hay wats up ! i have to charge a battery frm solar energy n if the battery is not charged fully by it at night then i have to charge the remaining part of it frm main AC power supply at night............any ideas for this kind of designing a cct.........any ideas abt logic cct
Diode.
Diode. and spelling/grammar lessons
Diode.
Only if you turn the AC charger off during the day.
Tam
A properly selected AC charger will output slightly less voltage than the solr panel. However, on further reflection, I notice that I erred. I should have said "diodes".
The two diode approach will still only work if the solar panel output is more than the AC charger at *all* times, and under load. Consider a dark cloud overhead, or early morning and late afternoon when the solar panels might be charging at a low rate. Also, if the AC charger voltage is turned way down, it won't be able to charge the battery overnight.
Tam
Agreed. A better approach is probably to divide the problem into two parts - isolation between the charging sources, and control of which source is actually enabled.
What I'd probably do, in a case like this, is to use a pair of Schottky diodes to provide the isolation, and have an entirely separate circuit to switch the AC charger on and off. The simplest method would be to just use an ordinary appliance timer, with the "on" and "off" cams set to switch the AC charger on well after local sunset and well before local dawn.
Another approach would be to have an independent light-level sensor do the switching... the sort of simple photoelectric sensor that turns on porch or security lights at dusk and turns them off at dawn.
If you want to get fancier, turn the power to the charger on only if [1] It's night-time (by the clock or by darkness) and [2] the battery's terminal voltage is low enough to indicate that it's not fully charged. Could be tricky to set the treshold voltage properly, though, and you'd need to make sure that the circuit doesn't turn on the charger and then immediately turn it right back off again!
I would _not_ try to do the switching based on the voltage coming down from the solar panels, because this voltage is likely to drop sharply when the panels are connected to the battery... this would be another way in which the charger might start switching on and off repeatedly.
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inal voltage is low enough to indicate that it's not
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thanks for replying and understanding my problem . actually i m having the option of which you referred to as getting fancier. when it gets dark then the systenm should check the battery level, if it is fully charged then tere is no need of getting it charged from the main supply, in case the battery is not fully charged then its remaining part should b charged from main supply. this in the complete problem if you have any idea of logic circuit which colud comply that or if u have any circuit diagram to solve the problem i will b very thankful to u.
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