# Aristo Revo TE - heating problem while idle?



## Greg Elmassian (Jan 3, 2008)

I'm completing my in-depth testing of the Aristo Revo system, and I happened to leave it on track power (about 18 volts) and just sitting there, with the throttle at zero.

I picked up the loco (an Aristo RDC) and pulled out the TE decoder. To my surprise it was warm. Now this unit was sitting on rollers, and had not been run at anything other than very slow speeds all day, on rollers, no load, and for the last half hour was sitting at speed zero.

I know there are scattered reports of overheating, but this is different, no load, or there should not be any load, and still heat was generated, the heat sink was warm, not hot, but why?

Has anyone else noticed this? I think that few people have the decoder where they can touch it, so maybe it's happening more that we realize.

Regards, Greg


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## TonyWalsham (Jan 2, 2008)

Greg. 
Is the REVO heatsink also used to sink the voltage regulator that runs the logic circuits?


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## Greg Elmassian (Jan 3, 2008)

No, the heat sink sits on 8 fets, 4 do the H bridge, and the other 4 are effectively the "DPDT reversing switch". 

Man are they small! 

Regards, Greg


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## Del Tapparo (Jan 4, 2008)

Posted By Greg Elmassian on 18 Oct 2009 06:53 PM 
No, the heat sink sits on 8 fets, 4 do the H bridge, and the other 4 are effectively the "DPDT reversing switch". 

Man are they small! 

Regards, Greg 
If you have an H-Bridge, why would you need a reversing switch?


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## Greg Elmassian (Jan 3, 2008)

That is how Dave Bodnar described what the FETs do.. weird huh? 

It's in his post on MLS or Aristo, or both, the one where he repaired his TE. 

I pulled the heat sink off mine to look at the material used to go between the FETs and the heatsink. It is a silicon based thermal elastomer. 

Regards, Greg


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## markoles (Jan 2, 2008)

Greg,

I haven't noticed any warmer than normal situations in any of the three locomotives using the revo. Seeing as we are getting in to the cold time of the year, I should be able to give some feedback when running in snow. If the RX's heat sinks are not able to dissapate the heat adequately, this should result in warming up the plastic shell boilers, and melt the snow.


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## Greg Elmassian (Jan 3, 2008)

Mark, please note the title: heating problem when idle, not overheating... I should have made it clearer. 

It does have a question mark, meaning I am not saying the Revo TE has a heating problem, I am asking if anyone else has noticed the heat sink getting warm when the loco is just standing still but powered? 

(track or battery I don't think it makes a difference). 

I'm just asking people if they have noticed the same thing as I have. 

I am not stating that the cooling or heat sink is inadequate. 

I'm just wanting to know if others have found the same thing as me, that even when idle, the heat sink is warm. 

To detect this, you have to touch the heat sink, which is not the usual case, in the RDC, it's easy since it's under a removable box. 

Regards, Greg


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## dbodnar (Jan 2, 2008)

Posted By Greg Elmassian on 18 Oct 2009 06:53 PM 
No, the heat sink sits on 8 fets, 4 do the H bridge, and the other 4 are effectively the "DPDT reversing switch". 

Man are they small! 

Regards, Greg 
Greg - the lower four Mosfets are used in place of a bridge rectifier. When voltage is detected of one polarity two of them turn on to pass the right polarity to the rest of the unit. When the opposite polarity is on the track the other two turn on again passing the right polarity. It is a clever design and does not drop the input voltage as much as a bridge rectifier.

My guess on the warmth that you see is that these devices will get warm when at idle because the transciever module and the microcontroller are still drawing power. This may be sufficient to see what you have observed.

dave


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## Greg Elmassian (Jan 3, 2008)

Thanks Dave, yes I read your posts carefully. Is the turn on resistance of the FET lower than a Schottky diode? Was curious on that one. 

I considered that the warmth was from the micro, but it seemed to be too much for a micro, and I know the Zigbee's forte is low power... I did not check the RDC to see if it was powering internal lights at idle... that would far more power than the micro and the transceiver, wouldn't you agree? 

Really was just surprised it was warm, but thinking more, it's probably the incandescent lights in the RDC interior. 

