Which sound board, PIKO or MLS?

FatherMcD

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The title isn't exactly my actual question, but I kept it since it was referred to in my earlier thread "Any Experience with a DC step up module?"

Let me describe my situation. I have two PIKO 25tonners.

Engine #1: PIKO factory R/C. 6 AAA batteries. Ran fine, longer life with Alkalines than NiMh, as to be expected. I added MLS card and it worked well, except, that as the batteries ran down, pressing a horn button would cause the loco to stop dead, as in a screeching halt and the sounds stopped. Not good for the gear train! (I believe I mentioned this on another thread.) I'm in the process of squeezing a 4x18650 battery pack wired for 7.4v in this loco in hopes that the slightly higher voltage and current available would prevent the problem. I'm waiting for a part to complete this installation. Talk about a slow boat to China...three months! Importantly, the sound trigger wires from the PIKO board were connected to the two terminals on the right in the attached diagram. I didn't have this diagram at the time of the installation. Also, this MLS didn't have the bell sound.

Then in February of '21 PIKO support told me that they were developing a sound card for the 25tonner which would be available by the c-word 2021.

So, I bought ;

Engine #2: PIKO factory track power. Ran nicely on track power. I converted this to R/C using the PIKO 35040, same board as the factory R/C. I had planned to add the upcoming PIKO sound board with the bell sound to this loco, however while locos with factory R/C and sound are finally available, add-on sound boards are still several months out according to PIKO customer support. :( Price not determined, but the cheapest current sound upgrade for other locos is US$170. :(:( So, I decided to add the new MLS with the bell sound using the diagram attached. (Courtesy of Peter Lucas) Ah ha, perhaps my screeching halt problem was caused by my incorrect wiring. I consider myself lucky that there was no blue smoke in Engine #1.

However, I now have the same basic problem;

(Note that the following voltage measurements are of the voltage available at the battery pack under NO load. i.e. removed from the loco. They would almost certainly be lower if I could easily measure under load. My concern is for the relative minimum voltages.)

A. With 6xAAA Alkaline, providing 9.59 volts, switch power on, cab light comes on. Press forward button, engine sound starts and loco moves forward and accelerates with additional button presses. This runs fine for about 50 min. then abruptly stops with sound still on. Voltage measures 8.23.

B. With 6xAAA NiMh, providing 7.72 volts, power on, cab light on, press forward button, engine sound starts but forward headlight only comes on for about a second and the loco doesn't move. Since this loco stops at 8.23v, it is obvious why it won't start at 7.72v. (Hmm. With my incorrect wiring of the MLS in Engine #1, it would run with the 6xAAA NiMh. I don't have any voltage measurements for that setup. Strange :smoke:)

PIKO sound boards aren't even available yet, so the answer to the thread title is MLS, at least for now. Of course, I could wait for the PIKO sound card to become available, but that is likely to take several more months and cost about US$70 more. For now, the real question is how to prevent the abrupt stopping. As an aside, I will be switching Engine #2 to Li-Ion for greater run time and to match my Li-Ion standard. The Stock PIKO 6xAAA packs allow me to experiment because they run out of power quicker. Battery type, size, capacity and placement aren't the issue at this time (I hope)

According to PIKO documentation, the 35040 specs call for 7-24 VDC. According to Peter the minimum voltage for the MLS is 7.2V. My testing indicates the MLS will still function at a relatively lower voltage than the 35040 when they are operating in parallel. I want to "reverse" that so the MLS stops producing sound, indicating that the battery is low, before the 35040 shuts down and locks up the drive train.

My hope is that adding a DC-to-DC step up convertor between the battery and the 35040, set to about 9V output, will allow the 35040 to continue to operate when the voltage to the MLS drops below it's operating threshold.

If you have made it this far, thanks for your interest. Any observations, thoughts, questions before I go to the time and expense of this experiment?
 

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Greg Elmassian

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yeah, try it.... notice you can fine tune the voltage out of the boost convertor, to get the MLS to fail first.

As you are testing, I would have it on rollers and monitor the voltages of the batteries themselves and the output of the boost unit.

The lithiums are a much better idea, as you really were asking too much of the AAA cells.

Greg
 

JimmyB

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I have a few MLS cards, and I appreciate Peter informs thes run at 7.2V, but I find that it may still produce sound (or maybe noise would be a better description) at lower voltages. Two of my locos are running on 2S lithium batteries (with MLS), and still manage to run when past the nominal voltage. I would think (from a lay persons perspective) your issue is the current draw, and not the voltage directly, and that your current batteries (not another pun :() haven't enough ummph (amps) when the voltage drops with sound and drive. I think PhilP PhilP mentioned Enloops, if you don't move to lithium these could be your answer.
 

PhilP

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Firstly, I would really like to see some build photos, to see how you are making things fit in the loco..

Now to the specific problem:
You probably know this, but for the benefit of others coming to this thread.

Alkaline batteries, have a fairly gentle and consistent discharge curve, before they hit the 'knee' and fall-away.
NiMH batteries, have a flatter curve, but then fall-away at a much steeper rate.
This ties in with your observations, and seeing an 'abrupt stop' from your loco.

