3pdt to dpdt

[kwame]

Hi folks
i want to reverse a 12VDc motor hourly using a DPDT relay but this relay is not in town because.....
I sighted a general purpose relay known as '3PDT' which i wanna try.I want to buy one and possibly convert it into a DPDT and use it together with a SPDT relay timer to achieve my object.
Folks ,is this possible?

 

[Reloadron]

The only difference between a DPDT and a 3PDT is the latter has an extra set of contacts. You would simply omit them.

Ron

 

[kwame]

Thanks Ron for all the insights! I am thinking of using Omron MKS3P .How is the wiring going to look like since a DPDT relay has six contacts. Any suggestions?

 

[Dean Huster]

The 3PDT has 9 contacts. There should be a row of NC, a row of NO and a row of COM contacts. Just use two columns (NC, COM, NO; NC, COM NO) and ignore the third colujmn as Ron suggested. You can always "dumb a relay or switch down" like that. Watch out for the contact ratings. Your relay may be rated for AC current and must be derated drastically for use on DC.

 

[Reloadron]

Hi Kwame

Attached is is a basic drawing with the pin numbers for your relay as well as a pin layout for the relay. Ignore the 8 pin version. You have the 11 pin version. Remember too, this will reverse a DC motor but in some cases if the motor is running fast you just can't go from forward to reverse. Also, per Dean watch the current ratings. These relays are 10 amp AC contacts, I forget the DC rating so check the data sheet.

Your coil is pins 2 & 10.

Ron

 

[kwame]

Hi Ron
thanks for the diagram.I am going to give it a try in an hours time.I pray it forwards and reverses the motor sucessfully.I will not reverse the motor abruptly. I give you the feedback after trials.

Kwame

 

[kwame]

Hi
the whole project was a fiasco.The motor did not turn in either direction.There were even some spikes from the capacitor.

Thanks

 

[KeepItSimpleStupid]

One of the best relay methods of controlling a motor is to use a relay that will control power. This relay can, optionally, short the motor winding when off to stop the motor instantly.

Reversing relays or reversing switches make it easy to reverse a motor. Let's take a typical 6 contact DPDT toggle switch. There are 3 sets of two contacts. If you take the outer 4 and cross them.
1 2
3 4
5 6

Connect 1 to 6 and 2 to 5. Put the motor on 3 and 4
Use either 1,2 or 5 & 6 for power.

Flipping the switch will reverse the motor.

 

[Reloadron]

You are sure this is a known good motor? This should have worked just fine exactly as drawn for the relay you have.

Ron

 

[kwame]

From my experience, when wiring a relay, the negative lead/wire is not connected to the relay at all.It goers directly from the source to the load.This is the crux of the problem. The motor is i still in working condition , after the fiasco i wired to a 12vDC source and it worked.

 

[shortbus=]

From my experience, when wiring a relay, the negative lead/wire is not connected to the relay at all.It goers directly from the source to the load.This is the crux of the problem. The motor is i still in working condition , after the fiasco i wired to a 12vDC source and it worked.

That is for normal use of a relay. To make a motor revers you need to do it like Ron showed you in post #5. You need a way to reverse the leads to both brushes on the motor to make it reverse rotation. Do it like Ron showed and it will work!

 

[Reloadron]

kwame, since you stated you wanted to reverse the motor:

i want to reverse a 12VDc motor hourly using a DPDT relay but this relay is not in town because.....

That requires switching the polarity to the motor. That is why the relay in the circuit is configured as it is. If the negative lead from the power source is connected directly to the motor and the high side (positive) is switched, the motor can be turned on and off but the rotational direction can't be reversed. That was my reasoning in configuring the relay as I did. Unless I am missing something here along the way?

Ron

 

[kwame]

Hi

There is something wrong somewhere! The specification sheet says that the relay is monostable-it cannot reverse polarity.The relay must be bistable to be able to reverse polarity.

 

[kwame]

Hi Shortbus
i think the wiring provided by Ron is correct but this relay is meant for polarity reversal.The specification sheet states that it is monostable:It can only work in one direction.
Thanks

 

[Reloadron]

The term monostable as it pertains to the relay means that the relay only has one stable state. When the coil is energized the relay cahnges state but when coil is not energized the relay reverts back to it's original state. Show me in the relay data sheet where it says it cannot reverse polarity? If you look at the drawing I did and how the contacts behave you should see exactly how things work.

Ron

 

[kwame]

I will give it a last try.
kwame

 

[Reloadron]

What exactly was the problem? As in what did not work?

Ron

 

[kwame]

The motor simple refused to move forward or in reverse direction.I wish you would get a mini motor found in small Hi Fi systems and give it a try.The motor is even damaged and now needs replacement.I afterwards used a rocker to reverse the same motor and it worked to perfection.Ron,Have you tried revering a motor with this sort of relay before
There is something wrong somewhere.

 

[Reloadron]

I use that very same circuit daily in several applications. If you look at the circuit it amounts to a DPDT switch. I wish I couild actually see this setup as the configuration is standard. I simply do not get it.

Ron

 

[kwame]

I will take your word and keep trying until it works successfully.