Cobalt point motors - wiring for DC - further queries

[Mallard60022]

I can't believe I actually knew something.....................I shall celebrate later.

You are all my favourites.

Ar$£

[newbryford]

I extensively tested some cobalts , and dismantled and traced the circuit. Refer to the classic omega version only . Internally the voltage is clamped at arround 6.5V. so voltages over about 7.5 voltages in effect do nothing and just result in increased dissipation when stalled , at 12 V the stall current is close to 60mA which rapidly adds up where you have lots of motors in stall. It’s a very poor design from that point of view. Our current layout has 50 , and as a result we consume 2.5A doing in effect nothing

 

 

I've got an Omega on the bench at the moment and just carried out a quick test

 

A quick read of stall currents (Using a good quality bench power supply)

 With the voltage switch [*] set to 12-18v range:

18v - 55mA

15v - 45mA

12v - 35mA

9v - 25mA

 

(with the voltage switch set to 6-12v range)

12 v - 60mA

9v - 55mA

6v - 38mA

 

So if you are using a 12v (or 9v) supply, switch the Omega to the 12-18v range.

 

TBH - even running them on 9v with the 12-18 setting is OK - they just run a fraction slower.

 

[*] the voltage switch is next to the terminal block for those that haven't noticed.

 

Cheers,

Mick

Edited July 25, 2018 by newbryford

[Vistisen]

Some DC controllers have "dodgy" waveforms.

 

Best option is a plug in wall supply. Key word is regulated.

I always used to point people in the direction of Maplins......

 

BTW, a Cobalt will quite happily work on 9v - all it does is run a bit slower.

 

 

 

Cheers,

MIck

I was at the Bodmin railway the other day and stood on a bridge watching the points changing. I was struck by the speed of the changes.Even though they are manually changed by pulling levers, they hopped back and forwards more like Pecos motors. My cobalt Alphas are unrealistically slow in changing!

[Mallard60022]

Rapid Online is good for electrical bits and pieces. RIP Maplin.

Phil

[Captain Kernow]

Well, that was incredibly quick - ordered at about 1530 hrs yesterday and the courier has just delivered it from Rapid Electronics - definitely living up to their name!

 

Of course, it's got a mobile phone plug type thingey, I'm more used to steam-powered 2-pin DIN ones. Presumably I could get a matching plug/lead for this from Rapid Electronics as well?

 

[Mallard60022]

Well, that was incredibly quick - ordered at about 1530 hrs yesterday and the courier has just delivered it from Rapid Electronics - definitely living up to their name!

20180726_094916.jpg

 

Of course, it's got a mobile phone plug type thingey, I'm more used to steam-powered 2-pin DIN ones. Presumably I could get a matching plug/lead for this from Rapid Electronics as well?

Dunno, but you can get a green socket thing to go on that plug kno# so that you can join two wires to it (would that be enough wires for DC?) I know because I i got some but I can't remember where; sorry.

Ar$£

[cpman46]

Just cut the plug off, separate the wires, check polarity with a meter (polarity of plug and wire marking may be on the adaptor somewhere) and wire to a small (3A) screw terminal block.

Regards

Mike

[Mallard60022]

Just cut the plug off, separate the wires, check polarity with a meter (polarity of plug and wire marking may be on the adaptor somewhere) and wire to a small (3A) screw terminal block.

Regards

Mike

or https://www.amazon.co.uk/Adaptor-100-240V-Transformers-Switching-Approved/dp/B019RO949C

Ar$£

Edited July 26, 2018 by Mallard60022

[St Enodoc]

You may find 12V is a little too much juice for your Cobalts.  They seem to prefer something less - around 9V.

 

Old laptop power supplies have been suggested as a possible source.  

 

I picked up my "wall warts" from DCC Concepts as well, and - obviously - they are fine.

Will the good Captain please tell us exactly which model(s) of Cobalt he has? That will help folk provide the correct information, as some of it is different for different versions.

[Junctionmad]

I've got an Omega on the bench at the moment and just carried out a quick test

 

A quick read of stall currents (Using a good quality bench power supply)

 With the voltage switch [*] set to 12-18v range:

18v - 55mA

15v - 45mA

12v - 35mA

9v - 25mA

 

(with the voltage switch set to 6-12v range)

12 v - 60mA

9v - 55mA

6v - 38mA

 

So if you are using a 12v (or 9v) supply, switch the Omega to the 12-18v range.

 

TBH - even running them on 9v with the 12-18 setting is OK - they just run a fraction slower.

 

[*] the voltage switch is next to the terminal block for those that haven't noticed.

 

Cheers,

Mick

I just finished a new version of a MERG cbus board specifically to drive cobalts , so I’ve soent several weeks characterizing them , I run them at 9.5V . I find that they have very little power at that voltage on the higher voltage range , as too much is lost in the internal dropper resistor

 

It’s ridiculous how much power is lost to heat in these devices. Internally the zener is set to 6.5V ,

[Mallard60022]

I just finished a new version of a MERG cbus board specifically to drive cobalts , so I’ve soent several weeks characterizing them , I run them at 9.5V . I find that they have very little power at that voltage on the higher voltage range , as too much is lost in the internal dropper resistor

 

It’s ridiculous how much power is lost to heat in these devices. Internally the zener is set to 6.5V ,

That sounds technical. As I have no idea what you mean apart from little power, lost resistor and lost to heat, could you put it a bit more simply for me? I am not being rude I just don't understand stuff like this, probably because I am really just a duck.

