12V bipolar supply needed- maybe zeners?

[BetterOffShred]

Hey guys.  I don't post new topics very much but I'm having some problems and was hoping a couple of you fellas who know about stuff could help a brother out. 

I built the bipolar supply from tagboard and then tried to use a couple of 12V regulators (+12 and-12) off their respective leads and then to the common ground.. but they got hot AF.. 

So I was wondering if I could adapt some 12 volt zener to this layout to get a bipolar 12V for this MFOS project I'm working on..  I also want to build that ken stone psycho LFO with like 15V if the zener trick can work. 

Anyone done something similar ?

Thanks for looking dudes

[Sooner Boomer]

I assume you're using 3-pin regulators (7812/7912)?  These are pretty bullet-proof.  Check to see you have them wired correctly.  The only time I got one to heat up was with a dead short.  Check for this also.

For breadboarding/prototyping, I use this https://www.jameco.com/z/JE215-Dual-Output-Adjustable-Linear-Regulated-Power-Supply-Kit_20626.html

I built mine a very long time ago.

[BetterOffShred]

Yeah I built it twice and bread boarded the regulator portion.  Never got it to work.  With just one regulator it works (either) but with both hooked up it starts cooking

[Sooner Boomer]

Is it the 3-pin 12 volt regulator that's getting hot?  Or is it the LT1054?  It seems strange that only one regulator hooked up would give you the correct voltage, but when two are hooked up, they get hot.  If it's the LT1054 that's getting hot, the problem might be that that particular chip only puts out 100mA.  3-pin regulators are not very efficient.

I assume what they're trying to do is what's described in figure 22 of the TI datasheet - dual-output voltage doubler.  It outputs only +/- 17 volts instead of a doubled 9v=18v because of diode losses in the circuit.

http://www.ti.com/lit/ds/symlink/lt1054.pdf

but, yeah, to your original question, I think zeners would work, just not very effeciently, either.

[duck_arse]

check your pinout on the negative regulator, it might not be what you'd think. also look for zener/series pass transistor regulator circuits. like this one:

[diffeq]

Down-regulating the doubler circuit with zeners seems a bit too wasteful...

LT1054 is a very fancy chip - there are feedback and fixed reference pins. You can use them to get a regulated output, in one go. See page 10, Fig.11, a regulator example. R1 recommended value is 20k, that makes R2 ~ 218k to get 12V.

It must be LT1054, other popular charge pumps do not have a FB/VREF pins.

[PRR]

If the 3-pin is getting hot, and *is connected right*, a Zener scheme will generally run much hotter.

What is your *load*?? (In amperes.) You can't design a bridge, a crane, or a power supply, without knowing LOAD.

[BetterOffShred]

That's a good point PRR..  I have not found any specifications of current consumption for this device, but it's 3xTL084s a 13700 a AD633 and a few 3906s .. 

I think my plan is to breadboard the bipolar supply and go through the datasheet and see if I can get ~13V no load out of it.