How display models in optimum size un three js?

Question

i have this script to show models(converted from obj using python) in three js.

var jsonLoader = new THREE.JSONLoader();
    jsonLoader.load( "/static/android.js", addModelToScene );   

}

function addModelToScene( geometry, materials ) 
{
    var material = new THREE.MeshFaceMaterial( materials );
    android = new THREE.Mesh( geometry, material );
    android.scale.set(1,1,1);
    scene.add( android );

}

this script working fine for some models. But some model are too small. so i need to change android.scale.set(1,1,1); to android.scale.set(10,10,10); to get optimum size. then some models are too big. then i need to change android.scale.set(10,10,10); to android.scale.set(.1,.1.1);. How can i automatically set the size of model in three js