N Gauge Forum

Your Layout and Models => Electronics => Topic started by: sparrowhawk on November 18, 2019, 06:33:55 PM

Title: Status LED
Post by: sparrowhawk on November 18, 2019, 06:33:55 PM
I have a brake control unit which controls entry to a terminal station . The dcc
supply just one leg is just routed through a switch to control its operation .
Can I use a led to show status although the supply A.C and if so how to I wire
it up ?
Title: Re: Status LED
Post by: ntpntpntp on November 18, 2019, 06:49:02 PM
It would help if you tell us what module it is exactly?  Is it some sort of "brake on DC" module?
Title: Re: Status LED
Post by: sparrowhawk on November 19, 2019, 03:49:31 PM
it is a standard lenz brake module BM1 the right hand rail supply is routed through it so the loco automatically brakes . To overcome the auto braking you can bypass the brake module via a switch it is this that I would like to link to a led to indicate
its status ie ON or OFF
Title: Re: Status LED
Post by: class37025 on November 19, 2019, 04:08:12 PM
I'd think a D/P-D/T on/off switch would be easiest, one side cut into the feed to the unit, the other with an input  feed for the LED, the other side feeding to the LED.

switch in on position would feed power to unit and LED, switch in off position feeds to both broken, so LED off.
Title: Re: Status LED
Post by: ntpntpntp on November 19, 2019, 06:23:49 PM
You can certainly use an LED with a suitable resistor - say 1.5k ohms if it's being powered from the DCC supply at around 15V?

With in AC supply it's usually recommended to fit an ordinary signal diode in inverse-parallel with the LED to protect the latter from the reverse voltage, but to be honest I've never bothered with that diode and I've not had any failures with my LEDs on AC at those sort of voltages.

Alternatively use a double pole switch as @class37025 (https://www.ngaugeforum.co.uk/SMFN/index.php?action=profile;u=311)  suggests, and power the LED with DC - still with a suitable resistor of course  :)
Title: Re: Status LED
Post by: Nigel Cliffe on November 19, 2019, 09:22:33 PM
You can certainly use an LED with a suitable resistor - say 1.5k ohms if it's being powered from the DCC supply at around 15V?

With in AC supply it's usually recommended to fit an ordinary signal diode in inverse-parallel with the LED to protect the latter from the reverse voltage, but to be honest I've never bothered with that diode

Or use two LEDs, back to back (ie. Anode to Cathode) with a shared resistor.  Thus, one LED lights on each half of the DCC signal, and in doing so, protects the other LED from an excessively high reverse voltage. 


- Nigel
SimplePortal 2.3.5 © 2008-2012, SimplePortal