Battery Supply for EW ? (condensed and meaningful posts)

I know that many people rely on the gas for a living like your brother but I have always thought it was an insane waste to release thousands of balloons for events to be gone out of sight and out of mind in seconds.  I thinks that humans can get by without tacky mylar balloons surrounding their hospital beds and crying children who lost their balloon because their parents somehow thought they could actually hold on to a small string while eating cotton candy and drinking a Slushie at the same time. Any resource that can be used for the good of mankind should not be wasted in that way.

But then we do that with everything!  If it isn't getting from the forest to the landfill fast enough we end up in a major economic collapse.  Waste is our way of survival now.  The only problem is that it is a linear system that will come to an abrupt and ugly end.

We are selfish theremaniacs! 

OFF TOPIC!

I wholeheartedly agree with every word you say..

But its like all our other follies and wickednesses - "If I didnt sell those balloons, someone else would" and "If I didnt design that missile guidance system, someone else would have"..

It will come to an ugly end.. Sadly, it wont be us who will pay though - it will be our children and grandchildren - Also, those who did least to pollute our planet are the ones who seem to be paying the price first..

There aint no justice.

They will just have to start filling the GoodYear blimp with hydrogen and we can have hotdogs ready when it lands at the airport.  On that note I will end this subject...LOL!

MORE PRACTICAL DETAILS ON GROUNDING:

A bit more on grounding..

This is a image from my Element-14 discussion, relating mainly to grounding of mains powered equipment..

I am now adding this, more related to "Grounding" of BATTERY POWERED THEREMIN SETUPS:

The above is specifically to show where to connect a ground mat or radiator for the proposed battery power supply scheme I have presented.

It should be noted that with an exclusively battery powered system I think the risk of ground currents between equipment is probably greatly reduced, so breaking the screens on audio cable and running a seperate ground link wire is not likely to be needed - these are extreme measures to get best performance in a studio environment - not really applicable to busking!

Even in a studio environment, it is usually possible to reduce signal coupled through the screens to acceptable levels by having all the equipment directly grounded to a common earthing point - breaking the screen connection on one side of the audio lead does eliminate any possibility of induced signal - but usually if there is a good other common ground path, induced signals are so low as to be undetectable.

Fred.

The main advantage of using batteries with any kind of electric device is the freedom from wires or cables. Like when I use an electric guitar with a small battery-powered amp for busking. 

If we still need to have a wire from the instrument to the ground, what's the benefit of using batteries with a theremin? Noise-free power? Just curious...

"If we still need to have a wire from the instrument to the ground, what's the benefit of using batteries with a theremin? Noise-free power? Just curious..." - Roguewave

The ability to play the theremin where there is no available mains power (or grounding point) .. As in, when busking.

"The main advantage of using batteries with any kind of electric device is the freedom from wires or cables."

The "main" advantage IMO, is that one does not need mains!

Where mains power is available, I see no advantage.. Although Russians I have spoken to often run their theremins off battery even when a mains supply is available - they say they get better performance, less noise, and better reliability... So I suppose it depends on the quality of your mains supply.

Fred.

Fred,

Just wanted to post a followup to my battery operated theremin project.  I did not end up using the connection ideas you presented in this thread but do intend to keep all the information for future purposes.   

It turns out my neighbor now works for an electric wheel chair company here in Pittsburgh and he offered me a nearly new 12V deep cycle sealed battery that he got at work.  I am using it with a small automotive power inverter to power both the theremin and amp.  The only thing is it is a total OVERKILL!  I have played on a single charge for over 8 hours total and no signs of running out of juice!  It is also heavy, about 15 pounds, but fits into my custom made busking case perfectly.  The weight is not really a problem since I have a small alloy folding dolly for moving it around and don't plan on playing on the beach or in the forest next to a waterfall ;^)

For grounding I am using a steel plate about 12" by 12" covered with thin vinyl floor runner material to keep it from slipping and rusting. It is simply connected to my Roland Base Cube amp's ground screw. This fits neatly into the back of the case on the door.   One foot on it is all I need to stabilize the pitch.  I also have a small aluminum ground rod with speaker wire and an alligator clip to also attach to the ground screw as a second option. 

I promise to post pictures and maybe even a video of the project as soon as I get out there and start busking!  

Brian

"The only thing is it is a total OVERKILL! "

LOL ;-) ... But you have the extra juice for whatever you want.. an electric kettle for a cup of tea while busking, or in cold weather change the towel for an electric blanket .. ;-)

Hope you have a lot of fun!

Fred.

Thanks....I will eventually want to trade out that boat anchor of a battery so be advised...LOL!   I wish there was a way to cut the Etherwave's plug off the wall wart and wire it directly into a power converter so that no modification has to be made to the theremin itself.....maybe in the future ;^)

It is possible to make a battery supply which would plug into the existing socket, without any mods to the EW..

All one needs to do is provide a low (12V) AC signal directly from the battery, emulating what the wall-wart does... Its not a difficult design, one can get power op-amps which will do it directly by running them as sine oscillators..

But my thinking was that if someone is capable of building one of these, then they are more than capable of the (much easier job) of minor modification and improvement on the EW PSU circuit..

Just seems crazy to go to all the bother of producing a sine wave which you must rectify and filter as soon as it comes in ;-) .. Also, when running from battery, one wants to eliminate any voltage drops across rectifiers etc, and remove any undue dissipation - as in, waste as little power as possible.

The EW PSU did not have this objective - it expects an input sine with enough amplitude that, after rectification, there is plenty of headroom - Losing 0.7V on each diode is no problem... But it is (or can be) a problem if one needs to get the 14VDC required, and get this from a 12V battery..

From 12V With an unmodified EW you would need a DC-DC step-up followed by a power oscillator, or you would need the power oscillator driving a transformer to step the voltage up.. The latter loses about 20% or more power through ineficiencies.

Fred.