Chapter 4. WIRING
4-10 External Switch Input Connection
●
Internal circuit diagram of the DCP551 connecting external switch input
HANDLING PRECAUTIONS
• The inputs of the DCP551 unit are provided with a built-in power supply (open
voltage type, 8.5V DC). Always use no-voltage contacts externally.
• For the no-voltage contacts, use gold contacts or other relays that switch on
small currents. Other types of relay contacts may not switch. Use contacts
that have ample margin over the minimum switching capacity with respect to
the current and open voltage ratings of contacts provided on the DCP551.
• If using semiconductors (open collectors, etc.) as no-voltage contacts, use
one that maintains a potential of no more than 2V across the contacts when
actuated, and a leakage current of no more than 0.1mA when shut off.
• Common terminals (12) and (41) of the external switch input are connected
internally.
8.5Vdc
8.5Vdc
Internal
circuit
4-12
