Blood typing has a vital contribution to the success of life-saving procedures, such as blood transfusions, and it can be critical, especially in emergency situations. For that, in this paper the main principles to the development of a miniaturized, low cost, portable and automatic system to human blood typing, in emergency situations, are presented. In a previous study, the authors validated a general experimental protocol to be applied in the automatic system. Now, the implementation of a specific light source system by using standard Light Emission Diodes (LEDs) was studied. Moreover, the specification of all electronic components to be used in the prototype device was performed.