Author Topic: Need Help Wiring DC Motor with PWM  (Read 16256 times)

Offline snub

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Need Help Wiring DC Motor with PWM
« on: June 13, 2016, 10:04:58 PM »
I found an interesting wiring diagram on the interweb showing how to control a DC motor with a SPDT switch and 2 automotive type relays. The motor is the kind where the direction of rotation is changed by reversing the polarity of the 2 input wires. The way it was wired seemed odd to me, grounding through the switch and power was going to 2 terminals on the relay. Anyways, I hooked it up as per the diagram, and it works just fine.

So then I'm thinking I'd like to hook up a Pulse Width Modulator to control the speed and wondering why I can't use a single PWM straight off the power supply. I didn't think it would work and I was right. It doesn't. At least not how I have it wired. I even tried a second PWM from a different manufacturer and same thing. Motor runs at full speed, won't slow down.

I'm wondering why it doesn't work and if there is another way to wire it. First diagram is the one I found at Burden Supply, the second is how I wired in the PWM.



.

Offline PK

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Re: Need Help Wiring DC Motor with PWM
« Reply #1 on: June 13, 2016, 11:29:15 PM »
Basically you need to PWM the power going to the motor, but NOT the power going to the relay coils. So wire both 86 terminals of the relays to the +ve terminal of the battery (and only to the + terminal of the battery).

PK

Offline snub

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Re: Need Help Wiring DC Motor with PWM
« Reply #2 on: June 14, 2016, 02:47:44 PM »
Thanks for the reply PK, but I'm not understanding. Are you saying to supply PWM regulated to the #87 terminals and battery voltage to the #86?

RobWilson

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Re: Need Help Wiring DC Motor with PWM
« Reply #3 on: June 14, 2016, 03:10:18 PM »
like so Snub

As PK mentioned the relay coil will  have some issues being supplied with a PWM supply  :zap:


Rob

Offline snub

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Re: Need Help Wiring DC Motor with PWM
« Reply #4 on: June 14, 2016, 08:48:01 PM »
Well, back to the drawing board. I hooked it up as you showed, but still no love. Motor runs at full speed. I tried another PWM with the same result. I even reversed the terminals at 86 and 87 just to be sure.

Offline PK

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Re: Need Help Wiring DC Motor with PWM
« Reply #5 on: June 14, 2016, 09:27:33 PM »
Are you sure that terminals 87 only connect to the PWM output (ie not to the battery) You should be able to measure the DC volts across the motor change as you vary the PWM.

Offline tom osselton

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Re: Need Help Wiring DC Motor with PWM
« Reply #6 on: June 14, 2016, 10:51:46 PM »
I dont know to much about wiring but shouldn't the fuse go directly to the + pulse width  control? The diagram shows it going to both the pw and the relay wouldn't that render the pw useless?

RobWilson

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Re: Need Help Wiring DC Motor with PWM
« Reply #7 on: June 15, 2016, 03:46:06 AM »
Hi snub

Just to clarify make sure the control side of the relays are wired up like so .

RobWilson

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Re: Need Help Wiring DC Motor with PWM
« Reply #8 on: June 15, 2016, 03:52:15 AM »
I dont know to much about wiring but shouldn't the fuse go directly to the + pulse width  control? The diagram shows it going to both the pw and the relay wouldn't that render the pw useless?

The fuse is just  supplying two separate curcuits .

1 . A supply to the PWM controller

2.  A supply to the direction control

In reality  they would  have their own fuse . But they would still be conecting to B+

Offline John Rudd

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Re: Need Help Wiring DC Motor with PWM
« Reply #9 on: June 15, 2016, 03:52:30 AM »
The coil is connected to pins 85 and 86, pin 30 is the common connection for the contacts on pins 87 and 87a.

Just wire up the relay contacts to give a double pole changeover arrangement.
The fwd/rev switch then acts to either energise or de-energise the relays giving the fwd or rev action,is another way of doing it.
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Offline Alan Haisley

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Re: Need Help Wiring DC Motor with PWM
« Reply #10 on: June 15, 2016, 11:36:12 AM »
Well, back to the drawing board. I hooked it up as you showed, but still no love. Motor runs at full speed. I tried another PWM with the same result. I even reversed the terminals at 86 and 87 just to be sure.
Where did you get the wiring diagram for the PWM? Have you tried wiring just the power supply, the PWM, and the motor to make sure that you can speed control at all? What does that working diagram look like?


Alan


Offline seadog

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Re: Need Help Wiring DC Motor with PWM
« Reply #11 on: June 15, 2016, 02:13:39 PM »
I've just had a look at the circuit and it occurs to me that you've commoned the battery negative and the motor negative output terminals. Have you metered the these terminals to see if they are electrically common. I've a feeling that they won't be.

Offline snub

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Re: Need Help Wiring DC Motor with PWM
« Reply #12 on: June 15, 2016, 02:23:36 PM »
Thanks for the help guys, I'm still plugging away at it. 'seadog', I think you're on to something with the way I have the negative terminals commoned.

