mobile regulated supply

[aviv6371]

hi,

i want to build a 5v regulated source based on 7805. i have 9v battery and 9v wall transformer 200ma. i would like to combine them together because i may use them both ( i want to mobile the unit ). can i only connect diode at the output of each source to prevent interference from the other source and than connect fileter capacitor ( in addition to that in the transformer ) in parallel to the regulator ??
the supply is for digital circuit based on pic and lcd.

thanx in advance,
avi.

 

[IanP]

Yeah, diodes as switches will work fine .. see the attached example ..

Regards,
IanP

 

[VSMVDD]

use a solar cell 17.5v 1.5 watts

and a sealed lead acid battery

a 3.3amph cell will give 3.3 amp for 1 hr
a solar cell will yield in poor light from a 17.5 v panel 12v @1watt or so

as long as you draw ~ 1 watt
the battery will act as a float

you want portable

be green and use the light {not nessisary is direct sunlight most solar cells run fine on poor light also }

your prob better using two 6v cells
and a 5.1 v zener

regulators use ~2-15ma
to operate

a waist of energy for sure

i got 5 X 17.5 v 1.5 watt solar panels

and i run my whole house on 12v lights

FREE !!!!

and its payed for its self in one bill period

using pwm charging circuit

to maximise solar cell output by pcwm charging

 

[aviv6371]

thanx for the reply you both....
ian thanx for the backup . i build the ciruit and its working fine.
the battery diode wo'nt let current from the transformer to flow and the transformer diode w'ont let current from the battery to disturb its work and they can both work together though its not recomended. ( we have to think about this opion when designing).

avi.