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Author Topic: Options for new sound unit  (Read 3390 times)

afb

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Options for new sound unit
« on: May 19, 2015, 07:27:27 PM »

I'm at a fork in the road to completing my new sound unit, and looking for some comment and guidance from you guys. After some years of synthesizing engine sound I've now moved into using 'real' (ie recorded) sound - see my post in the earlier 'ARDUINO' thread. However, on cost grounds I've now abandoned the idea of using the commercial class D amplifier you saw in that post and designed a new version with an integral (linear) bridge amplifier chip which delivers about 7W @ 12v or 15W @ 18v. I'm currently sourcing different engine sound sets to offer with the unit - the sound files are stored in the program memory of the microcontroller chip so units are configured by plugging in the appropriate chip. Special thanks go to Kim Belcher for providing me with his excellent recording of a Severn class lifeboat.

Up to now all my sound units have been packaged and then marketed by Technobots, but following their move to Rugby they are no longer local to me for such easy liason and they have a much bigger fish of their own to fry right now, probably keeping them busy for the rest of the year - but for the new unit with integral power amplifier I am reliant on them designing a custom laser-cut case that leaves the heatsink out in the open.

So, another option is for me to go it alone and use a standard ABS flanged box and supply the unit with a 3.5mm audio o/p jack to feed an external amplifier supplied by the user.

In the image below you will see both versions for comparison. The boxed version would have cut-outs for the throttle signal feed and the neutral/run LED. The integral power amp version has a volume control, which I've not been able to squeeze into the boxed version (yet!). I've also included a typical cheap stand-alone battery powered amplifier of the type often used with personal mp3 players which can be found for just a few quid on the internet or for slightly more in Tesco and the like. The sound is a bit weedy using one of these but it's small, lightweight  and cheap in comparison to a decent amp and meaty speaker.

In 'going it alone' I would be able to market it through an established vendor (an accomplished modeller himself) with a successful internet model shop, who is widely known for offering excellent product support.  He now wishes to diversify into model boats and in addition he is prepared to pro-actively sell this, my new rudder mixer and other gizmos I have up my sleeve at certain model shows.

I welcome your comments and suggestions. I will be at the Alfold show 30/31 May if you want to see and hear these units in the flesh and bounce any ideas around.

Alan Bond
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flashtwo

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Re: Options for new sound unit
« Reply #1 on: May 19, 2015, 10:20:14 PM »

Hi Alan,

Nice to see someone else in the "PIC" business.

You may have seen my Radio Controlled MP3 player thread ( http://www.modelboatmayhem.co.uk/forum/index.php/topic,50200.0.html ) where I've used a Sparkfun MP3 Trigger ( http://www.hobbytronics.co.uk/mp3-trigger-board?keyword=MP3 ).

Obviously, mine is the different requirement of playing "Gramophone" music, but could be easily used for different boat sounds - engines, sirens, winches etc. As you can see, it has 18 programmable inputs for sound selection, play next, play previous, and volume.

In my original thread it is associated with a joystick input, but with the completion of the "Voice Command System", the PIC board has been removed and it is now directly controlled via  a UART connection from the Voice Command System.

The only problem I had was with some of the music "warbling", but tracked this done to the particular MP3 tune playback rate being higher than the 192kbps. So, with the problem tracks I had to, using a downloaded MP3 quality modifier, change the rate from 230kbps, for example, to less than the 192kbps maximum.

The downside is the 36 for the board, plus extra for the microSD card and enclosure - I would imaging your devices coming in much cheaper than that.

Have you considered mounting the speaker on a "sounding" board or box to accentuate the lower frequency sounds?

I hope to be demonstrating the system at Wicksteed this weekend - voice permitting.

Ian
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afb

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Re: Options for new sound unit
« Reply #2 on: May 20, 2015, 07:26:48 AM »

Hi Ian

You may remember we chatted at Alfold last year when I was admiring your flash steam plant controller. Hope to bump into you there again this year.

Well it's the "ATMega 328" business this time - though all my previous work has been with PICs. The sound files are stored in the program memory and the samples modulate the mark/space ratio of a counter timer running at 66kHz - so low pass filter the result and you have audio (good enough for this application) for pennies! No expensive or complex D to A converter required (just a few Rs and Cs)

I saw your thread about the RC controlled MP3 player. I've had a similar system on the go for several years now using the same Sparkfun device and made quite a few for club members and others. Like you I used the serial interface to avoid the limitation of 18 triggers (pic attached). However, I am now using the Adafruit SFX module which if you research it you will see sells for 18 and has 10 trigger inputs, though you can stack up to ten sound effects on each trigger to be played sequentially or randomly per trigger activation. Files are stored in (2M) on-board flash memory (USB connect to your PC and it looks like another drive) or you can pay extra for 16M. Plays wav files or ogg-vorbis files (like mp3 but licence free) - easy to convert to this format using Audacity. For 22 you can get the 2M version with a class D power amplifier on the back to drive your speaker directly. I'll have one at Alfold you can see.

