Voltage Comparator

Discussion in 'The Projects Forum' started by ruairihev, Oct 28, 2008.

  1. ruairihev

    Thread Starter New Member

    Oct 28, 2008
    I have a voltage comparator circuit that I am having trouble with. I want to use it to turn on relays at certain voltages. I have a 24V wind turbine that charges a battery bank. When the batteries are full I want the relays to switch on a diversion load. The trouble I am having is that the relays are switching on when the voltage reaches say 26V but they don't shut off again when the voltage falls below 26V. I have a feeling that it has something to do with the 1000uF capacitors acting as time delays but I'm not sure. I want one relay to turn on at 26V and then the next one to turn on at 28V. Maybe I have the wrong resistances and capacitance choosen to achieve this? The op-amp is a LM1458. What does the feedback do for this circuit, the 500k potentiometer has only two pins connected, is this used for hysterises or gain or something else? Please can someone suggest correct values for the components to make this circuit work or point out why it doesn't work. The voltage rise in the battery is relatively slow, I think I read that comparator circuits sometimes don't work well if the change in voltage is slow.

  2. mik3

    Senior Member

    Feb 4, 2008