4 Motors Circuit Puzzle

djsfantasi

Joined Apr 11, 2010
7,693
Hmm, I got the following circuit, but not sure if it would work if one switch is set direct and the other on reverse

Thanks for the motivation btw!! And for your help :)
Good catch! If one switch was direct and the other was reverse, you’d have a direct short. Can you see how? Try using different colors and trace the power connections.

I’ll make a suggestion. What if you put the switches in series? One after another? Try to draw a circuit for that.

P.S. it will have a flaw, see if you can figure out what the flaw is. But draw the circuit anyway. It’ll help you understand the next step.
 

Thread Starter

jfran99

Joined Apr 21, 2021
30
Good catch! If one switch was direct and the other was reverse, you’d have a direct short. Can you see how? Try using different colors and trace the power connections.

I’ll make a suggestion. What if you put the switches in series? One after another? Try to draw a circuit for that.

P.S. it will have a flaw, see if you can figure out what the flaw is. But draw the circuit anyway. It’ll help you understand the next step.
In series would it be like in the photo below? In that case you could use the first switch to control if the motor receives direct and reverse current unless the second switch is set on the off (stationary motor) position, where you wouldn´t be able to control the current flow with the first switch.
 

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djsfantasi

Joined Apr 11, 2010
7,693
In series would it be like in the photo below? In that case you could use the first switch to control if the motor receives direct and reverse current unless the second switch is set on the off (stationary motor) position, where you wouldn´t be able to control the current flow with the first switch.
That’s what I had in mind. But I don’t understand your explanation.

Try to trace the battery’s polarity through each of the four possible positions of the two switches. You do know to reverse a motor, you have to reverse the polarity at its terminals? That’s what the wiring of the switch that I provided you does; reverse the polarity going to the motor.

There is NO off position in the second switch. I may have missed it, but I don’t remember an off setting.

Did you trace the wires to see why your previous schematic caused a short? It’s important for you to learn how this works. Now, do that AND trace the wires for polarity... In the latter case, draw four diagrams showing how the power and polarity gets to the motor for all four positions of the two switches.
 

MrAl

Joined Jun 17, 2014
8,249
Okay, I´ll give it a go with one motor and two switches. Also, for the correct DPDT symbol, is it this one?
That looks right now. Except for one little thing, if you have a DPDT with center "OFF' you can turn the motor off too without a special switch. I had this task long time ago too what i did was i made my own DPDT momentary switch which when you dont press either button it is off. Since then though i got a commercial DPDT with center off. I used it for a motorized computer monitor tilt mechanism and another one for a linear actuator. Dont use any of those anymore though.
 

Thread Starter

jfran99

Joined Apr 21, 2021
30
That’s what I had in mind. But I don’t understand your explanation.

Try to trace the battery’s polarity through each of the four possible positions of the two switches. You do know to reverse a motor, you have to reverse the polarity at its terminals? That’s what the wiring of the switch that I provided you does; reverse the polarity going to the motor.

There is NO off position in the second switch. I may have missed it, but I don’t remember an off setting.

Did you trace the wires to see why your previous schematic caused a short? It’s important for you to learn how this works. Now, do that AND trace the wires for polarity... In the latter case, draw four diagrams showing how the power and polarity gets to the motor for all four positions of the two switches.
I thought the DPDT switches had 3 positions: on1, off and on2? On1 being direct voltage, on2 being reversed polarity and off being like an open normal switch (no current flowing through), I´ve seen some dpdt switches online that do this. So, in that case if the second switch in series was set to off, you wouldn´t be able to control the motor with the first switch.

On a separate note, I designed the circuit in the attached photo, in theory it should work for the 4 motors with a total of 6 switches right?
 

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djsfantasi

Joined Apr 11, 2010
7,693
I thought the DPDT switches had 3 positions: on1, off and on2? On1 being direct voltage, on2 being reversed polarity and off being like an open normal switch (no current flowing through), I´ve seen some dpdt switches online that do this. So, in that case if the second switch in series was set to off, you wouldn´t be able to control the motor with the first switch.

On a separate note, I designed the circuit in the attached photo, in theory it should work for the 4 motors with a total of 6 switches right?
First, I haven’t had the chance to review your schematic.

But your concept of a DPDT switch is wrong. Normally, there is no off position unless you buy a special switch (called a center-off) and then it does. And a DPDT switch doesn’t reverse a motor. It can be used as such if you wire it correctly. But even then it likely won’t work unless you wire the rest of the circuit correctly.

The T stands for throw. Several switches can switch a common terminal to many outputs each output is called a throw.

The P stands for pole. It indicates how many circuits or poles can be switched. So a DPDT switch can switch two (double) poles to up to two (double) positions. Here’s a listing of several types of switches.

SPST Single Pole Single Throw. Commonly known as an on-off switch

DPDT Double Pole Double Throw. Can switch two circuits / poles to one of two throws / positions. It’s doesn’t reverse a motor; it has to be wired in a special way that reversed polarity at two of its terminals.

DP3T Double Throw 3 Throws. Switches two poles to one of three positions. My solution requires one of these. Or a DP4T...

