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RC Smoothness and Sound
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 Posted: Sat Jun 8th, 2013 12:32 pm
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Stanton
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Jim,

Thanks for your comments.

You wrote,
"I notice that comments are "closed" on "Neil's Blog" "
S-CAB.com has only been live for a few days and I'm considering how ambitious I should be with the site.

An S-CAB group already exists
http://groups.yahoo.com/group/S-CAB/
and I don't want to duplicate that open discussion.

FreeRails is also providing an excellent forum with several radio-oriented threads.

The subject of radio communication is technically and bureaucratically difficult and I want to focus on facts rather than opinions.

Neil.



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 Posted: Sat Aug 3rd, 2013 10:46 pm
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James Brown
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Herb and Woodie

I am disappointed to report that my effort to duplicate and document with lots of photos the "30-Minute Conversion" of a locomotive to R/C using a Futaba Attack transmitter with 27MHz crystal and a LOSI receiver/ESC ended up as a well-documented failure.

In fairness I did introduce points of potential failure by substituting LOSI connectors to connect the LOSI board both to the battery and the motor and the wiring of the two-truck locomotive was different than the prototype.

I would do more trouble shooting but I already had decided to switch over to an S-CAB system instead and I had other uses for everything except the receiver board. So I rewired the Bachmann FT-A Diesel Locomotive back to a simple DC pickup that I will use in a train set for the grandchildren. It runs as well as it did before the attempted conversion.

It is nice to see more manufacturers showing an interest in HO R/C. Hopefully a good standard will emerge and ready to run R/C locomotives will be as common as ready to run DCC equipped locomotives are now.

Jim

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 Posted: Sun Aug 4th, 2013 04:25 pm
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W C Greene
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James-sorry about the problem. May I ask if you disabled the track pickups to the motor before you operated the loco with r/c? There could have been a direct short which would fry the Losi board. I hope this doesn't discourage you from other r/c adventures, we all have had mishaps along the way. Keep the faith.

Woodie



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 Posted: Mon Aug 5th, 2013 01:41 pm
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James Brown
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Thanks, Woodie

I never had power in the rails when I had the LOSI board hooked up, so I'm pretty sure that I didn't fry the LOSI board that way. I did run the FT-A on DC from the front truck after I had clipped the rear truck, but the LOSI board and battery were still in the box when I did that. I suspect that I may have wired the locomotive incorrectly when I hooked up the battery and LOSI board but I don't see how.

In any event I am very excited about S-CAB right now and think that is the solution for me at this point in time. I have learned a great deal on FreeRails that has helped me make an intelligent choice and am more committed to R/C than ever. A friend here just ordered a pure DCC startup set and we have a friendly competition on the merits of battery power vs soldered rails. We'll see how that goes!

Thanks for all the help

Jim

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 Posted: Sun Aug 25th, 2013 06:01 am
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Craig W
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For now, R/C conversions can take a bit of work, but are absolutely feasible for most modelers who are willing to learn a bit about the systems and aren't afraid of a little hand work and some soldering.

Lately, my experiments have focused on track powered R/C control and I recently had the chance to test DCC against Track powered R/C back to back, on my local club layout. I found the results to be surprising.

The locomotives I used for the test were an NCE DCC equipped, Atlas Dash 8-40B and an Athearn GP-50, using an Orange R/C receiver with a home made ESC (electronic speed control) using a home spun H-bridge for reverse with some el-cheapo Radio shack power filtering, via some caps and a rectifier bridge. Total cost for the R/C package was a little over $30 in parts. I managed to stuff all of this junk into the stock GP, by cutting out an internal wall which is hidden directly below the dynamic brake fan. I added a brass platform for some of the extra components over the rear truck and made a similar weight for the front.



When I showed up at the club layout; neither locomotive had been tested and the DCC equipped loco required programming, which was gracefully handled by a fellow club member in about 10 minutes. The track at the club is cleaned at regular intervals, but as I found out, still had some problem areas which affected both R/C and DCC systems. Track power on my home layout and test rack is well filtered and I have never had issues using it with R/C, but the club layout was a different environment and I wondered if the rectifier and caps I used were up to the task.

I put the GP-50 on the rails first, only to find out that the singe 400uF cap and 2A rectifier made for a bad combo on the DCC layout. It left the loco stalled and buzzing, although it had worked flawlessly on my home set-up.

After replacing the rectifier and exchanging the 400uF cap for 2 smaller 100uF caps, I was ready for another try. This time I was off and running. I had expected a higher top speed for the GP, but it only managed a scale 70 MPH pulling 3 cars at max throttle, which was fine by me, since I don’t run my trains like slot cars, but still puzzling.

