Wheel chair motor protection

Using Arduino General Electronics
1

Hello every body
this is my first topic in Arduino community
I am going to design robotic arm using wheelchair motor 200 watt, 24 volt, (nominal current 8 amp)
I calculated the inrush current (3 times of the nominal current = 25 AMP).

so in order to decrease the inrush to 12.5 AMP (to the half) I need inrush current limiter (NTC) equal to 1 ohm with (energy) E = 120 joule. ( AMP * VOLT*Time), where Time equal to 0.2 sec.

also I used driver to contort by the motor, I found it on Alibaba site.

does my study right؟
can any one tell me how to connect NTC with dc motor ?

Thank you.

2

You might do better to simply use PWM ramp up and ramp down to avoid large surges in current and
combine with a fuse around 10A as a fall-back. Adding an NTC inline in the DC supply may have the
issue of dropping the motor supply too low and activating under-voltage protection in the controller.

3

Thank you for reply, what PWM ramp up and ramp down mean ?
do you mean control the start speed? make it low and increase it gradually ?

please explain to me

Thank you.

4

Yes, you figured it out. What you ramp is the duty-cycle of the PWM. The speed is a consequence
of this.

5

So I should start motor with low speed then increase it gradually?
do I need any other circuits in addition to the motor driver ?

Thank you.

6

So I should start motor with low speed then increase it gradually?

Yes. I'd recommend testing it out with a lower power motor if you have one initially.
The more power is involved, the more expensive when things go wrong, so test at lower
power if you can, then move up to full power.

7

Ok, Thank you for your support,
can I use the NTC with the AC line ?
I note many people make thing like that, is it true?
Thank you.

8

Hi,
Welcome to the forum.

Please read the post at the start of any forum , entitled "How to use this Forum".
OR
http://forum.arduino.cc/index.php/topic,148850.0.html.

If you are making a robotic arm, how did you think you would control the speed?

Can you please tell us your electronics, programming, arduino, hardware experience?

Thanks.. Tom... :slight_smile:

9

Hello Tom, Sorry I late with my reply because I have not notification with your reply,

I am going to make robotic arm to move a load with 25 kg and 2 meters distance from the center, until now it is just Rz Ry Ry Ry ( four freedom degrees)
I am using wheel chair motor with 250 watt and pulleys system as this:

I will use chines motor driver with 100 Amp load.

and linear resistor to measure the degree.

Thank you.

10

What you identify an "inrush current" is necessary to get you motor to begin moving in a short period of time.

How long to want to wait for the motor to begin moving?

Paul

11

Hi,
If you selected to receive an email when your thread is answered, its better for you to check your thread at least each day.
The email facility is intermittent if at all properly functioning.

Tom... :slight_smile: