Voltage Limit for Annie sound system

[Rob_TPA]

I have a 10 wheeler running on RC and battery power. The battery pack has 15 cells, giving a nominal 18 volts (charges to 20 volts) I would like to eliminate the separate 9 volt battery for the chuff sound system. Can I power the sound system from my battery pack, or would that be too much voltage?
Thanks, Rob

[mudhen]

If you r/c system is air wire and sound is a p5 from phoenix . DO NOT exceed 18 volts I have found two 7.2   6 packs charge to a maximum 16.5 volts. In mine anyway. 

[Rob_TPA]

Thanks, but I am using the delivered Bachmann chuff sound. I need to know the voltage limit for it. I can knock the voltage voltage down to 12 with a little solid state device from Radio Shack and maybe it won't blow it out. 

[JerryB]

Rob_TPA:

I don't have any direct experience with changing the voltage on the Bachmann sound, but I would caution against putting more than the 9volts as produced by the battery.

The good news is that you can use an LM317 voltage regulator to accurately provide the 9V. Here is a link to an LM317 data sheet:
http://www.national.com/mpf/LM/LM317.html

The only additional components required are two resistors (actually one potentiometer and one resistor) , two capacitors and a very small piece of perforated board. All this is available at Radio Shack or similar and will cost around $10. Easy assembly and no risk to the sound system.

If you Google "LM317", you will get hundreds of thousands of sites where there is lots more information, but basically, the LM317 three terminal regulator can accept input voltages up ~28VDC, will very accurately regulate the output at whatever you set (or calculate using some of the website information), at current draws up to 1.5 amps. Really a great solution for your use.

Happy RRing,

Jerry

[Rob_TPA]

Jerry,
Thanks. I will check it out.
Rob

[Rob_TPA]

I took the solid state transformer that reduces the voltage to 12 volts and I added 4 diodes for resistance and got the voltage down to 10.8. I figured that was close enough and sure enough it works. It is a little louder too.
Rob

[JerryB]

Glad you got something that seems to work, but transformers only work on AC. I doubt your (originally DC battery powered) sound system will last very long on AC. In fact I'm amazed that it works at all on AC.

That's why I recommended a DC to DC voltage regulator. It's designed to work on DC voltage in and out and the voltage can be set to exactly the specified value.

BTW, if you actually do have a DC to DC voltage reducing device, 10.8 VDC is still over 13% higher than the 9V design voltage. That's pretty high, especially considering that 9V batteries only put out ~9V when they are brand new.

Happy RRing,

Jerry

[Rob_TPA]

Jerry,
I used the wrong term for the device I used. It is a Voltage Regulator fixed at 12 volts, not a transformer. I added some resistors to get 10.8 volts. Of course, I am operating on DC from the battery pack to supply power to the engine.
For over a year I have been running this sound system from an 8 cell AAA pack separate from the engine battery pack. This AAA pack charged to 10.8 volts and has caused no problems. My goal was to eliminate the separate pack for the sound. 
I suspect that the sound unit will operate at even higher voltage. Some of the components are marked with "16V ". But,  I am not going to try anything higher. I had hoped that the Bach Man would jump in with some specs.
Cheers,
Rob

[reeveha]

Here a link to George Schreyer's tips that has a 9v constant voltage regulator that he uses to power Bachmann coaches from track power.  Just change the input from the track pickups to your batteries and you've got it.

http://www.girr.org/girr/tips/tips5/pass_lighting_tips.html#reg

Hope this helps.

Herb

[Rob_TPA]

Herb, Jerry
Thanks, I have a RAM sound system in another engine and I know that the RAM unit requires 9V, so I am going make a regulator for that one with the LM317 as you both described.
Thanks,
Rob

[Eugene]

I have used it for a long time operating at 14 to :)16v, that too is the rated voltage for a number of capacitors that are exposed to the max. It does raise the sound level significantly.

Eugene

[Rob_TPA]

Eugene,
I am glad that you jumped in since you have actually experimented with the Annie sound system. So, you have been using 14 to 16 volts. I thought it would take more than 9 or 10. because volume is so low with this voltage. I am going to bump my voltage up to get more volume.
Thanks,
Rob   

[Loco Bill Canelos]

Rob,

please post the results and let us all know how it works out!