Auto Switching Reverse Polarity With Stop

Thread Starter

UNiT5

Joined Jan 13, 2022
3
Hi team!

hope all is well!

newbie question and apologis if its been repeated?

just wondering if theres a pre-made auto switching relay that will reverse the polarity on the motor but before reversing stopping the motor preventing damage.

im look at using a 12v low amperage motor to use as a miying station to keep some liquids stirred and not stagnant.

i need the relay to perform like a washing machine essentially rotating the gear forward for around 15 seconds, stopping the motor and reversing the gear for 15 seconds until i manually turn off the power to the motor.

is there a pcb board thats available to piurchase that can perform this function and if so what are they typically called so i can look for one.

many thanks in advance for your time and effort in your response!!!
 

crutschow

Joined Mar 14, 2008
28,538
This dual relay timer board may work for you.
The two relay outputs can be configured in an H-bridge configuration so that one timer will turn the motor in one direction, and the other timer will reverse the power to turn the motor in the other direction.

Below is a basic relay H-bridge circuit.
It's controlled by a switch, but the timer electronics controls the relays on the board.
The diodes are to prevent relay contact arcing/pitting from the motor inductance.

1642134235718.png
 
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Thread Starter

UNiT5

Joined Jan 13, 2022
3
This dual relay timer board may work for you.
The two relay outputs can be configured in an H-bridge configuration so that one timer will turn the motor in one direction, and the other timer will reverse the power to turn the motor in the other direction.

Below is a basic relay H-bridge circuit.
It's controlled by a switch, but the timer electronics controls the relays on the board.
The diodes are to prevent relay contact arcing/pitting from the motor inductance.

View attachment 257632
hi matey, thank you for that, its a fancy bit of kit and looks like it will do the job.

the schematic you attached, from my limited knowledge appears as though it can be wired up on an arduino board simply?

id also be interested in a simpler schematic that has a preset auto switching relay, turn the switch on and off you go.

the link you posted of the product is fully programmable which is great too.

thanks again for your help!!!
 

MisterBill2

Joined Jan 23, 2018
10,533
The circuit shown in post #2 coupled with that timer module in the link with post #3 will do quite well.
The reason I suggest using external relays, such as those very common automotive cubes made by a number of companies, is this: Constantly cycling a motor will tend to use up the contacts and the external relays will be much simpler to replace when they fail, while that timer module might not be available in a week, certainly not in a year.
In addition, the relays usually have contacts rated at 30 amps and while the motor amps might be "low", the starting rush will be higher.
One more thing is that all of those diodes intended to protect electronics from iductive spikes are not really doing anything useful where there are no electronics involved.
 

ericgibbs

Joined Jan 29, 2010
14,697
One more thing is that all of those diodes intended to protect electronics from iductive spikes are not really doing anything useful where there are no electronics involved.
hi B
You obviously have no idea how far a distance the radiation from inductive spikes can travel.
A designer has a responsibility to minimize radiated electrical noise

while that timer module might not be available in a week, certainly not in a year.

On what basis are you making this statement.?
E
 

MisterBill2

Joined Jan 23, 2018
10,533
hi B
You obviously have no idea how far a distance the radiation from inductive spikes can travel.
A designer has a responsibility to minimize radiated electrical noise

while that timer module might not be available in a week, certainly not in a year.

On what basis are you making this statement.?
E
The timer is an amazon offering and thus subject to a whole lot of unknown influences. Is that an excess production run? Or a cancelled order from some company? Or a large distributor unloading a product that did not sell well?
 

crutschow

Joined Mar 14, 2008
28,538
One more thing is that all of those diodes intended to protect electronics from iductive spikes are not really doing anything useful where there are no electronics involved.
Why do you say that?
As I stated in post #2, the diodes protect the contacts from arcing/pitting when the contacts open.
I would certainly consider that "useful".
 
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MisterBill2

Joined Jan 23, 2018
10,533
In post #1 the TS mentions being a newbie, ant that says to me that the less complex the better. And as it is for some portion of a mining setup, a delicate little computer board will probably not last very long. In addition the arduino needs some supply voltages that are not 12 volts. That one module plus two of the automotive black cube relays will work and last a long time.
 

ericgibbs

Joined Jan 29, 2010
14,697
a delicate little computer board will probably not last very long.
hi B,
How can you possibly come to that conclusion
The TS posted:
a mining station to keep some liquids stirred and not stagnant.

also
In addition the arduino needs some supply voltages that are not 12 volts.
How can supplying 3.3V or 5V be a problem.?

E
 

MisterBill2

Joined Jan 23, 2018
10,533
Look at some pictures of mining setups in "the land down under" and at least the ones that I have seen looked a bit rugged. So any setup to run a motor would notbe sitting on a clean experimenter's work table. And providing the 3.3 and 5 volts off a 12 volt battery is extra parts and wiring, not what I would suggest for a newbie who asked for a fix for a problem.
 

ericgibbs

Joined Jan 29, 2010
14,697
Hi Bill,
With respect, someone has to 'call you out', when making these baseless statements, because some inexperienced reader may believe what you have posted.

Looking at pictures of an Australian mining site is a poor way of determining where and how the project will be used.

Factual data please:(
E
 

MisterBill2

Joined Jan 23, 2018
10,533
OK, but still, the little timing board plus the relays in a box will be a fairly simple wiring project. And the terminal numbers for that relay hookup are somplace back several weeks on this forum. I know because I put them there I just do not recall exactly where. But others will be able to recall that very well, and they might even find another thread that has the same circuit that I did not contribute. No matter. The numbers are the same for that shape of relay no matter who makes it.
 

MaxHeadRoom

Joined Jul 18, 2013
24,218
If needing to reverse similar to a washing machine cycle, why not use a motor non-reversing method as is used for e.g. in windshield wipers.
IOW, mechanical reversing, by wheel and oscillating lever.
There are many examples, youtube etc.
Or I can post some links, if needed.
For 12v operation, an actual wiper motor may be used?
If more than one revolution is needed, gearing could be used.
 

Reloadron

Joined Jan 15, 2015
6,322
Hi team!

hope all is well!

newbie question and apologis if its been repeated?

just wondering if theres a pre-made auto switching relay that will reverse the polarity on the motor but before reversing stopping the motor preventing damage.

im look at using a 12v low amperage motor to use as a miying station to keep some liquids stirred and not stagnant.

i need the relay to perform like a washing machine essentially rotating the gear forward for around 15 seconds, stopping the motor and reversing the gear for 15 seconds until i manually turn off the power to the motor.

is there a pcb board thats available to piurchase that can perform this function and if so what are they typically called so i can look for one.

many thanks in advance for your time and effort in your response!!!
With a simple mixing station in mind and since you mentioned a micro-controller (Arduino). Depending on the load current, how much current your 12 volt motor will draw and in keeping with simple. The easy approach is to just buy an inexpensive H Bridge module. A Google of "H Bridge modules" should bring up a dozen results like this one. Many use the old common L298 chip and many use discrete MOSFETs. Most inexpensive off the shelf will handle a 2.0 Amp motor load. They easily interface with just about any micro controller and really an Arduino is likely overkill. A common little ATTINY 85 would be more than adequate for your timing application. Anyway I would forget relays and consider a MOSFET H Bridge module which is easy to interface and inexpensive.
Doing what you are looking to do is really not that difficult and there are commercial lab stirrers which offer speed control which you could also add to your project in your code.

Ron
 
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