Will this battery power my midibox sid?

[mrpaul58]

Hi There

I'm super new to all of this and have not posted on this great forum yet!....Hopefully my question is not way too newbieish...

I've got my parts and SmashTV's pcb's on the way to make my first midibox sid, V2 with 2 6582 sids.

The catch is I want the choice to be able to run it on batteries aswell as a 12v wall PSU so I can busk out on the street....Because of this, I'm skipping the back light on a 16x2 lcd, and making control surface A with no extras except for 5 analog pots/sliders for live tweaking to keep the power consumption down...

I've done some reading on low drop regulators and thought a lot about different options.  I haven't been able to find much info on the net on replacing a 7805 and a 7809 with low drop regulators, and I really don't have much of a clue when it comes to electronics, so I'm hoping to not do that and keep it as true to the original schematic as possible....

I came across this 12v 1800mah rechargable battery on ebay...http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&rd=1&item=270182413327&ssPageName=STRK:MEWA:IT&ih=017

I believe it says the voltage when the battery has run out is 10.8V, and as the 7809 needs 11V(?) to run I'm thinking I'll get quite a bit of time out of this battery without too much wasted energy left over...

Just wondering if there is some big reason that I may have missed why this battery would not power both sids and the simple core hopefully for around 3-4 hours???  If there is,  is there another option I could try without too much modification to the original schematic?

Thanks Heaps!!!

Paul

[TK.]

Hi Paul,

welcome to the forum! :)

Note that a 2x20 LCD is recommented for MBSID, with 2x16 some messages are not completely visible.

I don't have so much experiences with supplying a MIDIbox from batteries, and also cannot give you a proven schematic for a low-drop regulator. Yes, it should already work with 7809 and 7805, the only danger I see is, that on a battery brown out something unexpected could happen - e.g., if you try to write a patch into the BankStick while there is no power anymore to finish the procedure, invalid data could be written, or the whole BankStick content could be corrupted (thats only an assumption - you wanted to be informed about possible issues...)

Best Regards, Thorsten.

[DragonMaster]

Hi, your battery will probably be on the edge of being drained out every times you'll finish using it, and considering batteries degrade with time, it's probably not the greatest solution. They claim 8 hours @ 200mA, I think you'll have to build the circuit first, measure how much current it takes and then buy a battery based on this. You can be sure to find the proper battery, as they're available in about every voltages and Ah possible, you just need to be sure of what you need.

The National LM2941 voltage regulator should suit your needs as an LDO regulator, the only thing is that it's variable so you have to do (simple) maths to get the proper resistor values. Dropout voltage on this one is 0.5V. If you need someone to get the circuit done for you there's no problem.

http://www.national.com/mpf/LM/LM2941.html

I don't think that there are low dropout exact replacements for a 780x that can handle 1A as well. The LM2941 is the closest I've personally found to replace an LM317(variable version of 780x) Even if you use National's regulator chart, it's the simplest solution. (I think there are some fixed voltage LDO regulators, but they're of the switching type, so we would have to start playing with inductors there.)

To save power, you could use efficient LEDs if you need some, and use low power version of certain parts(PIC, opamps)

Just wondering like that, what will be the power source of your other equipment? Is it possible to get power from a larger battery or something?

I see TK replied as I was writing. You should add a low battery indicator to prevent errors like that.

[mrpaul58]

Awesome! thanks so much for your help, :) I'm amazed at the kind heartedness of this whole midibox project, along with the forum and wiki, so much info that you guys have put in so much work for us all to use for free!! Thanks again!! :) 

So,

I'll build the circuit with the normal 78** regulators first and find out how much current it draws,  then, if its gonna be a lot, I might look at the low drop out ones, I didn't realise the LM2941 had adjustable output voltages, thats great....

I'm thinking the 16x2 might still do me fine, I plan on doing most of my preset making on the computer through midi, so I'll only really need it to see what preset I'm on...does that sound right or will it cause me trouble when debugging, etc? there are buttons you can use to move along the screen right? so I'll be able see as much as on a 20x2 just not all at the same time??

