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bugbrand
Joined: Nov 27, 2005 Posts: 846 Location: Bristol, UK
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Posted: Sun May 20, 2007 3:28 am Post subject:
Low power operation Subject description: Portable modular running off batteries / solar power |
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I'm trying to get more portable. Ok, already got the little vanity cases (drone machine and frac-case) but what I want is to be able to play outside running totally off solar power or SLA batteries charged from solar power.
Things I've been thinking about:::
1) SLA (Sealed Lead Acid batteries -- like little car batteries) - available in 6v and 12v and many different capacities (measured in AmpHours). The first issue is how to get a decent bipolar supply for modules --- I'm presuming that I def. need some regulation as the voltage from the SLAs varies from about 12.6v (fully charged) down to c.12v (just about empty). Problem is that for regular V-regs I've used (7812 / 7912) you'd need a voltage input of over 14v to get a stable 12v output.
So I was thinking of regulating the modules down to +/-8v -- I'm thinking this should work out fine though some things may need some tweaks.
Is there a better way to regulate things?
I'd consider running everything straight off the batteries, but I'm going to have a TDA2030 14watt mono-amp running straight off them and that can certainly suck some juice.
2) Still got to do some more figuring of the solar stuff -- decent power panels are not yet really cheap.. You can get trickle chargers for little, but decent power still costs $$$.
One thing (note big hole in electronics knowledge!) is - can I run the system off the two 12v batteries while also having the solar panels connected? Would this work --> the system is drawing power shared from the solar panels and the batteries - so the batteries don't run down as fast???
3) Other things I'm looking at are ways to get things visual -- I've fallen so deeply for the Oscillographics related projects but don't think there's a way to get an XYscope into the system. But have been looking at some DIY LED o-scope designs...
SUch as:::
http://www.geocities.com/SiliconValley/Lakes/7156/articl3.htm
http://www.geocities.com/rlaude2000/ledscope.htm
4) gotta decide what modules to put into this.
& make a decent custom mixer
& there's something of a time limit -- want to get the first performance out on the 1st weekend of June (argh!).
((( -- for the wonderful Venn Festival in Bristol))) _________________ http://www.bugbrand.co.uk
http://www.bugbrand.blogspot.com |
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Mooger5
Joined: May 02, 2007 Posts: 199 Location: Portugal
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Posted: Sun May 20, 2007 4:37 am Post subject:
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I´ve made an LM1875 Gainclone (google for these words) running off 12V 7AH SLAs and it would play endlessly with 90db speakers. It´s pin-compatible with the TDA2030 and it´s a more modern design, offers better fidelity and requires less components. As it´s more powerful, I think it´ll draw less current.
It also depends on loudspeaker sensitivity for the same reasons. Compared to a 90db speaker, a 93db will require half the current to play at the same loudness.
Full-rangers and horns are great for power saving.
Check the new class D, class T amplifier kits too. 90-95% efficiency. |
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Uncle Krunkus
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Joined: Jul 11, 2005 Posts: 4761 Location: Sydney, Australia
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bugbrand
Joined: Nov 27, 2005 Posts: 846 Location: Bristol, UK
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Posted: Mon May 21, 2007 2:18 am Post subject:
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Thanks both!
The LM1875 looks ideal - I'll have to try that out for sure.
Great!
UncleK -- also yes! I've been looking a bit at such things. Sure I'll get one into the system sometime soon.
Any thoughts about supply voltages?!
Anyone?! _________________ http://www.bugbrand.co.uk
http://www.bugbrand.blogspot.com |
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Uncle Krunkus
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Joined: Jul 11, 2005 Posts: 4761 Location: Sydney, Australia
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Posted: Mon May 21, 2007 4:55 am Post subject:
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Why not +/-9V? You could possibly even go for +/-10V if you used an LM317/337 pair, but it's probably more hassle than it's worth. Definately 9 though, if you're running off SLAs, there's no point in warming up heatsinks.
I just checked, the LM317/337 adjusted to +/-10V is not hard to do at all. It only needs 1.25V overhead, which would be fine for 12 SLA supply. Well over 1A, and it won't go towards heating. _________________ What makes a space ours, is what we put there, and what we do there. |
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Mooger5
Joined: May 02, 2007 Posts: 199 Location: Portugal
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Posted: Mon May 21, 2007 5:26 am Post subject:
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Best practical advice I can give you:
With SLAs split supplies make sure to power both rails at the same time or you´ll fry the circuits. Also be aware of loose wires in the proximity of the batteries when prototyping as shorts happen too much frequently. The bigger the A/H, the bigger the spark and possible damage..
With the 1875, connect it to the speaker only after making sure everything is working properly. Since it doesn´t use an output capacitor, with only one power rail connected it´ll send out DC enough to destroy your woofer.
This kit is excellent sounding and quite affordable http://www.quasarelectronics.com/3050.htm . It comes with protection fuses and sounds absolutely great, even running off +12/-12V. They ship fast, too.
I´d try just the batteries with 330uF across each rail (and some fuses) and see what happens, but if this exists http://www.quasarelectronics.com/cva678.htm, there must be a schematic somewhere. |
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bugbrand
Joined: Nov 27, 2005 Posts: 846 Location: Bristol, UK
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Posted: Mon May 21, 2007 4:11 pm Post subject:
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Uncle Krunkus wrote: | Why not +/-9V? You could possibly even go for +/-10V if you used an LM317/337 pair, but it's probably more hassle than it's worth. Definately 9 though, if you're running off SLAs, there's no point in warming up heatsinks.
