Voltage Regulator L78xx question po sa max Amp. delivered

[kenshee]

Mga Sir/Madam - question lang po.. what happens to L7805 regulator if the load asks for more current?

Like, sa DC motor po - if i stall the motor it it runs for like 900mA. what if there are two stalled DC motors? so (900mA x 2) = 1.8A.. the L7805 says it supplies 1.5A.

What would happen to the Regulator? or sa 2 motors? if the loads(motors) asks for more than the regulator is provided? or my concept is not right?

 i'm currently building an H-bridge and i'm stuck thinking and worrying on this part. pls help me po.

[rdpzycho]

babagsak ang voltage niya. 'yung TO220 size ba? kasi merong 78Lxx series na 500mA lang ang kaya.

[insomartin]

pwede mo na tangalin yung voltage regulator. most H-bridges have separate voltages (Vdd and Vmotor). much like the L293d or any other h-bridges.

but minsan kailangan mo nang (buck) regulation like yung supply mo is 12 volts. then 5 volts yung motor. the L7805 can withstand really tough abuse. but PUT A HUGE HEATSINK! you want the heat out as soon as possible. walang problem yun kasi stall current is very small.

another thing is maglagay ka nang current regulation mo sa h-bridge.

[pete]

pwede mo na tangalin yung voltage regulator. most H-bridges have separate voltages (Vdd and Vmotor). much like the L293d or any other h-bridges.

but minsan kailangan mo nang (buck) regulation like yung supply mo is 12 volts. then 5 volts yung motor. the L7805 can withstand really tough abuse. but PUT A HUGE HEATSINK! you want the heat out as soon as possible. walang problem yun kasi stall current is very small.

another thing is maglagay ka nang current regulation mo sa h-bridge.

agree

pwede siguro dalawang 7805 hehehe

[kenshee]

pwede mo na tangalin yung voltage regulator. most H-bridges have separate voltages (Vdd and Vmotor). much like the L293d or any other h-bridges.

but minsan kailangan mo nang (buck) regulation like yung supply mo is 12 volts. then 5 volts yung motor. the L7805 can withstand really tough abuse. but PUT A HUGE HEATSINK! you want the heat out as soon as possible. walang problem yun kasi stall current is very small.

another thing is maglagay ka nang current regulation mo sa h-bridge.

ok po thanks sir martin.

im thinking. the other way around po, to avoid heating the regulator, is it possible to make a parallel of 2 L7805 sir? (so they would add their supply currents)

ok, i'm off to test the heat sink approach. ty sir

[kenshee]

agree

pwede siguro dalawang 7805 hehehe

"siguro"? lol

[rdpzycho]

ano ba voltage nung motor? at ano 'yung input voltage mo? pwede kang mag-parallel ng regulators pero kailangan mo maglagay ng resistor or ORing diode. at any one time, isa lang talaga ang nagbibigay ng full current, lilipat-lipat lang as the voltage drops from that regulator.

ano 'yung H-bridge mo? pwede kasing wala ng voltage regulation, i-regulate mo lang 'yung maximum current na kayang i-handle nung motor.

[pete]

Voltage regulator IC’s, with 3 pins, from LM7805 and LM7812 series are excellent for usage in voltage regulator circuits. If you need higher currents, up to 3 A, you must add a complementary transistor, T2 in this schematic. In a normal design, in case of a shortcircuit, the power dissipation can be very high. This problem can be solved using the voltage regulator



ito baka makatulong sayo

[kenshee]

if i'm asking too much current sa output, what will happen sa input voltage ku? using a 9V battery - mabilis po bng maubos? hehe

cuz i tested a direct supply sa motor, which is (9V batt then DC motor)
ilang sec lang - i measure the battery, 7.99V nxa.. aun alarmed and worried again bka di mkaabot ng 1 lap e2ng line follower ko.

so, pairing it up with a regulator - will it lessen the consumption po b?

[tiktak]

line follower pala ang application , 4AA energizer kayang kaya 4 laps tapos H-bridge na transistor lang, no need sa regulator sa motor part, tapos separate battery sa MCU/logic circuit

[updated]

agree. or gamit ka rechargAble batt na 2700maH

[rdpzycho]

if i'm asking too much current sa output, what will happen sa input voltage ku? using a 9V battery - mabilis po bng maubos? hehe

cuz i tested a direct supply sa motor, which is (9V batt then DC motor)
ilang sec lang - i measure the battery, 7.99V nxa.. aun alarmed and worried again bka di mkaabot ng 1 lap e2ng line follower ko.

so, pairing it up with a regulator - will it lessen the consumption po b?

kung ang aim mo pababain ang consumption, hihina rin torque ng motor. go for other batteries. and mas magandang gumamit ng PWM control para mas tipid sa battery.

[kenshee]

line follower pala ang application , 4AA energizer kayang kaya 4 laps tapos H-bridge na transistor lang, no need sa regulator sa motor part, tapos separate battery sa MCU/logic circuit

Woah, gnun lang pla un? tpos lgay nlang agad ng 7805 pra sa MCU.
im planning the h-bridge plang.. I guess i know na what to do starting from here.

Thank you

[tiktak]

yup ganun lang yun

[kenshee]

kung ang aim mo pababain ang consumption, hihina rin torque ng motor. go for other batteries. and mas magandang gumamit ng PWM control para mas tipid sa battery.

Thanks sir, i'll experiment with PWM later.This is my 1st line follower pa po kc. so i'll start with the basics muna

[kenshee]

yup ganun lang yun

hehe lamat pogi point 4 u idol

[kenshee]

agree. or gamit ka rechargAble batt na 2700maH

bibili ako ng rechargable mamaya! haha

[tiktak]

salamat sa points, you may also want to check my blog may na post ako doon na line follower with PWM pero using discrete components lang no MCU

[kenshee]

Bookmarked! thanks

[glutnix_neo]

isa pang dapat tandaan, dapat may heatsink ang 78xx mo if you want to draw upto its rated output.