WANTED Aristocraft / Crest / Revolution PWC to linear converter 57091 (not the smaller low amp one 57090)

The old Aristocraft Train Engineer receivers (RX) handled the voltage from the transformer and sent the required voltage to the track depending on what the handset Transmitter (TX) had told them to do.
They had an onboard switch that gave the option of straight 'linear' DC (much like that from a battery)..... OR .... PWC (PWM) voltage

The motors did not see the 'background' PWC pulse as it was too high frequency for them to react to but it meant that the constant pulsing voltage was great for most lighting circuits as the loco lights came on fully bright, even when the output from the receiver was low (unlike with linear DC where the lights tended to come on dimly at about 4 to 8 volts and might only be at full brightness at about 12v.
But as Greg has said, it was not good for sound systems, but also some USA Trains lighting circuits and certainly not for DCC locos which could react very badly indeed!

The problem is that the old Train engineer, although a good system was working on 27mhz and the new Train Engineer Revolution came along with 2.4 Ghz BUT now the track-side receivers do not have the linear/PWC switch so you have to buy either a linear or a PWC version.

If you buy the PWC version of the receiver (RX) and have a switchable linear/PWC converter you can then have the best of both worlds.... have nicely bright lights...or... run sound equipped or DCC locos on linear.

BUT..... I always found that Phoenix sound boards (2K version and upwards) were fine with PWC DC, most probably due to the fact that they work on DC or DCC and were designed to work with linear or the PWM output from a DCC decoder.

I have a strange feeling that maybe I may be corrected on this though......... :(:sweating:
 
Thanks for the explanations chaps, not being involved with DCC I've got no real idea how it works. One day perhapß
 
Greg. Did I miss the info that the Zimo decoder doesn't like PWM? I usually do not run the PWM because most of my engines are USA's and the lights do not like it .. But I was wondering how the Hudson would do with PWM ..
Thanks for your insight ..
 
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Hi John
Do you know how well this will work with an Mtroniks viper loco 10HV? This can handle up to 24 volts and 10 amps and has a PWM frequency of 5k. I tried building my own a while back using the inductor out of a spare Aristo TE rx. It definitely converted the power to variable voltage but I couldn't get any low speed control out of it. Is that what Tony meant when he said the Crest ones were too "on/off"?

Could you give me information on the capacitor next to the resistor please.

Chris
 
chris m01 said:
Hi John
Do you know how well this will work with an Mtroniks viper loco 10HV? This can handle up to 24 volts and 10 amps and has a PWM frequency of 5k. I tried building my own a while back using the inductor out of a spare Aristo TE rx. It definitely converted the power to variable voltage but I couldn't get any low speed control out of it. Is that what Tony meant when he said the Crest ones were too "on/off"?

Could you give me information on the capacitor next to the resistor please.

Chris
Click to expand...

IMHO
That is the problem with many ESC's.. Mainly designed for the model car racers. - DC to light, in a fraction of a second! ;):giggle::shake:
 
chris m01 said:
Hi John
Do you know how well this will work with an Mtroniks viper loco 10HV? This can handle up to 24 volts and 10 amps and has a PWM frequency of 5k. I tried building my own a while back using the inductor out of a spare Aristo TE rx. It definitely converted the power to variable voltage but I couldn't get any low speed control out of it. Is that what Tony meant when he said the Crest ones were too "on/off"?

SNIP
Chris
Click to expand...
That is exactly what I meant Chris.
I put the MTroniks VIPERS in cases for trackside use. Well I did, but not any more.
If you put one of the Crest PWM - Linear converters in line you ruin the low speed performance.
Perhaps someone will come up with a suitable converter that still allows a PWM ESC to perform well at low speed.
 
Using the Mtroniks Viper with one of Phillip's rx102 receivers gives me excellent control from my Deltang tx22 including very good slow speed running. I really like using this set up because I think turning a knob for control feels right, the responsiveness is excellent and running is very reliable. Its only when I try to convert the PWM to linear that low speed disappears.

We come back to the old discussion as to whether PWM is a problem. I have been told that the Aristo TE in PWM mode has damaged some LGB electronics although I don't know how many times that happened. I also don't know whether that was entirely due to the PWM itself or maybe there are some spikes in the PWM output. I run USAT and Aristo and they all seem to run very nicely from the Viper. I do worry that a component on a PCB might blow if I continue using PWM. Although if a loco will run for say 5 minutes without problem does that mean it should be ok for hours on end? The only issue so far is that some of the lights at the wrong end come on.
 
chris m01 said:
The only issue so far is that some of the lights at the wrong end come on.
Click to expand...

I think you will find this is 'by design'..

IMHO,
The only way to get the lighting (something like) prototypically right, is to strip the supplied lighting electronics, and do it yourself!

Slow running:
Most the small PWM devices are pretty-much square-wave output. - Lots of harmonics..
If they gave sine-squared outputs, it would be 'kinder', and linear converters would have an easier time of it.

At low speeds, the pulse-width is quite small, so not much energy to charge those capacitors.. If you can find the 'sweet-spot' of your controller / filter / loco combination, you can set the control to a low setting, and then loco will very slowly start to move, and increase a little in speed. - You need a low-ish current loco to try this, else there is just not enough energy in those narrow pulses.
 
The reason the square waves are used is because you can use inexpensive FET transistors without heat sinks... their states are either off (no heat) or full on (low resistance and low heat).

To output a sinusoidal wave, you need a linear amplifier, a lot of heat, heat sink and more cost and bigger.

This is the main reason that motor control for decoders has evolved this way. You can indeed get "smarter" with the pulses, but normally you do this in conjunction with BEMF control... I can make my locos crawl at about 1/4 smph, so there's not much I need that is not available.

Greg
 
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