LED Dimmer query

[ge_rik]

You may recall a thread a couple of weeks ago about using a cheap LED dimmer as a remote control for battery locos.

http://www.gscalecentral.net/m171394

I invested in one for my railbus (still under construction)

I removed the circuit board from its housing and wired it in.

It works well (considering the price) - but I've hit a snag and wondered if any of you electronics whizzes had any suggestions. I thought I'd wire the LEDs I'm using for the headlights into the motor circuit so that the headlights would come on in the direction of travel. Simple, I thought. Wire them across the motor in opposite directions so only one set will glow dependent on the way the reverse switch is set.

(NB resistors in series with LEDs not shown)

Trouble is, when I power up, the LEDs glow dimly at first then get dimmer as the speed increases before going out completely when the dimmer unit produces full power. I assume it's something to do with the internal resistance of the motor. I'm using 12v of battery power as the dimmer unit works best on this and the resistors for the LEDs are those rated for 12v for the LEDs I'm using. When I connect the LEDs / resistors directly to the batteries they shine beautifully.

As I mentioned in the earlier discussion - I have a basic understanding of electrical circuitry and an inkling of practical electronics but stumble at the first hurdle when it comes to theory.

Any suggestions (polite and/or anatomically achievable?)

Rik

 

[Rhinochugger]

Thta's roughly how I wired mine for the blue and yellow diesel.

However, mine were lower voltage and have in line resistors.

It's a long time ago, and I can't remember the specifications.

How helpful's that? :impatient:

 

[Rhinochugger]

Still hunting for the parts list :thinking::thinking:

 

[Westcott]

Ge_rik,
When you say 'full power', is that with the railbus running flat-out on the track?

 

[tramcar trev]

Do you really have to have directional lights? I'd be wiring them seperatley directly across the supply with if necessary resistors. so you have a lighting circuit and the motor circuit. If you wire them up in series you can use 1 resistor. Using the polarity of the leds makes them directional ie on when going forward off ( or change) when reversing as you show in you're schematic...

 

[Rhinochugger]

Do you really have to have directional lights?

Oh, yus

The memory's beginning to work now.

the diesel that took the plunge (and survived) has headlights from IP Engineering. sadly they're not listed on his website any more, but I think they were 3v - they definitely have resistors in line.

 

[ge_rik]

Ge_rik,
When you say 'full power', is that with the railbus running flat-out on the track?

Yes, that's right. I don't think the dimmer unit produces the full 12v otherwise the motor would be screaming like mad as it's really only intended for 6v. I've not put a meter across to test as I'm happy with what goes for full power from the unit. Just curious as to why the LEDs seem to work inversely to the motor output.

Rik

 

[ge_rik]

Do you really have to have directional lights? I'd be wiring them seperatley directly across the supply with if necessary resistors. so you have a lighting circuit and the motor circuit. If you wire them up in series you can use 1 resistor. Using the polarity of the leds makes them directional ie on when going forward off ( or change) when reversing as you show in you're schematic...

Yes, I've resorted to a separate circuit, but have lost the directional aspect - unless I wire another changeover switch into that circuit as well. It would be good to have directional lights as each car has its own set of headlights and I intend to always run them as a pair to avoid a turntable at each end of the line.

I'm assuming commercially produced non DCC models with directional lighting must tap into the motor circuit somehow.

Rik

 

[Rhinochugger]

The circuit diagrams that I produced were really only for my own consumption, as they were drawn in a way that I could understand to solder the components to strip circuit board.

They probably aren't that easy to understand if I posted them on here.

I shall have to see if i can understand them now

I'll be back

 

[Rhinochugger]

I'm back

I think, effectively, my circuit diagram is the same as yours. Originally I was running a 7.2v battery pack, but now I've upgraded to 12v. the lights have worked perfick on both voltages.

I think the problem is having 12v LEDs. I think you need to have 3v with resistors in line - you can keep to your original circuit digram then you'll need to ask an expert (try Neil Robinson) for details of the resistor.

It works for me ( and they still work after the plunge)

Oh, Rik, sorry, just checking - have you got a fuse in the circuit? it won't affect the lights but will help your house insurance premium

3800 mAh can burn wiring at a pretty alarming rate if something ain't quite right

 

[ge_rik]

Oh, Rik, sorry, just checking - have you got a fuse in the circuit? it won't affect the lights but will help your house insurance premium
3800 mAh can burn wiring at a pretty alarming rate if something ain't quite right

Not considered a fuse, I must admit.

Rik

 

[Rhinochugger]

Oh, Rik, sorry, just checking - have you got a fuse in the circuit? it won't affect the lights but will help your house insurance premium
3800 mAh can burn wiring at a pretty alarming rate if something ain't quite right

Not considered a fuse, I must admit.

Rik

My sorry tale was written up in full on the old G Scale Mad site.

I burnt ot the wiring and trashed the 2300 mAh battery pack, burnt me little pinkies trying to rip out the glowing wires, all after smoke started billowing out of the engine cover on it's first charging attempt.

All of this was indoors. I now have a car type in line fuse, that you can stick the blade fuses into - rated at a wattage of you choice - 5watts for me.

 

[ge_rik]

I burnt ot the wiring and trashed the 2300 mAh battery pack, burnt me little pinkies trying to rip out the glowing wires, all after smoke started billowing out of the engine cover on it's first charging attempt.
All of this was indoors. I now have a car type in line fuse, that you can stick the blade fuses into - rated at a wattage of you choice - 5watts for me.