Offline John Rudd

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Re: Need Help Wiring DC Motor with PWM
« Reply #13 on: June 15, 2016, 02:44:06 PM »
Snub,
See the attached sketch....
Hope this is simple enough for you..
I used a simple changeover switch to energise/de-energise the relays for FWD and REV
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Offline snub

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Re: Need Help Wiring DC Motor with PWM
« Reply #14 on: June 15, 2016, 10:23:33 PM »
Thanks for the sketch, John Rudd, but schematics are my Achilles heal. If someone out there is bored to tears, maybe they could convert it into a diagram like the one in my first post. Also not sure why you wrote "Rev-Not Used"

Offline John Rudd

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Re: Need Help Wiring DC Motor with PWM
« Reply #15 on: June 16, 2016, 03:04:45 AM »
Snub,
I cant see how to make the drawing any simpler....

The wire connections are all identified by the numbers that appear on the relays....
The "rev-not used" simoly means that the second connection on my switch is not connected to anything.....in reality the relays are either in or off giving fwd or rev.

Might I suggest you get some books on basic electrics and have a read?

I'm always willing to help out, just ask if you're not sure..

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Offline daGrouch

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Re: Need Help Wiring DC Motor with PWM
« Reply #16 on: June 16, 2016, 11:19:17 AM »
Separate the BATT- from MOTOR-  ( electronic circuits like to switch or act on the (-) for some reason).
Power the relay coils from BATT+ instead of PWM+.

Yeah, it looks weird at first glance. 
With both relay's OFF both motor leads are connected to PWM- so nothing happens.
With UP relay ON the red motor lead goes PWM+ while black motor wires stays PWM- and motor spins.
With DOWN relay ON red motor wire remains PWM- and black motor wire goes PWM+.



CAUTION: I don't know how the PWM will like having the motor load switched or removed while it's on.

Offline shipto

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Re: Need Help Wiring DC Motor with PWM
« Reply #17 on: June 16, 2016, 11:29:32 AM »
beat me to it daGrouch I just did almost exactly the same drawing  :beer:
Although the switch would need to be center off or there would be no stopping the motor from running short of turning power off.
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RobWilson

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Re: Need Help Wiring DC Motor with PWM
« Reply #18 on: June 16, 2016, 11:47:22 AM »
Odd , is that not exactly what I had redrawn in post #3   :scratch:

And clarified in post #7

Rob

Offline daGrouch

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Re: Need Help Wiring DC Motor with PWM
« Reply #19 on: June 16, 2016, 12:06:54 PM »
beat me to it daGrouch I just did almost exactly the same drawing  :beer:
Although the switch would need to be center off or there would be no stopping the motor from running short of turning power off.

That's why my post has so many typo's - I was rushing to post before you!  :ddb:

He showed a SPDT-CO so he had center-off covered.  He doesn't show if or how he want's to switch the PWM so maybe it's a given.  If not then a DPDT-CO could be used instead to power the PWM only when needed provided the PWM retains it's speed setting when powered off.


Offline daGrouch

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Re: Need Help Wiring DC Motor with PWM
« Reply #20 on: June 16, 2016, 12:13:17 PM »
Odd , is that not exactly what I had redrawn in post #3   :scratch:

And clarified in post #7

Rob
Well, yeah.

Snub requested a drawing in his format to help him visualize it his way and I happened to be bored ATM. :) 
I could have changed the notation to Latin or Klingon but I didn't want to get yelled at.

Offline shipto

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Re: Need Help Wiring DC Motor with PWM
« Reply #21 on: June 16, 2016, 12:20:56 PM »
Odd , is that not exactly what I had redrawn in post #3   :scratch:

And clarified in post #7

Rob
So it is I had not looked at yours but I also didnt notice the center off switch on the origional drawing, must be old age  :lol:
Turns out this life c**p is just one big distraction from death but a good one. For the love of god dont give yourself time to think.
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RobWilson

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Re: Need Help Wiring DC Motor with PWM
« Reply #22 on: June 16, 2016, 12:23:23 PM »
Thanks for the sketch, John Rudd, but schematics are my Achilles heal. If someone out there is bored to tears, maybe they could convert it into a diagram like the one in my first post. Also not sure why you wrote "Rev-Not Used"

And It was my understanding he wanted Mr Rudds wiring diagram redrawn  :coffee:


Rob 

RobWilson

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Re: Need Help Wiring DC Motor with PWM
« Reply #23 on: June 16, 2016, 12:30:10 PM »
Anyway what I fined odd is that there is no pot shown in the wiring diagram  :scratch:  maybe its a wireless pot  :lol:



And a bit more info from the OP  like the make /model of the PWM controller would be a help .

Rob

Offline John Rudd

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Re: Need Help Wiring DC Motor with PWM
« Reply #24 on: June 16, 2016, 12:34:16 PM »
So is this sorted now? :scratch:
I guess we need sone feedback ?

Rob, could be the pot is an integral part of the speed controller?
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