The construction and evaluation of a simple, low cost, and versatile automatic mercury electrode, working as dropping (DME), hanging (HMDE), or static drop electrode (SMDE), is described. Fast action of the needle valve is obtained with two solenoids, one for opening the valve and the other for closing it. The electrode can be controlled from a microcomputer or with a digital circuit, The performance of this electrode compares favorably with that of commercial ones in terms of area reproducibility (std. dev. < 0.05%), response time of the valve, current profile during potentiostatic extrusion of the drop, and flexibility of use.