Cheapo diesel sound card

[Trevor Thompson]

I have been playing with one of these as well.

I have it working but the way it works is a bit strange. I have no idea why it is performing like this - maybe someone else will be able to explain it, and perhaps help me to get it to work the way I expected it to work.

It is connected to a Deleting RX 66 - and a loco into which I have just fitted a replacement motor. It has channel 1 set as a throttle, and channel 3 for direction (as I also use it for live steam locos).
That receiver has channel 1 programmed as a servo output on pad 8. Connected up and functioning. I have checked the programming and can confirm that pad 8 is set as a full throw servo (not centre off).

However the "speed of the diesel" does not follow the throttle. When actual throttle is fully anticlockwise the "sound speed" is about 1/3 full "speed", as the throttle is rotated (increased) the "speed" drops, until tick over is at about 1/3 actual throttle. Then as the actual throttle is increased further the sound "speed" goes up again until it is about the same as when the loco is stopped.

In other words when the loco speed it increased from standing to full throttle the sound card slows the engine noise and then speeds it up again. I would have expected tick over when stationary and the engine noise to increase with speed. If I turn the transmitter off the sound drops to tick over.

I have videoed this so you can see it: https://www.dropbox.com/scl/fi/24p2z4nd ... 7yf4e&dl=0

In the video you can see the wheels turning, the throttle being rotated and hear the noise. There is a servo attached to the sound card and you can see that moving the arm as you would expect.

Any ideas?

Trevor

[Phil.P]

To answer the last two posts, in order:

A 100 ohm pot getting hot, across the speaker output is a little worrying. - I don't have one of these cards to play with / work out the circuit, so advise caution, until 'we' can find more detail.

The second query, is easier to answer :
These cards are set up to work with a centre-off throttle, not low-off.
This means 'tickover' will be somewhere near centre-travel, speeding up in either direction.

Not sure if this can be altered by the end-user, on these cheap cards?

Phil.P

[ge_rik]

PS. It's probably advisable to protect the link from P3 to the soundcard with a 1k resistor, or maybe even a 4.7k resistor if you're powering the soundcard with 7.4v

Rik
PS - Now corrected the label for the switch and added the 1k resistor to the wiring diagram (see above)

I am no electrician nor technical guru, but won't putting a resistor on the signal wire reduce the range of the signal input thereby limiting the throttle range of the soundcard? Would a diode help to stop any current getting back? Please remember that me and electronics don't get on all that well, so I am really only guessing.

Sorry folks. Of course no resistor is required in the P3 output but one is advisable in the P1 output to protect the LED. Its value will depend on how bright you want the LED to be.

Rik
EDIT Now adjusted the circuit diagram in earlier post to reflect this - https://gardenrails.org/forum/viewtopic ... 80#p179135

[philipy]

Well.... I've been carefully playing.

Phil's pot does work, but the only presets I have, don't have a power rating, but I strongly suspected that is the problem.

So, I quickly adjusted it to about the sound level I wanted, switched off and checked the resistance of both legs.
Firstly, the 100R pot seems to actually have an overall resistance of around 112R. Then the two legs are showing approx 56R and 62R i.e almost exactly 50%. So, I went hunting in the box and came up with a 100R and a 47R fixed resistors, which is close enough to 50%, for what we need. Unfortunately, again these are small wattage items, not sure what but I suspect 1/8 watt, but 1/4w at most.
Anyway I took the pot out and replaced it with the resistors. The sound worked fine at about the right volume, but the resistors got red hot again in less than a minute.

Had a rummage through the junkbox and managed to find a 180R and an 82R at 1/2watt, so put them in. Worked fine but started to get warm after about 3 or 4 mins. so, going in the right direction.

Subject to what Phil, or anyone else thinks, I'm guessing that a 1Watt pot ( or fixed) could be the answer? I haven't got one to try it unfortunately.

[Trevor Thompson]

To answer the last two posts, in order:

A 100 ohm pot getting hot, across the speaker output is a little worrying. - I don't have one of these cards to play with / work out the circuit, so advise caution, until 'we' can find more detail.