Thanks for the idea of the low level battery indicator DragonMaster,  any advice on how to build one? I'm guessing there is lot's of info on the web where I can find out about making one...

My other busking equipment is all typical 9 volt gear that run on batteries...Sp404 Sampler, 2 looping pedals and an old Ht700 casio synth.  I guess if I got fancy, I could get some type of car battery and power it all on the one battery to stop having to recharge a whole bunch of little batteries after every time I play...hmmm, so I'd just put a 9 volt regulator between all the gear and the battery and skip the 7809 on the sid box, right?  ooo the more I think about that the more I think it is the way to go....yes yes,  so that would be a 12 volt lead battery? any advice on finding the right car battery?, weight is no issue as I will have a trolley, and does anyone know of a 9 volt regulator out there that can handle a heap of current going through it from 12 volts?

Thanks!!!

Paul

[Goblinz]

I can't comment on the neccessary circuit for your case but I have a friend who is a (proffessional) busker. He uses a fairly small lead-acid car type battery on a little trolley with a seat on top and an attached umbrella. He also has a car amp in the box and a speaker mounted in there too. It does everthing hee wants it to and he has somewhere to sit whilst playing the guitar. With a bit of thought and effort you could build the perfect setup for yourself.

            G

[nebula]

A "sealed lead acid" battery (sometimes called a "gell cell") offers the most amp-hours by weight.  They're not small, but they're simple to use.  This type of battery is most often found in emergency power-fail lights, uninterruptable power supplies, some rechageable flashlights, etc.  IMHO the best ones are made by Panasonic.

A good example of what I think you should look at is at http://www.batteriesplus.com.au/pd/821/273/panasonic-uprw1245p1/.  This is about the size of a big can of beer (but square of course), and offers 9 amp-hours of service!

Mmmmm, beer.....

To charge lead-acid batteries, you really should have a proper voltage-regulated charger.  It's got a little more smarts than a normal power supply and is designed for recharging lead-acid batteries.  A quick google check turned up this as the first hit.

This would probably be suitable to power up everything you've got.

Lots of your 9-volt equipment will probably work just fine with a 12V power supply, because it's usually regulated in exactly the same way we regulate the power supply on a MIDIbox.

[DragonMaster]

Hi,

lead acid batteries are much more than car batteries, they can be a few inches large to >200lbs monsters :

http://batterymart.com/c-sealed-lead-acid-batteries.html

http://batterymart.com/c-gel-cell-batteries.html

http://batterymart.com/c-deep-cycle-marine-batteries.html

(They don't ship to Australia, it's just a reference)

offers the most amp-hours by weight

I'm not sure, but they're surely the cheapest per Ah.

Chargers are like anything else, there are cheap ones which just charge(a power adapter with a rectifier), and there are triple-stage pulse chargers with LCD screens, etc...

Lots of your 9-volt equipment will probably work just fine with a 12V power supply, because it's usually regulated in exactly the same way we regulate the power supply on a MIDIbox.

To specify, it's not that simple, the regulator could start overheating with 12v maybe.

I'm thinking the 16x2 might still do me fine,

Note that a 2x20 will consume a few mAs more if not nothing more at all compared to a 2x16 LCD though. Remember calculators work without problem using incredibly small solar panels. I think that both sizes even use the same controller, so there's nothing to lose with a 2x20 unless it's much more expensive or if you already have a 2x16 LCD.

For a battery meter, I thought about it, and I think that an analog needle meter would be a better solution, you'd be able to keep an eye on voltage that way. I saw some circuits a few times, but I'm looking right now and can't seem to find one.

and does anyone know of a 9 volt regulator out there that can handle a heap of current going through it from 12 volts?

As nebula said, a good part of the equipment could run off from 12v directly. If there's one that consumes much current, then a 7809 would not be a good idea. There are 3A versions of the 7809, just make sure you use an heatsink with those, because linear regulator have about 40% efficiency. You could start dealing with switching regulators, but they need quite good PSU filtering. You can pretty much forget power supply filter caps with batteries, but with a switching regulator, you lose that advantage.