Performance was very smooth overall, but starting was noticeably affected as was speed stability on the monster club layout. The club layout is packed full of boosters for the DCC system, but my impression of the system, is that it may actually need more. After 10 minutes of constant travel, I hit my first section of dead rail and the GP-50 came to a halt. With a gentle push it was up and running for another 5 until hitting a second dead spot, which reminded me of why I decided to go with R/C in the first place. After 20 minutes of run time I felt that the R/C system had proven itself to be viable. I range tested the system from every place in the building and had perfect communication. The system is still missing the one item that would make it just about perfect; Batteries!


I honestly expected the DCC equipped Atlas engine to out pull and outrun the R/C loco by leaps and bounds, but much to my surprise, I found it to be way more sensitive to dirty track and had to push it through quite a few areas. You could see it slowing down noticeably at certain points between DCC boosters as well. At slow speeds control was good but at the lowest speed setting, the R/C loco had a much more impressive range and overall had better speed stability. All of this went against my own intuition. Having run both locomotives on straight DC, you could easily tell that the Atlas loco was far superior to the Athearn.

By no means was this a scientific test, but I think my observations are note worthy. What did I learn here?

Not much that I didn’t all ready know, but good voltage filtering is essential with DCC track power. I’m now running (3) 100uF caps.

Out of the box Athearn locomotives work fairly well with cheap R/C gear.

Batteries are a very good thing for R/C locomotives. Yes Woodie, you did say so!

Below is a picture of the GP-50 chassis with the front weight and shell removed. Another board sits next to it, waiting to go into the Dash 8-40b for the next test. At the bottom of the picture you can see one of David T's micro sized marvels, the DT/RC RX61-1, which is still undergoing some tests, but looks very promising!

Last edited on Sun Aug 25th, 2013 06:50 am by Craig W



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 Posted: Sun Aug 25th, 2013 08:26 pm
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James Brown
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Craig
Thanks for the interesting information.
With the S-CAB layout that I am in the process of getting going the only thing that I will use rail power for is a small section of DC powered rail to keep the batteries charged. I wouldn't want to rely on rails for anything else.
Jim

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 Posted: Sun Aug 25th, 2013 11:29 pm
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Craig W
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I hear you Jim and I have to agree that there are a few drawbacks for pure rail power.

When used in conjunction with batteries, I think providing track power to run locomotive lights and to keep batteries charged makes a lot of sense.

After doing a careful post test inspection on my GP 50, I noticed that the rear truck had a broken power wire, which would have explained at least some of the dead spot stalls it experienced. I ordered some micro sized SMD caps to replace the larger bank in the locomotive. The micro sized caps are a bit pricey at 5 bucks a pop, but will help to free some space for batteries later on. I feel that this locomotive will prove to be a worthwhile performer on track power and proves to me that an R/C conversion doesn't necessarily have to be expensive to provide good performance.

Last edited on Sun Aug 25th, 2013 11:31 pm by Craig W



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 Posted: Fri Aug 30th, 2013 08:47 am
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Helmut
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@Craig to be fair to DCC, your R/C loco had some ( unfair? ) advantage over the DCC loco in form of buffering ( not filtering ) capacitors. But let's start from square one. The initial problems with the retifier/capacitor combo cannot be blamed on the caps, but on the rectifier. The ready -to-use bridge types generally are tailored for operation on sinusoidal AC. DCC has  a rectangular waveform @4.5/9.0 kHz, that cannot be handled too well by normal silicon rectifier diodes. They will heat up and draw excessive reverse current, that in turn, together with the surge current of the capacitors, leads to the effects you reported. It is much wiser to employ Schottky or fast recovery silicon diode bridges, which may have to be built up. What you really have to filter away are the unavoidable spikes on the bridge's output, but that can be handled by an 1µF( low ESR ) cap easily. Every capacity value above that will only add to the buffering capability. Your R/C loco had a 200µF buffer, which the DCC loco didn't have. This buffer gives a small advantage on dead spots. Of course, the higher the capacity, the better. Remember the 'electronic flywheel', a bipolar capacitor bank offered some 40+ yrs ago? Any receiver, be it R/C or contemporary DCC, benefits from such a buffering. Some DCC receivers, e.g. LENZ 'GOLD' or ZIMO series, have a chapter in their manuals on how that is done. There is a caveat when operating high-capacity buffered locos on a DCC layout, however. The initial current surge of the empty caps may cause the booster's overload protection to cut the supply out. So there must always be a current-limiting resistor in series to the cap, bridged by a reverse diode for quick discharge when needed. So for fairness, jack up a DCC-loco in the same way by connecting a cap to the blue wire of the decoder ( Yes, I admit there a few that don't have that. Attaching a cap to those is a wee bit more complicated ). The higher the capacity, the better. What you'll find is also an improved speed regulation behaviour and a smoother operation. Of course, and someone has done that already, you can even connect a backup battery there and enjoy the same stall-free driving as with R/C. To sum it up, R/C operation has other advantages compared to DCC, but not on the supply side.

Last edited on Fri Aug 30th, 2013 09:07 am by Helmut



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