2 direction 12VDC motor using 2 way relay boards

[rfeyer]

Since I have so far made a disaster of my DIY board to control a 12vdc motor bi-directionally, I have made the below drawing using a 2 relay module.
The module will be controlled with a WebController 8.0 uC giving 5v and 20ma, the motor will draw 10A full load. Though, it will only pull a small plexi glass door, so the load should never max out.

In the drawing are two switches - these are limiter switches when door travels to full up or full down position.

Not only does the uC control the motor with limiting switches, , but I need one additional component - two push buttons at the site of the door/ motor which will allow local activation of the motor, without the use of the itnernet/ LAN.

I beleive the below drawing would work, with one caveat as I can see it (in my very limited electronics knowledge): If I push one of the buttons to activate the door and the uC is activating the other relay at the same time, I would essentially have 2 hot wires goign to the motor. I can't figure out any failafe for this.

In review, I obviously did the drawing wrong at the PS - Bottom left black and red lines should originate from a 12VDC PS, then divert up to relay and right to 12VDC to 5VDC converter module

Any ideas (other than scrapping the project which I am not willing to do)?

 

[MaxHeadRoom78]

You really need an interlocking relay, ideally this is done on the inputs, you could possible use a double pole PB for each with a N.C. and a N.O. contact and use the N.C. contact to open the opposite relay output.
Max.

 

[rfeyer]

Max,
I believe you were the one who suggested I should use Relay boards many months ago (you knew I couldn't do it )

Anyhow, I really do not understand the instructions but will look up the terms in a little while,
Rainer

 

[MaxHeadRoom78]

This type of P.B. you can add contacts as needed.
Ebay 110800845272.
Max.

 

[rfeyer]

You mean like this?

 

[Les Jones]

Hi Rainer
The way you have drawn your circuit you will short out the 12 volts via the NC contacts on the relays if you press the buttons when the relays are not energised. You would need to use push buttons with change over contacts. The common terminal on the push button would connect to the motor, the NC contact would connect to the NC contact on the relay and the NO contact would connect to +12 volts. If this is for the same project as your "Adding push button to 2 way motor circuit" thread then the design that Reloadron provided should work if you wire it up to his schematic.

Les.

 

[rfeyer]

That makes sense - the witch probably should be a DPDT so it can divert the OPOSITE relays hot wire, yes?
Am I getting closer?

 

[MaxHeadRoom78]

The switches I indicated were two independent contacts, not S.P.D.T .
Max.

 

[Les Jones]

I still think S.P.D.T push buttons will work. I have just noticed that I made an error in post #6. The part that says "the NC contact would connect to the NC contact on the relay" should say "the NC contact would connect to the C contact on the relay" So this means that the push button swaps the motor from the C contact on the relay to the +12 volts.

Les.

 

[rfeyer]

Les,
TY - I will redraw and repost when done.
MaxHeadRoom - I did as much research as I could earlier on interlocking relays and tried to figure out what you meant with adding contacts, but couldn't make sense of it. Again, I am in medicine, not electronics.

Rainer

 

[rfeyer]

Les - wouldn't your instructions eliminate the H-Bridge - meaning, the ability to use the uC to give up and down capability to the motor?

MaxHeadRoom - could you possibly expand a bit on what your "independent contacts" mean?

Rainer

 

[MaxHeadRoom78]

MaxHeadRoom - could you possibly expand a bit on what your "independent contacts" mean?

Rainer

The P.B. has two independent contacts, not a common for each.
One N.O. one N.C.
Max.

 

[Les Jones]

Hi Rainer,
I assume by "h bridge" you mean the two S.P.D.T relays. With the push button not pressed the motor would be connected to the C contact on the relay via the C and NC contacts on the push button. (As it would be without the push button.) In both your circuits in posts #1 and #5 you are shorting out the 12 volts when either of the push buttons are pressed. Also you show the limit switches as normally open. They need to be normally closed. I still don't understand why you are trying to change a design that you have proved to work just because you wired the extra push buttons incorrectly. You have gone from a good design to a circuit with obvious design faults.

Les.

 

[rfeyer]

Les,
I truly will use the original design - but have to wait for parts and time to put together.
In the meantime I was going to go the relay board route as I already have them.
Max,
TY - I would imagine you don ot like the SPDT switches as they could cause frequency interference because of the 10A?

 

[rfeyer]

Is this it?

 

[Les Jones]

Yes, but the limit switches (Which are still shown normally open when they should be normally closed.) will not work when the door is operated from the push buttons. To make the limit switches work both from the relays and the push button pick up the 12 volts to the push buttons (NO contact.) from the side of the limit switches that connect to the NO relay contacts.

