Analogue-sequencer

> So, do you think that the lazy option of putting a 6v feed pre-
regulator is acceptable
It may work on 6v but I don't think I'd want to try it with mine. 
You could try running the positive side of the power in through 
three or more 1N4004 or similar diodes in series, each gives a 
voltage drop of 0.3v so this would get it down to 5.1v which would 
be a lot safer. Do check the voltage of your batteries when fully 
charged though, they may give a bit more than 6V. 

Allan



--- In analogue-sequencer@yahoogroups.com, "Julian" <julian@2...> 
wrote:
> Im thinking again about the posibility of running my p3 off 
batteries.
> 
> The 7805 regulator emits 5 volts.  It would seem a good idea to 
feed in the battery supply post this regulator, to save on 
consumption, but then getting a 5volt cell combination may not be so 
easy, and those 6v sealed lead acid are easy to come by, and 
reconable capacities are still cheap.
> 
> So, do you think that the lazy option of putting a 6v feed pre-
regulator is acceptable, or do you have better suggestions?

> 
> Thankyou, Julian
> 
> 
> [Non-text portions of this message have been removed]

Im thinking again about the posibility of running my p3 off batteries.

The 7805 regulator emits 5 volts.  It would seem a good idea to feed in the battery supply post this regulator, to save on consumption, but then getting a 5volt cell combination may not be so easy, and those 6v sealed lead acid are easy to come by, and reconable capacities are still cheap.

So, do you think that the lazy option of putting a 6v feed pre-regulator is acceptable, or do you have better suggestions?

Thankyou, Julian


[Non-text portions of this message have been removed]

----- Original Message -----
> It may work on 6v but I don't think I'd want to try it with mine.

Ahh, no i ment pre-regulator, as in feeding in the same side as the power normally goes in.

Assuming that the 7805 dosnt need a greater voltage to regulate to 5v better (i suspect it might, but, no i havent looked at the
data sheet properly yet : / ), the only disadvantage would be running down the battery quickly, due to the waste of the regulator.

Julian

Alan, just a quick ps - any photos of your tr-606 online?

> > It may work on 6v but I don't think I'd want to try it with mine.

Most of the devices in P3 *should* tolerate 6v, but both CPU types are rated
to 5.5v absolute maximum at their highest clock frequency.
Both CPUs are clocked a bit under their maximum in order to generate
suitable baud rates for midi, so you *might* get away with running them half
a volt over.
But I certainly would not recommend running the supply voltage at any more
than 5.5v

You'd probably find the output voltage from a 6v battery pack would fall
below that voltage pretty quickly in use, but that's no guarantee fresh
batteries wouldn't harm the board.

I'd suggest using a higher voltage battery, and a switch mode regulator for
maximum efficiency.
The 5 volt linear regulator burns off a fair bit of heat in normal use.

You might also reduce power consumption by using larger values of pots.
I originally used 10k, then switched to 4k7 pots to reduce the noise levels
at the ADC input, and minimise ghosting.
Higher values of pots mean more noise at the ADC input.
But the software noise reduction seems to have eliminated ghosting from all
but the dirtiest pots, you might find 47k or even 100k pots could work
reliably now - though I've never tried them.
Obviously 34 4k7 pots are drawing a fair bit of the supply current - about
35mA by my calculation.
If you can get away with 47k pots, that would reduce to under 4mA, and your
batteries would last a lot longer.
You might find you end up haunted though...

Cheers,
Colin f

Of course, any DC bit of hardware can be battery powered, but you need to be careful not 
to damage your precious gear.

I think that going post regulator is a very bad idea. The reasoning being that batteries are 
never an exact voltage for any lenth of time. Regulators keep your equipment from getting 
fried and working sporadically. 

If battery life is not such a pressing issue, then you could do little better than buyin a 
surplus DC-DC converter. 5v is a very common value. Basically, it converts all of the 
battery output to 5v until they are drained. So you start with 6v, they run down to 5,4,3v... 
and it still always outputs a precise 5v for your circuits. Then when the batteries are 
"dead", it just stops. 

The tradeoff here is that DC-DC converters are not terribly efficient. Some of your juice 
goes to running the converter itself. Another bonus of this situation is that you could use 
almost any batteries at all, so long as they don't exceed the DC converter's ratings! They 
are usually rated for like 3v-30v. So you could score a pile of surplus LiION batteries for 
camcorders or computers and always have more juice than you need on hand. Of course, 
you'd need to buy or find a charger. All of this stuff is readily available.

More modestly, I'd lose the 7805 regulator, which is inefficient. The simple route is that I'd 
use Schottkey diodes to reduce voltage drop, and replace the 7805 with an LM317 
regulator. The LM317 is way more efficient, less noisy, runs cooler. There are datasheets 
out there which show how to connect them for 5v. As I recall, see the datasheet from On 
Semi for application notes, if you are interested. This way, your circuits are still protected, 
you can make a fitting for ordinary C or D cells, and you waste less current.

More good battery-powered equipment is always terrific. If you get this going then we will 
all go do an outlaw party in the woods.
YMMV! Good luck!
CJ

--- In analogue-sequencer@yahoogroups.com, "Julian" <julian@2...> wrote:
> Im thinking again about the posibility of running my p3 off batteries.
> 
> The 7805 regulator emits 5 volts.  It would seem a good idea to feed in the battery 
supply post this regulator, to save on consumption, but then getting a 5volt cell 
combination may not be so easy, and those 6v sealed lead acid are easy to come by, and 
reconable capacities are still cheap.
> 
> So, do you think that the lazy option of putting a 6v feed pre-regulator is acceptable, or 
do you have better suggestions?

> 
> Thankyou, Julian
> 
> 
> [Non-text portions of this message have been removed]