Realay hold time

Discussion in 'General Electronics Chat' started by Sarfaraz47, Aug 10, 2014.

  1. Sarfaraz47

    Thread Starter New Member

    Jun 10, 2014
    5
    0
    how many hold time take a relay to switch on and off?
     
  2. crutschow

    Expert

    Mar 14, 2008
    13,055
    3,245
    Hold time? :confused: If you talking about the operate and release time, it depends upon the size of the relay. It's usually in the tens of milliseconds range. If you look at the datasheet for a specific relay, it will tell you that information.
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,566
    2,379
    Depends on the armature inertia of the relay.
    Max.
     
  4. ian field

    Distinguished Member

    Oct 27, 2012
    4,415
    784
    If you need a fast release time, a simple back emf protection diode across the coil won't do, when the field collapses producing a back emf - which is shunted by the diode, that causes current to continue to flow in the coil longer than would happen without the protection diode. This delays the release.

    You need 2 emf protection diodes - one of them a zener, with the zener oriented to clamp the back emf, its forward voltage will prevent coil energising, so you have to put an ordinary diode in inverse series to prevent that problem.
     
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