DC Motor Forward/Reverse Control

Thread Starter

fignewton83

Joined Nov 6, 2021
12
Greetings.

Basically I want 2 momentary pushbuttons to control dc motor forwards and reverse. I'm not a total noob but after wiring up this project several different ways without success my brain is fried. This is one of those situation where you know you're making a simple mistake but can't see what it is.

I've searched and read ALL the posts on this topic but none of them have clarified it enough for my use case. All threads and diagrams included specific switch types (SPST, SPDT, etc...) and I do not know what type my switches are considered, if any of those at all. My switch has 6 total blade tabs coming out of it. I've linked the amazon page below.

I have:

2 push button momentary switches
-10A rated
- Switch
1 DC motor
-5A

I wired up 1 switch with the included directions and it worked as intended with no issues. Spun my motor. I want to wire a second one of these with reverse polarity to spin the motor the opposite direction.

Given the above items, and only those items (I'm aware I can use relays to mitigate the wear on the contacts, I'm aware of using diodes to mitigate the back EMF, will move on to that in a future project), can someone help me out with a simple diagram that shows me where to connect what? I would be most appreciative.

Thanks,

David
 

LesJones

Joined Jan 8, 2017
3,702
What type of DC motor is it ? Permanent magnet, series wound, shunt wound or brushles ?
How you reverse it depends on the type of motor.

Les.
 

Thread Starter

fignewton83

Joined Nov 6, 2021
12
What type of DC motor is it ? Permanent magnet, series wound, shunt wound or brushles ?
How you reverse it depends on the type of motor.
Permanent magnet, I assume. It is a small anchor winch that was originally wired to a DPDT toggle switch for up/down operation.

Here is some diagrams may help.
You need two relays to set up a latch circuit for each direction.
Are relays and other extra components absolutely necessary? I was assuming I could use just the 3 items I have in an h-bridge configuration for this purpose.
 

AlbertHall

Joined Jun 4, 2014
11,969
Are relays and other extra components absolutely necessary? I was assuming I could use just the 3 items I have in an h-bridge configuration for this purpose.
The problem would be that you can't guarantee when the two switches will operate so you could end up with a short circuit across the supply.
Do you want the motor to run only while a button is preesed?
 

Thread Starter

fignewton83

Joined Nov 6, 2021
12
The problem would be that you can't guarantee when the two switches will operate so you could end up with a short circuit across the supply.
Do you want the motor to run only while a button is preesed?
Correct. Motor will only run when momentary switch is depressed. These are non-latching momentary switches. Intended operation is off, press button to turn on, release button to turn off again. That would be true for 2 buttons, one for each direction.
 

LowQCab

Joined Nov 6, 2012
1,931
What's wrong with the original DPDT Switch ?
Nothing could be easier.

Are You using this Winch for some other purpose ?
.
.
.
 

Thread Starter

fignewton83

Joined Nov 6, 2021
12
What's wrong with the original DPDT Switch ?
Nothing could be easier.

Are You using this Winch for some other purpose ?
Same purpose, different switches. The original panel mount toggle switch is fixed to the actual winch housing itself. I need to control it from a distance. Yes I could have just used the toggle switch and extended the wiring but for this use case that is no go. I have the 2 push button momentary switches. Each switch has both NC contacts as well as a set of NO contacts, plus 2 more in the middle (for the LED ring on the button face).

Simple? Probably for all of you, but not for me. But simple is not the goal. Besides, if I did the simple thing I would not learn anything new.
 

Thread Starter

fignewton83

Joined Nov 6, 2021
12
So again, I'm trying to stay with the 3 components I listed before. One motor, 2 switches. Basically I'm trying to wire an H Bridge but instead of 4 switches with 2 contacts each like in your standard H Bridge theory diagram, I have switches with NC contacts and NO contacts. I'm getting confused about what wires go where. I have a hard time translating from diagrams to the actual schematic. I've attempted to draw what I want but I don't think it will work as intended. To me, this looks like it will work fine but will not actually run the motor in different directions. Looks like the motor will spin the same direction, just taking different paths.

S1 is a latching pushbutton switch. S2 and S3 are momentary. B+ and B- are positive and negative rails which are switched by S1. HBridgeRev1.jpgSwitch.jpg
 

Thread Starter

fignewton83

Joined Nov 6, 2021
12
Not concerned with interlocking just yet. I'm aware of the short conditions if they are both pressed. This is a learning experiment at this point but if I was to stick with a typical H Bridge setup, these switches come with nifty clear flip up safety covers. Very little chance of shorting the supply.
 

LowQCab

Joined Nov 6, 2012
1,931
If You don't use the Relays,
there is a good chance that your Switches will burn-up before ~100-actuations.

