Relay for a large rolling door

Discussion in 'The Projects Forum' started by bumclouds, Sep 5, 2012.

  1. bumclouds

    Thread Starter Active Member

    May 18, 2008
    Hi everyone,

    I'm intending on embarking on a small project to control a rolling door in my office using a Beagle Board (or perhaps an Arduino board).

    I am thinking about using Alberto Panu's "Ardupower" for this project (scroll down a little for the schematic).

    I have some questions:
    1) On his list of components he has: 6 x relays 12 volt 10 ampere. What does "12 volt 10 ampere" mean? Is it the threshold at which the contacts "pull" together? Is it the maximum/rated voltage you can put across the coil?
    2) I can see that he has a 560Ω resistor in series with an LED. Is this included inside the relay, or is something you have to add yourself?
    3) I read somewhere that an arc will form when the contacts come together and when they come apart. I would imagine this would be a problem for large motors such as the one I'm using.
  2. bigjohnson

    New Member

    Sep 5, 2012
    here the replies:

    1. 12 volts is the relays coil voltage, 10 ampere is the maximum switch contact current (at 220 volt main supply).
    2. The led and the resistance are separate from relays, see Ardupower photos in the page.
    3. In the project schematics there are 0,047 micro farad capacitors on the relay contacts to stop arcs.

    Alberto (the Ardupower maker)
  3. BMorse

    Senior Member

    Sep 26, 2009

    To answer your questions:
    1) From what I can see from his circuit, those relays run off of 12 volts DC (they get actuated via the ULN2003 relay driver which is connected to 12 volts), the contacts must be rated at 10 amps (I doubt the relays will need that much current to actuate)..

    2) No, from the pictures on the site you linked to, the LED's are added to the circuit.... (The RED bulbs sticking up in front of each relay).

    3) Yes, the arcing will shorten the contact life of the relay, you will need a snubber circuit (If using an inductive motor) parallel to the contacts driving the motor (which is already in place by original author).

    What is the power/rating of the motor you are planning on using??
  4. BMorse

    Senior Member

    Sep 26, 2009
    Welcome to the forum Alberto....:)
  5. crutschow


    Mar 14, 2008
    You might consider using solid-state relays. They are more expensive but they require very low control current (can generally be driven directly from a microprocessor), and they don't have contacts to wear or pit.