+/- voltage regulators: which is better to us?zener, regulators, ic's or opamps?

[ivan_c",)]

mga sir,

i am about to design a power supply w/c produces +/- 12, +/-5, and +/-3.3 volts dc and a max current of 1.5 A..

w/c is better, easier yet affordable materials to be used?
yung zener kase po eh mejo hindi ko kabisado yung behavior ña and also don't want to use it..
but if it will best siut my specs and requirement no choice..
if i use regulators, mejo madami po eh,about six and also di pa po ako sure if available yung iba nito..
pag ic's and opamps..wa pa po ako background dealing with them po, but in case na ito yung pinaka ayos there will be no problem,madali na magpaturo nun..hehehe

thanks sa mga advice in advance...

more power!

[rdpzycho]

'yung Regulators meron na kaagad amp and precision reference sa loob, some mannufacturers, laser-trimmed ang voltage reference para malapit talaga 'yung voltages. 'yung 3.3V lang ang mahirap hanapin na regulator dito.

use zeners only for reference, bihirang ginagamit ang zener as power supply na high current.

[ivan_c",)]

sabagay madali nga po yun gamitin..kaso hindi po ba yun mahal??

what particular regulator po yung makakapagproduce ng +/- voltage?and is it available sa market??

[rdpzycho]

'yung Opamp plus transistor, maraming components at kailangan ng isa per voltage (unless switching pwedeng slave voltages lang 'yung ibang output).

'yung regulators 7812(+), 7912(-), 7805(+), 7905(-). starts from 10 pesos kung magtatanong tanong ka sa iba ibang tindahan, mahal 'yan sa Alexan. 'yung 3.3V kailangan mo ng variable regulator like LM317(+) and LM337(-). nung naghahanap ako dati ng 7833 (+3.3V), wala akong makita locally. ewan ko lang baka meron na sa e-gizmo.

[ivan_c",)]

ok po thanx..

is it necessary to put short-circuit protection?

[rdpzycho]

'yung mga regulators merong built-in short circuit protection at thermal shutdown. pero pwede ka pa ring magdagdag or maglagay ng fuse.

[ivan_c",)]

yun ba yung fuse na nabibili sa market or fusing circuit ba yung sinasabe nyu??
at what value po ng fuse safe yung regulators?

[rdpzycho]

kung 1.5A, pwede na ang 2A. pero per 1.5A 'yung 2A fuse. kung summed at lahat sila 1.5A equals 9A ang max, pwede na ang 10A. pero kung masyadong malapit at may mga peak draw ka, dapat slow blow 'yung fuse.

[ivan_c",)]

okei po thanx sa advice

mas nakapagdecide ako ng maayos..hope mapadali yung project ko..hehehe
as soon as possible i have to finalize my design para makapagfinalize na rin ng parts list...hirap isabay ng project sa academics eh...nahahati yung time..


anyways thanx a lot po sir
godbless!!

[ivan_c",)]

uhm. sa design ko po, what transformer should i use??center-tap, multi-tap, or yung ordinary step-down transformer lang po??

kase most of dual power-supply designs sa internet ay center-tap yung ginagamit po eh,kelangan ba talaga yun for negative regulators??

[eveready battery]

usually sa mga op-amps yung gamit ng dual supply,nasa sayo parin kung ano gusto mo

[ivan_c",)]

no i mean i will use regulators like lm317 & lm337

center-tap ba talaga ginagamit dun?or pwede nang ordinary stepdown nalang?kasi po when i analized the circuit eh sa negative port nila kinabit yung input para sa lm337 then positive input for lm317 (center-tap ginamit nila,tapos yung nasa gitna yung ground)..

for regulators such as lm337, 79xx(a negative regulator)..pwede po bang naka-parallel nalang sya sa mga positive regulators??i mean pwede kayang positive supply input for both +/- regulators then share nalang sila sa negative supply(ground)...

[eveready battery]

pwede syang dual power both negative and positive,gamit ka ng center tap na transformer.

[ivan_c",)]

sir my forrmula po ba how to compute ng resistance value na gagamitin sa lm337 to produce Vo?

[akosiikem]

for regulators such as lm337, 79xx(a negative regulator)..pwede po bang naka-parallel nalang sya sa mga positive regulators??i mean pwede kayang positive supply input for both +/- regulators then share nalang sila sa negative supply(ground)...
[/quote]

Hindi pwede. Dapat sa negative sya nakakabit ng rectifier mo.
I suggest gumamit ka ng LM317 and LM337. Mas maganda kasi ito compare sa fix regulator IC.
Kung 1.5A ang requirement mo, gamit ka ng series pass transistor. Mag download ka ng datasheet
ng LM317 nandun yung mga example circuits.

[akosiikem]

For V out computation nandun na rin sa datasheet

[ivan_c",)]

okei thanx po..example i need 6 outputs, makakaya kaya po ng regulator yun w/o using rotary switch??i mean gagamitin ko po yung 6 or kahit 3 outputs po ng sabay sabay using only the two??or gagamit po ako ng 6 din na regulators na puro lm337 and lm317??

[macky]

sali ako ha?

makakaya ng regulators yun DEPENDE sa INPUT voltage at OUTPUT na ilalabas ng regulator na gagamitin mo, i supposed 15V ang max input voltage mo para ma-obtain mo ang 12V-regulated UNLESS you will use a Lo-droput regs.

then kung ang input mo nga is also 15V sa gagamitan mo ng 3.3V output, masyadong mataas na HEAT ang magegenerate if you will use LM317 for the 3.3V, 15-3.3=11.7 volts ang tatanggalin ng LM317 galing sa input mo, which will generate much heat, sobra iinit ang LM317.

siguro iba-ibang regs ang gagamitin mo like lo-dropout, or another linear regs, pero mas maganda gumamit ka na rin ng SEPARATE input voltage, para di pwersado ang ibang regs(for low voltage outputs) mo.

pakitama lang po ako kung may mali sa post ko... 

[akosiikem]

Iba iba bang output voltage yun? Kasi depende yun sa current requirement mo. Yung LM317/337T 1.5A ang max current. So dapat hanggang 1A lang ang current mo. Kung isang output voltage then mataas na current kaylangan mo, gamit ka na ng series pass transistor.

hope this help

[ivan_c",)]

if i am going to use 6 regulators<4 fixed voltage regulators & 2 adjustable regulators>, max 12V, then what value of transformer is safe to use?is it 18-0-18 @3A, 18-0-18 @2A, or 24-0-24 @2A?providng that i can useany of them at the same time?

then kung may 7812, 7912, 7805, 7905, lm317, & lm337, mga ilang capacitors kaya po yung dapat kong gamitin and what value? is it also necessary to put capacitors at my output per regulators?, mga what value kaya po safe?hehehe

sorry, mejo magulo po ako mgisip eh...hehehehe