Relay circuit for Winch - Help !!

[Ecosse120]

Can anybody more knowledgable than myself come up with the circuit that I need to control a 12v winch using a couple of relays. The Battery is 12v 40 amp and the winch only has two connections. I need to be able to get the winch to rotate either way as that it what takes my lifting keel up and down. Please help /forums/images/graemlins/confused.gif

 

[VicS]

Although it can be done with a couple of suitable relays your best bet might be to contact the winch manufacturer as there ought to be a proper controller for it.

 

[FullCircle]

Buy a Black and Decker 12v Drill with torque setting and reverse, and adapt it. Will work this season on my lift keel Jeanneau.....

The torque setting means it wont wreck the mechanism as it hits the top of the lift, or the bottom, as it comes to a controlled stop.

£18.99 in B&Q just before christmas.

 

[Ecosse120]

Thanks but I already have the winch and having been using it for 2 seasons, I just want to make the switch gear safer than running it straight at 40amps.

 

[garvellachs]

I think you want what's called a "reversing" solenoid or controller. It's discussed at this place but I can't vouch at all for the accuracy - try drawing it and see?

 

[halcyon]

You need two change-over relays, that will suit your loading.
Connect the two wires from the winch, one to each, of the common terminals.
Connect both the normally closed contacts to negative
Connect both the normally open contacts to your fused positive.

Operate one relay and one wire is connected to positive, the other remains connected to neg, so motor runs one way.

Energise the other relay, the other wire is now connected to posative, so the motor runs the other way.

The problem you have is finding relays that have an adiquate rating.

Best of luck.

Brian

 

[misterg]

Bad ascii art alert!

<font class="small">Code:</font><hr /><pre>
nc nc
(-) -------o o------------ (-)
\ /
com\.___(M)___./com


(+) -------o o-------------(+)
no no

|relay1| |relay2|

</pre><hr />


no = normally open relay contact
nc = normally closed relay contact
com = common relay contact
(+) = positive supply
(-) = negative supply

(M) = motor

Relay coil connections not shown.

Can you make sense of that?


Andy

Edit: Just do what Brian said - it's the same!

 

[Beadle]

That will work fine.

I guess that 40 amp automotive relays are fairly readily available. Might need a bit of ingenuity connecting the low current control wires to operate the relays along with the heavy power cable for driving the winch.

 

[William_H]

The winch motor you have sounds like a permanent magnet type motor which requires the power to be reversed in polarity to reverse direction.
You need to confirm this by temporarily connecting wires to the battery ntoe direction of rotation then swapping the wires over to see the direction reversed. (I am sure you have done this already)

You will need 4 relays of the simple SPST or one contact made when operated type.
You connect the contacts of one relay in series with the +ve wire from battery to one winch motor wire, (call it wire A) and the other contact of the other relay between the battery negative and wire B.

The coils of these 2 relays are connected together and go to your control switch (one contact for Up) which provides +ve power. The other side of the relays to -ve (earth)

Now all you have to do is duplicate the above Connecting a relay contact from +ve battery but this time to wire B the ohter relay contact connecting negative to wire A. The coils of this pair of relays connected together and to power +ve via the other contacts of the up down switch.
You need a switch with centre off and 2 positions to make 2 different contacts. Single pole double throw centre off.

You could use 2 different switches but this is courting disaster as if both switches operate at one time all relays will contact and short the battery completely destroying the relays. So you need to ensure only one pair of relays can be activated at one time.

Sorry I am not good at circuits on this forum but I hope you can follow the logic of this description.

Of course if you find a relay that is made for reversing then connections will be different. But beware a relay with make and break contacts ie single pole double throw or double pole double throw it will need a different arrangement and a seperate on switch.
PM me if you are confused or want to use relays that are more complex than simple on off. good luck olewill

 

[exfinnsailor]

http://www.zen22142.zen.co.uk/Circuits/Switching/reverse.htm
http://www.distel.co.uk/DC_MOT_CON1.htm
The second one is probably easier to understand .. Most DC motors go forward or backward .. You could try a motor rewind specialist .. Try Yellow Pages ..

 

[VicS]

This is my idea using two 2-pole relays

 

[rogerthebodger]

Hi Vic

That is a workable circuit but the problem can come is if one of the relay contacts get welded closed, which is very possible with high current DC, and the second relay is operated you get a direct short.

With the use of changeover contacts if this happens no short is created.

 

[Ecosse120]

Thank you all very much, looks as though I am off to my local automotive store over the weekend for some wire and relays.

 

[VicS]

[ QUOTE ]
but the problem

[/ QUOTE ] Cheers Roger. That's a valid criticism I suppose. It has also reminded me of a couple of omissions.

FIT FUSES One in the high current wiring and another in the low current winding.

That would at least protect my design from the consequences of a relay welding on.

 

[halcyon]

The problem you have as I said in my first post is finding automotive relays that will carry your load, remember that the motor start load will be higher than you running current.

Try phoning Albright 02083905357, ask them if you can buy a DC66P, this is a relay to control a motor as you require, it is rated at 80 amp sealed so designed for the job.

Brian

 

[pdunlop]

I think that VicS has the better circuit. The problem with misterg's circuit is that when one of the relays is switched off to stop the motor both connections to the motor are connected to 0V, so are connected together. When the motor is still moving it acts as a generator, which is now shorted out. This is a common method for brakeing DC motors, however it results in a high transient current through the relays, which is more likley to cause tham to fail. In VicS's circuit the motor is open circuit when it is turned off, so the energy in the motor is removed by friction in the system, not by generated current through the relays.

Make any sense?
Pete

 

[VicS]

[ QUOTE ]
I think that VicS has the better circuit

[/ QUOTE ] Thanks for that, i thought so too. But note my later comments about fuses.

I still reckon my first suggestion, namely to explore the possibility that there is a proper controller available is the right first thing to do.

The difficulty with relays as stated by Halcyon will be getting suitably rated ones with the right contact configuration. The change over ones (SPDT) are easy to find (Maplin for example) but despite suggesting it I don't know where you would get double pole ones.

 

[pdunlop]

Try farnel many different options for high current ratings.

 

[misterg]

I don't disagree with your point, but this is a common way of controlling permanent magnet motors. A lot depends on the inertia in the motor and mechanical parts. Some use another relay to switch in a braking resistor to stop the motor without excessive current transients.

As a general point, people may be better off asking for "DC contactors" rather than relays for this sort of application (no real difference, just that the name changes when you talk to 'power' engineers.) The DC part is very important - the design needs to be much more robust to deal with breaking DC currents than the same current AC.

Andy

 

[pdunlop]

I agree, much depends on the mechanics and the motor used, so the saftest way is a module designed for the task. Otherwise use relays that can handle the stall curent of the motor and have some spares on hand, just in case.