need circuit to switch from burned out bulb to spare,with led indicati 1

[k1366758]

circuit switch must be instantanous, bulbs 100 watt,24 VAC halogen.Circuit to operate from 24VAC.
remote led to indicate burned out bulb so bulb can be replaced.
circuit to go back to normal when bulb is replaced, high reliability
small pkg, inexpensive,

 

[nbucska]

Can you tell me more about the requirements ? <nbucska@pcperipherals.com>

 

[dpc]

You should be able to sense the current to the primary lamp using small toroidal current transformer. No current would indicate a burned out lamp. You could use the loss of current to transfer to the backup lamp using a relay. The LED would just sense that the backup lamp was energized. You will need a short time delay on startup.

Transfer won't be quite instantaneous, but could be quite fast - a few milliseconds.