
What is the voltage/current rating of the motor?
Max.

4. ### rigerman Thread Starter Member

Apr 25, 2014
40
0
20mA.

PS: Sorry, around .50 Amps.

5. ### rigerman Thread Starter Member

Apr 25, 2014
40
0
But the voltage varies from 0 to 12V when the pot is adjusted.

6. ### MikeML AAC Fanatic!

Oct 2, 2009
5,450
1,066
So the pot varies the max speed. The 0.33Ω resistor controls the rate of acceleration (if it is set to an appropriate value, like 4X what it is now).

7. ### rigerman Thread Starter Member

Apr 25, 2014
40
0
Should I change the resistor?

8. ### MaxHeadRoom Expert

Jul 18, 2013
10,832
2,502
I have used a LM317 in a simple ramp up circuit, should be possible to modify to ramp down also.
Probabally less components.
Max.

9. ### MikeML AAC Fanatic!

Oct 2, 2009
5,450
1,066
You are not reading these posts very carefully. I say again from post #2 .

Making the 0.33Ω larger in steps of 2X would help that.

10. ### rigerman Thread Starter Member

Apr 25, 2014
40
0
I am not much of an electronics person. So, I don't know what "Making the 0.33Ω larger in steps of 2X would help that" means.

11. ### MikeML AAC Fanatic!

Oct 2, 2009
5,450
1,066
Double 0.33Ω t0 0.68Ω (2X) and see how fast the motor accelerates. If still too fast, double it again to 1.2Ω and try again..., and so on...

rigerman likes this.