In this work we present the electronics developed into a complete data acquisition system (DAS) for a water Cherenkov detector (WCD) in order to detect cosmic rays with energies from 1 × 1014to 1 × 1016eV. The components are: a high voltage source, a bleeder circuit for each photomultiplier, an electronic unit to amplify, compare, determine coincidence and sum the signals produced by the PMTs, a control circuit to digitalize and store the information corresponding to a valid event and finally an interface to a PC to record data for further analysis. The sampling rate of the system is 40 MHz. © 2003 American Institute of Physics