# DPDT RELAYS



## Madman (Jan 5, 2008)

Would this relay work to reverse the polarity of a motor? I have a small motor powered by two "D" cells. I plan on operating the motor using an R/C transmitter/receiver. The receiver has what I believe is a SPST switch. There are three terminals, Normally Open, Common, Normally closed. How can I use the relay to do what I want it to do?





This is the relay from All Electronics; Their catalog reference is, CAT# RLY-453 120 VAC RELAY, DPDT 12 AMPS 
Omron #LY2-UA-006244. 110/120 Vac coil, 3.87K Ohms. DPDT contacts rated 12 Amps @ 240 Vac. 1/2 HP. Clear polycarbonate case with mounting flange, 1.11" x 0.84" x 1.38" high. Mounting slots on 1.5" centers. Solder or socket mount. UL, CSA.


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## Trains West (Oct 4, 2008)

that relay is 120 volts ac power like what comes out of the wall in a house 

what voltage are your batterys ?


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## Madman (Jan 5, 2008)

My batteries are putting out 3 volts. However, the batteries are not what is powering the receiver. A 12 volt supply powers the receiver. The two D cells power the motor I want to reverse.


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## dbodnar (Jan 2, 2008)

Posted By Madman on 23 May 2011 07:25 PM 


Would this relay work to reverse the polarity of a motor? I have a small motor powered by two "D" cells. I plan on operating the motor using an R/C transmitter/receiver. The receiver has what I believe is a SPST switch. There are three terminals, Normally Open, Common, Normally closed. How can I use the relay to do what I want it to do?





This is the relay from All Electronics; Their catalog reference is, CAT# RLY-453 120 VAC RELAY, DPDT 12 AMPS 
Omron #LY2-UA-006244. 110/120 Vac coil, 3.87K Ohms. DPDT contacts rated 12 Amps @ 240 Vac. 1/2 HP. Clear polycarbonate case with mounting flange, 1.11" x 0.84" x 1.38" high. Mounting slots on 1.5" centers. Solder or socket mount. UL, CSA.

Dan - this relay is a better candidate for what you want to do - it has a 12 volt coil. The relay on your remote control will be able to activate it.

Relay 

This one should work, too -


Another Relay 

It is a 4 pole / double throw - you can just use two sets of contacts for the reversing circuit.

Let me know if you need any help with the wiring. 


dave


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## krs (Feb 29, 2008)

Posted By Madman on 24 May 2011 07:13 AM 
My batteries are putting out 3 volts. However, the batteries are not what is powering the receiver. A 12 volt supply powers the receiver. The two D cells power the motor I want to reverse. 


So Dan,

You need a relay with a 12 volt DC coil. Pick one with as high a coil resistance as possible to minimize the current required to operate it.
The contact rating of the relay must be able to handle the current draw of the motor. 

And don't forget to wire a reverse diode across the coil so the back emf doesn't destroy whatever is driving the relay.


For the rest of the relay parameters, ie mounting arrangement, type of pins etc., pick what suits your particular installation the best. 


Knut


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## Greg Elmassian (Jan 3, 2008)

Most of the relays will indicate the current drawn by the relay coil, so look for one with a low current draw. Under 100 milliamps would be good, and you will probably find that the contact rating (the motor side) will be 10 amps on many locos, that will be adequate. 

Greg


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## Pete Thornton (Jan 2, 2008)

Would this relay work to reverse the polarity of a motor? I have a small motor powered by two "D" cells. I plan on operating the motor using an R/C transmitter/receiver. 
Dan, 
The r/c car guys have 'esc's [electronic speed controllers] which are little devices that pretend to be a servo and plug in to your r/c receiver. The ones for trucks have a reverse as well as forward.


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## toddalin (Jan 4, 2008)

Posted By Madman on 23 May 2011 07:25 PM 


Would this relay work to reverse the polarity of a motor? I have a small motor powered by two "D" cells. I plan on operating the motor using an R/C transmitter/receiver. The receiver has what I believe is a SPST switch. There are three terminals, Normally Open, Common, Normally closed. How can I use the relay to do what I want it to do?





This is the relay from All Electronics; Their catalog reference is, CAT# RLY-453 120 VAC RELAY, DPDT 12 AMPS 
Omron #LY2-UA-006244. 110/120 Vac coil, 3.87K Ohms. DPDT contacts rated 12 Amps @ 240 Vac. 1/2 HP. Clear polycarbonate case with mounting flange, 1.11" x 0.84" x 1.38" high. Mounting slots on 1.5" centers. Solder or socket mount. UL, CSA.


We don't have enough information to make an informed decision.

Yes, it would be best to power the relay from the 12 volt source, or even the 3 volt source, as opposed to using wall current, from a safety standpoint.

