Latching relay for generator start

Discussion in 'The Projects Forum' started by kd7ura, May 8, 2010.

  1. kd7ura

    Thread Starter New Member

    Apr 12, 2010
    27
    1
    Well here goes again , the other circuits were getting to complicated for me to get done quickly
    I ordered a latching relay from digikey part# 255-1872-ND
    9.6 max VDC 7.5ma single coil latching.
    i have on hand zener diods 1n4724 through 1n4744 3.3V to 18V
    ive got a bunch of resistors and a mixture of other parts still on circuit boards from broken printers and radios/CBs.
    i want to turn this relay on at 12VDC and off at 14 VDC.
    as simple as a circuit as possible for fast assembly.
    once batt is down to 12 turn on relay till 14 volt then off or reset and wait till batt low repeat.
    the guy im making this for is going into the hospital on friday and his wife cant go out to turn the generator on.
    they are off grid and she will empty the batteries in a day with out the generator to keep up. he wanted somthing with lights and looks fancy but now he just needs to get the gen to start while he is in the hospital.
    i have a radio shack in town for any other parts that i dont have.
    i can put together a dead bug board to get it going and neaten it up later.
    i just dont have the skills to put a design together.
     
  2. kd7ura

    Thread Starter New Member

    Apr 12, 2010
    27
    1
    got a basic lay out i think we can work with here its a charge monitor
    with a relay that disconects the bat when low, how would we modify it so it could just trip the relay to closed till the bats are charged then trip to open.
     
  3. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    You will need a comparator IC to monitor the voltage of the battery and control the relay.
     
  4. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    You can use zeners for a rudimentary way to conduct at certain voltages.

    If the level get over 14v (using a zener) it will conduct and can open a NC 12v relay.
    For the lower level, it could be a little harder.

    when the power gets below that 14v point, the relay will close.

    But that would lead to a very active generator.
     
  5. kd7ura

    Thread Starter New Member

    Apr 12, 2010
    27
    1
    ive looked at an mc34161 voltage monitor how would i implement it at the voltages required of 12vdc on and 14vdc off for the relay?
    how would it be setup so that it didnt come back on when the voltage started droping back to say 12.5?
    i can plumb and wire a house but for the most part i get lost in electronics circuits my brain starts running like a cdrom trying to boot a dvdrom disk. been trying and reading i under stand how aech part works, but somthing is missing for me i get lost in the maze.:(
     
  6. kd7ura

    Thread Starter New Member

    Apr 12, 2010
    27
    1
    :confused:ive got a pdf on the mc34161 i was looking at figure 17 on page 8 in the pdf and though it was the best way to go with a non latching relay.
    then im told tu use a latching relay.
    this relay has a + or - trigger input next to the power inputs.
    and will trigger at 12V 1.2ma
    i thought i could tie the two together for somthing simple but havent gotten much help? will these work and how do i tie them together?
     
    Last edited: May 8, 2010
  7. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    A relay isn't going to take much juice. So it will be easier to use a non-latching type.

    The latching types need a pulse to be sent or polarity reversed to change states.

    Lemme see.

    The max8211 can detect a low battery voltage that you set.
    And max8212 detects over voltage that you set.

    Do you feel comfortable working with these?
     
    Last edited: May 8, 2010
  8. kd7ura

    Thread Starter New Member

    Apr 12, 2010
    27
    1
    i can follow a schematic and solder very well ive put boards for cnc controlers together for lathes before and test as i go every thing went well then so i figure i can do it again. my math skills are sadly lacking brain injury as a teen you put latters and numbers together and my brain freezes up, i can picture the flow of just about any thing, i designed a valve and patent about 11 years ago im verry sKilled in machining/manufacturing but math with alphabet soup thrown in and ill look like an idiot. im no einstein with the numbers.
     
  9. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    Ok, see if you can get them in time for when you need it by. If not, we will find another way.

    Maybe someone has a simple idea that I am not thinking of.
     
  10. kd7ura

    Thread Starter New Member

    Apr 12, 2010
    27
    1
    ive just looked at the max chips they ar similar to the mc34161,
    the graphig on page 8 fig 17 of the pdf posted above shows the "led" on sequence or threshhold?
    sgt wookie help a guy on another post setup for an 8 volt monitor with the mc34161
    i figured it would do the same for the relay as an led,, just dont know how to tie them together looking at the picture the led output is tied to pins 5and6 i dont know if its a negitive or positive would it be a grnd since the other end of the led is tied to the V source?
    would i tie pins 5/6 to the neg Trigger on the relay board?
    on the relay board the trigger can be bypassed by adding a jumper from +input to + trigger or from -input to- trigger but not both
     
  11. kd7ura

    Thread Starter New Member

    Apr 12, 2010
    27
    1
    i have to leave the coffe shop they close here will be back 11 am til close sunday thanlk you thank you
     
  12. kd7ura

    Thread Starter New Member

    Apr 12, 2010
    27
    1
    i spent a bit this morning copying the relay board and tied the mc34161 in on the rigt side i dont know what resisters to use with the bridges at pin 2 and 3 and if id need a resistor at pins 5/6 to the -trigger on the relay board its -12V 1.2ma would this setup work.
    pin 2 on the mc34161 is for the low voltage setting and pin 3 is the high setting . if i can still read i think this would work and act like the led in the graphic on page 8 of the pdf posted above
     
  13. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Yeow! That schematic is SCARY! :eek:

    Any chance you can avoid running wires diagonally?

    Oh, you don't need junctions where wires connect to pins - only if two or more wires join.

    Try using Erc and see what Eagle complains about.

    You should have values for all of your components.
     
  14. kd7ura

    Thread Starter New Member

    Apr 12, 2010
    27
    1
    on the pdf above i copied the board part layout and laid the wires as they apeared on the circuit board underneath to keep from confusing my self.
    im not an expert just trying to get started. the resistor bridges on the mc34161 have values now 120K and 14.2K for pin 2 and 120k and 11.2 k for pin 3, i think they will work?
    added them to new pdf here i built the circuit in a sim it kinda worked
    i havnt the money yet to order the mc34161 to try it on a variable power supply i got sick with the food poison friends will kill you if you trust there cooking you know.
     
  15. kd7ura

    Thread Starter New Member

    Apr 12, 2010
    27
    1
    How would i tie these together to get them to work for what i need?
     
Loading...