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where to find a pulse relay

Discussion in 'Robotics & Mechatronics' started by igeorge, Apr 14, 2015.

  1. igeorge

    igeorge New Member

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    I have a thermostat project which run from 2AA batteries
    The microprocessor has a minimum consumption current
    In fact the whole project run in just 1-2 miliamps.
    The big issue is the output of thermostat.
    Most thermostats, to conserve power , and change the battery maybe once a year , use latching relays.
    2 coils take too pins from micro
    1 coil is complicated to drive
    I heard about pulse relays. One pulse = ON; take the power out and still ON, like a latching relay. Next pulse, on the same line, turn it OFF.
    I found circuits to drive 1 coil latching relays, but most of them use capacitors, which of course will drain my battery
    I need a suggestion of a manufacturer for this PULSE relays.
    Contacts 2 A, coil 5-12 VDC
    Thanks
     
  2. MikeMl

    MikeMl Well-Known Member Most Helpful Member

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    Do you require the isolation that a relay provides? If isolation is not an issue, and you are switching DC or AC, modern NFETs will switch 2A of load current with almost zero power into their gate(s) circuit and only requires one port pin to control it.
     
    Last edited: Apr 14, 2015
  3. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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    Magnetic Reed relays have an effective current ratio from coil to contact ranging from 200 to 1000 but very ! expensive above 300 depending on voltage ratings.
    Latching magnetic relays are much less ~<=100 using 2 coils

    Toggle Relays would have no feedback with one connection and I have not seen these.

    Your best bet is to use a MOSFET switch and if source is 24Vac ( typ) then use a full diode bridge and cap between source and MOSFET.
     
  4. dave

    Dave New Member

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  5. MikeMl

    MikeMl Well-Known Member Most Helpful Member

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    But a reed relay requires constant power to the coil, which would kill his battery. A magnet-biased reed relay requires no standby power, but requires an H-Bridge (likely two port pins) to pulse it...
     
  6. granddad

    granddad Active Member

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  7. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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  8. MikeMl

    MikeMl Well-Known Member Most Helpful Member

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  9. granddad

    granddad Active Member

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    Not so ... MikeMI To quote the article .. what is described is a single coil latching relay.
    Battery life is good since the load is only 400uA –there is no relay coil current in either the On or Off states.
     
  10. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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    also too power hungry
    Bipolar single coil relay takes 300mW @3V http://www.kemet.com/Lists/ProductCatalog/Attachments/524/KEM_R7002_EC2_EE2.pdf
    or https://www.components.omron.com/co...E03885359085257201007DD68A/$file/G6S_0514.pdf

    But MOSFET and AC bridge still a better deal.

    But you must state load explicitly in terms of AC DC resistive or inductive , voltage & current.
     

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