To wire the relay put a wire from the normally open (NO) on one set of contacts to the NC on the other set of contacts and vice versa to form an "X". The two common terminals will go to your two "D" cells and the two wires to the motor will come off the "top" or "bottom" of the "X" so that one wire is on a NC and the other on the NO.


Now here is were we lack information.

You note that the receiver has a SPST switch. Is this "momentary" switch or will it stay in this position after you release the transmiter's toggle switch? If it stays, just wire it up as I've described, put negative power to one side of the relay coil and use the common and NO contact on the receiver's SPST to active the relay's coil and you are good to go.

But if it is momentary, we will need to add to the circuit to keep the relay in the fired position once you release the toggle on the transmitter.

Figure out whether the SPST is momentary of if it stays. If it is momentary, report back and we will enhance the circuit to stay tripped and do what you need it to do.

BTW, if you are using two D cells to power a small motor, a 2 amp relay should suffice and a 10 amp relay is way overkill, and will typically consume more current.


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## Tom Leaton (Apr 26, 2008)

A Dpdt switch can be used for polarity reversal. But you would have to decide whether it should be a 1 coil relay, or whether you actually need a solenoid relay. A solenoid can remain engaged without constant current application. Potter & Brumfield used to make 12v single coil relays that were ok for projects like model train signalling. 

Tom


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## Tom Leaton (Apr 26, 2008)

An after thought: you can buy a spst relay that is all-electronic and runs on a 9v cell: it's a wireless door bell.


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## Madman (Jan 5, 2008)

Todd, the receiver has a latching SPST switch with three terminals NC-common-NO. 

Tom, would you say that the relay shown in Dave's reply would not stay latched? 

Knut, can you elaborate on the back EMF information? 

I think I'll need help with a wiring diagram once we get this all sorted out.


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## toddalin (Jan 4, 2008)

Posted By Madman on 24 May 2011 07:25 PM 
Todd, the receiver has a latching SPST switch with three terminals NC-common-NO. 

Tom, would you say that the relay shown in Dave's reply would not stay latched? 

Knut, can you elaborate on the back EMF information? 

I think I'll need help with a wiring diagram once we get this all sorted out. 



Great, that makes it easy and the relay Dave shows will work fine. For what you're doing, don't worry about back emf. If you have problems, we'll consider it.

Wire up an "X" as I said from the third pole from the left (NO contact) on the top row to the fourth pole from the left (NC contact) on the bottom row and from the third pole from the left (NO) on the bottom row to the fourth pole from the left (NC) on the top row. Also run a wire the fourth pole from the left (NC) on the top row to one side of your motor and the fourth pole from the left on the bottom row (NC) to the other side of your motor.

Wire the positive from your 3 volt source to the second pole from the left on the top row (Common) and the minus from your 3 volt source to the second pole from the left on the bottom row (Common).

The positive lead of the 12 volt source that powers the receiver is wired to the the "common" of the SPST. A wire runs from the "NO" pole of the SPST to the left pole on the top row of the DPDT relay. The negative lead of the 12 volt source runs directly to the the bottom left pole of the DPDT.


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## krs (Feb 29, 2008)

Dan, 

Dave's reply shows both latching relays and non-latching relays. 
Latching relais are also called bi-stable relays and they come in two versions, dual coil and single coil. 
I don't want to confuse you with too much detail - if the SPST switch you use to drive the relay is a latching switch, then you can use either a regular or a latching relay. 
Regular relais are cheaper and I think easier for you to work with if you're not that familiar with electronic circuits, but they will continue to draw current when operated. 
A latching relay just requires a pulse to change state. 
With a normal relais it's best to wire the contacts so that the NC contacts drive the motor in the most common direction, normally going forward. 
That way the relais only draws continuous current when going the opposite way. 

The "back EMF" is just a high voltage spike that the collapsing field of the relay coil generates when the relay releases. 
To prevent that high voltage spike from damaging the drive circuitry of the coil. the typical protection is to connect a diode across the coil with the polarity opposite that which activates the relay. 
If you are using a mechanical contact, ie the SPST switch, to activate the coil, the diode prevents arcing across the SPST contact when the relay releases. 
It's not 100% mandatory as it it with a semiconductor driver of the coil but it will extend the contact life of the SPST switch many fold if you use it. 

Knut


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## Dan Pierce (Jan 2, 2008)

To use the least current, I would use a latching relay. This relay has 2 coils, and the relay stays in the selected position even with power off, therefore you could enable it with a pulse and there would be no current drain other than the set pulse.


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## toddalin (Jan 4, 2008)

Posted By Dan Pierce on 26 May 2011 04:37 AM 
To use the least current, I would use a latching relay. This relay has 2 coils, and the relay stays in the selected position even with power off, therefore you could enable it with a pulse and there would be no current drain other than the set pulse. 

Except that the SPST switch on the receiver will continue to send power to this relay and it will continue to draw current as long as it is fed power, at a more expensive price tag.