Regards, Greg


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## Del Tapparo (Jan 4, 2008)

Posted By Greg Elmassian on 20 Oct 2009 11:09 AM 
... Is the turn on resistance of the FET lower than a Schottky diode? Was curious on that one. ...



The FETs I use for a similar purpose in my controls have an ON resistance of 0.07 ohms. So the voltage drop is only .07 volts per amp. Even, at 5 amps, that is only 0.35V. Typical Schottky diode drops are .15 V to 0.46V. However, the ON resistance of FETS can be much higher than 0.07 ohms, and could easily result in larger voltage drops. Then multiply by 2, for two FETs in the circuit. It all depends on the parts used.


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## George Schreyer (Jan 16, 2009)

Synchronous rectifiers have long been used in high performance power converters, especially when the load voltage is low. A lot of high end applications use ASICs that operate at 2.5 volts or less and draw LOTS of current, many 10's of amps. At these low output voltages, even the .35 or so volt drop of a high current Shottkey diode materially impacts the efficiency of the converter. Low on resistance FETs can cut this drop in half. 

The downside is that FETs don't automatically turn on and off. In a power converter application, the power converter controller is making the drive for the chopper FET so it also knows when each FET used in the synchronous rectifier needs to go on and off. 

In the Revo application, the unknown polarity input comes from somewhere else. The Revo has to characterize the input polarity BEFORE it turns on any of the "rectifier" switches. If the input polarity changes fast enough, the Revo MAY not be able to keep up and find itself in a situation where the wrong switches are turned on resulting in a transient short circuit until it cleans up it's act. 

Dave, do you know if the Revo can handle DCC as an input signal? I suspect that it will either have troubles with it and heat more or it will simply blow up. 

This may be a cleaver way to reduce dissipation BUT it also may bring on the liability of being susceptible to rapid polarity reversals.


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## George Schreyer (Jan 16, 2009)

I may be climbing out on a limb here because I've never been inside one of these puppies, BUT here goes... 

When running from a battery, no issue, the rectifier portion doesn't even have to be there. So the issue will be with track power. 

If the track power is DC, reversing events will usually come from the user flipping a switch, maybe by accident or maybe in a reversing loop or wye tail track. The delay of a mechanical switch or relay will result in a total power dropout of a few milliseconds and the polarity detection circuitry can probably handle that. When the power first goes away the circuit will shut off ALL the switches and get ready to start again when power is reapplied. 

While running on DC track power, the circuit will need to be able to differentiate the beginnings of a true reversing event (this is reversal of the polarity of the track, NOT a command to reverse the motor) from power pickup noise. In order to protect itself, the circuit will probably have to assume that any dropout of a few volts is the precursor to a polarity reversal and the circuit will need to act. This will have the effect of stretching out the period of a mere power dropout. I suppose that sufficient local charge storage can help mitigate that problem. 

When running from PWC on the track (pulse power) the circuit will see the end of pulses continually and go through it's shutdown sequence to turn off the switches. It will then have to turn them on again at the onset of the next pulse. This will tend to chop off the beginnings of each pulse and reduce the duty factor somewhat. This is probably also no problem as the dead time between pulses will allow it to reset and get ready for the next power up event. 

When running from DCC where the polarity reverses in a few microseconds, the circuit MAY run into trouble if it does not detect the end of one cycle fast enough. Some boosters may also become confused at the rapid changes in current vs time. The current may spike up because the circuit didn't prepare for the reversal fast enough and gets caught with the wrong switches on. The current may also go to near zero at each transition if the circuit catches the "falling" edge fast enough and shuts off waiting for the next "rising" edge.


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## dbodnar (Jan 2, 2008)

Posted By George Schreyer on 20 Oct 2009 11:53 AM 


Dave, do you know if the Revo can handle DCC as an input signal? I suspect that it will either have troubles with it and heat more or it will simply blow up. 

This may be a cleaver way to reduce dissipation BUT it also may bring on the liability of being susceptible to rapid polarity reversals. 
George - the Revolution receiver does not operate on DCC or AC track power. Aristo Craft offers a non-plug & play board that has a bridge rectifier on it that takes care of the problem rather nicely. I demonstrated this at last month's ECLSTS when I ran a Revolution equipped engine on a DCC powered track along with a DCC engine. Both worked just fine. I then ran it on AC without problems.


