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Adding Capacitors to a circuit board Answered

I have a circuit board I made, very simple, you connect a 9 volt battery to it, power opens a relay, and turns on a green led, there is a zener diode (6.1v maybe, cant remember) for a flashing red led, the led flashes if the voltage drops below the voltage of the zener diode. 

My questions are;
1.) If I add capacitors to this, will it extend battery life (about 4 hours right now)
2.) If 1 is yes, what kind of capacitor will I use? I work with capacitors every day, but bigger ones like 5mf 330V, 35mf 440v, dont know much about the smaller ones.
3.) If you can make something better, please let me know, it needs a power light, a low battery light, and a relay (SPDT, 9 volt battery is on the coils to keep relay open). Ideally I would like this board to have a long battery life. 

Any help would be great.


It has to have a relay? If all you want is to flash an LED there are much better ways to go about it. The coil in the relay is your main source of power use. using a 555 timer would be better. You can do a search and find a simple battery indicator circuit online.

No a capacitor isn't going to give you longer battery life.

Yes, it has to be a relay, I figured that was the problem, when the battery dies the relay closes an powers another circuit with a different power source. Thanks for the reply.

Whats the power source of the other circuit? I'm sure you can find a better way to deal with this that is more efficient.

Other power source is a battery as well, I think I will switch to larger batteries, like 8.4 volt 5000 mah batteries. I was just curious if a capacitor would make it any more efficient.

No capacitors are typically used to help filter out any noise from the power source among other things but it doesn't improve efficiency. The more components you add the more power is being used. Though it's typically very minimal. Every component adds resistance causing you to loose a bit of the power, typically through heat. So if you want better efficiency then use more efficient parts and try to remove any unnecessary components or features.

Have you looked into digital switches/relays that would not have a coil?

A capacitor, in line, in a DC circuit would block voltage and one in parallel would supply the voltage for a few seconds after the batter died...but that is about all.

No i have not but i will look into that