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Using TIU with PWM Power Supplies and/or Controllers


John Carmichael
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Hello all (especially Ray Manley)

 

I've read several letters saying that track power supplies and/or controllers with PWM (Pulse Width Modulation) can sometimes be problematic with some older engines, some sound cards, and with DCC.  Reports say that this is especially true with low frequency PWS.  Since the MTH DCS system is similar to DCC, I wonder if it could also be affected negatively by PWM input power on the TIU?

 

I currently have an old Crest Train Engineer connected between my regulated linear power supply and the TIU, but I always have the Train Engineer receiver set to linear mode, and the TIU works just great.  But I will be replacing Train Engineer with the new Railboss 4 Trackside R/C which has built-in PWM (20 KHZ).

 

According to Del Taparro, the owner of G Scale Graphics and inventor of the Railboss, his Railboss 4 PWM is different from other PWM power controllers in that it has a much higher frequency which prevents the problems that other PWM power sources have (overheating, improper sounds, and light flickering). 

 

So here's my question:

 

Have any of you had problems with your TIU when it is supplied with PWM?  If so, do you think the TIU will be immune from the Railboss (20 KHZ) PWM since its frequency is much higher?

 

thanks!

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  • 3 weeks later...

Sorry on my delayed reply here on the forums I know we have been chatting offline.  

 

I'm not sure I can answer if the concerns about running a TIU and protosound engines under the Railboss PWM power would be any different than other PWM power supplies.  I do know that MTH notes in their manuals to not use PWM power and on that basis I would advise against it.  (I'm unsure if the concern is simply due to bad operation or if there are concerns with it being bad for the hardware)  That said, based on my experience I personally probably would not.  I have experimented with a number of power supplies and (as you and most folks already know) I now use Bridgewerks power supplies exclusively.  I use a big Power Mag regulated power supply (which isn't made any more) but outside of that I recommend the throttle type.

 

The way DCS handles communication is a bit different in that DCS only adds a carrier frequency to the layout power, it doesn't use the actual power sine wave to communicate.  With DCC it uses a varied chopped sine wave to provide both power and handle the communication.  

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  • 5 months later...

Here is an electrical diagram showing how I isolated the power from the TIU from the power from the trackside Railboss 4 by simply using a 3 position DPDT toggle switch. You could use this to isolate any PWM power source from the TIU.  This way, I can run either DCS engines or conventional DC engines.  But you can not run both at the same time!

GARDEN RAILWAY  (electrical connections).jpg

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  • 2 weeks later...
 

Because Bridgeworks doesn't quite fit in my electrical box, and they are expensive, I've been using an MG Electronics PS-10AD Regulated and Filtered Power Supply.  It's similar to the higher end model made by Bridgewerks in many ways.  It's clean DC output works well with TIU and all brands of PWM radio controls.  Very Powerful and doesn't overheat. But it's heavy!

http://mgelectronics.com/power/power-supplies/bench-top/bench-top-dc-output/13-8vdc-bench-top/10-a-ps-10adps12c/

  • Input 110 Volt 60Hz
  • Output 13.8VDC
  • Adjustable 0-20VDC 10 Amp constant
  • Input fuse protection
  • Short circuit protection with auto reset
  • Built-in voltage surge protection
  • Low ripple
  • Heavy duty housing
  • Illuminated on/off switches
  • Multi-color bar coded display packaging
  • Universal binding post terminals
  • Extra heavy duty grounded line cords
  • AMPS/Constant: 10
  • AMPS/surge: –
  • Wattage: 320
  • Dimensions (L)X(W)X(H): 7.88” X 3.94” X 9.06” dual meter system
  • Weight: 19.62 lbs

 

 

PS10AD

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John,

The reasons I don’t use Bridgewerks  #1 cost. They tend to run very warm. I picked up a couple of used industrial supplies. The output is highly filtered and very precise.  Another one of the features these type of supplies have that I like is you can set the current trip point as well as voltage output. The output on the power supply that I have will remain off when tripped, until it’s manually reset. Which is a must have when running DCS engines, to help prevent runaways. I noticed MG Electronics unit states short circuit protection with auto reset ?  

