What's in a controller? Build yer own perhaps?

[alec dawe]

I'm told my Aristocraft 2-8-8-2 is quite a power hungry beast(when it arrives) and trawling though the forum seems the Gaugemaster G scale controllers don't much like a continuous draw of 2amps+, which got me to wondering exactly what is in them.
I'm assuming a 240v to 18 or 24v transformer plus a bridge rectifier and a potentiometer, what else lurks inside?
Are they a PWM type controller of just simple voltage reg?
I've got a pre dcc book on model rail electronics with diagrams and instructions for all sorts of feedback controllers etc.
ok so they are for oo/ho gauge, but just need the components beefing up to take 24v and 5amps (in fact the author recommends 5amps capacity anyway to cope with double heading old Triang and Hornby locos.
Anyone made their own? Bits should be available from the likes of Maplins etc. What are the cost comparisons like?

Alec

Growing old disgracefully.

 

[sparky230]

try looking up circuits based on LM317 adjustable voltage regulators

 

[spike]

Try these.......supposed to be bombproof.

http://home.cogeco.ca/~rpaisley4/SCRCircuits.html

 

[alec dawe]

Thanks spike.
Now I need to brush up my soldering skills (not helped by being red green colour blind).

Alec

 

[Rhinochugger]

I did build an 18v 3amp controller, and it worked.

The difficulty is with the current overload. Most of the devices based on car parts are too slow to protect the electronic gubbins.

My controller used to go to warp factor 9 when re-set after a short, and needed to be stripped an re-soldered before it would 'control' again.

It currently resides on a shelf and I use a Helmsman. Geoff confirmed that the overload protection is the issue, and after designing his own electronic cut out, had to slow it down to prevent it tripping too early !!

Have fun, and let us know the outcome

 

[Glengrant]

There's an interesting question, what's inside a controller. Do you mean like me and Don and Ross and one or two of that ilk? Well, probably a horrible mess of confusion and devious methods of how to fiddle the expenses etc. plus a weird ability of how to stop aeroplanes banging into each other. Eh? Oh, not that sort of controller? Sorry, I'll go and pour another wee dram
My apologies, you are asking a serious question

 

[Neil Robinson]

Geoff confirmed that the overload protection is the issue, and after designing his own electronic cut out, had to slow it down to prevent it tripping too early.

If anyone has a link to a suitable electronic cut out circuit that may be adjusted to suit slightly differing conditions I, for one, would be interested in it.

 

[Brixham]

I find that the LGB 51070 controller hut is 'nearly' ideal. Or the bare bones controller without hut for panel installations.

It can deliver high currents for long periods without getting hot and tripping out, as it is a switching design. Not pwm, but switches the incoming power ( ac or dc ) rapidly, then smooths it to near dc.

The only downside is that I think it is too sensitive for brief overloads, like a contact shoe touching an adjacent rail. The unit trips, and the only way to reset it is remove and reapply power, or turn the controller to 0, and then back to where it was. I havn't tried it with a car headlamp in the supply lead to reduce the tripping.

As your loco isn't LGB but Aristo, why not try and find an Aristo unit which uses pmw, and surely has been tested with Aristo locos.
The old Train Engineer base unit is rated at 10? amps with a cooling fan.

Malcolm

 

[Rhinochugger]

Geoff confirmed that the overload protection is the issue, and after designing his own electronic cut out, had to slow it down to prevent it tripping too early.

If anyone has a link to a suitable electronic cut out circuit that may be adjusted to suit slightly differing conditions I, for one, would be interested in it.

The only person I know would be Geoff Helm himself (or it could be Jeff - I forget) - met him at the one and only Reading show

 

[spike]

try looking up circuits based on LM317 adjustable voltage regulators

You could use a LM317 but it's only 1.5amps on it's own.

I suggest the circuit in the link below that uses an LM723 and several 2n3055 to
give a nice 10Amp supply, plus current limit etc are still retained.

http://www.thebackshed.com/windmill/articles/VariablePowerSupply.asp

 

[Railway42]

You can use a LM338 5amp regulator use the TO3 can type it is fully protected for temperature and current limits
cannot find how to put on an attachment so i cannot design one for you but if you let me have your email i will do it for you.

Railway42

 

[nicebutdim]

try looking up circuits based on LM317 adjustable voltage regulators

You could use a LM317 but it's only 1.5amps on it's own.

I suggest the circuit in the link below that uses an LM723 and several 2n3055 to
give a nice 10Amp supply, plus current limit etc are still retained.

http://www.thebackshed.com/windmill/articles/VariablePowerSupply.asp

I am currently in the process of building this controller. The components are quite cheap but the heatsinks are double the price of everything else. Without the power supply the cost is around £40.

 

[spike]

try looking up circuits based on LM317 adjustable voltage regulators

You could use a LM317 but it's only 1.5amps on it's own.

I suggest the circuit in the link below that uses an LM723 and several 2n3055 to
give a nice 10Amp supply, plus current limit etc are still retained.

http://www.thebackshed.com/windmill/articles/VariablePowerSupply.asp

I am currently in the process of building this controller. The components are quite cheap but the heatsinks are double the price of everything else. Without the power supply the cost is around £40.

I have at times seen various heatsinks in the scrapyard I visit.
It's hit or miss when you need one but may be worth a look if
you have a friendly scrapyard.

 

[Railway42]

To make a cheap heat sink use a piece of aluminium bend in a U then a smaller piece bend in a smaller U do this 3 of 4 times, fit on inside the other then you have a heat sink make it as long and as wide as you like.
A circuit that is using npn 2N3055 is very old hat FET's are the best.

Railway42

 

[Rhinochugger]

Yes, I found that the heat sink was probably the dearest component - more expensive than the toroidal transformer (we won't go into that story).

I think I bought mine from RS - but I was also trying to co-ordinate the dimensions with the size of the box.

I'll try and post a shot later - got to go and give SWMBO a hand. :wave::wave:

 

[tramcar trev]

I used a switch mode power supply and each section of the tramway has its own PWM controller via ebay.

http://www.ebay.com.au/itm/DC-12V-5...ent&hash=item20cae30fe7&_uhb=1#ht_5786wt_1006 < Link To http://www.ebay.com.au/it...;_uhb=1#ht_5786wt_1006

This PWM is reversable but there are many cheaper ones without the reverse feature that is as simple as a double pol, double throw switch..... put it in a plastic box.....
http://www.ebay.com.au/itm/5V-30V-5...ment&hash=item1c27c0c637&_uhb=1#ht_2410wt_899 < Link To http://www.ebay.com.au/it...p;_uhb=1#ht_2410wt_899
http://www.ebay.com.au/itm/5V-30V-5..._ET&hash=item20d0efa099&_uhb=1#ht_1878wt_1097 < Link To http://www.ebay.com.au/it...;_uhb=1#ht_1878wt_1097

 

[Rhinochugger]

Here's a shot of the controller with heatsink.

You have to use a special washer system - to isolate the transistor from the chassis, but that allows transfer of heat (forget the name now - senility looms)

 

[nicebutdim]

That looks very good. I've just found an old car amplifier upstairs. The heat sink is HUGE. Bit too big for these needs.
Trev, just be careful using PWM control. It is totally fine on simple motor stock but I did read somewhere it can cause the loss of magic smoke from dcc equipped stock.

 

[Rhinochugger]

The heat sink is HUGE. Bit too big for these needs.

Never send a boy on a man's errand

 

[nicebutdim]

It really is enormous, about 30cm by 60cm and weighs about 3kg. It would seem a shame to dismantle a 2x3000 watt amp too, but I'm well past my car modifying days.