Trainworld sent me a free shipping offer so I went for the Bachmann HO GS64 4-8-4 steam loco with DCC they had on clearance ($99.99 still in stock for those interested). The box says downward compatible with DC and I read that DCC locos don't work well with pulse power so I used an MRC 1400 to test it.
The beautiful loco ran excellent (with slow speed operation of 6 ties a minute, wow) and it growls a little but I guess it needs breaking in. My question to all is, will my Troller autopulse transrail power pack damage the DCC board or just make it run poorly?
Thank you, Rob
i built a simple PWM throttle that plugs into an NCE PTP just like a PowerCab that i use to test DC locomotives (obviously without decoders) with.
i hadn't thought about the DCC locomotives and saw one start to move. i think it recognized the DC voltage on the track and began operating in the DC mode. i subsequently disabled that mode on all my decoders
bottom line is the PWM pulses didn't damages the decoders which rectify the signal and probably filter it a little, resulting in a relatively constant DC voltage to operate on.
greg - Philadelphia & Reading / Reading
gregc i built a simple PWM throttle that plugs into an NCE PTP just like a PowerCab that i use to test DC locomotives (obviously without decoders) with. i hadn't thought about the DCC locomotives and saw one start to move. i think it recognized the DC voltage on the track and began operating in the DC mode. i subsequently disabled that mode on all my decoders bottom line is the PWM pulses didn't damages the decoders which rectify the signal and probably filter it a little, resulting in a relatively constant DC voltage to operate on.
Not in all cases.
Cheap PWM throttles that use low frequency pulse rates, and "soft" waveforms will most likely be seen by most dual mode decoders as DC.
But better high frequency PWM throttles like the Aristo Train engineer and others will confuse the decoder resulting in erratic operation or no movement at all.
There is nothing wrong with lower frequency PWM throttles, but higher frequency throttles to provide better control - that's why better decoders use higher frequency PWM for motor control........
I never damaged a decoder with the the Aristo throttle, but a great many of them would not work. Some would just sit a buzz, other had two speeds - on and off. Others would randomly start in any old direction no matter how the direction switch was set.
The use of any PWM throttle with a DCC decoder is questionable at best, as there is no way to predict the behavior for each throttle design with each decoder design.
Quality high frequency PWM throttles have flat topped "square" waveforms and most decoders do not recognize the signal as DC because of its speed and waveform.
Sheldon
I can't predict how the Bachmann GS4 will perform on the Troller pack, but the Troller pack is not a true PWM throttle.
It is a transistor throttle that uses 60 cycle pluses at lower voltages which disapear as the voltage increases.
ATLANTIC CENTRAL I can't predict how the Bachmann GS4 will perform on the Troller pack, but the Troller pack is not a true PWM throttle. It is a transistor throttle that uses 60 cycle pluses at lower voltages which disapear as the voltage increases. Sheldon
thanks guys. Sheldon will that 60 cycle pulse damage a dcc module? It's not AC is it?
Mister Mikado ATLANTIC CENTRAL I can't predict how the Bachmann GS4 will perform on the Troller pack, but the Troller pack is not a true PWM throttle. It is a transistor throttle that uses 60 cycle pluses at lower voltages which disapear as the voltage increases. Sheldon thanks guys. Sheldon will that 60 cycle pulse damage a dcc module? It's not AC is it?
The DCC signal is AC, with an encoded information signal. The decoder rectifies it into DC to run the motor.
There are no guarantees that any DC power pack will work or be harmless to a DCC decoder. There have been too amny different DC throttle designs over the years for any DCC decoder designer to insure that.
The Troller output is not AC, it is half wave DC until you reach higher speeds/voltages at which point it becomes ful wave DC.
Do you plan to convert to DCC? Do it now.
Mister Mikadowill my Troller autopulse transrail power pack damage the DCC board
i don't see how
ATLANTIC CENTRALQuality high frequency PWM throttles have flat topped "square" waveforms and most decoders do not recognize the signal as DC because of its speed and waveform.
i believe most decoders have some capacitance across the rectified output. i've seen schematics with 20 to 470 uF.
the shape of the waveform doesn't matter, although square waves maximize output power. input capacitance should maintain a more constant DC signal, less ripple the higher the frequency or capacitance.
gregc Mister Mikado will my Troller autopulse transrail power pack damage the DCC board i don't see how ATLANTIC CENTRAL Quality high frequency PWM throttles have flat topped "square" waveforms and most decoders do not recognize the signal as DC because of its speed and waveform. i believe most decoders have some capacitance across the rectified output. i've seen schematics with 20 to 470 uF. the shape of the waveform doesn't matter, although square waves maximize output power. input capacitance should maintain a more constant DC signal, less ripple the higher the frequency or capacitance.
Mister Mikado will my Troller autopulse transrail power pack damage the DCC board
ATLANTIC CENTRAL Quality high frequency PWM throttles have flat topped "square" waveforms and most decoders do not recognize the signal as DC because of its speed and waveform.
I don't disagree with any of that, although I have never bothered to look at a schematic of a DCC decoder.
All my observations are based on actual observed field testing with many of the locomotives I have purchased with DCC decoders and tested using my Train Engineer throttles before removing the pesky decoders. This includes some with sound, some DCC only, and covers a variety of brands over a multi decade period.
I am not remotely interested in finding out EXACTLY why, I have a good enough working understanding of why, and I have things of considerably more interest to spend my time on.
But my field observations are hard fact. These locos ran poorly or not at all using the Train Engineer throttle with the dual mode decoders installed.
They all run perfectly with the decoders removed.
In my humble opinion, dual mode decoders are a joke, a gimmick to sell locos and lore people into DCC.
I'm not saying that is a bad thing, I tell most new people they should go with DCC.
But dual mode decoders are not a solution for serious DC operators with no plans for DCC. The decoders have to go.
Mister MikadoMy question to all is, will my Troller autopulse transrail power pack damage the DCC board or just make it run poorly?
Rob, this is all I can tell you...
The only locomotive I have with a dual-mode decoder is my Bachmann 2-8-8-4 EM-1. With my Troller 2.5 Transpak it makes more noise than it does with a Kato DC power pack.
So far, it still runs OK. Neither power pack seems to have dmaged it.
I do not have an oscilloscope, so I can not tell you how the DC waveform looks leaving the Kato powerpack.
-Kevin
Living the dream.
So I ran the Bachmann loco with the Troller. It ran normally in forward, likewise in reverse. Then it wouldn't run at all in forward again. I thought I cooked the decoder, but I ran the loco again in both directions with the MRC 1400. Guess this is what is called "erratic behavior".
It still growls even with a 9 volt battery so I don't think pulsing is causing the noise. Maybe it's not lubed enough or it needs breaking in. Soon I'll pop the boiler to see what's up.
Anyway you guys were so kind and generous with all that info, thanks a bunch. -Rob, OP