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DelTang 2.4GHz receivers - pt.I
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 Posted: Sun Oct 7th, 2012 06:35 pm
   
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DavidT
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Hi Bernd,
Yes, you can control any number of receivers with one transmitter although they have to be of the same 'type'. For example, they have to all be 1024 accuracy, 22m frame timing and no more than 7 channel. You cannot mix those with 2048 accuracy, 11m frame timing or greater than 7 channels. All of my receivers (and most other DSM2 compatibles) have the same characteristics (1024/22/7).

Why do people use a consist? Improved traction?

Lipos have risks but every camera, cell phone, PDA and almost every cheap modern toy has one. So it's good understand and respect them but also reasonable to reflect on how the rest of the world accepts and uses them. With my receivers, 4 nicads are a good fit and quite a bit more volts for motors that benefit from that.

I think the convenience of track charging would be great but I wonder if a "constant 12v" is real and reliable. The effectiveness probably lies in how the charger handles an eratic supply. I believe a few traditional train suppliers have developed solutions like what you suggest. It's not something I've looked into in any depth.
Regards, David.

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 Posted: Sun Oct 7th, 2012 08:04 pm
   
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mwiz64
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I had once thought a charge track would be good but then Woodie reminded me that I'd still need pickups, and clean wheels and clean track for it to work well and I decided that it wasnt worth it. That's the stuff we're trying to get away from here. FWIW, if using a 3 cell pack made up of A123 cells, one can charge them off a 12V battery without any charger at all. Just connect them for several minutes and let them find their balance. Caveat: I've never used A123s but I've seen a few people at airplane events just connecting their packs to a car battery with some zip cord. If you are going to go this route, do some more research to be sure your doing it right.

Anytime you are going to try running more than one loco from the same transmitter you'd best be sure they run about the same speed at the same stick position. There will be no individual throttle trimming between locos.. or is there, David? In fact, that raises a good question. Can you bind more than one receiver to the same transmitter at the same time?

Mike

Last edited on Sun Oct 7th, 2012 08:07 pm by mwiz64



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 Posted: Sun Oct 7th, 2012 08:49 pm
   
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Bernd
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Hi David,

The real or prototype use any were from 2 up to 6 engines to pull a train. It depends on how much tonnage they need to pull and what the grades are along the route. Not so much for improved traction as much more horse power to pull a long train. Our trains over here easily consist of 100 cars or more. Our trains are a lot longer than in Britain.

@ Mike, David answer that question when her replied to me. You can control more than one receiver but as you said they all need to run at the same speed at one setting. I missed that one. And your right putting power to the track. Why would you want to if your running on batteries. I figured that you could charge the batteries at full voltage while running. The batteries just help get over the rough spots plus there would be hardly any complicated wiring.

One thing to remember though is that if you put in a signaling system you will run into complicated wiring. Kind of a catch 22 if you ask me.

Bernd

Last edited on Sun Oct 7th, 2012 08:52 pm by Bernd



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 Posted: Sun Oct 7th, 2012 09:51 pm
   
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mwiz64
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I would imagine if a person wanted to it might be possible to run two separate throttles from two separate sticks by assigning one stick to say channel #1 and having one receiver operate the ESC with channel #1 and then assign the other stick to channel #2 and have the other receiver operate it's ESC from channel #2. Of course, that only two locos but 2 is better than one. Maybe that's too confusing to operate... What do you think David?

Mike

P.S. I'm glad I like little industrial railroads where running one loco at a time will be just about right. I couldn't imagine having several of those little transmitters laying around everywhere and trying to make sure they were all charged and keeping straight which loco each one went to. FWIW, my Airtronics 10 channel TX can be bound to 50 different receivers and I can select 50 different models but I can't control more than one at one time.... But if I could switch from one to the next to the next with just one TX that would be an improvement from having several transmitters to keep track of and keep charged. Could I use something like a Spektrum DX8 and bind it to several different locos where I could shut one off and turn another on?

Mike

Last edited on Sun Oct 7th, 2012 09:57 pm by mwiz64



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 Posted: Mon Oct 8th, 2012 05:25 am
   
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DavidT
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Mike,
The Spektrum bind protocol requires a response from the receiver. So trying to bind more than one receiver simultaneuously may work but is more likely to complicate things.

