Help finding a relay for a project

Discussion in 'The Projects Forum' started by joshv, Mar 31, 2015.

  1. joshv

    Thread Starter New Member

    Mar 31, 2015
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    I really need some help with a home automation project. I am looking for a relay to fulfill the following requirements and need some recommendations. I have searched all over and I must be using the wrong terminology for this relay, because I can't find what I am looking for.

    I need to use a dry contact closure to activate the relay (input). I have taken measurements from the source and it is truly dry contact, not low voltage. I have seen suggestions that require me to add a voltage source to input and I'd like to avoid this because I am not confident that the source can handle the additional voltage.

    On the output side, I would prefer SPST Type C (that is, both NO and NA options - if I am using terminology correctly). But a NO (type A I think) would suffice if type C is not possible given the input requirements. I am controlling 12V DC load, but would be happy if it could handle 5V DC as well for future use.

    Price needs to be sub $20 each as I need 6 of these relays.

    As far as form-factor, I am wiring this up to home security type devices (16ga wire in most cases) - so something that is either pre-wired or has a plug in option might be best. But I can work with anything that I can solder to or use crimped wire connectors, etc. Price and function are more important than form to me in this case.

    TIA if anyone has ideas!
    -Josh
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    What kind of current/voltage are you working with? Resistive/Inductive load?
    Dry contact usually implies not switching the primary load directly.
    From what you have posted, the demands do not seem that high?
    Max.
     
  3. joshv

    Thread Starter New Member

    Mar 31, 2015
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    The dry contact sources are things like motion sensors, while they are 12V DC devices, their output is just a dry contact closure. I am trying to close a 12V DC circuit to turn on another security related device - this device uses 12V DC to trigger with very low amps (resistive). My entire circuit is running on a 4W 12V power supply, it is driving dozens of devices.
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Then it would seem that the motion sensors could drive directly?
    A circuit may give a better idea!
    Max.
     
  5. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    is it to switch a 12volts supply for a home security alarm, ?
     
  6. joshv

    Thread Starter New Member

    Mar 31, 2015
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    I am not an Electrical engineer so drawing a circuit, accurately, is a bit out of my league - I'd probably do something misleading, but I can take a stab at it if that would really help.

    How would I use the motion sensor dry contact to drive directly? All I can think of is to introduce 12V into the dry contact circuit? I would be concerned that whatever mechanism they are using in the motion sensor to close the dry contact couldn't handle the current. I'll try to find specs on the sensors and see if they give any help.
     
  7. joshv

    Thread Starter New Member

    Mar 31, 2015
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    My source of power in the circuit is presently a 12V DC security system. If you want to know the entire project, I am actually replacing my panel completely. I am using combinations of wired security system parts, Insteon (RF/powerline automation products), and Indigo (MAC based automation software) to write a security panel. Insteon has dry contact I/O modules so that I can use to get the status of the sensors into Indigo. The need for the relays requested in this post is to create an emergency backup system. In the case of power failure (yes I am using a UPS, but it to will die after about an hour), I am planning on driving the motion, glass break, and door sensors off a 12V battery based system (actually I am replacing the security panel completely with a battery-backed power supply designed for security cameras, but same difference) and will use the relays to trigger a 12V security cell-network uplink that needs a momentary 12V DC signal to activate and then it calls the monitoring company.

    Let me know if you want more details.
     
  8. joshv

    Thread Starter New Member

    Mar 31, 2015
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    I would also like to add a relay (would not be the same relay as above) into the circuit that prevents multiple triggers during a time window. For example, the sensors may trigger multiple times, but I really only want the cell uplink to actually activate once per hour to avoid spamming the monitoring center. So I am thinking I'd add one last relay into the design, just before the cell uplink, that has a one hour delay after momentary activation (if I could find such a thing). This relay can trigger with 12V DC (because it will use the output of the sensor relay I am looking for above) and should be Type C or A. Any thoughts on this one would be great as well.
     
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