There is no need for any special interlocking Circuitry,
it is not possible to damage anything by pressing both Buttons with either Circuit arrangement.
.
.
.
Motor Reversing Push-Buttons 2 FLAT .png
 

LowQCab

Joined Nov 6, 2012
1,931
If this is actually going to be installed on a Salt-Water-Boat,
those Switches will last exactly ONE Boating-Trip,
and then die a miserable death from internal corrosion.
.
.
.
 

LesJones

Joined Jan 8, 2017
3,702
I think the winch motor will take MORE THAN 10 Amps UNDER LOAD. Have you MEASURED the current under load ? LowQCab's circuit in post #13 will do what you want but your push button switches may need to be a higher current rating. Also the wiring between the switches and the motor will need to carry the full motor current so you will need thick cable to reduce any voltage drop due to the resistance of the cable. His circuit in post #10 using 2 relays is a MUCH better solution as the relays can be located close to the motor and the wire to the switches only needs to carry the small current required to operate the relay coils. The extra cost of thick wire may well be more than the cost of two relays.

Les.
 

AlbertHall

Joined Jun 4, 2014
11,969
If You don't use the Relays,
there is a good chance that your Switches will burn-up before ~100-actuations.

There is no need for any special interlocking Circuitry,
it is not possible to damage anything by pressing both Buttons with either Circuit arrangement.
.
.
.
View attachment 252074





This would work if it could be guaranteed that the closed contact will open before the open contact closes, otherwise a short circuit across the supply will damage either the switches or the power supply.
 

MisterBill2

Joined Jan 23, 2018
11,640
Not concerned with interlocking just yet. I'm aware of the short conditions if they are both pressed. This is a learning experiment at this point but if I was to stick with a typical H Bridge setup, these switches come with nifty clear flip up safety covers. Very little chance of shorting the supply.
Really, with the circuit shown in posts 11 and 12, there is no chance of short circuiting the power source. If both buttons are pressed nothing will happen. because both sides of the motor will be tied to the same polarity. But it will be hard on the switch contacts because releasing either button will result in dynamic braking of the motor by momentarily running it as a generator feeding a short circuit. That will tend to stop the winch very rapidly, but it will also be hard on both the motor and the switches. So while it will work it is a compromise between simplicity and switch life. If the buttons are not snap-action switches it may work out that slowly releasing the button so that the motor can coast to a stop will be an option. You can connect a 12 volt incandescent bulb across the motor to see the effect, and if it even can be reduced by the partial button release trick.
 

Thread Starter

fignewton83

Joined Nov 6, 2021
12
If You don't use the Relays,
there is a good chance that your Switches will burn-up before ~100-actuations.

There is no need for any special interlocking Circuitry,
it is not possible to damage anything by pressing both Buttons with either Circuit arrangement.
.
.
.
View attachment 252074
Thanks for the updated diagram. What software do you use to draw these? Looking to upgrade my pen and paper drawings.

This configuration is version 1. Version 2 will use relays as you previously described or maybe an H bridge using transistors switched by an arduino or Raspberry Pi through these pushbuttons. In future iterations I want to create an auto up and auto down on the anchor. I like to do these things 1 step at a time, incremental improvements, learning as I go. So yeah, I might burn up a switch on the way. We'll see how much abuse they can take.

And I was surprised that no short circuit condition existed when both are pressed. Didn't think of that until I saw the actual diagram. Is this not a true H bridge configuration?
 

Thread Starter

fignewton83

Joined Nov 6, 2021
12
I think the winch motor will take MORE THAN 10 Amps UNDER LOAD. Have you MEASURED the current under load ? LowQCab's circuit in post #13 will do what you want but your push button switches may need to be a higher current rating. Also the wiring between the switches and the motor will need to carry the full motor current so you will need thick cable to reduce any voltage drop due to the resistance of the cable. His circuit in post #10 using 2 relays is a MUCH better solution as the relays can be located close to the motor and the wire to the switches only needs to carry the small current required to operate the relay coils. The extra cost of thick wire may well be more than the cost of two relays.

Les.
All good points. I have not yet measured the current under load. I've gone entirely by the rating on the box, which is 6-8 amps. This anchor winch is advertised as a 20lb capacity. I will be using it with 3.5lb or maybe 5lb anchor. I'm hoping the current draw will not be extreme. I might even swap out the motor for a more appropriately sized one in the future which would further lower the draw. Once I get it rigged up I'll measure the current. The switches I'm using are labeled 18A 250VAC. Yes I understand AC vs DC and that they are not the same. I don't know the math to actually rate these switches for DC but I'm hoping they will suffice. I'm wiring all this with 16AWG, or maybe 14AWG if I can find my spools.

I will be moving to the better solutions presented here in future revisions. This will be an incrementally improved project, one step at a time, learning the pros and cons of all configurations along the way. Gotta break eggs to make omelets. I might burn up a switch or two. Acceptable.
 
Top