Advertisement
If you have a new account but are having problems posting or verifying your account, please email us on hello@boards.ie for help. Thanks :)
Hello all! Please ensure that you are posting a new thread or question in the appropriate forum. The Feedback forum is overwhelmed with questions that are having to be moved elsewhere. If you need help to verify your account contact hello@boards.ie

Low signal 5vdc relay non pcb

Options
2»

Comments

  • Options
    #32
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    2011 wrote: »
    Good article here:

    http://www.ixys.com/Documents/AppNotes/IXYS_IGBT_Basic_I.pdf

    Looks interesting alright,


  • Options
    #33
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,593 Mod ✭✭✭✭2011


    This puppy will do everything that you want:

    http://www.lightobject.com/25A-Solid-State-Relay-SSR-DC-In-AC-Out-P61.aspx


  • Options
    #34
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    DublinDilbert wrote: »
    I don't know the full set up, but if its a 230V contactor, I'd just use an AC SSR to control it from 5Vdc control signal.

    Yea its not clear so far, but definitely a 230v ac contactor.

    There is no obvious reason why the 5v relay is not working. It sounded at first like the 5v relay coil was taking too much current, which would be sorted by a simple transistor.

    But probably need to see a clearer description, as to exactly what energises the 5v relay and why different loadings on the contactor chage its behavior.

    Its like as if the relay is a current sensing one, or has a current sensing circuit controlling it.


  • Options
    #35
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,593 Mod ✭✭✭✭2011


    Solid State Relay

    Input: 3 to 32VDC
    However it can switch up to 380 VAC up to 25A


  • Options
    #36
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    2011 wrote: »
    This puppy will do everything that ou want:

    http://www.lightobject.com/25A-Solid-State-Relay-SSR-DC-In-AC-Out-P61.aspx

    But why is the 5v dc relay not working?


  • Advertisement
  • Options
    #37
    DublinDilbert
    Registered Users Posts: 5,379 ✭✭✭DublinDilbert


    Bruthal wrote: »
    Yea its not clear so far, but definitely a 230v ac contactor.

    There is no obvious reason why the 5v relay is not working. It sounded at first like the 5v relay coil was taking too much current, which would be sorted by a simple transistor.

    But probably need to see a clearer description, as to exactly what energises the 5v relay and why different loadings on the contactor chage its behavior.

    Its like as if the relay is a current sensing one, or has a current sensing circuit controlling it.


    Yea many systems with 5V outputs will have some sort of current limiting resistor in series with them. I've seen some recently with 1K in series with the output, so had to use a low side n channel mosfet to turn on the load.


  • Options
    #38
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,593 Mod ✭✭✭✭2011


    Bruthal wrote: »
    But why is the 5v dc relay not working?
    Don't know to be honest. Perhaps it is faulty. Try changing it out for same.
    I like my solution though as it provides everything required in a single device.


  • Options
    #39
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    2011 wrote: »
    Input: 3 to 32VDC
    However it can switch up to 380 VAC up to 25A

    You can make them up as well, triac controlled by an opto coupler. Opto coupler has an LED in it, so dc in, and low level triac output, to switch a power triac.

    Just as a matter of interest I mean.


  • Options
    #40
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,593 Mod ✭✭✭✭2011


    Bruthal wrote: »
    You can make them up as well, triac controlled by an opto coupler. Opto coupler has an LED in it, so dc in, and low level triac output, to switch a power triac.

    Just as a matter of interest I mean.
    Nice one :)
    Radionics ?


  • Options
    #41
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    2011 wrote: »
    Don't know to be honest. Perhaps it is faulty. Try changing it out for same.
    I like my solution though as it provides everything required Ian single device.

    Yea but it would be nice to know the exact problem first. Why is the load on the contactor altering the working of the relay? Is it a current sensor in the circuit?

    If that is the case, and it simply wont switch on the 5v relay at low current level, there may be zero output to the 5v relay until a certain current level is reached on the contactor load, in which case replacing the relay wont be the solution.


  • Advertisement
  • Options
    #42
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,593 Mod ✭✭✭✭2011


    Bruthal wrote: »
    Yea but it would be nice to know the exact problem first.
    Yes, but you really need a diagram to see the "big picture" and diagnose properly.
    Without it we are just speculating.


  • Options
    #43
    leeomurchu
    Site Banned Posts: 957 ✭✭✭leeomurchu


    Hey sorry.

