DC motor turns both ways

Thread Starter

Adamf001

Joined Sep 5, 2011
67
Hi guys just wanted to know how can I get a DC motor spin clockwise then counter clockwise automatic in a circuit, I need this to be quite simple because I'mm going to use this for a Christmas decoration. is it doable? :confused:
 

KMoffett

Joined Dec 19, 2007
2,911
What is the motor's voltage and current requirements?Do you intend the direction of spin to be changed after a period of time, or by the position of whatever the motor is turning (i.e. limit switches). What is the motor turning? Does it need to stop before changing directions?..as motors don't like suddenly reversing directions under load.

Ken
 

Sparky49

Joined Jul 16, 2011
833
I don't think it would be very simple to do, but I would see about using relays to switch the current flow through the motor.

I'm sure those who are more experienced than myself can help you more, but I'll see what I can do.:)

Sparky
 

samin

Joined Oct 14, 2011
32
There is a much-simpler way.. you can make the project with a double-pole double-throw switch and not use any relays at all. The only problem is the motor is constantly turning in one direction or the other. The alternative is to use two double-pole push switches or 4 switches as shown in the following diagram. You need to push both of the forward switches at the same time. By pushing the reverse switches very briefly you will get braking when travelling in the forward direction.
 

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BMorse

Joined Sep 26, 2009
2,675
Depending on the size and current ratings of your motor ( I am assuming this is a small decoration?? maybe a Tree ornament??) It can easily be done with a couple of NPN and a couple of PNP transistors (setup as an H-Bridge), coupled with the all too famous low power NE555 timer IC in an astable setup, you can set the delay (or how long it rotates in either direction) by just using 2 capacitors and 2 resistors.....

Or

You can still use a 555 timer to switch a DPDT (Double pole, double throw) relay via a transistor and just have it swap the leads of the motor to reverse the motors direction...
 

BMorse

Joined Sep 26, 2009
2,675
There is a much-simpler way.. you can make the project with a double-pole double-throw switch and not use any relays at all. The only problem is the motor is constantly turning in one direction or the other. The alternative is to use two double-pole push switches or 4 switches as shown in the following diagram. You need to push both of the forward switches at the same time. By pushing the reverse switches very briefly you will get braking when travelling in the forward direction.
It is going to be used as a decoration, meaning it would be kind of tedious to keep having to push a switch or 2 to get it to move....
 

chrisw1990

Joined Oct 22, 2011
551
There is a much-simpler way.. you can make the project with a double-pole double-throw switch and not use any relays at all. The only problem is the motor is constantly turning in one direction or the other. The alternative is to use two double-pole push switches or 4 switches as shown in the following diagram. You need to push both of the forward switches at the same time. By pushing the reverse switches very briefly you will get braking when travelling in the forward direction.
only issue is, when your using switches is the cost, its ok, its simple, makes sense, but you dont really want a 10quid/dollar/(insert currency) motor with a 30quid/dollar.. switch?
hence h-bridge, relays etc.
 

Thread Starter

Adamf001

Joined Sep 5, 2011
67
What is the motor's voltage and current requirements?Do you intend the direction of spin to be changed after a period of time, or by the position of whatever the motor is turning (i.e. limit switches). What is the motor turning? Does it need to stop before changing directions?..as motors don't like suddenly reversing directions under load.

Ken
Well Im not sure about the motor, its a smnall one used for Toy cars, i wanted the motor to turn a arm on a santa decforation. i need the motor to turn one way for a second or two then stop, pause. then turn the other and then repeat the turns.
 

BMorse

Joined Sep 26, 2009
2,675
Well Im not sure about the motor, its a smnall one used for Toy cars, i wanted the motor to turn a arm on a santa decforation. i need the motor to turn one way for a second or two then stop, pause. then turn the other and then repeat the turns.

Well, in this case I would just use some mechanical attachment to move the arm, you can just have the motor turn one way without switching directions..... basically build a cam system that would move the arm back and forth if the motor is just left on, but then couple that with a 555 timer IC and a relay to turn on the motor say every 2 seconds to move for 1 sec, using simple machine techniques to build the arm cam should not be too hard, and you would only require a few components for the circuit to keep it simple....
 

chrisw1990

Joined Oct 22, 2011
551
555 slow oscillator? doesnt have to be precision.. could hook up a little transistor circuit or buy an hbridge ic.. should be fairly cheap for that size motor, and then get the 555 to toggle the direction? :)
 

BMorse

Joined Sep 26, 2009
2,675
Instead of a cam like BMorse, it would be easier to use a offset crank pin. Look at how windshield wiper motors work. http://auto.howstuffworks.com/wiper1.htm
Then you just have to slow the motor down to the right speed.

actually, (as I said) those widshield wipers DO use a cam to actuate :rolleyes:

here is a quote from your link:

A short cam is attached to the output shaft of the gear reduction. This cam spins around as the wiper motor turns. The cam is connected to a long rod; as the cam spins, it moves the rod back and forth. The long rod is connected to a short rod that actuates the wiper blade on the driver's side. Another long rod transmits the force from the driver-side to the passenger-side wiper blade.
FYI: Here is what wiki says about CAM's and Cranks:

CAM
The cam can be seen as a device that translates from circular to reciprocating (or sometimes oscillating) motion
CRANK
The opposite operation, translation of reciprocating motion to circular motion, is done by a crank.
 
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shortbus

Joined Sep 30, 2009
8,057
actually, (as I said) those widshield wipers DO use a cam to actuate :rolleyes:

here is a quote from your link:



FYI: Here is what wiki says about CAM's and Cranks:

CAM


CRANK
Not to argue with you but look at the animation in the link or the wiper motor in your car and see if it looks like a cam or a crank. The text is some times written by some one that doesn't really know what their talking about. :)
 

BMorse

Joined Sep 26, 2009
2,675
Not to argue with you but look at the animation in the link or the wiper motor in your car and see if it looks like a cam or a crank. The text is some times written by some one that doesn't really know what their talking about. :)



Not trying to argue either, but to turn a rotary motion to linear you use a cam, and to turn linear /reciprocating motion into a rotating motion, you still use a crank.... and by looking at the picture and my windshield wiper setup, it uses a cam to move my wipers (regardless if it it just a small rod coming off of the motor shaft), anything coming off of a rotating shaft that converts rotary motion into linear is a cam regardless if it looks like a crank..... that is just my understanding of it, and it is the only logical explanation for those terms. If you find a different meaning somewhere else I would be glad to say you I was wrong....;)
 

shortbus

Joined Sep 30, 2009
8,057
Any cam I've ever saw has a follower. Any crank has a connecting rod. A crank also has a pin that changes the rotating motion to another motion by the connecting rod. Since a windshield wiper uses a pin and connecting rod to make the movement and not a follower it where for is a crank mechanism. :)
 

djsfantasi

Joined Apr 11, 2010
6,973
IMHO...

From Wikipedia said:
A crank is an arm attached at right angles to a rotating shaft by which reciprocating motion is imparted to or received from the shaft. It is used to change circular into reciprocating motion, or reciprocating into circular motion.
From Wikipedia said:
A cam and follower is formed by the direct contact of two specially shaped links. The driving link is called the cam (also see cam shaft) and the link that is driven through the direct contact of their surfaces is called the follower. The shape of the contacting surfaces of the cam and follower determines the movement of the mechanism.
I tend to agree with Shortbus. a cam requires a follower; a crank is used to convert linear to rotary motion or vice versa.

How big is your Santa?
 
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