SPDT vs DPDT

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SPDT vs DPDT

Postby tschua » Mon Aug 23, 2010 10:39 am

Hi,

Currently, i am designing a high current (around 20A) DC brushed motor (power window) driver using relay.

I wonder using 2 SPDT relay is better or 1 DPDT relay? Or got others better and simple solutions to drive Power Window in bi-direction? I have attached the pictures.

Please help me.

Regards,
TSCHUA
Attachments
DPDT.jpg
1 DPDT relay to driver DC brushed motor
SPDT.jpg
2 SPDT relays to driver DC brushed motor
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Re: SPDT vs DPDT

Postby ober » Tue Aug 24, 2010 5:48 pm

Seem to be the DPDT method, you cannot stop the motor.
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Re: SPDT vs DPDT

Postby tschua » Wed Aug 25, 2010 12:17 pm

I will use 1 MOSFET to control speed. Maybe can stop it by giving PWM=0.
is it ok?
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Re: SPDT vs DPDT

Postby ober » Wed Aug 25, 2010 7:55 pm

Should be fine...... still need to test, do let us know the result.
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Re: SPDT vs DPDT

Postby royalstorm7 » Tue Sep 07, 2010 3:19 pm

tschua.....your spdt circuit similir as mine...but i got n-channel mosfet online....for me...it is the most simple way to have bi-dir and speed control at the same time..

but ur dpdt....will never turn on the motor...
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Re: SPDT vs DPDT

Postby robosang » Wed Sep 08, 2010 6:07 pm

The DPDT seem like cannot stop..... not cannot on :lol:
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Re: SPDT vs DPDT

Postby redips_id » Sat Sep 18, 2010 8:58 pm

My friend have developed driver motor by using DPDT relay and it works. To turn ON and OFF the motor just need to control the PWM as tschua said. Maybe it will have a problem on braking system. I'm not sure because I don't know how to make the DC motor brake. Anyone know how to brake the DC motor? (I mean: torque brake > torque stop)
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Re: SPDT vs DPDT

Postby shahrul » Sun Sep 19, 2010 11:05 pm

You cannot apply PWM to ON/OFF relay. Because relay is mechanical device, when it's ON/OFF with fast switching, it will be heated.
You must apply PWM to varies Motor current. You can use this
Image
But, it's better you use L298. 20V for drive motor, I think no problem on L298 because the datasheet state max 50V.
Image
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Re: SPDT vs DPDT

Postby redips_id » Sun Sep 19, 2010 11:18 pm

Haaa, this is my friend, I forgot about the mosfet (I mean control the PWM at that mosfet), hahaha, really sorry.. :lol:
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