Logic latch circuits for relay drivers?

Collapse
X
 
  • Time
  • Show
Clear All
new posts
  • Brian C
    Senior Member
    • Dec 2006
    • 156

    #21
    Re: Logic latch circuits for relay drivers?

    Please add "Free Wheeling Diode" across the relay's coil for protection. 1N4148 would be just fine.

    Comment

    • starfury1
      Badcaps Legend
      • May 2006
      • 1256

      #22
      Re: Logic latch circuits for relay drivers?

      yes shadow I know what you mean, sounds simple till you start trying to work the logic out With gates and can get complicated.

      just going to post the pdf links on the above circuit Maxxarcade posted for reference.

      74LS374 3-STATE Octal D-Type Transparent latches flip flop HERE

      74LS27 Triple 3-input Positive NOR Gates HERE or HERE


      74LS10 TRIPLE 3-INPUT NAND GATE HERE or HERE


      Since BC550 may be a bit harder to find in the US (2N whatever use to be the main stay) and it may depend on the relay I'll include the pdf for it too.

      BC550 (549~550) NPN SILICON AF SMALL SIGNAL TRANSISTORS HERE


      This should make it a little easier to understand and put it all in one place for you maxxarcade.

      (er yeah take back a little on what I said on the trannie relay thing did show resistor but true no diode)

      cheers
      You step into the Road, and if you don't keep your feet, there is no knowing where you may be swept off to." Bilbo Baggins ...

      Comment

      • starfury1
        Badcaps Legend
        • May 2006
        • 1256

        #23
        Re: Logic latch circuits for relay drivers?

        I think this is the original source page HERE

        Note the "fixed" on it, still looking to see what that means but it is drawn a little different.

        So the original link thread did ask this question would it work as it was drawn? EDIT NO!!!!
        So maybe there is an error in the diagram as posted.

        THERE IS!!!!!

        The 74LS374 on the diagram is showing the outputs as inputs and visa versa with the pin numbers



        So do not follow the Diagram in this thread

        grab the one from the link above.

        Any other errors if the exist I haven't found yet.
        If in doubt refer back to the PDF's

        Cheers
        You step into the Road, and if you don't keep your feet, there is no knowing where you may be swept off to." Bilbo Baggins ...

        Comment

        • Maxxarcade
          Badcaps Veteran
          • Jul 2006
          • 973

          #24
          Re: Logic latch circuits for relay drivers?

          Thanks, I didn't notice that it was backwards. I would have gone to build it and said wtf...

          As for the missing kickback diodes on the relay coils, I would have added some. I work on pinball machines for a living, and I know all too well about inductive kickback

          I'm hoping to dig up my breadboard soon, I think I already have the parts laying around. I'll probably use lighted switches that I'll have to buy, along with some nice matching relays.

          How much current should the relays be rated for? I think I have a whole bunch of 2A relays from a phone system in my parts collection.

          Comment

          • starfury1
            Badcaps Legend
            • May 2006
            • 1256

            #25
            Re: Logic latch circuits for relay drivers?

            well the heaver the better I think and possibly gold contact
            (try the surplus places you might pick up a bargain)
            2A you could try for proto type...(but no guru on relays an audio currents)
            maybe they will be fine. Id try them anyway
            I suppose it depends on if you listen like the Grateful Dead or shopping music

            The circuit does have indicators on it for the relays but light up switches would be a good idea.
            possibly 2 colours so you know whats input and output quickly

            Are you going to use just one setup or two ?

            Iam sure I don't have the ic's needed so I can't build it to have a look at what going on.

            anyway keep us posted

            Cheers
            Last edited by starfury1; 02-03-2008, 06:53 AM.
            You step into the Road, and if you don't keep your feet, there is no knowing where you may be swept off to." Bilbo Baggins ...

            Comment

            • shadow
              Badcaps Veteran
              • Feb 2007
              • 732
              • Australia

              #26
              Re: Logic latch circuits for relay drivers?



              This is the circuit that I have thought of. I know it is a little bit late now, however I could not be bothered drawing a circuit with 8 switches. It is a tedious method for 8 switches. However it is perfect if you want to switch up to about 4 switches.