I have used some PWM supplies when running my engines on a club layout. It runs but we get poor command control, feature drop outs, and even an occasional runaway. The club had upgraded to bridgewerks later on and things ran better, except the bridgewerks seem to overload too often and overheat. I started bringing my power supply and problems went away.

 

john

 

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On July 27, 2016 at 8:56 AM, John Carmichael said:

 

GARDEN RAILWAY  (electrical connections).jpg

 

 

John,

Up until this spring my son & I belonged to a garden railroad club. We used to have a lot of signal problems due to the layout having a lot of sidings that were wired to a panel as to isolate different sections. Looking at your schematic you might have some trouble someday. 

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Yardtrain:

 

Do you have a way to run conventional DC engines on your own layout using a hand-held remote in conjunction with your Sorensen DLM?  If so, what remote do you use? 

I wonder what type of hand-held remotes the Forum Bridgewerk guys use when running their conventional DC engines? It would be very limiting to have to use the stationary throttle on a Bridgewerk power supply.   I wasn't too impressed with the specs on Bridgewerk's "keychain" remotes.  Ray, if you are reading this, what remote do you use?

 

Since I like to walk around my layout, I can't imagine having stay glued to my electrical box.

 

From what I understand, it is possible to run a conventional DC engine using an MTH remote, but only if the power source is AC. (I might be wrong about this)

  

john

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I don't run any engines on conventional track power.  If I ever did I would use the throttle on a throttled power supply.  Any time in the past that I did run analog engines I would set the throttle to the right voltage and let it run then keep a wireless remote (on/off) for the main power supply power cord as an emergency power cut of switch if there was any derailment or emergency.

 

You can vary track voltage on the Variable 1 or 2 channels on the TIU with the MTH Remote but the input power must be AC.  You could then use something like a bridge rectifier on the outputs to convert it to DC power but you would only be able to run in one direction, there would be no reverse unless you wired up a manual switch.

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John,

i only have MTH engines and use DCS only. However the train club I did belong to use to have. Crest train engineer. All you need with this is a fixed power supply. All this does is vary the voltage to the track. Cheap on eBay. Crest updated these are the older ones. They work fine except response is slow   

 

https://www.ebay.com/itm/331930032508

Crest 10-Channel Train Engineer Walk-Around Control System CRE-55470 

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Hi Yardtrain:

 

I began my layout using Crest Train Engineer and most of the guys in our club still use it.  (Crest Revolution is now out of business I hear.) The Crest trackside receiver had a switch that let you choose between PWM and Linear Power.  With this old system, I was able to run my MTH engines on Crest's linear power setting only. The power from my power source was fed into the Crest trackside receiver which sent it into the TIU before it went out to the track.  I could run an MTH engine on either conventional DC (using the variable current from the Crest receiver) or on MTH DCS.  The DPDT switch seen in my electrical diagram above was not needed in that old setup because there was no PWM power coming from the Train Engineer.

 

I have a feeling that like Ray, most of the MTH owners in this forum only use a remote (specifically an MTH remote or android or apple device with WIU) when they run their trains using DCS, and that they do not use any remote when running non DCS engines on conventional variable DC.  I bet they operate their non DCS engines using the throttle on their power source (like a Bridgewerks throttle)- not a remote.  But I'm just guessing... 

 

I still think you can configure your electronics box to do both: use a popular PWS trackside radio controlled receiver with a hand held remote for conventional DC, and use an MTH remote for DCS control for the MTH stuff- but not at the same time. And I think the safest way to do this is by isolating the two systems simply by using a DPDT switch.  That way, you have the best of both worlds and have hand-held mobile remote control for all your engines, not just the DCS ones!

 

John C.

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