I’ll look at your schematic when I get home. But, did you trace the polarity in the two schematics I requested? Until you do that, I’m afraid looking at the schematic will be a waste of time because I don’t think you understand the concepts yet. Particularly with your (IMHO) bizarre explanation of a DPDT switch. No disrespect, I just want you to learn more about what you’re doing.
 

MrAl

Joined Jun 17, 2014
8,249
The drawing in post #16 looks right, as long as the motor is connected to the right lines correctly.
Start from there. One motor at a time.
 

djsfantasi

Joined Apr 11, 2010
7,693
On a separate note, I designed the circuit in the attached photo, in theory it should work for the 4 motors with a total of 6 switches right?
Don’t you want to control the direction of each motor either individually or all at the same time? The schematic in post #16 controls the direction of all motors but allows some to be turned off. You can’t have motor #1 going forward and motor #2 going in reverse.

Your schematic in post #22 allowed you to control one motor (and hence 4 motors) with two switches. But, if you trace the polarity, the first switch doesn’t control the direction consistently but reverses the direction of each motor.

That is, if motor #1 starts out going forward and motor #2 is reversed, then operating the first (leftmost) switch makes motor #1 go in reverse and motor #2 go forward... I thought you wanted the first switch make all motors either be controlled by their individual switches OR all go forward or all go reverse controlled by the first switch?

That’s where you’ll need a DP3T or DP4T switch as your first switch...

You were so close in post #22. And if you look again at post #20, you might get an idea of how to do this with a DP4T switch...

That first switch? What do you think each of the throws or positions would do? How about:
  • All motors off
  • Individual motor control
  • All motors forward
  • All motors reverse
 
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Ramussons

Joined May 3, 2013
973
I presume that:

Each of the 4 Motors has its Local Control.
Each of the 4 Motors has a Common Master Control.
1 / 2 / 3 / All motors can be Controlled by the Master. (For example, 2 motors can be under a Common Control, 2 Locally Controlled)

For such a working,

Take 1 motor.
It needs to be OFF, CW run, CCW run, Hand over the control to a Master switch.
Does this give you an idea how it can be done?
How many Poles in the Switch? How many Throws?

Apply this to all 4 motors.

The Master switch. How many Poles? How many Throws?
 

djsfantasi

Joined Apr 11, 2010
7,693
Do you know how to reverse a DC motor?

Nice drawings of the four positions of two switches. But I don’t see a trace of how the current flows to the motor and back to the battery again? Use one or two highlighters and trace the wires of the path the current flows in each case.

For the future, do you see the flaw in this design? If one or more motors are going forward and one is going in reverse, what happens when the master or first switch is activated?

I have a picture of a solution on my phone. But this is homework help; not homework done for you. When is it due?

I’ve given you four questions. Please don’t reply unless you have at least four answers.

By the way, please try to use the hints I’ve given you. I’m on vacation for two weeks and may not be online as much
 

Thread Starter

jfran99

Joined Apr 21, 2021
30
Hi @djsfantasi , sorry for that, I hope the following diagrams are more clear. The first one is in the 4 configurations in series and the second one the 4 configurations in parallel. The current going to the motor is in blue and the current going back to the battery is in red. For the ones in parallel, there are 2 configurations that would short circuit. I´m still trying to figure out a combination that would work but still haven´t found one tbh. The deadline is for this friday evening, as you asked
 

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djsfantasi

Joined Apr 11, 2010
7,693
I’m not going to be able to help as much. So I’m going to ask you some questions,that if you can answer will give you the final solution.

The problem with this solution is the “master” switch just reversed the motor from its current direction. You need it to be a master switch. It does four things.
  1. It turns all motors off
  2. It sends power to the individual DPDT switches
  3. It sends power for forward polarity to all motors
  4. It sends reverse polarity to all motors
Each motor will be wired for individual and master control
 

Thread Starter

jfran99

Joined Apr 21, 2021
30
I found a circuit that can send power to individually through a DP4T and change the polarity with a DPDT before in series. I can´t find a way to power all of them simultaneously though, or switching them all off.
 

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Thread Starter

jfran99

Joined Apr 21, 2021
30
With a DP4T on the left, the following circuit should work. With the dp4t switch on the right, you can select the individual motor you want to operate. With the first and second positions of the left dp4t, you can supply power to the dp4t on the right with direct or reversed current. On the left switch, on the third position, you supply direct current to all of the motors simultaneously and on the fourth position, you supply reversed current to all the motors simultaneously. The only thing left would be to have every motor "off", I´m thinking this can be done with a normal switch before the left motor.
 

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Ramussons

Joined May 3, 2013
973
....... Operating each motor individually.......
How do you operate each motor individually? Your power feed is from the left switch, the right has no role.

Suppose the Motor connection has a switch that offers 4 options as i hinted at ny earlier post?
 

Ramussons

Joined May 3, 2013
973
want to operate 4 dc motors clockwise, anticlockwise (i.e reverse polarity) and stationary (not moving). Operating each motor individually. And also be able to do the same to the 4 of them simultaneously (eg. move all anticlockwise at the same time). Does anyone have an idea of a circuit that could accomplish this?
The highlighted requirement requires at least 4 switches to start with.
 
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