OMRON Twin Timer Relay - Battery Driven Fuel Pump

Discussion in 'General Electronics Chat' started by jameseraymond, Oct 25, 2012.

  1. jameseraymond

    Thread Starter New Member

    Oct 25, 2012
    18
    0
    Hi all, I’m new to the forum. I use CNC/PLC forums frequently and figured it was time to join this circuit forum. I need HELP! haha

    I am trying to figure out what twin timer relay I need and if my design will work?
    I’m trying to run a fuel pump off a standard 12v car battery (150Ah or so). I want the pump to turn ON for 20 minutes and off for 60 minutes and keep repeating an infinite amount of times. (While the battery is charging of course)

    I am looking at OMRON’s twin timer “3CR-F8N 12DC”
    http://www.ia.omron.com/product/item/h3cr3009e/index.html
    Basically I would be using the flicker mode with t1=20 minutes ad t2=60 minutes.

    My first concern is that the car battery when charging will be receiving about 10 amps and 14.4V (I think). This means that the relay could see a fluctuation of battery voltage. When the battery is at 20% (should never get that low) it would see 11.58V and when it is 100% it would see 12.6V. When the battery is charging it could see 14.4V.
    The specs on this relay state:
    Rated Supply Voltage: 12 VDC, ripple: 20% max.
    Operating voltage range: 90% to 110% of rated supply voltage.
    Seeing how 14.4V is outside of the rated supply voltage range, will I have an issue with the relay when my battery is charging (which would be ALOT)?

    Also, looking at the pin schematic I had a few questions on how to wire this. FYI: I will only be using one side of contact outputs (right side)
    [​IMG]
    Do I have to connect pins 8 & 7 together with a jumper? Or is this done internally?
    Then I connect my pump (+) to pin 6 (Normally Open) and my pump ground to pin 2?
    When pins 2(-) and 7(+) are connected to the power supply the pump will turn on for t1 (20min) and off for t2 (60min) and repeat? Am I looking at this correctly?

    Anyone have any other ideas or can help me out?
     
  2. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    5,003
    745
    yes link 8-7 and take your pump feed from 6.
     
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