[sdiy] problems running circuit off of DC TO DC converter-HELP!

[René Schmitz]

Hi Dan and everyone,

Without wanting to go too much into your detailed problems, I'd like to 
give you a few thoughts: I would say in that case use a DC/DC which is 
designed for 9V->+-15V conversion. (If none is avail, design one.) Any 
sort of linear preregulation will "burn" one way or the other almost 
half of your precious energy from the battery. Speaking of which: Even 
when your converter can handle 100mA per rail on the output, that 
doesn't say your battery can deliver it. (a standard 9V "block" battery 
can't sustainably deliver currents in the 100mAs) Also consider that 
your input current is higher (by at least (Uout/Uin) divided by 
conversion efficiency plus the convertors own current standing 
consumption) than your output current.

Or use AA style batteries, put 4 in series for ~5.2V (if using 
rechargables). Then your convertor might do fine, just as it is.

Testing the current consumption of your circuit should be done first. If 
you have a meter, use it. :-)

Cheers,
  René

dan snazelle schrieb:
> OK
> 
> i figured i would throw this out there to get some help as the
> situation gets more confusing.
> 
> I am trying to make a decent sized +/- 15 volt circuit work on a 9v
> battery/9v dc adapter
> 
> the circuit has got about 10 opamps (all tl062's), a few ota's, some
> resistors, and a tiny bit of cmos,
> 
> a second possible circuit i am working which would also use a DC TO
> DC  has about 10 cmos chips and 4 tl072's.
> 
> I am trying to use a CHICON  EC3AE05  +/- 15volt DC TO DC converter
> as the main part for these designs which is stated as having around
> 100ma per rail. (these would also work with a +/- 12 volt setup)
> 
> 
> 
> http://www.cincon.com/data/products/dcdc1_2/EC3AE.pdf
> 
> http://www.mouser.com:80/Search/ProductDetail.aspx?R=EC3AE05Mvirtualkey14670000virtualkey418-EC3AE05M
> 
> 
> 
> 
> it needs to be driven from 5volts.
> 
> 
> i also tried with this guy but it had even worse droop with a 5v
> regulator before it
> 
> http://www.murata-ps.com/data/power/ncl/kdc_nmh.pdf NMH0515SC
> 
> 
> SO..ON TO THE DETAILS...
> 
> THERE ARE TWO SETUPS I HAVE TRIED , BOTH OF WHICH DIFFER IN HOW THEY
> TURN THE 9v INTO 5v for the DC TO DC.
> 
> SETUP A:
> 
> 9 volt battery into 78ml05 or 7805 into the DC TO DC converter (this
> is setup A)
> 
> or SETUP B:
> 
> 9volts
> 
> into a 20 ohm 2 watt resistor, which connects to a 5.1v 1 watt zener
> to ground (providing around 5.3 volts) which goes into the DC TO DC
> 
> 
> 
> 
> WITH SETUP A, the regulator AND the DC TO DC get super super hot.
> enough t burn me. it works fine though. the battery doesnt last too
> long but its workable. with a dc adapter, there is no issue of time,
> only of INSANE HEAT. i thought about putting a resistor BEFORE the
> regulator to keep it from sucking so much power, but i have been told
> this is a bad idea.
> 
> with setup B, the DC TO DC starts sagging super super quickly with
> the 9v, literally draining the battery within 20 minutes. THIS TIME
> THE DC TO DC converter stays cool BUT EITHER THE RESISTOR (depending
> on the wattage) or the ZENER (depending on the resistor size) Get
> SUPER SUPER HOT OR BURN UP.
> 
> also...with this method, i seem to get voltages often far lower than
> +/- 15 volts out of the DC TO DC>
> 
> 
> MY QUESTIONS ARE MANY!!
> 
> 
> should i use a regulator?
> 
> if so, how can i avoid the heat if i use a regulator?
> 
> isnt the DC TO DC supposed to be regulated internally? so why is it
> sagging and putting out 12 or even 10 or 8 volt rails???
> 
> if i go with the zener and resistor to avoid heat, how can i keep it
> from sagging and killing the battery???
> 
> what is a basic way to test how much current this circuit needs?
> 
> The DC TO DC is rated at 100 ma per rail (for 15v) or +/- 120 ma i
> think for +/- 12volt....maybe i should try the 12 volt version?
> 
> i know this is a lot but it would be so helpful to me and hopefully
> to others in the future!!!!
> 
> 
> 
> thanks so much!!!!!! _______________________________________________ 
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