Computers are routinely used to control experiments in modern science laboratories. This should be reflected in laboratories in an educational setting. There is a mismatch between the power that can be delivered by a computer interfacing card or a TTL logic circuit and that required by many practical pieces of laboratory equipment. One common way of avoiding this problem is to connect only low power devices such as LEDs and buzzers to circuits boards containing logic chips. This allows the students to learn the principles of control systems but fails to provide the satisfaction of seeing something "real" under logic or computer control. This paper describes two easily built interfacing devices which allow the user to control mains or high current 12 V devices with low power logic chips. An example of how this system may be used to model thermal regulation in mammals is presented. (Contains 10 figures and 1 footnote.)