There is a transient voltage protector (part # SMBJ30CA) that is included on the Revolution receiver board - my best guess is that it protects the rest of the receiver from connections to DCC or AC. 

For what it is worth I did try to run the Revolution on DCC during the beta testing phase of its development and it did not work but it did no damage.

dave


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## George Schreyer (Jan 16, 2009)

ok thanks. The polarity reversal circuit is then to handle mistakes during user connection and occasional track polarity reversals.


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## George Schreyer (Jan 16, 2009)

Although I don't know why anybody would want to run track powered RC. That seems to be the worst of both worlds. You still need clean track AND you have to put up with the unreliability inherent in a wireless connection AND the costs of the radio gear.


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## markoles (Jan 2, 2008)

Greg,

I did read your title and your post carefully before responding. Since I am an active user of the system, I am responding with my experience. I have left locomotives sitting for hours on the track, idle, with no noticeable heating on the shell. That was on the open house day when we had three E8s,two S-4s, one mallet, one mikado, and one FA on live track. No hot electronics smells either. That MeanWell 24v 10 amp power supply worked like a champ, too! No problems with speed or voltage detected. 


Mark, please note the title: heating problem when idle, not overheating... I should have made it clearer. 
You are asking about a heating problem, so I beg to differ. If the heat sink is hot, and I mean 150+, then that is a problem. Even if you aren't directly calling it out as a problem, certainly it is a red flag. I haven't noticed it, but I will be on the look out for it. Hence, if it is getting hot enough to warm up my boiler shells on 25 degree days to melt snow, that might be a concern. Especially considering the speakers and electronics inside the shell I would rather not get wet.

I'm just asking people if they have noticed the same thing as I have. 

Nope. But then, as long as it is working for me, I am not fooling with it. This is more related to the crappy screws that hold my locomotives together than anything else. The less I unscrew and screw it back together, the less likely it is that I will have stripped out heads!


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## Greg Elmassian (Jan 3, 2008)

Gotcha Mark... to make sure no one gets confused, only warm, so I figure hard to tell from outside. Thanks for the response. Hear you on the screws! I put armorall on the screw threads, lubes them and keeps plastic from disintegrating. 

Regards, Greg


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## Semper Vaporo (Jan 2, 2008)

You wimps... You'd better be talkin' Celsius! If ya mean Fahrenheit.. cain't boil water at 150!

How you gonna get yer train to go if you only heat the boiler to 150!


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## markoles (Jan 2, 2008)

Charles,

What elevation? Water boils at lower temps the higher you go! Just harder to get stuff to burn...

Greg, Armorall on the screws? Never thought of that. Then again, once I get the screws out the first time, I usually don't have to worry about them. It is that first unscrew that is the doozie!!


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## Greg Elmassian (Jan 3, 2008)

Yeah, been doing that for years, I use the stuff in the lime green bottle from Turtle wax... and of course I always do the trick of turning the screw slowly counterclockwise with a light touch, to feel the screw "drop into" the original thread. 

I've been very successful in "preserving" the fragile threads in locos that way over the years. I leave a little bowl (about the diameter of a 50 cent piece) with a bit of the armorall in it, drop the screws in it as I disassemble, then pick them out of it to reassemble. 

The toughest thing is as you say, getting the little ##[email protected]@'s out of there the first time. I have a collection of favorite screwdrivers and my Aristo one is different than my USAT one, go figure. 

Regards, Greg


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## aceinspp (Jan 2, 2008)

C.T. What type of funny stuff are you smoking.? Later RJD


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## East Broad Top (Dec 29, 2007)

My primary test install was a C-16 with a Phoenix sound system. I recall the heat sink getting mildly tepid with 4 incandescent bulbs and the sound system. (I turned off the smoke unit, so it wasn't drawing anything) but I never noticed anything that seemed out of sorts. I don't think it was ever just sitting there idling for minutes on end, it was almost always moving one way or the other unless I was changing control variables. 

Later, 

K


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## Jerry McColgan (Feb 8, 2008)

Posted By George Schreyer on 20 Oct 2009 12:36 PM 
Although I don't know why anybody would want to run track powered RC. That seems to be the worst of both worlds. You still need clean track AND you have to put up with the unreliability inherent in a wireless connection AND the costs of the radio gear. 

