Can linear DC be converted to PWC?
I ask because the sound system in my Aristocraft slope back tender (really lame sound system) only works on my club’s PWC. It does not work on my Bridgewerks linear system on my home track.
Sure, but it is called a throttle… you would have to hook up an Aristo throttle to the output of your Bridgewerks… ugh…
Greg
Greg,
So you are saying that the PWC is developed in the throttle? I am using the Bridgewerks R/C throttle along with a Bridgewerks 15 amp power supply.
Are you meaning the base station and throttle like this? 
Or any throttle that will accept DC and output PWC/PWM. I know the sound system in some of the Aristocraft locomotives don’t work well at low DC voltages. There was a provision in the tender of one of my Pacifics to add a 9 volt battery so the sound system would work at low DC voltages.
David Maynard said:
Or any throttle that will accept DC and output PWC/PWM. I know the sound system in some of the Aristocraft locomotives don’t work well at low DC voltages. There was a provision in the tender of one of my Pacifics to add a 9 volt battery so the sound system would work at low DC voltages.
David,
Now I am confused. A 9 volt battery puts out linear DC. How can that make an Aristo sound system work if they only work on PWC?
PWC will allow many units with lights to work at low voltages, but sound units without mechanical triggers will go to full speed!!!
To answer the 9 volt battery, depends on the sound unit as LGB used the 9 volt battery for low voltage/power losses (read track bad power pickup/plastic frogs, etc.).
Phoenix sound units do the same thing and use 3.6 volt batteries now.
I think I am understanding now about the linear DC and the Aristo sound system. At linear voltage higher than I would ever run this engine, the sound system works (above 8 volts), so I now see how a 9 volt battery can make the sound system respond. I am usually running this loco in the 3-6 volt range. I’ll stay with my Bridgewerks throttle and for go the sound system in this tender on my railroad. I’ll use the sound system on my club’s layout only. Thanks guys. (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)
Joe, you could use a diode dropping bridge to the motor so the lights and sound will see track voltage and the motor will see the diode drop.
I use a full wave bridge rectifier in series with one motor lead (use the ~ connections), and I add diodes between the + and - to increase the voltage drop.
Just make sure you use 2 amp or mode diodes for this.
So, the confusing part is that linear is just constant voltage… PWC is pulses of full voltage, like flipping a light switch on and off… full throttle is flipping it so fast and leaving it mostly on, and slow is flipping it on every once in a while and only leaving it on a little bit.
The important thing is what when there is voltage to the motor, or on the rails, it is always the same, full voltage like whatever the max your power supply puts out.
Now in a electric motor, the motor sort of “averages” the on and off times, it cannot instantly run at full speed and then instantly stop, just like doing this to the gas pedal in a car does not make you go instantly 100 mph and then zero.
Light bulbs will do the same “averaging”
But electronics seeing PWM can “interpret” or “remember” the highest voltage, so this is the reason some sound systems go “full speed” on PWM, and it’s also the reason some sound systems go sort of nuts on PWM.
It all depends on the design of the circuit, and this is why, for example, people put a PWC to linear converter between the power from the rails and a Sierra sound system, which only seems to “remember” the full voltage of the pulses, it does not “average” the on and off cycles.
I hope this explanation helps understand the fundamentals.
Greg
Yes it does. Thanks Greg.
I had a Sierra sound system go Tango Uniform on the Aristo PWC. I don’t know if it was the PWC, or some other factor that made it go south. When I sent it back to Soundtraxx (this was back when they still made the darn things) they told me it was irreparable. So be careful. Some things really don’t like PWC/PWM.
It should not be damaged from PWM, just go to full speed. But there are a lot of connections to the Sierra, and maybe you fed too high a voltage into the wrong input.
Greg
With PWC you must remember that the pulses will be almost full power supply input voltage. Motors may average this pulse, but electronics with storage caps will go to the max voltage in less than a second and if this exceeds the voltage rating of the electronics (read sierra sound) then electronics will fry!!
The older power supplies did not have constant/regulated output so at no load the voltage can be over 24 volts. Older Bridgeworks had 38 volts and at no load would reach 45 volts internally, very dangerous to our trains. I had a shorted LM317 regiulator in one that turned the output stage on to full input voltage!! This has been addressed for the newer units.
Yeah, I have a funny story about Bridgeworks… I kept saying that under a light load the voltage went dangerously high, and could damage electronics.
One of my prime antagonists then posted a youtube video that “disproved” me and defended Bridgeworks, by hooking up a light bulb to the Bridgeworks to show it worked and did not damage the light bulb.
A case of confusing light meaning not heavy with light meaning photons or a light bulb. Actually pretty humorous.
Subsequently Bridgeworks issued a notice that the units should not be used with DCC… when in reality they can indeed damage sound cards or other devices. Oh and the owner hates me too.
In their “defense” many locomotives have enough of a load on the rails that it “pulls down” the high voltage enough, but more than a few sound boards have been fried.
Greg
Greg Elmassian said:
Yeah, I have a funny story about Bridgeworks… I kept saying that under a light load the voltage went dangerously high, and could damage electronics.
One of my prime antagonists then posted a youtube video that “disproved” me and defended Bridgeworks, by hooking up a light bulb to the Bridgeworks to show it worked and did not damage the light bulb.
A case of confusing light meaning not heavy with light meaning photons or a light bulb. Actually pretty humorous.
Greg
Yeah that is funny! (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-smile.gif)
Dan, yea, the sound board ran for a few hours just fine. Then I stopped the train, shut things off and put my toys away for the night. The next time I fired up the F3, it was mute. So I guess, when I stopped the engine, the motors stopped turning and somehow that allowed the voltage pulses to cook something on the board. I dunno what nor why it fried, all I know is it was really dead.
As for the board going full speed, I didn’t notice that, it did rev up and down, and the dynamic brake fans turned on and off. What I did notice is the board acted like the train was going faster then it was, and I could not trigger the horn.
Update…I picked up a new in the box, never opened Crest 27mhz TE set for my track powered throttle. I am impressed with it’s operation. Locos run smoother, lights light sooner and the sound in my slope back tender now works just fine. I just wish the handheld TX had a rubber ducky antenna. (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)
Joe,
The telescopic antenna seems to work better for me with more range and a better connection.
Yes, I have less range with the rubber ducky antenna, but still enough range for my little railroad.
My club uses the rubber ducky antenna with no range problems and that RR is much bigger than mine, so it should be OK I think.