The transmitter assumes it is only communicating with the last receiver it bound to. That's why they all have to be the same type. So they will all get the same throttle position.

Bernd, thanks for your explanation of the consist. I had not realised there was the horsepower requirement. I see traction supplementing that, particularly in overcoming stiction which I think is the greatest challenge in controlling train motors. Rod made the point that smaller wheel sizes make it harder to pick power of the track and to put power down. For me these have the same challenges.

PWM-based motor controllers (like mine) pulse power on and off. The longer the ON duration relative to the OFF period, the higher the average voltage applied to the motor. When trying to overcome stiction I found that the PWM frequency had a big effect when used with little gearing. I think high gearing like Bernard recommends reduces this challenge.

A low frequency has longer ON pulses than a higher frequency. Longer pulses 'try harder' to make the wheels turn because they apply full power for longer. This has the effect of increasing torque. But if the frequency is too slow, the ON pulses become too long and the wheels tend to slip so there is an optimum for each setup. There will be people who understand this much better than I but I found it very interesting exploring some of these dynamics.

I mention this because my N gauge was made to perform better by trying different PWM frequencies. In a consist of multiple engines, I'd expect the wheels to need to turn at the same speed. So I'd expect the same throttle setting to be appropriate. Again I would experiment with PWM settings in engines to see the effect. I'm not sure if they should all be the same or if there would be advantage in some being different.

Do engines need to be 'driven' to join the consist or does big man from above pick them up and put them where they need to be? This affects how we approach controlling multiple engines separately and binding implications, etc.

For track charging the train would probably need a bridge rectifier so that reversed polarities don't cause problems. After that you need to have the appropriate voltage range for your charging system (neither too high nor too low). And you need to be able to handle eratic behaviour. So several issues to think through but fine as a concept. From a safety perspective, continuous charge would be appropriate for nicads but less so for lipos.

Interesting stuff; thanks.
dt.

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 Posted: Mon Oct 8th, 2012 07:08 am
   
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DavidT
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mwiz64 wrote: That's wonderful stuff, there David. That sir, is the future of model railroading, in my humble opinion. Why anyone would want to do all that wireing in this day and age, is beyond me. Next step, get an RC system like that to operate sound.

One question, how long will that little guy run before having to recharge?

Mike

Mike,
It ran for an hour and 15 minutes today on a small 103mm radius oval. I started at half throttle and gradually nudged it up to max as the battery went down. So with an 80mAh lipo it drew an average of 64mA. About 14 of that will be the Rx so the motor draws around 50mA.

You can get sound generators for boats that take a servo signal to vary the noise with speed. They do diesels but not sure if they have steam. Main challenges will be speaker size and power consumption.
dt.

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 Posted: Mon Oct 8th, 2012 09:58 am
   
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Herb Kephart
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One other thing about PWM-

If the frequency is too low--and I have no idea what that Hz that is--there is an annoying sound--something between a buzz, and a hum--at low speed.

My hearing is poor, but this occurs at a range that my hearing is less impaired. This was with Losi boards and was particularly bad with one of my locos. Tried to hide this with capacitance across the brushes, but this only helped slightly.

I must say, that others using Losi boards say that they don't notice this so it must be amplified by certain mechanisms.

Herb 



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 Posted: Mon Oct 8th, 2012 10:03 am
   
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mwiz64
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Wow... Over an hour on a charge for a little battery like that is great! It's amazing how little power these trains use. I'm thinking any railroad I'm going to build would only use 2 locos at one time at the most. I can deal with two transmitters. I'm sort of surprised that MRC or one of the big companies doesn't latch on to this idea and run with it. I suppose that's good for you, David.

Cheers,
Mike



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 Posted: Mon Oct 8th, 2012 10:06 am
   
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Herb Kephart
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MRC probably spent a bundle of money developing and selling the DCC idea, and wants to milk as much money out of that cow as they can.

Herb  



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 Posted: Mon Oct 8th, 2012 10:08 am
   
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mwiz64
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I always thought the noise was coming from the ESC itself. You can definitely hear it on most of my planes at low throttle (some more than others) but once you advance the throttle the prop noise drowns out any other sound. I never knew if the ESC was still emitting the noise or not. I didn't notice any sound like that in David's video of the N scale engine.

Mike



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