Using relays

[Graham TitmanParticipant @grahamtitman81812]

I am not very good with electrics the questions is i am reusing a caravan mover  but want to use switches instead of the hand held gadget do i need to use a relay on both live and neutral wires? Thanks Graham

[Ian PParticipant @ianp]

I am not conversant with a ‘caravan mover’ but your mention of live and neutral infers that it is mains powered.

In general it is not necessary to have switches (or relays) in both the supply leads to a load but more information is needed to give sensible and safe advice.

Is the remote control a wired or wireless type?

Ian P

[John HaineParticipant @johnhaine32865]

Caravan movers usually work off the 12v supply so live and neutral are not applicable.  Your best bet would be to connect your switches between whatever receives the remote control signal and the mover motors so you can reuse the power control electronics (which may use relays but more likely solid state). If you are not very good with electrics you may find this project a challenge! From what I recall of having one fitted the mechanical work was also rather involved.

[Clive FosterParticipant @clivefoster55965]

Although it may not be strictly necessary to switch both “hot”(eg mains live, DC power) and “cold” (eg mains neutral, DC ground) lines when using relays my personal preference is always to switch both when connecting accessories.

Even if for no other reason than neatness of circuit diagram and installation with everything going to the input side of the really and everything coming off the output side. If you are using plug in socket relays this also makes it very easy to isolate everything just by pulling the relay from its socket. With mains powered systems its not unknown to get MCB / RCD weirdies when working on a system that has a continuous neutral even though the power side has been disconnected and safely isolated.

Embedded car and motorcycle systems using 12 V DC power are about the only time I use single sided switching relays. Slightly different in that case as there has to be a ground connection for one end of the operating coil anyway.

Clive

[Graham TitmanParticipant @grahamtitman81812]

Hi Ian no 12 volt  it is the auto one second hand no controls just 2 lengths of about 6mm cable for the motor and 2 thin wires for the auto i want to use it for reversing a motorbike and sidecar so 1 switch to turn power on 1 switch to p0wer the auto back and forward and a switch to put it in reverse. Graham

 

[Speedy Builder5Participant @speedybuilder5]

I don’t know what sort of ampage the motors take and if your switches would be up to it.

If not, you could put in relays to switch the current, and switches to control the relays. Note, select relays that would be capable of switching the loads.

[Ian PParticipant @ianp]

If the two lengths of ‘6mm cable’ are the power leads into the motor then your relays or switches will have to handle quite a few amps. A photo of the rating plate of the motor and of the switches would be helpful.

Did you means 6mm outside diameter for the cable, or 6mm csa?

A center-off rocker switch to handle the motor current without relays might not be an easy thing to find, relays to switch significant current are expensive once the current is outside the range of automotive relays.

Ian P

 

 

[noel shelleyParticipant @noelshelley55608]

As you say your not good with electrics do you have a wiring diagram to hand or in mind ? If the motor is a permag then to reverse it you swap the motor connections so it would be safer and easier to do this with relays set near the power source This will keep wires short and voltage drop low. Your switches then only have to switch the coil current and be thin rather than may be 20 or 30A, a stall could easily draw this current. Noel.

[Ian PParticipant @ianp]

Just to second what Noel said but to also to qualify the bit about putting the relays near the power source.

Its the cabling between the power source and the load that will be carrying the high current, it does not matter whereabouts along that cable the switching is actually done, its more a packaging or constructional matter.

Ian P

[Graham TitmanParticipant @grahamtitman81812]

The 6mm wire to the drive motor i swapped them over on a battery to get forward and reverse .I only want reverse  so just a on /off switch and there is no plate to tell the output .The small auto motor i think only draws about 1 amp it moves the drive roller back and forward so i need that to do the same . The feed wire to the drive motor will be kept as short as possible no more than 4 foot, a separate battery will be kept in the sidecar boot and have no other connection to the bikes electrics. Graham

[Grizzly bearParticipant @grizzlybear]

Hi Everyone,

Just for info.

EGO Titanium Motor Mover Single / Twin Axle Lightweight E-GO 400 Caravan | eBay

 

https://www.ebay.co.uk/itm/354523773758?mkevt=1&mkcid=1&mkrid=711-53200-19255-0&campid=5338690639&toolid=20006&_trkparms=ispr%3D1&amdata=enc%3A12MMSlmTYT3Wxgqzzt1CNKA18%26customid%3Ds%253AGS%253Bgc%253A24014380f2be180bae4a24bb88cf3935%253Bpt%253A1%253Bchoc%253A1&customid=s%3AGS%3Bgc%3A24014380f2be180bae4a24bb88cf3935%3Bpt%3A1%3Bchoc%3A2

[Graham TitmanParticipant @grahamtitman81812]

The 6mm wire to the drive motor i swapped them over on a battery to get forward and reverse .I only want reverse  so just a on /off switch and there is no plate to tell the output .The small auto motor i think only draws about 1 amp it moves the drive roller back and forward so i need that to do the same . The feed wire to the drive motor will be kept as short as possible no more than 4 foot, a separate battery will be kept in the sidecar boot and have no other connection to the bikes electrics. Sorry cannot post photos as apple and microsoft refuse to communicate with each other  Graham

Just looked at the ad for ebay above i payed £50 for half a unit and it works.

[Graham TitmanParticipant @grahamtitman81812]

Had another play got the big hammer out they are now talking nicely

[SillyOldDufferModerator @sillyoldduffer]

Graham says he’s repurposing a Caravan Mover, so I think the answer boils down to how many amps have to be switched.    Here’s an example of the beast (two movers needed per caravan, with one controller):

The circuit shows the movers are powered by a 12Vdc battery, and judging by the size of the wires I guess 10A to 20A.

