Capacitor Discharge Unit Circuit Diagram

A capacitive discharge ignition unit also called the cdi unit is the modern alternative for the age old contact breakers which were quite crude with their functions and reliability.

Capacitor discharge unit circuit diagram.

A capacitor discharge ignition works by passing an electrical current over a capacitor. This type of ignition builds up a charge quickly. It then shows how to c. The effect of a capacitor is known as capacitance while some capacitance exists between any two electrical conductors in proximity in a circuit a capacitor is a component designed to add capacitance to a circuit the capacitor was originally known as a condenser.

The led can be placed on the main control panel of the layout to indicate the condition of the unit. See the completed wiring diagram for the connections to the capacitor discharge unit. Referring to the above capacitor discharge ignition circuit diagram we see a simple configuration consisting of a few diodes resistors a scr and a single high voltage capacitor. The modern cdi is an electronic version of the contact breaker which uses sophisticated electronic parts for generating the required arching across the spark plug.

However 12 volts dc provides too little power to move the points reliably. Capacitor discharge unit cdu1c cdu2c cdu4c. This video shows how to connect a capacitor discharge unit up to a power supply and a set of points using a switch to set the points. Capacitor discharge ignition cdi or thyristor ignition is a type of automotive electronic ignition system which is widely used in outboard motors motorcycles lawn mowers chainsaws small engines turbine powered aircraft and some cars it was originally developed to overcome the long charging times associated with high inductance coils used in inductive discharge ignition idi systems.

Too high a voltage can also be a problem as the point motor may move the point over with so much force the point tiebar is shaken to bits. The input to the cdi unit is derived from two sources of the alternator. Cdi circuit using an scr a few resistors and diodes. The capacitor discharge unit can also be powered with dc.

When a point is operated the led wilt extinguish then come back on as the capacitor charges. A cdi ignition starts by generating a charge and storing it up before sending it out to the spark plug in order to ignite the engine. Should a solenoid be left in circuit by the switch being held for a long period the current flowing through the coil after the initial surge will be less than 0 05a so it will not damage to the coil.