Controling the speed and direction of a DC motor (got now a circut doing it using Potentiometer)

Thread Starter

ofiryaish

Joined Jan 10, 2018
25
Hello,
I got a working circuit doing it using Potentiometer. When the voltage across is below 6 volts it is in in one direction (6 in stop and 0 volts for high speed) and when it's above 6 volts it's in the other direction (6 for stop and 12 for high speed). the circuit is then concocted to kind of H-BEIGE circuit
I want to "update " this circuit so that I can control the speed and direction using dip-switches (4 dip switches for 16 types of speed (0-zero, 15- high speed) and 1 switch for direction). my problem is how to create this kind of range of range unsing only BJT, mosFET and operational amplifier. I thought about using somehow voltage summer using operational amplifier, but I don't see how because in one hand I need to choose direction and in the other hand I need to choose the speed and it the Potentiometer it was all together.
 

MaxHeadRoom

Joined Jul 18, 2013
19,012
That application seems to cry out for a small picmicro with bi-directional PWM output.
Max.
 

Bernard

Joined Aug 7, 2008
5,259
When using DIP SWs , you must be careful not to have more than one SW on at a time. It is not advisable to
be at a high speed & reverse direction.
 

Tonyr1084

Joined Sep 24, 2015
3,577
16 switches seems cumbersome and a bit wasteful. But if this is your goal, we can help. Understand that we're going to recommend alternative methods for controlling speed and direction of a motor. The FIRST thing that comes to my mind is my variable speed reversible drill. Everything is already done for me. But to use switches, each one will need to be a DPDT, and using 1/2 of the poles you control speed. With the other half you need to interrupt power to the remaining switches so that only one circuit is controlling motor speed. The LAST DPDT switch would control direction.

I'll bang out a quick drawing but it won't be complete. Hopefully it will set you off in the right direction to solving the problem you present.
 

Tonyr1084

Joined Sep 24, 2015
3,577
OK, here's a reference diagram. Each switch interrupts power to the next switch so you don't have two switches trying to control motor speed at the same time. The first switch is a DPDT center off switch. The rest only need to be DPDT (not with center off). Pin 6 is either unconnected OR you can connect it to an LED circuit to indicate switch state. LED ON means SWITCH ON [edited].

01 motor speed.jpg
 
Last edited:

ericgibbs

Joined Jan 29, 2010
8,723
hi ofiryaish,
I see that you are a Student, is this project a college or homework assignment.?
E
 

Thread Starter

ofiryaish

Joined Jan 10, 2018
25
16 switches seems cumbersome and a bit wasteful. But if this is your goal, we can help. Understand that we're going to recommend alternative methods for controlling speed and direction of a motor. The FIRST thing that comes to my mind is my variable speed reversible drill. Everything is already done for me. But to use switches, each one will need to be a DPDT, and using 1/2 of the poles you control speed. With the other half you need to interrupt power to the remaining switches so that only one circuit is controlling motor speed. The LAST DPDT switch would control direction.

I'll bang out a quick drawing but it won't be complete. Hopefully it will set you off in the right direction to solving the problem you present.
I'm sorry, but I think you didn't understand me (maybe because of my fault). I have 4 switches controlling the speed (0-15 like binary number (4 digits 2^4 options)). and one switch to control the direction (if it's needed).

I thought maybe to use voltage summer using op amp, but I struggle to form the configuration.
(like here https://www.electronics-tutorials.ws/opamp/opamp_4.html).
another thought I had is to put 5 resistors in series and and put the switch in parallel to each resistor, and some how the create voltage divider that will work, but I faild.
the thing is that I know that there is solution because someone with those exact parts done it.
 

Thread Starter

ofiryaish

Joined Jan 10, 2018
25
hi ofiryaish,
I see that you are a Student, is this project a college or homework assignment.?
E
You are right. this is kind of work I have been given, and I'm trying to find solution for this problem and find new ideas.
 

Tonyr1084

Joined Sep 24, 2015
3,577
I'm sorry, but I think you didn't understand me
Yes, I see that now.

Eric Gibbs asked if you're a student and this is homework. I was wondering the same thing. [edit] you beat me. Thank you. [end edit]

As for the digital (4 switch) arrangement, you'd likely need a binary converter as a starting point. Because (for two reasons) this may be homework, I'd like to help you solve your problem as opposed to solving it for you; and for me to solve this problem it would take some thought and effort on my part, as I'm not very accomplished in binary. I understand it. It would just take me a while to come up with something. I think it better serves you if we direct you in ways to help you find your own solution to the problem.

Good luck.
 

Thread Starter

ofiryaish

Joined Jan 10, 2018
25
Yes, I see that now.

Eric Gibbs asked if you're a student and this is homework. I was wondering the same thing. [edit] you beat me. Thank you. [end edit]

As for the digital (4 switch) arrangement, you'd likely need a binary converter as a starting point. Because (for two reasons) this may be homework, I'd like to help you solve your problem as opposed to solving it for you; and for me to solve this problem it would take some thought and effort on my part, as I'm not very accomplished in binary. I understand it. It would just take me a while to come up with something. I think it better serves you if we direct you in ways to help you find your own solution to the problem.

Good luck.
I would appreciate any help you can give and some guidelines will be good. as I said I'm restricted to use only BJT, MOSFET and OP AMP, and that is the big obstacle here.
 

ericgibbs

Joined Jan 29, 2010
8,723
hi ofiryaish,
I see that you are a Student, is this project a college or homework assignment.?
Moderation: I would like an answer.

E
 

Thread Starter

ofiryaish

Joined Jan 10, 2018
25
hi ofiryaish,
I see that you are a Student, is this project a college or homework assignment.?
Moderation: I would like an answer.

E
I'm student in university. this is a task I have been asked to do (part of task that I'm got stuck in). you can call it homework or project to do at home. why it's matter?
 

ericgibbs

Joined Jan 29, 2010
8,723
hi,
It matters when academic grades are based on the students abilities to solve college or homework assignments.
E
 

Thread Starter

ofiryaish

Joined Jan 10, 2018
25
hi,
It matters when academic grades are based on the students abilities to solve college or homework assignments.
E
So I can tell you that it's not a factor, and I allowed to ask for help. I not asking someone to do my job I tried couple of things and they didn't worked, so I'm asking for advice . if you want to help, then it is your choice :)
 

bertus

Joined Apr 5, 2008
20,048
Hello,

In the homework help forum, we can give you directions that might help you to find a solution.
We will not provide complete solutions.

Bertus
 

ericgibbs

Joined Jan 29, 2010
8,723
Moderation Note:
Its always the choice of a member to help or not.
If they decide to offer help, their help will be based on whether its a private project or homework.
If its homework they will only offer guidance not a complete solution.
 
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