Transformer

[Puddles]

I have a plug in transformer from an internet hub.
Input 230V. 50Hz. 300mA
Output 12V=1500 mA
Can I use it on my railway for lighting ? Or anything else on the layout or just recycle it?

Puddles

[darkscot]

Depends on the lights, Gaugemaster do station lights that take 12V DC.

Well to be pedantic I think the lights are 3V, but they come as a set which includes a circuit board to drop the voltage. You can also buy bundles of 20 or so 3V LED lights for about a fiver and then buy a separate power control board to drop the voltage to 3V.

The cheap LED lights are not as authentic looking as the Gaugemaster ones, but they are cheap.

[Brian]

I have a plug in transformer from an internet hub.
Input 230V. 50Hz. 300mA
Output 12V=1500 mA
Can I use it on my railway for lighting ? Or anything else on the layout or just recycle it?

Puddles

Hi
Yes it should be ideal, assuming the output is DC? But as it fed an electronic hub device its very likely to be DC.
Are you able to obtain a matching socket for the moulded low voltage plug? If so I would use one otherwise it means cutting off the moulded plug and terminating the wires somehow - terminal blocks etc. You will also need to determine which is the positive connection especially where LEDs are used, as LEDs are polarity conscious devices and won't light if connected the wrong way around.
1500ma is a good output current = 1.5Amp and will run many lights filament or LEDs. I use as a 'rule of thumb' calculation to ensure you do not overload the supply that each Filament lamp draws from the supply 0.07A and LEDs 0.01A per lit item and then times that by the number lit. Additionally allow about 15% headway too as you don't want to stress the supply.

If you use LEDs then before you connect them up to a supply, ensure they are either supplied as 12 volt rated (have a build in resistor) or you add a series current limiting resistor in one lead to the LED (doesn't matter which lead it goes in) or use a dedicated voltage and current limiting circuit board. For a single LED on 12 volts DC I would use a 1K (1000 Ohm) resistor as this will give a lower current drain and a reasonably bright light. To dim the LED increase the resistance to around a maximum of 10K (10000 Ohms) or possibly higher but its really a matter of trial and error with resistance values to get to the right brightness level, until the LED won't illuminate at all.

For lower than the supply voltage where filament lamps are used add two or more lamps together in series to give a 12 volt total. i.e. 3 volt rated lamps then wire four together in series (daisy chain them) to allow the four to connect across the 12volts. Equally 6volt filament lamps then two are connected in series across the 12 volts. If you use a series resistor on a single filament lamp it will get very hot so it must not be against anything likely to burn and its rated wattage needs to be higher than a resistor used for LEDs. For GoW or GoR filament lamps I would be looking at a resistor rated at a minimum of 0.6watt and higher wattage would be better. A single LED resistor need only be 0.25watt but larger wattage wont hurt.

[Puddles]

Thank you for the reply Darkscot and Brian very helpful, I will put it in my bits to use box instead of the recycle box.

Puddles

[Tricky Dicky]

As Brian has said getting the appropriate light emitted from an LED is a matter of experimentation so rather than sitting with a a big mixed bag of resistors and trying out various combinations getting a potentiometer will allow you adjust light levels easily starting with a 10K trimmer for a single LED.

WARNING NEVER CONNECT A POTENTIOMETER ON ITS OWN TO AN LED

If you connect the potentiometer on its own it can inadvertently be turned down to zero ohms at which point you will get a spectacular release of the magic smoke. Always put a minimal value resistor in series a 1K(1000R) as Brian has said is a good starting point at 12V. Adjusting the potentiometer can quickly establish the appropriate dimness. Using a multimeter to measure the reading across the potentiometer terminals and adding that to your fixed value resistor will establish which value resistor you need.

Richard

[teedoubleudee]

As Brian has said getting the appropriate light emitted from an LED is a matter of experimentation so rather than sitting with a a big mixed bag of resistors and trying out various combinations getting a potentiometer will allow you adjust light levels easily starting with a 10K trimmer for a single LED.

WARNING NEVER CONNECT A POTENTIOMETER ON ITS OWN TO AN LED

If you connect the potentiometer on its own it can inadvertently be turned down to zero ohms at which point you will get a spectacular release of the magic smoke. Always put a minimal value resistor in series a 1K(1000R) as Brian has said is a good starting point at 12V. Adjusting the potentiometer can quickly establish the appropriate dimness. Using a multimeter to measure the reading across the potentiometer terminals and adding that to your fixed value resistor will establish which value resistor you need.

Richard

That's what I normally do but I recently bought one of these to do the same job. Bit more expensive than a pot I agree but you know I collect test equipment like toys

https://smile.amazon.co.uk/Iycorish-Res ... 806&sr=8-5

Same warning, easy to dial in zero 0hms.

[darkscot]

I am a big fan of the products from RK Education. They have lots of little electronic gadgets that can be used on a model railway. Including various power supplies with variable outputs, such as:

https://www.rkeducation.co.uk/rkpsu-v1- ... 2918-p.asp

This costs a measly £2.99 and you can buy 100 LEDs on eBay for a about £1.50, so it doesn't matter if you pop a few while determining the optimum voltage. Once you have that sorted you can then connect up the more expensive streetlamps or whatever.

For £5.99 you can get a version with three outputs, so you can split your 12V supply to say LEDs, incandescent bulbs and a motor?

[teedoubleudee]

Absolutelly agree about RK Education products. I've bought a few of their Picaxe kits for various microprocessor projects. Keen pricing too.