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Pros & Cons - 'DelTang' & 'S-Cab' Radio Control ?
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 Posted: Fri Dec 21st, 2018 07:44 am
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davecttr
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Tom Harbin wrote: Just a quick update.

I was at the DelTang site again and found the answer about speed steps, at least for DelTang.

They do use speed steps (which makes sense since it is PWM),
but it is 256 steps in each direction.

So twice as fine a control as the best you can get with DCC,
and about nine times finer than the 28 steps offered with S-Cab.

This is all theoretical as I have never had a problem controlling the speed with DCC.
But it is nice to know that using BPRC with an ESC can give equal or better speed control.

Tom


Tom

Some more information about DelTang speed steps, there are 256 but you can't select an individual step.

In effect the throttle approximates a smooth DC throttle.

In addition you can change the low and high voltages expressed as a percentage.

Some programming is needed for this, but straightforward once you master the art!




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 Posted: Fri Dec 21st, 2018 01:22 pm
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davecttr
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Tom, you might want to consider some things.

How long is your typical operating session?

How long would a locomotive be moving within that session?

This Porter loco seems to need about 250mAh of battery to run for one hour.
If it is switched on but not moving the RX/Pololu combination will still draw slightly less then 20mA per hour.

For example if the loco ran for 30 minutes it would use 125mAh,
leaving enough power in the battery to leave it switched on for an additional 6 hours!

If you do a few calculations you might be able to use a smaller battery taking up less space. 

Rather than 1 large battery you can connect 2 or more in parallel and they behave as 1 battery even when recharging.
I think the batteries can even be different capacities as LiPo batteries in parallel will automatically equalise their Voltages.




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 Posted: Fri Dec 21st, 2018 04:27 pm
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Tom Harbin
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Dave,

Thanks very much for those these two very informative posts.

What I really want is to be able to set the min and max voltage percentage and have a linear (non-notchy) throttle.

One of the things I don't like, is using a 28-step decoder with a 128-step throttle.
While it isn't horrible, I invariably want something like step 8.2 out of 28,
and at lower speeds the notches just make the "momentum" rather jerky.
 
A smooth DC throttle is exactly what I want.

Your information on running time is very helpful.
I can't really afford to make a lot of guesses getting started.

After I'm started, I can sell off DCC components to fund BPRC,
but right now this conversion has to come out of next year's modeling funds.

A one hour run time is about ideal for the Porter.
I actually planned to have run times of about: Porter 0-4-0 - 0.5 hours, Porter 2-4-0 - 1 hour, 4-4-0 - 2 hours, 2-6-0 - 2 hours.
These run times should add some semi-realistic operations opportunities to the layout.
Taking into account idle times, I think this will work out very well. 

If I could be so bold, can you tell me which Pololu you are using for these estimates?

I think I have pretty much locked into DelTang for my conversion as it seems fairly idiot-proof and a purer BPRC solution than the S-Cab.
I really like S-Cab's battery management solution though and will continue to look at where the system goes. 

Tom


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 Posted: Fri Dec 21st, 2018 06:20 pm
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davecttr
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I mostly use 9V Pololu regulators with one 12V.

DelTangs Rx are typical 15mA idle, current and the Pololu 2mA.

Here is the 9V version    https://www.pololu.com/product/2116





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 Posted: Sat Dec 22nd, 2018 12:26 pm
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Bob R
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I also use primarily Pololu 9 volt regulators. 

Most engines are geared to run way to fast at 12 volts. 
You should test run an engine to see how it runs at various voltages. 
I have found on some 5 volts is plenty for prototype operations.
 
Keep in mind that the more you boost the voltage from a battery the less efficient the regulator is. 
Boosting from a single cell lipo (3.7 volts) to 9 volts is not very efficient. 
Boosting from a two cell lipo (7.4 volts) to 9 volts is very efficient. 
If 5 volts will do the trick the Pololu 5 volt with a single cell is very efficient. 

The Porter, as an example, runs one hour using a single cell. 
I have other Bachmann engines with the same motor using a two cell that run in excess of two hours. 

Carefully consider your running needs/desires and the configuration that best suits you and space available for the battery.




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 Posted: Sat Dec 22nd, 2018 02:21 pm
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davecttr
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Tom, Check out the graph on the Pololu page.

You can see using a 1S battery with a 250mA loco should give 80% efficiency even when the battery is nearly depleted.

Contrast this with a 2S battery and you get over 90% efficiency with a 600mA loco!

I usually install 2 batteries in locos needing more than 250mA.




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 Posted: Sun Dec 23rd, 2018 08:12 pm
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dan3192
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...and if you take a look at the "Wireless Charging" topic, some guy is trying to do on-board induction charging. 

I think you'll find the way you're heading has many options.

Dan

Last edited on Sun Dec 23rd, 2018 08:14 pm by dan3192

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 Posted: Sun Dec 23rd, 2018 10:14 pm
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Tom Harbin
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davecttr wrote: Tom, Check out the graph on the Pololu page.

You can see using a 1S battery with a 250mA loco should give 80% efficiency even when the battery is nearly depleted.

Contrast this with a 2S battery and you get over 90% efficiency with a 600mA loco!

I usually install 2 batteries in locos needing more than 250mA.


Dave,

Looks like I'm going to need to buy a new meter and set up some kind of DC supply if I want to do this right.
I bought my multi-meter back when I became a computer tech, 1973, it doesn't know what a milliamp is, well not very accurately.
My last DC train supply blew up eight years ago and gave me the excuse to go to DCC.
I think I have some old battery holders squirrelled away somewhere though.

I like the idea of limiting an engine's capacity based on its type.
A tender loco should have more range than a tank loco.

Tom


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 Posted: Sun Dec 23rd, 2018 10:20 pm
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Tom Harbin
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dan3192 wrote: ...and if you take a look at the "Wireless Charging" topic, some guy is trying to do on-board induction charging. 

I think you'll find the way you're heading has many options.

Dan


Dan,

I agree.
The more I look at this the more sure I am that this is the way to go.

I like the idea of wireless charging but I also like the S-Cab approach.
It could be set up much like we set up DCC programming tracks,
with charging connected to specific track locations and still not need to "wire" the track...
and any loco you buy today already has track pickup wires installed.

Tom


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 Posted: Mon Dec 24th, 2018 04:24 am
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Rick Dow
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Hi Tom,

One point I would add here, is that I find it extremely easy to charge my LiPo batteries with my "balancing" charger. 

I can't imagine that I'll ever require "On Track Charging",
because I can't envision charging ever becoming an issue for me.
(at least I can't foresee it happening)

I'm still trying to get all my trackwork installed, and so not running my locomotives all that much.

But the experiments I've tried (although rather unscientific),
have seemed to give a little bit over an hour and a half of running time (mostly switching duties),
on a 2 cell LiPo with 250 mAh.
 
Just saying'.

I've taken to recharging my 2 cell LiPos in the kitchen, one battery at a time, while I watch TV in the next room.
Maybe ten minutes each and Safe and Easy.
Charger shuts down when fully charged.

Have a great Christmas season, Tom........... and everyone else too.

CHEERS

Rick




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