If you look on the side of your NiMH AAA cells, you will find their capacity, in mAh, probably 700 or 800mAh?
This means that the battery should provide (up to) 800mA for one hour before it hits the 'knee' of the discharge curve. - This is a slight 'lie to children' as it is normally just on the curve, at about 80% of the nominal cell-voltage, but let's keep it simple.
Peter tells us the MLS card takes 500mA. Without measuring it, 300ma for the loco, sounds like a reasonable figure, so your observation of approximately an hour run-time would make sense.
If you were running the motor directly from the battery, then you would probably have something similar to the result you want;
The loco would get progressively slower. The sound would distort, then stop, and eventually the loco would come to a halt.
But you also have the Piko RC in the equation. So, what is happening, is that at a certain voltage, the Piko RC cuts-out, giving you an abrupt stop.

I think you need two bits of elektrickery to solve this in the way you are thinking :
1. The step-up, to keep an acceptable voltage feeding the Piko RC. - There are any number of these available, but as a rule of thumb, those with the multi-turn potentiometer, are normally more robust, 'better', than the ultra-cheap 'buck' convertor. Especially when you are setting things up.
2. A device to (some how) stop the MLS card working. - Good luck with this!
Turning off the battery supply (only) will not stop a MLS card working. - The motor-sense wires, will still provide a route for power to the card.
NOTE: I have not tried this, with the latest release 'premium' cards, with a black finish to the PCB.
So you would need to switch (at least) the positive supply, and both motor-sense leads to the MLS card.
This would be possible, but 'something else' you would need to find the space for.

In conclusion:
I think you would be better, switching to a battery technology, which will give you a greater run-time, so that you do not get to the problem within a running session.
Lithium-based batteries should give you the result you want.
You could probably get away with a higher capacity 2S pack (using 18650 cells) or a 2S2P package, to extend the run-time. - You may be able to go down to 14500 cells (these are physically the same size as conventional AA batteries).
To size the battery pack, we need an idea of how long you wish to run the loco, in a single session?

PhilP.
 

dunnyrail

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Interesting what Phillip says, on my 25tonner I find that the MLS keeps burbling quite happily but the loco wont move when batteries get low. But I am using 10 aaa NiMh and I get 3-4 hours (or more) out of a full charge.

 

PhilP

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What also needs to be remembered:
The battery loco, uses a different motor to the track-powered one..

PhilP
 

dunnyrail

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What also needs to be remembered:
The battery loco, uses a different motor to the track-powered one..

PhilP
Ok mine was a track powered one, presumably higher power draw?
 

PhilP

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Ok mine was a track powered one, presumably higher power draw?
I think I know what you meant..

Battery - 7.2-9V depending on type of battery..
Track-powered - 19-24V depending on system used..

So different voltage-rated motors.
But to get the same 'power' from a lower supply-voltage, would require more current for the lower voltage motor.
(more 'lies to children') - ish.. ;)

PhilP
 

dunnyrail

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I think I know what you meant..

Battery - 7.2-9V depending on type of battery..
Track-powered - 19-24V depending on system used..

So different voltage-rated motors.
But to get the same 'power' from a lower supply-voltage, would require more current for the lower voltage motor.
(more 'lies to children') - ish.. ;)

PhilP
Oh as mine has severe reduced speed on the viper and mostly used for shunting and manoeuvring wagons out of the shed to their starting sidings I guess the power draw not as high as continuous runs round a circle. Though I did do that to test it out when newly converted.
 

Greg Elmassian

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There are indeed adjustable "low voltage" alarm devices, even ones that can transmit back, besides ones with an audio alert.

But I think we will be hitting the wall with available space.

I would pack the loco with batteries and forget the boost which may take the space of 2 lithium batteries and add the batteries.

simpler to maintain and debug.

Greg
 

Moonraker

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I should have mentioned that the current draw of a MyLocoSound soundcard of 500mA was assuming a 3 watt speaker. It is proportionally reduced for lower powered speakers.

Regards
Peter Lucas
MyLocoSound
 

Moonraker

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Greg,

The soundcard amplifier will output up to 3 watts to an 8 ohm speaker.

Regards
Peter Lucas
MyLocoSound
 

Greg Elmassian

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Thanks Peter!

By the way, I am working on updating my page on MyLocoSound, so if you see errors, let me know... it is still very incomplete though.


Greg
 

FatherMcD

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What also needs to be remembered:
The battery loco, uses a different motor to the track-powered one..

PhilP
PhilP, what is your source on this? I just asked PIKO-America support and they say "The 25-Ton loco all use the same exact motor." I asked because I have one of each and need to know if I have to make changes in my conversions.
 

PhilP

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If you have both, you should have parts lists for both?

Go by the published part numbers.

PhilP
 

Moonraker

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Thanks Peter!

By the way, I am working on updating my page on MyLocoSound, so if you see errors, let me know... it is still very incomplete though.


Greg
Greg,

I took a look at your page. The only oversight is that we have both Universal Heavy Diesel and British Heavy Diesel soundcards.

Thanks for including us.

Regards
Peter Lucas
MyLocoSound
 

Greg Elmassian

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Corrected... I think I went by the dropdown on your site... I will read more and probably have some questions, like the number of bells and whistles in the various versions, since I think at first people would be wanting to see more different versions. I think you can also change the motor/prime mover.

If there is a document I could read instead of bugging you let me know.

Greg