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Wiring for DCC Update Announcemen

wirefordcc
 

All,

I have added a section on cutting power to yard and roundhouse tracks in my website.  You can find it at the What's New link at:  http://www.wiringfordcc.com/wirefordcc_toc.htm#a1

Allan Gartner
Wiring for DCC

Gary Chudzinski
 

Alan,

On your website, “Wiring for DCC, Cutting Power to Yard or Roundhouse Tracks,” you state the following:  “Radio Shack carried a 12 position rotary switch, but it was only rated for 300mA. It might work for a while, but eventually may fail due to pitting of the contacts when used at higher currents”

In the smaller scales, where the locomotive draw current less, would it not be helpful to install capacitor(s), maybe  .01 - .05 ufd, across the contacts of a rotary switch?  Seems like I read something about this year’s ago that it can reduce/eliminate contact arcing, which causes pitting.  Or, am I mistaken about this procedure or capacitor value?  Maybe having a senior moment????

Enjoy your website....great information for the DCC learning curve!

Gary Chudzinski

Don Vollrath
 

What Allan said is correct. Adding a capacitor across the switch may also further degrade the lifetime as the charged capacitor becomes short circuited when the switch closes. 

A capacitor across switch or relay contact is intended to act like a snubber to reduce sparking in circuits where the load is highly inductive, like a relay or magnet coil in DC circuits. 
DonV 

Max Maginness
 

Arcing effects are less likely on DCC that with the low voltage  DC that the switch ratings are usually given for, because any arc is interrupted when the DCC voltage goes to zero as the polarity reverses.

That aside,  an 0.05 ufd capacitor has only about 400 ohms impedance at the 8 kHz fundamental frequency of the DCC waveform so if present across open contacts will leave the power still slightly on.

 

Max

 

From: w4dccqa@groups.io <w4dccqa@groups.io> On Behalf Of Gary Chudzinski
Sent: Wednesday, August 7, 2019 5:12 PM
To: w4dccqa@groups.io
Subject: Re: [w4dccqa] Wiring for DCC Update Announcemen

 

Alan,

On your website, “Wiring for DCC, Cutting Power to Yard or Roundhouse Tracks,” you state the following:  “Radio Shack carried a 12 position rotary switch, but it was only rated for 300mA. It might work for a while, but eventually may fail due to pitting of the contacts when used at higher currents”

In the smaller scales, where the locomotive draw current less, would it not be helpful to install capacitor(s), maybe  .01 - .05 ufd, across the contacts of a rotary switch?  Seems like I read something about this year’s ago that it can reduce/eliminate contact arcing, which causes pitting.  Or, am I mistaken about this procedure or capacitor value?  Maybe having a senior moment????

Enjoy your website....great information for the DCC learning curve!

Gary Chudzinski

Gary Chudzinski
 

Good info guys...thanks!

Gary C