              The basic logic follows like this:

              The buttons are attached to the clock signal of a Flip-Flop. Every time a button is pressed, the output will be the logic value '1' (this is because the JK flip-flop is setup to output a logic '1' on a clock edge. A D flip-flop can also be used easily). The button attached to one particular flip-flop is attached to all the other flip-flops 'reset' signal through an OR gate (the more switches you have, the more inputs the OR gate needs to have, no OR gate is required if you are switching between two switches). Therefore when a button is pressed, the output of that particular button will be a '1' and all the others will get reset to '0'. If two or more buttons are pressed at the same time, all the buttons are reset to '0'.

              From there you attach the output of the flip-flops to your relay driving circuit or connect it directly to the relay if you are using compatible Solid State Relays.

              The main limitation of the circuit is that when the flip-flops are first powered on, their output's are undefined until a button is pressed. This may potentially cause a problem. The solution is to somehow reset the switches when it first powers on. Or use a different solution.
              Attached Files

              Comment

              Related Topics

              Collapse

              • jm1234
                9V relay temperature 40C
                by jm1234
                Hi, I'm seeing one 9V relay having temperature 40C on its 9V (primary) side. Does that seem right? I switched 2 relays on that board and the temperature was the same (on the same position), so I'm sure it's not a faulty relay. I measured voltage on that relay and it was 9.5V DC, so that looks good. I don't see any other relay on that board having that kind of temperature and they have 9V on them too.
                I thought maybe the transistor that is switching this relay keeps switching on/off, so I also checked for AC and there was almost none: 0.3V using mV range. No steady frequency was shown, but...
                05-09-2024, 03:03 AM
              • edugimeno
                Biomass Boiler not driving cleaner motor relay. ENERTRES BIOMASA BI-650
                by edugimeno
                Hi everyone!
                I have this board that suddenly stopped supplying power to an output that drives an interchanger cleaner motor.
                I checked while the board was in place with all wires attached and there's no AC voltage on the corresponding plug X5
                This X5 is driven by fuse F8 (tested OK) which comes from the second orange relay
                To make sure there are no charcoaled contacts inside the relay, I got a 24VDC power supply and got it ready to manually power up the coil side of these relays.
                I respected the polarity, positive to cathode of protecting diode
                So provided all...
                04-18-2024, 01:15 PM
              • sam_sam_sam
                Mitsubishi CNC switching power supply board dead / relay board bad diode failure
                by sam_sam_sam
                I was working on this CNC machine today found no keyboard functioning no control relay powering on
                The screen powered on and was giving an operation error but the manual was not very clear about what the error exactly was but with a little bit of troubleshooting and finding out that the control relays not powering on and no keyboard functions we narrowed down to this one switching power supply which of course does not have any indicator LED light they are on the keyboard interface/relay controller board

                Found shorted diodes on main controller relays there are 3 of them that...
                01-07-2023, 05:43 PM
              • ohren
                Upgrading a Samsung ue55nu7096u with logic board from an ue55ru7105k -- good idea?
                by ohren
                I hope this is the right forum to post in despite not technically being a repair, but still a question of swapping boards.

                I thought I'd explore the possibility to upgrade an existing working Samsung ue55nu7096u with the logic board (and power board if needed) of a newer model (ue55ru7105k) of the same size and appearance (and resolution). The reason being I'd like the extra inputs of that board including component in, an extra HDMI port and bluetooth. Its panel is broken so I have no use for the board otherwise.

                The models launched in 2018 and 2019 respectively....
                09-08-2023, 05:24 PM
              • korben_dallas
                Will I have a bricked logic board after reflow of the GPU v-core U8900 chip on my Mid-2012 15" Retina Macbook pro?
                by korben_dallas
                Hi everyone! I'm trying to fix my black screen / failed U8900 GPU v-core on my Mid-2012 Macbook Pro 15" Retinaby doing a rework/reflow of the chip (once I determine that's the real issue; but it likely is).

                I've been disabling the GPU in NVRAM for a few years... but it's just time for a better solution.

                I'm new to soldering but the only feasible way to fix this issue is to do something myself.

                MY QUESTION:
                I've been seeing some people (on this forum mostly) run into issues with the logic board needing a serial number or it being deactivated (?)...
                02-14-2024, 12:23 AM
              • Loading...
              • No more items.
              Working...