battery plus outboard power source.how does it work?

[garfo]

This new thread is related to my own build but it is a general concerne.
This might be basics electronics, but, what happens when we use a circuit that has a battery powered connection but is Also being powered via external power?Does the battery get drained at the same time, or does it Only starts  to work If there's not a dc chaon feeding the unit!?
I ask this because I'm considering running my bass with external ppower but want to leave a battery in in case something goes wrong.

[jubal81]

It's usually done with a switched jack, but a bass is a different challenge. Are you planning on using a stereo jack and running the power on the ring connection?

[garfo]

My idea is to apply the same teclnique as within pedals.I'll have to build in a dc Jack and make the connections as If wiring a pedal.I believe that way the battery will Only operate If there's no dc Jack in.
The reason why I decided to give it a try is because the system will draw around 18mA.

[RobA]

You have to use one of the switched DC jacks in combination with a stereo jack to switch the battery when there's nothing in the DC jack. The DC jack handles turing off the battery when there is a plug in it. Personally, I'd go with a power on a stereo cable as Jason suggests. Right now, I'm playing with using rechargeable Li-Po batteries on my active guitars, but if that doesn't work out well I'm going to move to the stereo power idea.

[jubal81]

You're going to put a DC jack on your bass?

[garfo]

Stereo Jack???using the second wire to use it as power?the cabeleira would need to be stereo, right?it could be a possibility.
Yes, my bass is custom made and is endless unfinished.

[RobA]

Yeah, a stereo cable to the first pedal. It could either be dedicated to supply power or have some other function as well. I'd put a switch on it to turn the power on and off. That way, if you needed to put another instrument into the board, you could flip off the power and it would work like normal.

[garfo]

Two Questions, I I use the stereo Jack, do I loose the battery option?
If I want to use another instrument, can't I use another cable, or that wouldn't work and a switch had to Go on there in order to block that tip!?
Regarding the rechargable batteries, I believe that with time they hold less and less current.

[jubal81]

This was a solution I came up with:
http://www.madbeanpedals.com/forum/index.php?topic=14819.0

[RobA]

I think there would be a way to keep the battery option. I'd have to think about it some though and you might end up having to use some sort of transistor switch or relay or something to turn the battery off when the power is on the stereo input.

If you plug a normal cable into the power box, it's going to ground the power to the sleeve. If you put a stereo cable in it's going to send power to the instrument and then the instrument's jack is probably going to connect the ring and the sleeve.

Li-Po batteries hold up on the power side for at least a couple of years and they don't have memory issues. They do eventually wear out though. The bigger issue is the charge circuit and the power boost circuit, but that can be done with the Li-Po and still be in a space less than a normal 9V battery.

[RobA]

This was a solution I came up with:
http://www.madbeanpedals.com/forum/index.php?topic=14819.0

That's slick.

[garfo]

Didn't know those, they look like chewing gum.
I think I'll just add the dc jack input.It's the quickest fix for now and it is ok to always be there.~The guy who made the bass is actually going to put some tru oil on it and he could do the extra hole.
http://www.batterymart.com/p-ultralife-9v-lithium-battery.html
These batteries have 1200mA.They should be long life.Yet, if my device consumes 18mA it would be dead within weeks if I play everyday.
I think I'll have the option to have a battery in and have the DC to be the main power source.I was thinking of using a 1 Spot since it has a really long cable and it is stabelized.

[RobA]

I don't know about that specific battery, but one of the things to look out for on lithium 9V batteries is that most of them aren't really 9V. They are usually closer to 8.4V or so because they don't have enough cells in them.