18 V DC down to +12 V / -12 V - will this work ?

[Gokarna]

HI,

I've just made a schematic for a power supply to get neagtive and positive 12 volts out of two 9 volts batteries. (see attachment.)

Can anyone tell me, if this will work fine ?

My main concern is, if the two voltage regulators will "stand" the 18 volts at the input side ? Will they get very hot, if it works ?

Thank you very much for every help.

Best Regards

Gokarna

[Mark Hammer]

The 1044 is not able to provide much current output; certainly not even the 100ma that the smallest 3-pin regulators are spec'd for. So, while the circuit should "work" (i.e., measure +/-12vdc), it is unclear if the things you want to power with it will.

[Gokarna]

Hi,

thank you for your answer, Mark.

The 1044 is not able to provide much current output; certainly not even the 100ma that the smallest 3-pin regulators are spec'd for. So, while the circuit should "work" (i.e., measure +/-12vdc), it is unclear if the things you want to power with it will.

I also figured out, that the 1044 are just build for max. 10V power input. So I can't use it anyway. Does anyone know a DC/ - DC converter-IC, that'll be useful for 18 V ?

Have a nice weekend,

Best regards,

Gokarna

[km6xz]

Maybe you are over thinking this, "what is the need?" when clearly determined, will reduce or expand the options. For example, if low current, and it is really a bipolar need, why not just an active artificial ground? Does it have to be efficient? Buck regulators are cheap and highly efficient whereas 78xx series regulators are not. Does it need to be regulated at all? I doubt it, if it is for a bipolar opamp, then probably not.
Instead of picking circuits tell us what you are doing and why you need +/- 12 volts regulated? How much current, how long do you need those batteries to last, now many part do you want to limit it to?

[Gokarna]

Hello km6xz,

thank you very much for your answer.

Maybe you are over thinking this, "what is the need?" when clearly determined, will reduce or expand the options. For example, if low current, and it is really a bipolar need, why not just an active artificial ground? Does it have to be efficient? Buck regulators are cheap and highly efficient whereas 78xx series regulators are not. Does it need to be regulated at all? I doubt it, if it is for a bipolar opamp, then probably not.
Instead of picking circuits tell us what you are doing and why you need +/- 12 volts regulated? How much current, how long do you need those batteries to last, now many part do you want to limit it to?

I want to build an old effectpedal for electric keyboards, a Maestro PS-1b.
Here's a link with the schematic:

http://www.wingspreadrecords.com/oberheim_ps-1.pdf

Only difference: Some sources quote that this device also runs with 12V. I don't want to power it with 220V AC; instead I like to use two 9V batteries.

Everything should be fit into a Hammond BB or BBDD enclosure, so the pcb for power supply should not be to big and I want to build it on Vero.

I hope to answer your questions, please excuse my english - I hope, it`'s understandable.....

Best regards,

Gokarna

[Jazz P Bass]

The schematic shows a bipolar +15 -15 Vdc, regulated (zener diodes) supply.

So, 2 batteries in series, at 18 volts would supply the +15Vdc.
Likewise, 2 batteries in a reversed ploarity setup, would supply the -15Vdc.

If the 3 volts headroom is not enough you could go to three series batteries, with a suitable dropping resistor.

[km6xz]

Hi Gokarna, The circuit is not very critical for supply and can be powered by two 9 volt batteries if you wanted. You can lower the the total current drain by using CMOS low power opamps designed for battery power. That way, you could get by with a single 9volt battery developing two rails of +/- 4.5 volts. Or you could use a standard 9volt pedal power supply and split that with a spare opamp section to create an active ground reference. The original 4558 opamp is a low performance general purpose chip that has two amps per IC. Their downside is higher current drain at idle, and higher input current plus low slew rate. Newer ICs do not have these problems and can run on very low voltage, and work to rail to rail input or output signals.
An example of a cheap battery powered general purpose audio opamp is the ST TS925 that does not even need the artificial ground, it has one built in so works with single supply. The circuit you intend to use, if run on low voltage.
A 4 opamp IC is lower cost than a 4558, has much lower distortion and noise. Many modern chips are not even available in DIP8 packages any more, you have more choices in ultra low power low voltage if you build the unit with surface mount devices. Were you going to make a PC board or wire point to point?

[Mrsices]

I'd use one of the National Semiconductor Simple Switchers.