Micro controller for Solar & Emergency Bulb

Thread Starter


Joined Jul 6, 2018
I need some suggestion about micro controller for two of my projects
1) Solar based street light
2) Emergency Bulb

1) Solar based street light- I want to develop a 9W street light which charges the battery during day time and discharges it at night or at the time when there is no light.
The recommendation for corresponding solar panel and battery will also be appreciable.

2) Emergency Bulb- This product should turn on when there is AC light and also charge the Li ion battery inside it. When there is no electricity it should turn on and consume the charge stored in battery.
Recommendation for the battery will be appreciated.

Both the project should have the turn on time for about 10 Hours alt least in one go when operating on battery.

Himanshu Dwivedi


Joined Sep 9, 2010
so any other recommendation from your side
Batteries are specified in amp•hrs of capacity. That's not a measure of stored energy, as is watt•hrs. To estimate watt•hrs from amp•hours, you have to use the nominal voltage of the battery. This only works because a battery voltage is fairly stable. By contrast, the storage capacity of a capacitor would be senseless to quote in amp•hours since the voltage is constantly dropping during discharge.

So anyway if you use a 12V battery and want 90W•hr, you need a battery capacity of 90W•hr/12V = 7.5A•hr.

And you need a solar panel that can supply at least 90W•hrs in a day. That 'day' has to include the shortest days of the year and the worst weather, at the same time. It's your judgement how well you can tolerate failure of the light. If it must never fail, you need a massively (4X?) over-sized panel and should size the battery to allow for aging and to ensure performance in frigid weather. I'd go at least double, to 15 A•hr. No one can answer these questions for you without the specifications for sunlight where you live, your ability to tolerate blackouts, and all the other specifications.

Many solar energy projects we see in this forum have unrealistic expectations and become uninteresting once the full reality is considered. I'm not trying to discourage you, just arm you with the facts so you can plan your path.

Oh, and I wouldn't even bother building your own controller. You can buy full-featured solar controllers off the shelf that would be fine for your application. It'll tend the battery, power the load and so on and it'll probably cost less than anything you could build yourself.

-live wire-

Joined Dec 22, 2017
You can easily get an SLA with more than enough capacity for about $30.
If you discharge it to 50% SoC you should get a few hundred charge/discharge cycles at least.

I recommend a hand alternator instead of solar. Have someone you don't like turn the generator all day and night to get decent power. Those types of generators are far less expensive than an equivalent solar panel. ;) Actually, think about the size solar panel you need. 1W is about $1, so they can get pretty expensive.