Freeze protection

Discussion in 'General Electronics Chat' started by Vince D, Nov 6, 2010.

  1. Vince D

    Thread Starter New Member

    Nov 6, 2010
    I have battery operated irrigation valves that I would like to protect from freezing by providing a pulse on at a temperature, sensed on piping, close to freezing and then pulse off when pipe temperature rises above a set point. Low power consumption is the key. Can be operated by up to 12 volts DC.
    Appreciate any help,
    Last edited: Nov 6, 2010
  2. retched

    AAC Fanatic!

    Dec 5, 2009
    Well, first things first, a temperature sensor.

    The LM83 is a sensor that will sense from freezing to 125deg C.

    That can be used with a comparator, as a switch to turn on and off your device.

    You are gonna have real trouble finding parts that operate reliably at temperatures so low.

    You could use a low current microController that wakes up every few hours and checks the temperature via the LM83. When the temp has fallen to your preset low point, you can pulse what you wish.

    The temp can continually be monitored and the uC can shut off the pulsing when the temperature in the pipe rises to your second pre-set.

    The uC (microController) can then revert to sleep mode to meet your low power requirement.

    BUT, like I said, finding parts that operate that cold will be a challenge.

    The next option would be resistive heating.
    You could use a little enclosure for the circuit that is heated with a few resistors. A second LM83 could regulate the temp of the circuit. This would increase the power consumption of the circuit, but you gotta do what you gotta do.

    If you are using battery power, can a solar panel be used to keep the battery topped off? This would allow you to use more current, and keep everything happy.
  3. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    I think he just needs to get the water to keep flowing a little to stop it from freezing. Something that lets a little water go through every thirty seconds or so. It might be wise to use a temp sensor on a 555 timer as a variable resistance that would give you more pulses per minute as the temp gets lower. As well as one which would turn everything off above freezing.
  4. Vince D

    Thread Starter New Member

    Nov 6, 2010
    I could use a mechanical thermostat with remote bulb and a SPDT contact, but I need a circuit that will send a pulse, for maybe one second, of one polarity for temperature fall, and a reverse polarity pulse for temperature rise.
  5. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    What is the limit for power, other than "low"?

    Is it under 100mA, under 500mA?

    What will the power source be for this, as batteries really get weak below around 50° F
  6. someonesdad

    Senior Member

    Jul 7, 2009
    Nobody irrigates in freezing weather -- why don't you just blow the lines out until spring?

    I guess a frozen valve isn't too bad, as they are usually accessible and easy to fix. However, if you ever have to dig up a sprinkler line that froze over winter and replace it, you'll swear you'll never again do a poor job of blowing your sprinklers out... :p
  7. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    I was thinking he had the equipment out/active, and some early freeze hit overnight. There were a few nights like this around here, it even hit 32 one night in september. I wouldn't suggest this as a "Year around" solution, but a temporary patch for above ground pipes and hoses. It has little chance of working if the freeze gets very far into the ground.