Transformer tap switching circuit? help please?

[AmmoJammo]

Does anyone know of a simple circuit to trigger a 12volt relay, with the output voltage of an adjustable supply reaches a preset voltage.

Basically, I have a centre tapped 9+9 volt transformer, and wish to use the first tap when the output voltage is below ~10volts, and switch to both taps in series above this.

Thanks!

[madires]

A simple comparator circuit will do the job, e.g. LM311.

[Jon86]

Yep, comparator connected to a relay. Just setup a divider on one input of the comparator and connect the other to the output.

[AmmoJammo]

I dont suppose anyone would know of any basic applications circuit diagrams?

[madires]

I dont suppose anyone would know of any basic applications circuit diagrams?

You should train your google fu :-)
- http://www.physics.unlv.edu/~bill/PHYS483/comparators.pdf
- http://home.cogeco.ca/~rpaisley4/Comparators.html