Low voltage / high current

[1400mza]

Hello everyone


I want to do a fuction decoder for my coaches.
With one decoder I want to controll the lights of three cars.
It's possible that the decoder have low voltage outputs (5 volts) but high current in the outputs?

¿Its possible to implement a stay alive capabilities?

[suzie]

I have tried doing one of these, it is quite straightforward.

1. Use a high power function decoder (3 or 8 output).

2. If you need more than 100mA you might like to replace the 78L05 regulator with a (much larger) 7805 regulator. The pinout is the same and you can mount it over the other components. you might need to bolt it to something as a heatsink if it gets too hot depending on how much current you are drawing, so make sure that you can get a mounting bolt in to the hole OK.

3. You might like to replace the 1uF tantalum capacitor (C1) with something larger, the biggest you can fit in that is rated at 35V. You can use a regular aluminium electrolytic, it does not have to be tantalum. This will improve the stay alive capability.

4. Replace R15 with 4R7 5W. If you are not using the full 1A available you can increase the value of this resistor proportionately (eg. 10R 5W will be OK for 0.5A). Increasing the value reduces the power dissipated in the regulator, but has a trade off of reduced stay-alive effectiveness.

5. Use the +5V supply on pin 1 of the processor in place of the blue wire as the common for your function outputs.

You will now have outputs rated 200mA each at 5V (max decoder current load 1A). If you need more current just parallel some outputs and make sure they are all set to work together from the same function button. Stay alive will be very effective because the stay alive capacitor voltage can drop from normal track voltage to about 7V before there will be any dimming of the lights. It should be very flicker free if a big enough capacitor can be accommodated in the coach.

All things considered I would favour having a decoder in each coach, bear in mind that a low power decoder can supply 0.5W of lighting at five Volts (0.375W for 3-output), usually enough for most coaches in smaller scales. The high power decoder described here will provide five Watts total (3W for a 3-output version).

Suzie x

[1400mza]

Thank you.

I will try with your recomendations