Date
1 - 9 of 9
Updated album Car lighting keep alive cap #photo-notice
|
w4dccqa@groups.io Notification <noreply@...>
Don Weigt <dweigt47@...> updated the album Car lighting keep alive cap: Greg Harter's passenger car lighting board with added capacitor. Greg reports lighting is constant for more than five seconds after power is removed from the rails. One photo is of the car with DCC power on the rails, the other after about five seconds without power. Can you tell which is which? The lighting board is from Walthers. The wires to the capacitor can be thin, as typically used wiring decoders. lt is possible long passenger trains with multiple cars would cause a problem by briefly drawing too much current when power is applied. If that happened, one fix would be to put a ten to about twenty Ohm resistor in either capacitor lead. This would reduce "keep alive" time a bit, as well as add complexity. The total modification cost per car would still be under half a dollar if the parts were bought from most online sources.
|
|
|
|
george hohon3
Here's my solution for passenger car and caboose lighting on an HO scale DCC layout:
There are no apparent "in-rush" current problems.
Brightness might be too bright, requiring a higher rated resistor (dependent on strip LED).
Flicker free operation is perfect, as in, there is no flicker!
If you're interested in the details, photos and the wiring schematic, let me know.
George
From: w4dccqa@groups.io <w4dccqa@groups.io> on behalf of w4dccqa@groups.io Notification <noreply@groups.io>
Sent: Sunday, March 6, 2022 7:23 AM To: w4dccqa@groups.io <w4dccqa@groups.io> Subject: [w4dccqa] Updated album Car lighting keep alive cap #photo-notice Don Weigt <dweigt47@...> updated the album Car lighting keep alive cap: Greg Harter's passenger car lighting board with added capacitor. Greg reports lighting is constant for more than five seconds after power is removed from the rails. One photo is of the car with DCC power on the rails, the other after about five seconds without power. Can you tell which is which? The lighting board is from Walthers. The wires to the capacitor can be thin, as typically used wiring decoders. lt is possible long passenger trains with multiple cars would cause a problem by briefly drawing too much current when power is applied. If that happened, one fix would be to put a ten to about twenty Ohm resistor in either capacitor lead. This would reduce "keep alive" time a bit, as well as add complexity. The total modification cost per car would still be under half a dollar if the parts were bought from most online sources.
|
|
|
|
Robert Heroux
George -
toggle quoted messageShow quoted text
I would be interested in the details etc. Thanks Bob
|
|
|
|
Pete
toggle quoted messageShow quoted text
|
|
|
|
george hohon3
Pete, I tried the email address from your post and it failed to go through. Do you have another one?
From: w4dccqa@groups.io <w4dccqa@groups.io> on behalf of Pete via groups.io <Kayakerpc@...>
Sent: Thursday, March 10, 2022 7:02 AM To: w4dccqa@groups.io <w4dccqa@groups.io> Subject: Re: [w4dccqa] Updated album Car lighting keep alive cap #photo-notice George,
I would like to have the schematic too.
Thanks,
Pete
|
|
|
|
Pete
George,
toggle quoted messageShow quoted text
Looks like you have a = sign in the email address instead of an @ sign.. Kayakerpc@... Thanks,
|
|
|
|
Thanks George,
Can I get a copy of the details. - Michael Boyle boyle10017@...
|
|
|
|
Don Weigt
The values George gave will work fine. The bridge rectifier is about as low a rating as you can get, so it will be small and inexpensive. The 270 Ohm resistor will limit the inrush current to about 0.06 Amperes, so many lighted cars in a train will work without overloading most boosters. The peak inrush current and voltage across the 270 Ohm resistor momentarily creates a 1 Watt power level, but it will drop off quickly to about 1/100th Watt, so a 1/4 Watt resistor, which is much smaller, can be used in place of the 1/2W. Same for the 4.7k Ohm resistor. If the cap reaches 16 V DC, which is highly unlikely, the current will still be less than 4 milliAmps (0.004 Amperes) That gives a steady state power level less than 0.064 Watts. A quarter Watt resistor would be fine here, too. The 470 uF capacitor will indeed keep the lights on for a long time used with that 4.7k resistor. The time constant (time to drop to 37% of the initial voltage) of the resistor and capacitor is about 2.2 seconds, and many of these capacitors have a higher capacitance than their nominal value, tolerances being something like +50% or +100% and -20%. Given the working voltage for HO and smaller gauges should be less than 16V, a 25V capacitor of about half the size could be used in place of the 35V one. The 35V part will have a longer life, all else being equal, but both will probably last for the lifetime of the cars. -- Don Weigt Connecticut
|
|
|
|
Paul R Greenwald
George -
How about a putting schematic in photos or files?
|
|
|