electronic component to use for a switch?

Question

I would require a switch that works as follows:
The switch would be by default closed with another circuit A, but if the voltage at the pt where the switch is below say 5 volts, it will switch itself to circuit B. The moment circuit A has a voltage above 5V, it would switch it self back from A to B. What type of electronic switch that works as stated? And how do we connect it?

how do we connect a relay if it is to be used as above?

Answer 1

You just need a comparator circuit to monitor the voltage. You need to decide how low the voltage has to be to trip the comparator. This circuit is really very simple.

Then the output of the comparator can go to a relay driver circuit, again an easy circuit to design.

This is simple electronics and you should be able to put this together easily. If this medium allowed pictures I would draw you a schematic.

Answer 2

Get some cheap µprocesser with an A/D converter to measure the voltage(s) and use an output to drive a transistor to pick up a relay. Something like a PIC 12F675 should work fine.

Doug

Answer 3

Now you have defined the problem we can help. You need to find out if the shutter is light sensitized for auto exposure. If it is mechanical, the delay of the photo resistor, may be so great as to set off the light booster after the shutter has closed. It is better if possible, to tap into the supply to the internal flash, and repeat this power via a transistor at the remote flash.

Answer 4

A relay
or
A switching transistor
or
A thyristor

Answer 5

relay

Answer 6

use a relay

Answer 7

you can use transistor to use it as a switch.