Fitted to a caravan, there is only one switch fitted in the red positive lead.  But this is an isolating switch and most of the serious switching is done inside the blue/grey controller.  It obeys orders from a hand-held remote.  As the controller is slim, I guess it’s semiconductor switched, not by a relay.  No matter: Graham can switch his motor however he wants, provided the contacts in the switch or relay can cope.

One thing to watch is that many switches are rated for mains AC, which is much less demanding of the contacts.  All switches arc, which burns and tends to weld the contacts, but AC is self-extinguishing, because AC falls to zero volts 50 times per second.   In contrast a DC arc is only extinguished after the contacts move sufficiently far apart.   Thus DC rated contacts tend to be beefier than their AC equivalents and are often spring loaded to open and close faster too.

This double pole example from RS might do what Graham needs – rated at 20Adc.  I’d switch both Positive and Negative leads because if a contact welds, then the other will still open and stop the motor. Safer.  (Switching both Line and Neutral AC lines is avoided because a jambed closed contact leaves the equipment live and dangerous – looks switched off and isn’t.  This safety concern doesn’t apply to 12Vdc.)

High-current DC switches are a little difficult to find, in which case it might be necessary to use a relay, or same thing, a contactor.  (Folk with an electronics background tend to call them relays, chaps who do power tend call them contactors: same difference!)  Relays allow a small or remote switch to control a big current, just make sure the contacts are rated for it.

Any need to reverse the motor?

Dave

 

 

 

 

 

 

[Graham TitmanParticipant @grahamtitman81812]

The Hi-win moves the drive motor in  and out  then i just want to use the big motor to go  backwards i am to weak to push it out and up the drive and it will not fit in the garage backwards. Graham

[Ian PParticipant @ianp]

This is part of the specifications for the Titanium EGO400

Operating Voltage  12V DC
Avg Current Consumption  25 Amps
Max Current Consumption 76 Amps

Its not clear from the data sheet whether the numbers are for one or two of the motorised units but even if its one (which I think its is) then a switch with substantial contacts is required. The relay that Graham showed a picture of should be suitable as a m/c and sidecar is a lot lighter than (half of) caravan.

Ian P

[noel shelleyParticipant @noelshelley55608]

Check out DURITE they do a good range of relays of the type you need. and are available through any good motor factor. Noel.

[John HaineParticipant @johnhaine32865]

I’ve always wondered, what is a motor factor?

[duncan webster 1Participant @duncanwebster1]

According to Collins dictionary, a factor is someone to whom goods are consigned for sale and who is paid a factorage. Not just the mathematical meaning. Not quite what Halford do, but perhaps historical?

[Michael GilliganParticipant @michaelgilligan61133]

Confirming Duncan’s post … amongst the multitude of meanings, you will find this:

.

.

 

MichaelG.

.

Ref. https://en.wiktionary.org/wiki/factor

Ref. https://en.wiktionary.org/wiki/commission_agent#English

[Ian PParticipant @ianp]

What John Haine actually asked was, what is a ‘motor factor’.

Wiktionary give this more relevant answer,

Noun
motor factor (plural motor factors)

(British, Ireland, chiefly in the plural) A retail supplier of car parts and accessories.

Ian P

[John HaineParticipant @johnhaine32865]

Not a term in common use.  To my surprise though, Halfords have a useful range at reasonable prices.

[Ian P]

On Ian P Said:

What John Haine actually asked was, what is a ‘motor factor’. […]

You are quite correct, Ian

Apologies for concentrating my attention upon the word which my Commercial/Contractual mind finds more interesting.

MichaelG.

[John Haine]

On John Haine Said:

Not a term in common use…

It’s a shame when common terms fade away.  When I was a little boy most towns had a High Street full of speciality shops, mostly now destroyed by super-markets, hyper-markets and now internet shopping.   Alas, Haberdashers, Milliners, Tobacconists, and even Greengrocers are no more.

Alway been thus, all change!  My parents used Emporium as a joke word, and Purveyor was half joke, half respectable.  Some of these old names have longer legs than others:  a few Arcades and Galleria about, but Boutiques didn’t last long!  After a brief spell as top buzzword, Discotheque was replaced by Disco,  which took over the world for about 15 years.  Try asking youngsters if they’re going to a disco.  They’ll probably repress their sniggers, just as I did when an uncle asked teenage me if I was going to a hop.

A few weeks ago I had to buy medicine from a Pharmacy.  They may be the last survivor of the old system whereby goods were kept behind a counter, and you had to ask an assistant for what was needed, and nothing was handed over until wrapped and paid for.   I remember a old-fashioned coop where buying meat involved queueing at the butcher counter to order it, after which the butcher sent a ticket through a pneumatic tube to an enclosed booth who handled the money.  Then the customer queued again to pay, and be given a voucher which he took back to the butcher – more queuing.  Only then was the meat handed over!     Pneumatic tubes are still common: big supermarkets often use them to transfer cash from tills to the back-office.

Just started to snow here in Zummerzet!

Dave

 

[noel shelleyParticipant @noelshelley55608]

MOTOR FACTOR = A business that in this day and age sells parts for cars and vehicles, I hardly call Halfords a motor factor.  Eg MPD look it up !

Dave, ‘In that case it aint Zummer any more ?  Noel.

[Author]

Posts