Deactivate Heater while monitoring thermostat status (120VAC version)

Discussion in 'Analog & Mixed-Signal Design' started by Mustang1965, May 2, 2017.

  1. Mustang1965

    Thread Starter Member

    Feb 20, 2013
    15
    0
    OK.... you all did a great job with approving my last circuit for a 12VDC version of this request, but after getting my hands on the actual schematic I found that I was misinformed as to the source voltage of the RV's Refrigerator's heater, it is actually 120VAC. So upon looking at the specs the heater draws 450 watts (3.7 Amps on AC). These fridges are now installed in RV's as an option and are powered off of a 1000 watt inverter connected to the battery(s). When connected to shore power this is not an issue, but if you are dry-camping (no shore power) and the defrost heater kicks in, it hits the battery(s) for 37+ amps. The heater runs for 24 minutes each request about 2 or 3x a day. Needless to say the battery(s) will drain very rapidly. The switch part is not an issue as it will disconnect the heaters supply voltage, nor is the POWER "ON" LED (A), but it is trying to add a LED (B) to indicate if the thermostat is open or closed while the heater is disconnected.

    The DC version would have worked out OK, but now that the circuit is actually powered by AC, I am thinking that the same wiring will work, because it has a current limiting resistor and diode(s) enclosed in the LED housing. The Granger 120VAC led statistics states it is 4.4mA. See the diagram attached.

    Original Post with 12VDC circuit:
    https://forum.allaboutcircuits.com/...er-while-monitoring-thermostat-status.134790/

    Thanks and Your thoughts again,

    Don
     
  2. Mustang1965

    Thread Starter Member

    Feb 20, 2013
    15
    0
    Sorry I forgot to add the 120VAC LED that will be used.
     
  3. #12

    Expert

    Nov 30, 2010
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  4. Mustang1965

    Thread Starter Member

    Feb 20, 2013
    15
    0
    Thanks #12, I never thought of the Neon indicator lights. Low power also. Will defiantly keep them in mind for future projects. Unfortunately, I have already ordered the 120VAC LEDs. I guess my question is still will the 120VAC compatible LEDs work, and not cause any issues. I know the takes only 4.4mA so I am assuming (hate that word) there has to be a current limiting resister inside the LED circuit. I just do not want to cook anything.

    Thanks
    Don
     
  5. #12

    Expert

    Nov 30, 2010
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    Component level LEDs in the 4ma to 20 ma range never require as much as 6 volts, so you have to believe that an LED assembly rated for 120 volts has an internal current limiter.
     
    Mustang1965 likes this.
  6. Mustang1965

    Thread Starter Member

    Feb 20, 2013
    15
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    Thanks...

    You are a Florida member... I am down the road a piece in the Clearwater area.

    Thanks

    Don
     
  7. Mustang1965

    Thread Starter Member

    Feb 20, 2013
    15
    0
     
  8. Mustang1965

    Thread Starter Member

    Feb 20, 2013
    15
    0
    #12
    I just noticed that I did not respond to your suggestion. It worked perfectly. it is never too late to say Thank you!!!
    Thanks
    Don
     
  9. MaxHeadRoom

    Expert

    Jul 18, 2013
    15,675
    4,565
    @#12 hasn't been around since July, not sure why, hopefully nothing serious.
    Max.
     
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