So far, I'm not using rechargeables. I bought 100 x alkaline AA batts from Maplin for £15 which should see me through a season (or maybe 2) - not very environmentally friendly I know but my success with rechargeables is a bit patchy. I'm on my fourth NiCad battery operated drill - I never know whether to keep them fully charged, discharged, top them up, wait until they go flat, or whatever.

It's one reason I've resisted battery power for so long, I don't think I'm well organised enough to get the best out of rechargeables.

Rik

 

[Neil Robinson]

I've resorted to a separate circuit, but have lost the directional aspect - unless I wire another changeover switch into that circuit as well. It would be good to have directional lights as each car has its own set of headlights and I intend to always run them as a pair to avoid a turntable at each end of the line.
Rik

A separate circuit is probably the best way to go. Rather than a second switch I be tempted to use one four pole On Off On switch.
http://www.rapidonline.com/Electronic-Components/4PDT-On-off-on-Min-Toggle-Switch-75-0094 < Link To http://www.rapidonline.co...-Toggle-Switch-75-0094

 

[Gizzy]

So as I understand it, motor not running, LEDs bright?

Motor running, LEDs start to dim?

I would say the current draw for your motor is lower than for the LEDs. Or put another way, the resitance of the motor when running is lower than the resistances used with the LEDs. The current will always take the path of least resistance.

I would need to know the resistor used with your LEDs and if possible, the current rating.

LED resistance can be calculated using a conversion formulae available on the web:

http://led.linear1.org/1led.wiz

Note that the current is in mA, so the resistor will be in kilo ohms.

Ohms Law Formula

V = I x R or I = V / R

We know you have 12 volts, so I will need the forward current to be able to work out the resistance....

 

[Del Tapparo]

If your LED controller were acting like a typical PWM circuit, your LEDs would be working. The controller would be a voltage source, with a variable duty cycle. The result is an average voltage that increases with duty cycle.

It sounds to me that your device may be acting more like a current source, which is the way LEDs operate. Add to that the fact that the motor inductance may really be screwing up the waveforms, since the controller isn't designed to run a motor, and it is hard telling what is going on. So as stated in a previous response, the motor hogging all the current at higher speeds.

I'm really curious to know what you paid for the LED controller. I sell a device designed specifically for large scale trains, that is about 10 times smaller, for $29 US.
Simple Critter Control: http://1stclass.mylargescale.com/DelTapparo/gscalegraphics_1_018.htm

 

[ge_rik]

A separate circuit is probably the best way to go. Rather than a second switch I be tempted to use one four pole On Off On switch.
http://www.rapidonline.com/Electronic-Components/4PDT-On-off-on-Min-Toggle-Switch-75-0094 < Link To http://www.rapidonline.co...-Toggle-Switch-75-0094

Good idea, thanks Neil. Fits my philosophy - Keep it Simple

Rik

 

[ge_rik]

I'm really curious to know what you paid for the LED controller. I sell a device designed specifically for large scale trains, that is about 10 times smaller, for $29 US.
Simple Critter Control: http://1stclass.mylargescale.com/DelTapparo/gscalegraphics_1_018.htm

I got mine for 6.50 UKP - but they can be cheaper - eg

http://www.ebay.co.uk/itm/DC-12V-Wi...8570?pt=UK_Light_Fittings&hash=item1c1e77233a < Link To http://www.ebay.co.uk/itm...mp;hash=item1c1e77233a

Rik

 

[ge_rik]

So as I understand it, motor not running, LEDs bright?
Motor running, LEDs start to dim?
I would say the current draw for your motor is lower than for the LEDs. Or put another way, the resitance of the motor when running is lower than the resistances used with the LEDs. The current will always take the path of least resistance.
I would need to know the resistor used with your LEDs and if possible, the current rating.
LED resistance can be calculated using a conversion formulae available on the web:
http://led.linear1.org/1led.wiz
Note that the current is in mA, so the resistor will be in kilo ohms.
Ohms Law Formula
V = I x R or I = V / R
We know you have 12 volts, so I will need the forward current to be able to work out the resistance....

Does the resistance of a motor drop the faster it runs?

Not sure about the value of the resistors - I bought them with the LEDs from Cambrian - L1 on this page:
http://cambrianmodels.co.uk/16mmele...= Gold - then brown, purple, yellow Rik

 

[Gizzy]

So as I understand it, motor not running, LEDs bright?
Motor running, LEDs start to dim?
I would say the current draw for your motor is lower than for the LEDs. Or put another way, the resitance of the motor when running is lower than the resistances used with the LEDs. The current will always take the path of least resistance.
I would need to know the resistor used with your LEDs and if possible, the current rating.
LED resistance can be calculated using a conversion formulae available on the web:
http://led.linear1.org/1led.wiz
Note that the current is in mA, so the resistor will be in kilo ohms.
Ohms Law Formula
V = I x R or I = V / R
We know you have 12 volts, so I will need the forward current to be able to work out the resistance....

Does the resistance of a motor drop the faster it runs?

Not sure about the value of the resistors - I bought them with the LEDs from Cambrian - L1 on this page:
http://cambrianmodels.co.uk/16mmelec.html

Colour bands = Gold - then brown, purple, yellow

Rik

Rik,

I make that resistor to be 470 ohms, which seems rather low, from the colour bands, yellow, purple, brown. You could check it if you have a multimeter.

(Gold is a tolerance value)

http://www.google.co.uk/imgres?imgu...a=X&ei=MB_RTqvcA4Wg8gOY6sD4Dw&ved=0CBYQ9QEwAA
Calculating this I = V / R makes your current 25 mA = 12V/470 ohms which seems high to me. (I would expect to see a value of less than 2 mA).

I'm wondering if you have been supplied with a resistor of the wrong value....