Neither of the cards discussed is suitable for engine sound if you want it proportional with throttle - alas you can't alter the playback rate of the cards to achieve that - but they're fine for fixed speed operation like the ModelSound gizmo with the benefit of RC operation if you have a flashtwo or afb interface attached. 

As a consequence of the compression algorithm, MP3 files necessarly start with a short silence - not an issue if it's an album track you're selecting - but if you try stacking say 20 tracks of incrementally increasing engine speed you get a serious hiccup when switching from one to the next. WAV files go a long way to solving the problem as there is no decompression delay, but the file access system takes about 8mSec to switch tracks so it's still very gritty.

Yes, speaker mounting is crucial to getting decent sound quality and I always mount the speaker on the deck (under an open windowed cabin) utilising the hull as a speaker cabinet - I even have a bass reflex port at the other end of the deck!

Alan
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Re: Options for new sound unit
« Reply #3 on: May 20, 2015, 08:48:18 AM »

Hi Alan,
     Wow what can I say, your knowledge and skills with all these electronic gizmos is amazing. I struggle getting the red and and black wires in the right place, I'm okay with 100 watt Marshal amps and a guitar but that's about it, the work that you are doing fascinates me and hopefully you will have it sorted later in the year (I am building a Portgarth and would love to have a quality sound unit). Do you attend Haydock? I would love to hear one of your units. Keep up the good work.
      Kind regards,
            Pete/faz :-)) :-)) :-)) :-)) :-)) :-)) :-))
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afb

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Re: Options for new sound unit
« Reply #4 on: May 20, 2015, 09:00:15 AM »

Hi Pete

Well if it's any consolation I struggle with boat-building and use upturned Flora tubs for the cabins and toilet rolls for the funnels.

Haydock? - sorry no - a long haul from the south coast - but I could let Andy Griggs (Models by Design) have one to show you there - I imagine he'll be attending. Prod me nearer the time. But there's a link to a youtube video of the first prototype in the 'ARDUINO' thread somewhere below in this forum.

But which route to completion should I follow? What does the market want? That was the point of my original post.

Alan
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The Old Fart

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Re: Options for new sound unit
« Reply #5 on: May 22, 2015, 12:20:48 PM »

Hi Alan,

Dave H here.

I'm experimenting with the trigger wave board.
using first 8 channels for engine sounds, the other 8 for horns and bells.

tried using the on board amplifier, but used external amp instead.


If your over Norfolk way on the 31st May, we are having BBQ at the Great Yarmouth Waterways.


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www.greatyarmouthmbc.co.uk

afb

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Re: Options for new sound unit
« Reply #6 on: May 22, 2015, 02:15:10 PM »

Hi Dave

Good luck experimenting with the wav trigger board - it's an interesting unit as it is polyphonic (can play multiple tracks simultaneously). Keep us updated.

Thanks for the invitation, but I'll be at the Alfold show on the 31st May.

Last time I was in Norfolk, I tried to buy a pair of gloves, but they all had six fingers . . . . . . .

Alan
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The Old Fart

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Re: Options for new sound unit
« Reply #7 on: October 16, 2015, 06:50:10 AM »

afb

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Re: Options for new sound unit
« Reply #8 on: October 16, 2015, 07:56:51 AM »

Thanks for a MOST interesting link - just goes to show there's no fart like an old fart! A fraction of the price of the Adafruit SFX for which I'd laid out a PICAXE R/C interface PCB some time ago, but fortunately not yet ordered! I'll definitely be looking at these. However there is a version of the SFX module with a built in 3W stereo class D amplifier which does make for a neat package.

I'm very busy with model aircraft projects at present and boats have taken a back seat, so it may be a while yet! In the meantime I've started a website for all my various projects that you may be interested to check out  www.forge-electronics.co.uk

Best regards

Alan
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The Old Fart

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Re: Options for new sound unit
« Reply #9 on: October 16, 2015, 08:08:02 AM »

Hi Alan,

thanks for link,

I'll post a pic of the board I've put together. 67mm x 47mm.

TOF

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Re: Options for new sound unit
« Reply #10 on: October 16, 2015, 08:47:27 AM »

Here is a project I made for a model church.

no RC required on this one!!.

Pot controls volume, in this project.

led shows when new sound selected, handy for debugging.

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Re: Options for new sound unit
« Reply #11 on: October 16, 2015, 08:57:52 AM »


Some very intersting oiptions going on here!   :-)
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