Resistance for a lightbulb circuit

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SUMMARY

The discussion centers on optimizing a lightbulb circuit that activates in darkness using a photoresistor and a relay switch powered by a 9V battery. The current setup drains the battery quickly, lasting only a couple of minutes. To extend the battery life to at least one hour, participants suggest calculating the required current draw to not exceed the battery's capacity of approximately 570mAh. Recommendations include using multiple 9V batteries in parallel to increase runtime.

PREREQUISITES
  • Understanding of basic electronic components, specifically photoresistors and relay switches.
  • Knowledge of battery capacity and current draw calculations.
  • Familiarity with circuit design principles for optimizing power consumption.
  • Experience with connecting batteries in parallel for increased capacity.
NEXT STEPS
  • Research how to calculate current draw for lightbulb circuits.
  • Learn about connecting batteries in parallel to extend circuit runtime.
  • Explore the use of resistors to limit current in electronic circuits.
  • Investigate alternative power sources for longer-lasting lightbulb circuits.
USEFUL FOR

Electronics enthusiasts, hobbyists building light-activated circuits, and anyone looking to optimize battery life in low-power applications.

badaboom
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So I've made a circuit that lights up a light bulb whenever it's dark. I did this using a photoresistor and it is working. However, I have a relay switch with a 9V battery and a 7.2V lightbulb. When it was supposed to turn on, it lasted a couple of minutes and the battery is now dead. Should I place a resistance in that circuit so it lasts at least an hour? If so, what should I add?

Thank you
 
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do you have any more info on the lightbulb? you are putting a little too much current through it, but it sounds like you won't get much improvement in performance as 9V don't have a lot of capacity. The top end ones have ~570mAh of capacity for the disposable kind. This means that if you take 570mA for an hour the battery will be flat. Seeing as you want it to last an hour, this is a nice easy calculation and you need your light to draw 570mA.
Maybe you could try several 9V batteries in parallel, this will up your running time but it sounds like you are going to need a lot of them to run for any significant amount of time...

sam
 

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