Hi George,

Since Aristo is selling them as fast as they can make them apparently there are a lot of folks who want it.

A lot of people criticized LGB's MTS for being a dumbed down version of DCC but it was made by LGB to be pretty easy to understand. Perhaps most importantly it was plug and play. I still prefer my MTS over other DCC systems because it pretty much works out of the box but I have always found DCC being limited to the power of a central station a problem in that upgrading to a bigger central station and or a central station and transmitter with bidirectional signals is quite expensive.

For someone who owns a recent production Aristo-Craft locomotive the Revolution offers plug and play installation, they are instantly switchable from battery to track power, it eliminates the amperage limitations of previous Train Engineers (per loco as the amps are going through the on-board receiver rather than through a track side receiver), and, combined with the capacitor circuit the full track voltage helps the Revolution overcome poor contact with dirty track, and with bidirectional communication with between the transmitter and receiver the user can tell if he is in control or not.

I cannot even remember when I last cleaned my brass track but then most of my locos have a minimum of 8 (usually more) track contacts.

What is also nice is that unlike battery power or DCC the Revolution completely bypasses the power consumed by lighted coaches and cabooses. Most battery operators I know tend to avoid lighted coaches and my lighted coaches are often what pushes me beyond the amp limit of my central stations.

The Revolution, rather than being the worst of both worlds is to me anyway a combination of the best of both worlds with no expensive central station, perhaps the cheapest bidirectional transmitter and receiver/decoders that are cheaper than many decoders. It has the benefit of DCC's constant track voltage without the need for a central station to communicate a signal via the rails (in my opinion less satisfactory than a RC signal).

In short I think the Revolution is sort of Track Power on Steroids[/b].

Is it the best? I don't know.

Is it the cheapest? I don't know.

Did I make a detailed comparison with other systems before I bought it? No. I simply liked what I saw and bought it.

Sometimes I don't know exactly what it is about something that determines whether I do or do not buy it but I suspect that is true of most of us.

I expect that those who like battery power will keep on buying battery power and those who like DCC will keep on buying that. In my opinion the folks who are most likely to buy the Revolution are those who like track power with radio control (people who in the past bought Train Engineers) or who want some of the features of DCC combined with radio transmitted signals rather than track transmitted signals.

The one disadvantage for me is that I can flip a switch and change from track power to MTS and run my MTS locos with track power but it would be more complicated to try to run both Revolution equipped locos and track powered locos on the same layout since I cannot run a Revolution equipped loco without a Revolution transmitter.

I think Aristo has a winner with the Revolution that is creating a new category of train control that will not replace other systems as much as create its own niche in the market. Perhaps that is what the hobby really needs.

Regards,

Jerry


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## East Broad Top (Dec 29, 2007)

Back to the heat-while-idle issue, I had to do some electronics testing last night, so I set a section of track up with a K-27 tender with the Revolution board plugged in. No lights, sound, smoke, or anything--just the board plugged into socket sitting on a live track. After two hours, no noticeable heat at all; very cool to the touch. 

Later, 

K


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## Ward H (Jan 5, 2008)

Greg, 
On my RS3 and GP40, the cab and marker lights run off of track power, without going through the receiver. Headlight power does go through the receiver. Having read the 12 pin diagram, I believe that would be the same for the RDC car. The interior lights are probably running on track power without going through the receiver. Headlights wil go through receiver. 

Now here is where you can explain it way better than I can and will understand it more than I do. 
I believe that the motor outputs never really shut off. Because it is PWC, the pwc spikes have just slowed down, or however they change, so that the motor does not move. Headlights which are wired to the motor will be dim. I believe that is why there was at least on report of a loco crawling at 0% throttle. I know I can easily push my locos at 0% but can not do so when track power is off. It seems like they always have some power to them, just not enough to move them. 

May be why the heat sink gets slightly warm while standing still.


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## Greg Elmassian (Jan 3, 2008)

You just might have something there Ward. I've noticed what you said about the PWC motor output never really shutting off. I'm going to pull the unit from the socket and see just what is connected to the track, and what is connected to the motor. 

Thanks, Greg 

p.s. again, I am NOT seeing a "problem", I just want to know why the "off" state seems to still be drawing power.


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