I just checked, the LM317/337 adjusted to +/-10V is not hard to do at all. It only needs 1.25V overhead, which would be fine for 12 SLA supply. Well over 1A, and it won't go towards heating. |
Great - I'll look more into those - I've only ever used 78xx & 79xx v-regs before. That's where i'd got the +/-8v -- I was sure there were 9v versions but appeared not to be when I was checking..
Yeah, basically, I want the highest supply voltage but regulated - so, yeah, 8v was seeming overly low to me too.
Hey, and thanks Mooger5 -- those are some very useful pointers. Cheers. _________________ http://www.bugbrand.co.uk
http://www.bugbrand.blogspot.com |
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bugbrand
Joined: Nov 27, 2005 Posts: 846 Location: Bristol, UK
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Posted: Sat May 26, 2007 2:43 am Post subject:
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All is looking very hopeful....!....
I've got 317/337 boards now and they seem to be very happy supplying a bipolar 10v supply off of 12v SLAs. I've been putting in many hours getting together the new case for this porta-modular system -> power rails, routing in the endcheeks of the frac-cases, rack-mount mixer, and all the power considerations (battery charging, LED power meters etc). [its built in one of those rack and mixer flight cases - 10u space sloped at the top and then 8u rack space at the front. So I'll be fitting four frac-racks in there along with a special Frac-width but 5u tall section for I/O mixer and all the power supply stuff ====> whoah!]
And I changed over from the TDA2030 to LM1875 --> I did some initial tests yesterday and got really great results out. I was playing loud modular rhythmics for about an hour and it made little dent in the 12v 7Ah SLAs --- ie this is looking really sweet! And sounding good too.
Just a bit more internal wiring to do and then I'll get some more details and images up. Next week I'll start putting the modules into the racks and see how they react to being run off a +-10v supply rather than +-12v.... _________________ http://www.bugbrand.co.uk
http://www.bugbrand.blogspot.com |
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Mooger5
Joined: May 02, 2007 Posts: 199 Location: Portugal
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Posted: Sat May 26, 2007 4:51 am Post subject:
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I modded my Moog Rogue to run at +10V/-10V after reading an article by Kevin Lightner ("Why a Moog sounds like a Moog"). I think the sound improved and will be curious to know about your findings.
I had to make some changes to the CV circuits though as the pitch was two octaves lower. Had to increase the range of the calibrating trimmers.
I would still try just the batteries with no regulation. They deliver the purest DC and if the amplifier which eats a lot of power "only made a small dent", the consumption made by the synth´s circuits will be almost negligible. In the worst case you could start the performance in C and finish playing in D but it would be so subtle noone would notice
If you encounter problems with 10V another thing you could do is to connect two smaller 6V batteries in parallel to the 12V ones to get 18V at each rail. |
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Mooger5
Joined: May 02, 2007 Posts: 199 Location: Portugal
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Posted: Sat May 26, 2007 4:51 pm Post subject:
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Oops, I meant starting in C and finishing in B, not D (Dó ->Si)... |
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zipzap
Joined: Nov 22, 2005 Posts: 559 Location: germany
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Posted: Mon May 28, 2007 9:25 am Post subject:
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I´m not an expert, but i don´t think the batteries need to be regulated. If the voltage drops over time this shouldn´t matter. Only problem could be when one side drops much lower and the supply becomes unbalanced.
Anyhow, votage regulators are kind of opposed to low power design. Say you have 12v, regulate it to 9v. You throw away (heat up) 1/4 of the power.
Lots of descrete circuitry for audio parts (sometimes one fet can replace an whole opamp, with 1/100 the current),
and low power opamps where needed.
Whith these car type batteries (and they are dirty and heavy - mobile!!)
a modular might run for days... _________________ http://www.myspace.com/lorolocoacousticpop
http://www.myspace.com/petrolvendor
music and transcribed jazz basslines |
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bugbrand
Joined: Nov 27, 2005 Posts: 846 Location: Bristol, UK
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Posted: Mon Jun 11, 2007 3:13 am Post subject:
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Updates!
Yeah, I'm not so sure whether I really did need to regulate via 317/337s down to 10v... Well, right now I'm doing another (smaller) rack without any power amp that'll run straight off two SLAs.
THere's some new details of this porta-system over on my blog page. Its actually not very portable -- freaking massive mixer rack case - don't walk far with this monster. My ideas of taking it to europe are dashed! (hence making the smaller rack right now)
Here's a pic - more on the BugBlog & there's a you-tube squelcher video demo too...
_________________ http://www.bugbrand.co.uk
http://www.bugbrand.blogspot.com |
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bugbrand
Joined: Nov 27, 2005 Posts: 846 Location: Bristol, UK
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zipzap
Joined: Nov 22, 2005 Posts: 559 Location: germany
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bugbrand
Joined: Nov 27, 2005 Posts: 846 Location: Bristol, UK
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zipzap
Joined: Nov 22, 2005 Posts: 559 Location: germany
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