Model railway power supply
- Thread starter FiremanT
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That is a very good idea, presumably the batteries would last a good while, given the low demand?
Should I be concerned, given that I sometimes shave with the electric razor plugged in?
Good point, but most razor sockets are fed from isolating transformers anyway
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As before:
If you could utilise a power bank, you would have ample 5V power and it would be easily rechargeable.
The choices are endless!
I had some Christmas tree LEDs that ran on a couple of AAs continually for at least two weeks
If you mean mine, it won’t be terribly exciting. Basic kit with added scenery, for the grand kids.
IfI can get around to clearing one of my sheds, I would like to do a big one, if the kids get interested .
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I would love that myself. I used to do model railways when i was much younger...
Most of the fun is in the building, improving and changing it.
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I agree
If you chose to use leds, these run at 2 volts taking about 20mA
Can help you with power supply and circuitry
Flashing lights too
When higher voltage introduced, the led fuses
Led that normally ran at 2 volts, I applied 50 volts to it, one went off with a crack, another just fused with no noise
The element that gives off light is a semiconductor junction like a diode ( led also passes current, like a diode in one direction only)
Question re secondary on transformer going live. The case or the core would go to earth as would a leg of the secondary winging
Pump in the boiler- when it blows the fuse because the terminal block is flooded- it is the earth that results in blowing the fuse
Resistor value for 12 volt supply R equal voltage divided by current. 10/20mA equals 5k ohms. Often 4.7k resistor used
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I'm afraid that is a little backwards.
LEDs are current driven devices, that typically range from 5 to 20mA.
They also have a forward voltage of 1.8 to about 3.3V (for a blue LED).
So, the supplied voltage should be greater than the forward voltage - 2V may not be enough for a blue LED.
Using a 50V supply wouldn't be an issue, we just have to limit the current. I.e.
50V - 2V (forward voltage of LED)/0.01A (10mA) = 4.8K Ohm resistor would be fine.
I believe your maths may be slightly out with this one
A 1k Ohm resistor would work.
Most of the power supplies we have been talking about have been SMPSU, that don't have an earth connection.
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