Thanks

Philk

[Mallard60022]

Zener = "a form of semiconductor diode in which at a critical reverse voltage a large reverse current can flow" That doesn't help me either.....

Sorry

Duck

[Captain Kernow]

Will the good Captain please tell us exactly which model(s) of Cobalt he has? That will help folk provide the correct information, as some of it is different for different versions.

I couldn't tell you the precise specification but here are some photos of one of the motors. All the motors are the same type.

 

 

 

 

 

I would add that thanks to a kind person who has been in PM correspondence with me, I do now know how to wire these up.

[Captain Kernow]

And in any case, I've got another query now as well! - http://www.rmweb.co.uk/community/index.php?/topic/136053-how-good-is-this-gaugemaster-controller/&do=findComment&comment=3245437

[newbryford]

I couldn't tell you the precise specification but here are some photos of one of the motors. All the motors are the same type.

 

IMG_9377.JPG

 

IMG_9378.JPG

 

IMG_9379.JPG

 

IMG_9380.JPG

 

I would add that thanks to a kind person who has been in PM correspondence with me, I do now know how to wire these up.

 

An original CB1 Cobalt. They do have two different types of internals, but the connections are essentially the same as a Tortoise

Edited July 27, 2018 by newbryford

[St Enodoc]

An original CB1 Cobalt. They do have two different types of internals, but the connections are essentially the same as a Tortoise

These are the early ones that were less reliable that the present versions. Personally, I wouldn't use them for that reason.

[newbryford]

These are the early ones that were less reliable that the present versions. Personally, I wouldn't use them for that reason.

 

I would recommend running them with a 9v supply. (Or 12v with say a 270/330 ohm resistor in the power feed to it)

Edited July 27, 2018 by newbryford

[St Enodoc]

And in any case, I've got another query now as well! - http://www.rmweb.co.uk/community/index.php?/topic/136053-how-good-is-this-gaugemaster-controller/&do=findComment&comment=3245437

Saw that. NHN is right, it's no good for coreless motors and not very good for other modern motors. The Digitols are superb bits of kits but like rocking-horse droppings these days.

 

Although I don't use them, folk tell me that the conventional Gaugemasters (without an F in the name) and Morley are very good.

I would recommend running them with a 9v supply. (Or 12v with say a 270/330 ohm resistor in the power feed to it)

Agreed, but even so they aren't as good as the redesigned ones.

[Captain Kernow]

(Or 12v with say a 270/330 ohm resistor in the power feed to it)

Unfortunately I haven't got a clue about what one of these looks like or where I might find one and even if I did, how I would wire it up?

[newbryford]

Unfortunately I haven't got a clue about what one of these looks like or where I might find one and even if I did, how I would wire it up?

 

Resistors come in all shapes and sizes.

Typically the one you would require would look like these

They are about 6-8mm long.

You would wire one in series with one of the power connections to your Cobalt

[Junctionmad]

That sounds technical. As I have no idea what you mean apart from little power, lost resistor and lost to heat, could you put it a bit more simply for me? I am not being rude I just don't understand stuff like this, probably because I am really just a duck.

Thanks

Philk

I can’t locate my sketch of the internal circuit of the Colbalt Omega , but from memory , there is a 5v motor , so to control the voltage a 6v5 zenner diode is used , this in effect creates a regulated power supply to the motor . Hence any voltage over about 7v does nothing , except dissipate heat in the dropper resistors

[Captain Kernow]

Well, thanks to those kind folk who have posted on this thread and also PMed me separately, I have made some progress.

 

I have obtained a 12v uncontrolled power supply and have wired this temporarily into one of my Cobalt motors, to see how it works.

 

As the uncontrolled 12v supply is fixed at one polarity, I was only able to get the motor to change direction by swapping the wires in terminals 1 and 8.

 

I've sat looking at a piece of paper for a while, but I can't get my head around how you actually wire these up to get them to change polarity.

 

My question now is, with regard to the diagram below, what kind of switch do I need to fit where it says 'Switch of some kind', in order to get the motor to operate and change direction, please? Many thanks.

 

Edited July 30, 2018 by Captain Kernow

[Mallard60022]

I believe it could be a DPDT 'cross wired' as per an instruction wot I have seen on another Cobalt sheet.You can find that diagram on the DCC website.

Yo CK, get those shorts on and play.

P

[St Enodoc]

I believe it could be a DPDT 'cross wired' as per an instruction wot I have seen on another Cobalt sheet.You can find that diagram on the DCC website.

Yo CK, get those shorts on and play.

P

Wot 'e said.

[Mr.S.corn78]

Well, thanks to those kind folk who have posted on this thread and also PMed me separately, I have made some progress.

 

I have obtained a 12v uncontrolled power supply and have wired this temporarily into one of my Cobalt motors, to see how it works.

 

As the uncontrolled 12v supply is fixed at one polarity, I was only able to get the motor to change direction by swapping the wires in terminals 1 and 8.

 

I've sat looking at a piece of paper for a while, but I can't get my head around how you actually wire these up to get them to change polarity.

 

My question now is, with regard to the diagram below, what kind of switch do I need to fit where it says 'Switch of some kind', in order to get the motor to operate and change direction, please? Many thanks.

 

Cobalt wiring diagram query.jpg

Hi Capitan,

 

As has been mentioned you will need a DPDT switch and cross wire it.

There is a diagram on the Tortouse instructions that will help.

I’m not near my copy of the instructions in my folder to send a copy over to you. A google search should bring them up.

 

Cher’s

Simon