a switch based on power consumption?

[icydash]

Hi! This is my first post on the threads, and I'm kind of new to electronics, so all help would be appreciated.

I'm trying to design a circuit that connects between a battery and a load. When there is less than 1W being drawn from the battery, nothing happens. However, when the battery exceeds the .5A limit, the circuit cuts off power to the load and turns on a red LED.

Kind of like a circuit-breaker basically.

Does this look like it would work (modified for .5A): **broken link removed**


Thanks!

 

[Brevor]

Google "electronic circuit breaker schematic" You will get lots of hits.
The discover circuits website is usually pretty good to look for things.

 

[MikeMl]

Another idea. Look at the data sheet for the ZXCT1009 and similar "current-monitor" ICs. I am using one of these to detect when the charging current to a lead-acid battery in my RV drops below 0.25A so that the charging voltage is reduced to the float voltage automatically.

 

[icydash]

Ok will do, thanks for the suggestions guys.