!!

Not Registered?

Welcome!  Please register to view all of the new posts and forum boards - some of which are hidden to guests.  After registering and gaining 10 posts you will be able to sell and buy items on our N'porium.

If you have any problems registering, then please check your spam filter before emailing us.  Hotmail users seem to find their emails in the Junk folder.


Thanks for reading,
The NGF Staff.

Author Topic: Which capacitor?  (Read 1196 times)

0 Members and 1 Guest are viewing this topic.

Offline Alex

  • Trade Count: (+13)
  • Full Member
  • ***
  • Posts: 1975
  • Country: scotland
  • Gender: Male
    • Facebook
    • Awards
Which capacitor?
« on: January 24, 2014, 08:33:19 PM »
Hi,

Having recently fitted lights to one of my coaches I need to fit a capacitor to combat the light flicker as it goes around the track.

I know I need to fit a capacitor, but which type? A ceramic or elctrolytic one? Also if I'm using 12v, which value would be best?  :confused2:

I should know this as I studied electronics at college but my brain just refuses to let me know.

Alex  :wave:

Offline EtchedPixels

  • Advertiser
  • Trade Count: (+44)
  • Full Member
  • ***
  • N Gauge Society Number: 16353
  • 2mm Association Number: 4412
  • Posts: 8388
  • Country: wales
  • Gender: Male
    • Ebay
    • Google+
    • Twitter
    • YouTube
    • Etched Pixels
    • Awards
Re: Which capacitor?
« Reply #1 on: January 24, 2014, 08:55:33 PM »
If you are using 12v DC then you want 16v+ (I'd probably go higher just to be sure). Some capacitors are polarised (electrolytic and some others). Those don't respond well to being charged backwards (they tend to explode). A resistor in series is also a good idea so that the inrush current is limited otherwise a rake of coaches can trigger short circuit detectors with the sudden big current draw. So basically you want a similar set up to the LEDS as now but with the capacitor after the rectifier and the resistor also present

If you are using DCC its a bit more complicated as you really should be a bit more careful not to mash the DCC signal up.

The high end units are a bit fancier and use supercapacitors to drive LEDs at 5v or so. That allows you much much longer flicker free times (a minute or so typically - handy for train stopped in station on DC) but needs 'real' electronics.

Alan
"Knowledge has no value or use for the solitary owner: to be enjoyed it must be communicated" -- Charles Pratt, 1st Earl Camden

Offline Lawrence

  • Trade Count: (+9)
  • Full Member
  • ***
  • N Gauge Society Number: Closed
  • Posts: 4287
  • Country: scotland
  • Gender: Male
    • Awards
Re: Which capacitor?
« Reply #2 on: January 24, 2014, 10:04:58 PM »
Stop teasing us Al, give us a number  :D
Would a 25v 1µF do the trick?

Online Only Me

  • Western Destroyer
  • NGF Technician
  • Trade Count: (+17)
  • Full Member
  • ****
  • N Gauge Society Number: 23206
  • Posts: 5979
  • Country: gb
  • Gender: Male
  • Loco Repairs - Direct message me
    • Northants & Cambs Area Group of the NGS
    • Awards
Re: Which capacitor?
« Reply #3 on: January 24, 2014, 10:08:02 PM »
16v 220uf...25v a bit high..

Offline EtchedPixels

  • Advertiser
  • Trade Count: (+44)
  • Full Member
  • ***
  • N Gauge Society Number: 16353
  • 2mm Association Number: 4412
  • Posts: 8388
  • Country: wales
  • Gender: Male
    • Ebay
    • Google+
    • Twitter
    • YouTube
    • Etched Pixels
    • Awards
Re: Which capacitor?
« Reply #4 on: January 24, 2014, 10:21:43 PM »
16v 220uf...25v a bit high..

16v should be fine for DC - with the rectifier its effectively good to 17.4v or so. Enough in theory for DCC in N.

"Knowledge has no value or use for the solitary owner: to be enjoyed it must be communicated" -- Charles Pratt, 1st Earl Camden

Offline A.Carter (BiG-T)

  • Trade Count: (0)
  • Full Member
  • ***
  • N Gauge Society Number: 22937
  • Posts: 264
  • Country: gb
  • Gender: Male
    • Awards
Re: Which capacitor?
« Reply #5 on: January 24, 2014, 10:32:25 PM »
If it's only to stop flicker and space is an issue you could look at Tantalum capacitors a lot smaller than electrolytics a lot higher quality but more expensive.

Tony

Offline Alex

  • Trade Count: (+13)
  • Full Member
  • ***
  • Posts: 1975
  • Country: scotland
  • Gender: Male
    • Facebook
    • Awards
Re: Which capacitor?
« Reply #6 on: January 24, 2014, 11:34:18 PM »
Hi Alan,

Thanks for that. I run DC so the simple option is best. So would the capacitor be soldered between the resistor and the +ve side of the LED strip? I'm not bothering with a rectifier as the coaches only run the one way.

Alex  :wave:

Offline EtchedPixels

  • Advertiser
  • Trade Count: (+44)
  • Full Member
  • ***
  • N Gauge Society Number: 16353
  • 2mm Association Number: 4412
  • Posts: 8388
  • Country: wales
  • Gender: Male
    • Ebay
    • Google+
    • Twitter
    • YouTube
    • Etched Pixels
    • Awards
Re: Which capacitor?
« Reply #7 on: January 24, 2014, 11:57:15 PM »
Hi Alan,

Thanks for that. I run DC so the simple option is best. So would the capacitor be soldered between the resistor and the +ve side of the LED strip? I'm not bothering with a rectifier as the coaches only run the one way.

Alex  :wave:

Thats ok until you accidentally put them on backwards. 4 pin rectifier chips cost pennies. If you don't have a rectifier you also don't want to use an electrolytic capacitor - LEDs might object or maybe blow but the capacitor will explode and make a mess.
"Knowledge has no value or use for the solitary owner: to be enjoyed it must be communicated" -- Charles Pratt, 1st Earl Camden

Offline Alex

  • Trade Count: (+13)
  • Full Member
  • ***
  • Posts: 1975
  • Country: scotland
  • Gender: Male
    • Facebook
    • Awards
Re: Which capacitor?
« Reply #8 on: January 25, 2014, 12:07:46 AM »
Ahhhh ok... I'll get some rectifiers as well then. Don't want any nasty explosions on the railroad.

Thanks.

Alex  :wave:

Offline Lawrence

  • Trade Count: (+9)
  • Full Member
  • ***
  • N Gauge Society Number: Closed
  • Posts: 4287
  • Country: scotland
  • Gender: Male
    • Awards
Re: Which capacitor?
« Reply #9 on: January 25, 2014, 01:50:02 PM »
Ahhhh ok... I'll get some rectifiers as well then. Don't want any nasty explosions on the railroad.

Thanks.

Alex  :wave:

Keep me posted on how this goes Alex, might have to pay you a visit  ;)

Offline Alex

  • Trade Count: (+13)
  • Full Member
  • ***
  • Posts: 1975
  • Country: scotland
  • Gender: Male
    • Facebook
    • Awards
Re: Which capacitor?
« Reply #10 on: January 25, 2014, 02:41:06 PM »
Well if I get it wrong you can always pick your way through the pieces.... :D

 

Please Support Us!
August Goal: £60.00
Due Date: Aug 31
Total Receipts: £25.00
Below Goal: £35.00
Site Currency: GBP
42% 
August Donations

SimplePortal 2.3.5 © 2008-2012, SimplePortal