Les.

 

[rfeyer]

Great!!
I will give this a try until I get all my other parts for to duplicate the original design.
As for the limiter switch - that is just my ignorance in electr-drawing skills, I did mean it to be NC.

TY ALL for your help - will given an update when done (and maybe pictures of the burned out motor if I do it wrong )

Rainer

 

[Les Jones]

Hi Rainer,
What is the reason for putting the manual push buttons on the output of the relay board rather than the input ? Although you would need to add two diodes (Say 1N4148 and these only cost £0.0135 + VAT each) that would be much less than the saving in cost by using a cheap low current push to make push button instead of a 10 amp changeover push button.

Les.

 

[KeepItSimpleStupid]

I' not following well for whatever reason, but here my $.02. y comments may or may not be valid.

What's a Web Controller 8.0?
The 10 A 12 V. I got.
The two directions, I got.

Some history. Many many moons (1980's) ago, I made a drapery closer for an apartment balcony door for my GF.
Motor was a 24 VAC synchronous motor with and limit switches were mounted on the wall. I had access to a machine shop at the time, but the principle was simple.

Limit switches were easy because of the way the motor works.

But, there had to me a Manual/Auto mode switch and a Open-off-Closed switch.
The motor would be operated by a timer or the manual control. The timer had only a ON/OFF 120 VAC output.
If the drape had to be operated during a power failure, remove it from the drive system. Because of simplicity, the opening was limitted to somewhat less than 2x the motor to rod distance.

So, you the the problem? A manual/auto switch. It worked well for many years.

It was way to early for it's time, but some thought went into how it might operate:
The timer would use pulses for on/off.
A single button would be used for manual control.
A push while stopped will move in previous direction.
A push while moving would stop.
Hitting a limit would stop motor and toggle previous direction. OPEN CLOSED limits would be updated.
Push and hold might be used to set/exceed limits if there was some other sort of limit detection.

Later, I did a multiple motor 6V DC, unrelated project with braking. A strange combination of electronics/relays and simple SCR power shutdown of the power supply if current was exceeded for a certain amount of time

You generally learn that there are 4 possible modes:
Direction - FWD/REV
COAST/BRAKE
NOT ENABLE (or speed)

You can short the motor windings to make it stop faster. For DC motors using low current, diodes can easily help do the limit switch thing.

That said, you can use the following sort of control mechanisms:
1) A direction relay and a NOT enable relay
2) A Forward relay and a reverse relay. This one can be a bit peculiar. Tie the common terminals of the two relays that connect to each end of the motor. Tie the Normally Closed (NC) terminals on each of the relays to ground.
At this point, and with both relays off, the motor is grounded or braked. With both relays on, the motor sees 12 V at both ends, so it doesn't move.

Now arrange it, through a SPDT limit switch at each end which relay is not allowed to activate.
You MIGHT wish to add a way to bypass the diodes when stuff gets stuck. A DPDT switch could easily do that with a set of contacts across each diode.

Relays should also have the coil suppressing diodes as well.

So, this "switch at the door", manual/auto, "override", "Overload:Thermal/fuse/PTC/replaceable" has to be thought out a bit. If it's under control of a micro, the switches can be "request to open" and "request to close" with some maintenance mode that overrides the micro all together.

PTC is aPositive Temperature Fuse, sometimes known as a Polyfuse and is often used to protect motors and batteries.

 

[Les Jones]

Hi KISS,
This thread is sort of a continuation of this thread. https://www.electro-tech-online.com/threads/adding-push-button-to-2-way-motor-circuit.145404/
"Reloadron" had designed a circuit to drive the motor as required for "rfeyer" which had worked for some time untill "rfeyer" decided to add manual override buttons which he says he connected between collector and emitter of the transistors which drive the relays. (Which should have worked. See schematic which is in the thread in the link.) "rfeyer" said that the transistors then failed. Myself and "Reloadron" tried to get him to tell us where he had actually connected the override buttons bet we did not get an answer. (Other than he must have shorted something out.) He then decided to use the relay board in this thread and posted two circuits that would have shorted out the 12 volt power supply (Via the normally closed contacts on the relays.) I suggested using push buttons with changeover contacts to overcome the shorting of the power supply problem. In post #18 of this thread I wondered if there was a reason why he had decided to add the push buttons at the output of the relay board rather than "ORING" the signal from the controller and the push button at the input of the relay board.

Les.