You didn't mention any amplifiers to get the sound out of that equipment, what are you going to use?

As for the battery size, it really depends of the total power usage the lot will have. A 250Ah battery is not necessary, it would make a great 200lbs weight though, or make miter saw busking possible ;D

[mrpaul58]

Thanks for the replies....

Nebula, that panasonic battery with 9 amp hours seems like just the thing, so I think I'll go that way, thanks.

I'd rather not power my equipment straight from a 12 volt battery as none of the manuals of my pedals say 9-12v input so to avoid risk I'm gonna go for a 9 volt regulator for sure. 

I calculated how much current the gear I already have uses up, its 435Ma + the casio which I think is about 780 Ma....The manual says its 7W power consumption and if it runs on 9V do I divide W by V to get amps??? If so thats .78 so I'm guessing it's 780 Ma...correct?

So everything plus the sid box I'm guessing will be around 2 amps max maybe even 1.5, which means the 3A 7809 will work? I couldn't find one of those but I found a 3A LM350K,  would that do it? I'd have to make a circuit wouldn't I?...thats ok I think I could figure it out.

Dragonmaster, just wondering what you mean when you said linear regulators are 40% efficient? does that mean I'll waste a big chunk of battery power?  I found this http://www.powerstream.com/dc6.htm which is a switching power supply but looks like it may do the job...

What is PSU filtering? is that a filter to get rid of the ground buzz? you said you can't filter a PSU when it's battery powered? do you think this regulator converter thing above would work or will bring in lots of buzz which I wouldn't be able to get rid of?

You asked about my amp, I've got a pignose hog 30 on the way so it comes with it's own rechargable lead battery so that will be covered.

I've already ordered a 16x2 LCD so I'll start with that, I'll leave some room if down the line I want to switch to a 20x2.

Paul 

[DragonMaster]

What is PSU filtering? is that a filter to get rid of the ground buzz? you said you can't filter a PSU when it's battery powered? do you think this regulator converter thing above would work or will bring in lots of buzz which I wouldn't be able to get rid of?

PSU filtering is the capacitors around the voltage regulator to remove the voltage ripple when converting AC to DC. Rectifiers aren't perfect, and capacitors are needed to make DC constant. The thing with batteries is that they output ripple-free power, so no filtering is needed. A switching power supply converts DC to high-frequency AC and then converts everything back to DC. It creates noise in the power supplies lines, and it could be heard at the audio output if you don't use good filtering. Since your 9V-powered equipment probably has regulators in it(regulators remove a good part of the ripple), you would just have to put an electrolytic capacitor between the equipment connected and the SMPS PSU, it should be enough.

This switching PSU you linked to is probably a good option to keep a longer battery life, even if you have a few caps to add, which isn't really a problem anyways. Just make sure you don't exceed two amps usage with it, it's the max current for 9V. It's not much more expensive than building a switching regulator.

I've never built switching regulators as they need inductors, possibly one of the hardest to find component(in the required values).

[mrpaul58]

Great! thanks for all the help, I'll try it out for sure and post up my results when it's all done.

Paul

[/tilted/]

If you are using guitar pedals, I'd suggest you continue running them on individual batteries.

It can be a pain to keep changing batteries, but running regulated 9v over any kind of distance presents its own problems.

Guitar type effect pedals typically employ NO regulation (as they are intended to be powered by batteries), so be careful there. Also a lot of older battery powered synths had no regulation, so be careful,. Feed these babies too much juice, and you'll be sorry.

The basic calculation to bear in mind with mAh ratings on batteries, is that the rating given is the current required to discharge the battery to a certain level, over an hour. So if your rig is around the 2A mark, your 1800mAh battery will be flat in under an hour.

If you need to run this rig for 3-4 hours (or let's just say 5 and be safer) - you need at least 10000mAh capacity. This may sound like a lot, but bear in mind you can gang these batteries together in parallel to get greater capacity.