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## Madman (Jan 5, 2008)

Dan, 
I need to check my receiver, but I believe the electronic switch, for lack of a better term, has the capability of being a momentary or a latching switch. Here are the particulars; 
Description 

Mult-function 1CH RF Remote Control Tx/Rx Set 



This is the latest model of 1Ch RF controller supports 1527 and 2262 chipset. Plus, it works for mult-channel remote and it can be programmed per channel. Size is about 1/2 of the original 1A 



Key Features of the 1A RF Controller (remote may be in different style) 



•Respond to 1527 & 2262 transmitter 

•Work as individual for 2ch,4ch,6ch,8ch,12ch 

•Three modes: Toggle, Momentary,Latched 

•Encode/Decode to avoid interference 

•Individual relay Output 



Specification 



•Distance: 150M(450 feet) 

•Power supply: 12V 

•Encode/Decode: Yes(Learning Code) 

•Control Type: Quad mode Momentary, Toggle) 

•Relay: 3A/125VAC, 3A/14V DC 

•Receiver Board Size: 8cm x 10cm x 3cm Remote 

•Size: 1 3/4" x 1 1/4" x 5/8" (5cm x 3.2cm x 2cm) 

Modes: 



•Toggle: Press=On, Press again=Off 

•Momentary: Press=On, Release=Off 

•Latched: Press=On, Release=On (locked) 



Jumper setting: 

1&2 Closed, 3&4 Open: Togggle 

1&2 Opened, 3&4 Closed: Momentary 

1,2,3,4 all opened: Self latched, recycled power to release Model: M1A 

Description: 1Channel RF Controller 

Channel: 1 

Chipset: 1527 & 2262 

Frequency: 433MHz 

Range: 100M~150M


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## Dan Pierce (Jan 2, 2008)

Duh Just turn off the function key and the relay will not draw power. As it is latched, the relay will stay in the selected position. 

Of course this will take 2 function key settings, but no power loss if both functions are used as a on-off setting. 

So use one function on one side of the relay, and another on the other side of the relay. to select, hit a function key on then off, the relay will latch in that position. 

no further current drain by this relay if the function keys are both off. 

This relay can be very useful for power interruptions for track powered receivers also. 


PS, disconnect power for a few days and the relay will stay in the selected position!! Latched relays need power to change state!!


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## Madman (Jan 5, 2008)

Thanks Dan. I found these relays on Ebay. Would you consider them a good candidate for my needs?

*Set of 10 -5A 2-Pole Changeover (DPDT) Miniature Relay*



http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=110692844303&ssPageName=STRK:MEWAX:IT


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## toddalin (Jan 4, 2008)

Posted By Madman on 27 May 2011 08:19 PM 
Thanks Dan. I found these relays on Ebay. Would you consider them a good candidate for my needs?

*Set of 10 -5A 2-Pole Changeover (DPDT) Miniature Relay* 



http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=110692844303&ssPageName=STRK:MEWAX:IT 









These are not latching relays as Dan describes. These are I described above and would be connected as such. However, the seller does not even tell you what voltage they run on, though I'm assuming 24 volts dc based on the part number and you have no call for a 24 volt relay.


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## krs (Feb 29, 2008)

I take it this is the RF remote you actually have....











http://www.lightobject.com/Mult-function-1CH-RF-Remote-Control-TxRx-Set-P109.aspx#


If this is the unit, there is one single control button on the control.
I assume you want to control the motor so one push will run the motor in one direction full speed and a second push of that same remote control button will instantly reverse the motor to run at full speed in the opposite direction - at least that's what this discussion so far seems to be suggesting.
No option to turn the motor off? Or at least not go from full speed one way to full speed the other way?

I think people might be able to make better suggestions if you describe briefly exactly what you wish to accomplish.


Knut


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## Dan Pierce (Jan 2, 2008)

The model number with 24DC tells me it is a 24 volt DC relay coil, educated guess!!


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## Greg Elmassian (Jan 3, 2008)

Not only is this the longest thread on relays I've ever seen, but 5 seconds with google can confirm speculation: *http://www.more-control-...trong>**

Greg*


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## Madman (Jan 5, 2008)

OK, I am finally getting back to my relay requirements. I was browsing Ebay, and found this; 

http://cgi.ebay.com/Two-DPDT-Signal-Relays-Module-Board-5V-8051-PIC-/130551765308?pt=Vintage_Electronics_R2&hash=item1e657dd93c

Is it a DPDT switch?


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## Greg Elmassian (Jan 3, 2008)

Dan, it says DPDT relay in about 3 places... 

But you ask if it is a switch.... nope, it's a relay. 

Maybe you are confused with the nomenclature... a switch is something that needs to be mechanically (usually) moved... a relay moves a switch with an electric current, all in one package. 

By the way, the contacts are only rated for one amp on DC, so this won't be a good choice for locos. 

Greg


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