The second query, is easier to answer :
These cards are set up to work with a centre-off throttle, not low-off.
This means 'tickover' will be somewhere near centre-travel, speeding up in either direction.

Not sure if this can be altered by the end-user, on these cheap cards?

Phil.P

Interesting! I suppose it shows my limited understanding of the differences in the signals between centre off and low off. I think I can work around it by reprogramming this receiver to work as centre off. I will just have to remember that this loco is different to all my others!

(Edited half an hour later) I tried centre off , and it made no real difference. I then moved the sound card control to the inertia control, and that seems about the best compromise. So my conclusion is that this cheap sound card doesn't really work well - the servo input isn't well adjusted to the sound control. If it is intended for Centre off it is poorly set up - about 30 degrees off. It was inexpensive (for the first one) but I don't think I will invest in another - especially as the next one would be much more expensive.

The control of the volume is my next task. I am following the comments on that with interest.
Trevor

[gregh]

Anyway I took the pot out and replaced it with the resistors. The sound worked fine at about the right volume, but the resistors got red hot again in less than a minute.

Had a rummage through the junkbox and managed to find a 180R and an 82R at 1/2watt, so put them in. Worked fine but started to get warm after about 3 or 4 mins. so, going in the right direction.

If BOTH resistors are getting hot there is something Weird going on. Just wondering have you got these two resistors 'across' the two leads from the sound unit or have you connected one to circuit negative?? I'm guessing that the sound module uses a bridge amplifier output which means the speaker does not have one side connected to circuit negative

The resistor which is ' across' the speaker should not get hot. You've got 8 ohms (speaker) across 50 or 80 ohms so the resistor will be taking very little current.

Also you don't need a second resistor - take the one across the speaker off and there will be no volume difference. Just try the 82R in series with the speaker.

[philipy]

Here is the latest news.
Firstly, thanks Greg. I've done as you suggested and just put the 82R in one of the speaker leads and it works a treat, although it does still get a bit warm.

I've put it all temporarily inside the body and run it up and down a couple of yards of track in the garden and everything seems to be basically fine. However a reasonable volume on the bench fades away outside, as I might have expected. I did try putting the little 100R trimpot back in, in place of the the 82R, just to use as a variable resistor, but it gets hot in no time so I've taken it out again. I guess I'll just have to try a variety of fixed resistors until I find a value I'm happy with.

[Trevor Thompson]

I wonder if there is a simper way of cutting the volume down?

How about a bit of foam in front of the speaker to absorb some sound? I am going to experiment with that to see how much of the speaker needs to be "obstructed".

Trevor

PS I have solved my issue with the sound. I have reprogrammed the receiver so that it is centre off, and takes its input from channel 3 ( the forward/reverse pot) on my transmitter. It now works correctly! So the issue is with my transmitter. It doesn't work properly on channel 1 for some reason.

[philipy]

How about a bit of foam in front of the speaker to absorb some sound? I am going to experiment with that to see how much of the speaker needs to be "obstructed".

Be interested to know how you get on. I did try putting a piece of 2mm plasticard in front of the speaker and it didn't seem to make much difference, but I didn't persue that method because I don't have a lot of space going spare.

[gregh]

Here is the latest news.
Firstly, thanks Greg. I've done as you suggested and just put the 82R in one of the speaker leads and it works a treat, although it does still get a bit warm.

Try putting the 100R in parallel with the 82R.
I usually find I need a 22 or 33R. But they have to be 1W

[Trevor Thompson]

How about a bit of foam in front of the speaker to absorb some sound? I am going to experiment with that to see how much of the speaker needs to be "obstructed".

Be interested to know how you get on. I did try putting a piece of 2mm plasticard in front of the speaker and it didn't seem to make much difference, but I didn't persue that method because I don't have a lot of space going spare.

I have glued a piece of expanded neoprene rubber in front of the speaker. It is like wet suit material, and sold for gaskets. It has reduced the sound level - to my ear to an appropriate level. Reasonably loud when the loco is near me but as it goes further away the volume diminishes until I can just hear it when its 30 ft away, and cant really hear it when it is at the other end of the garden. That seems about right to me.

[philipy]

I have glued a piece of expanded neoprene rubber in front of the speaker. It is like wet suit material, and sold for gaskets. It has reduced the sound level - to my ear to an appropriate level. Reasonably loud when the loco is near me but as it goes further away the volume diminishes until I can just hear it when its 30 ft away, and cant really hear it when it is at the other end of the garden. That seems about right to me.

That sounds OK. How thick is your material, it seems to come in a wide range of thicknesses.

[ge_rik]

More seriously, what do you use to produce the lovely schematic diagrams like this one. It obviously doesn't take all that long to do, given the response time from my post to your reply.

Just created a blog post explaining how I do it - https://riksrailway.blogspot.com/2024/0 ... rcuit.html
As with most things, I do it the cheapest way possible - in this case using LibreOffice and Paint

Rik

[philipy]

Thorough as always, Rik, thanks.

[Trevor Thompson]

I have glued a piece of expanded neoprene rubber in front of the speaker. It is like wet suit material, and sold for gaskets. It has reduced the sound level - to my ear to an appropriate level. Reasonably loud when the loco is near me but as it goes further away the volume diminishes until I can just hear it when its 30 ft away, and cant really hear it when it is at the other end of the garden. That seems about right to me.

That sounds OK. How thick is your material, it seems to come in a wide range of thicknesses.

Looks to be about 4 or 5 mm thick

Trevor

[philipy]

[FWLR]

On reading this thread I am glad it's all worked out Philip, yet for me and I presume most of use who are not that well informed with electricity stuff, buying a 'Cheapo Sound Card' isn't something that would be worth it for use, possibly because we would end up blowing stuff up with all those resistors and things like buck something or other So we would be better off having someone who sells a complete system like Phil.P to provide anything that is sound related.

It's been an interesting read although most of it has gone about a mile over my head, to late in the day for me to get to grips with anything that complicated to learn electrical stuff, not that I am not interested, I am, but for me and I suspect others, it's something that you can grasp or you can't grasp. I am one of those that can't

It's been a brilliant thread and hopefully other members who don't know much or even those who do can get something from the experience that our brilliant members who post such wealth of knowledge on a subject that without them we would not be able to progress with battery locos to the extent that we do.

[philipy]

Rod, I think the whole point of a thread like this one is that at the end of the day, between us we've worked out what is and isn't doable, so that you don't need to understand the technicalities, just follow the final "recipe".

I'm hoping that this weekend I will have the whole loco finished, including the sound. I'm expecting the sound issue to have become much simpler than this thread may have made it appear!

[-steves-]

On reading this thread I am glad it's all worked out Philip, yet for me and I presume most of use who are not that well informed with electricity stuff, buying a 'Cheapo Sound Card' isn't something that would be worth it for use, possibly because we would end up blowing stuff up with all those resistors and things like buck something or other

To be fair this is the most simple to use sound card there is going, others are way more complicated. If you use it with a standard receiver then you simply plug it into that and it works. If you use a Deltang / Micron / RCTrains RX then you may need to programme one function, for most you would generally need to programme at least one output , this is the most simple, easy to use soundcard going.

I think between us and with various issues we may have made it appear difficult, but it really isn't, there is nothing I know of that is simplier to use.

[FWLR]

Thanks for your replies guys. I wasn't having ago at anyone in the thread and like I said I did find it interesting reading, but far too complicated for me to understand and I know that between you all you have sorted the problem out. I still don't think I could do anything like the programming at and tuning the finer things would sometimes need to be done. I have never understood electrics at all during my life time and I simply haven't got the brain power to realise how important and enjoyable my hobby would be to get to understand electronics So I leave that kind of thing to more members who are better and more experienced than I am...

And the help I have had with electrics by members has been so helpful in the past, and if I needed any help with electric thingeiy things again. I know that other members are always willing to help me.

I am looking forward to Philip making the video for us all to see how the sound is in his loco and I am sure it will be brilliant just like all the stuff you guys do on here.