    Bath night for the rug rats. right so clearly you guys know your relay so go easy on me :)

    I was using the solid state relays but they seemed to work intermittently depending on the load being switched through the contactor.

    I've no idea of the reasoning for this.

    I'm just gonna have a read back through the posts I see a couple of solutions thrown out there.

    Thanks everyone for their input.


  • Options
    #44
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    2011 wrote: »
    Nice one :)
    Radionics ?

    They can be got on ebay as components as well.

    Here is an moc3062 opto triac

    And an moc3042 coupled to a power triac to form a solid state relay.

    And a bit more on them here

    The 3042 (400v peak to peak) is like a lower peak to peak voltage version of the 3062 (600v peak to peak). They are simply low power triacs in a 6 pin configuration used to optically isolate the dc input from the ac switching output. They can then switch power triacs. That is in effect what a solid state AC relay is.


  • Options
    #45
    DublinDilbert
    Registered Users Posts: 5,379 ✭✭✭DublinDilbert


    leeomurchu wrote: »
    I was using the solid state relays but they seemed to work intermittently depending on the load being switched through the contactor.

    There's obviously something funny happening there. A SSR should be able to switch a contactor no problem.

    If the contactor is switching a large load (or possibly and inductive one), you could end up with big voltage spikes on the 220V supply causing other bits of the circuit to misbehave.


  • Options
    #46
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    2011 wrote: »
    Yes, but you really need a diagram to see the "big picture" and diagnose properly.
    Without it we are just speculating.

    Yes but we know the relay is having problems switching the contactor.

    And that the current the contactor is switching seems to affect the relay operation. So there is where to find out whats happening.


  • Options
    #47
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    DublinDilbert wrote: »
    Yea many systems with 5V outputs will have some sort of current limiting resistor in series with them. I've seen some recently with 1K in series with the output, so had to use a low side n channel mosfet to turn on the load.

    I had a mosfet overheating last week when switching at 1khz. I noticed input capacitance in the mosfet gate in the data sheet. With the 1k resistor, and continuous rapid switching, id say the delay to full on due to the reisitor-capacitor time on the gate was causing it. No problem for switching on and off like a manual switch, but seems significant for high rate switching.

    I got a transistor to directly switch the gate with no resistor, and it worked perfect then, and put the 1k resistor between gate and 0v as a pull down. It was all just experimental, but interesting enough.


  • Options
    #48
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,593 Mod ✭✭✭✭2011


    Bruthal wrote: »
    I had a mosfet overheating last week when switching at 1khz.
    What were you doing, PWM ?
    What chip was controlling the gate signal?


  • Options
    #49
    2011
    Moderators, Home & Garden Moderators, Technology & Internet Moderators, Regional East Moderators Posts: 12,593 Mod ✭✭✭✭2011


    Bruthal wrote: »
    Yes but we know the relay is having problems switching the contactor.
    As I said, it would be nice to change the unit out to see if it is simply a faulty component.


  • Options
    #50
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    DublinDilbert wrote: »

    If the contactor is switching a large load (or possibly and inductive one), you could end up with big voltage spikes on the 220V supply causing other bits of the circuit to misbehave.

    Yea I was thinking that same thing myself.

    But it seems to fail to work when switching smaller currents. Again, its like there is a current sensor in the mix, like a shower priority unit, and leo is just trying to get it to work at lower currents.

    A shower priority unit for example, will let both showers operate if they are on cold with no elements on, because the pump and solenoid current draw is below the threshold of the sensor circuit operating the contactors.


  • Options
    #51
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    2011 wrote: »
    What were you doing, PWM ?
    What chip was controlling the gate signal?

    I was actually just testing a mosfet I had, irl540n one to see was it working, or faulty. I just set it dimming a car headlamp up and down with a pic chip 12f675, just counting up and down a pulse width to dim it up and down every few seconds.

    A mosfet transistor just needs a voltage on its gate to set it on. The on resistance will be higher for lower gate voltage, and the gate voltage rise is not instant due to inherent gate capacitance. So when it has voltage applied, it is like charging a capacitor, there is a time factor, and during this very tiny time, the mosfet has some resistance.

    It is a tiny capacitance, of no significance for normal on and off use, but can be for high speed switching for pwm control, and the time factor will be increased with a gate resistor added in. They can be used without a gate resistor anyway.

    A standard transistor needs a base resistor, as it is switched on by current flow into the gate, and without the resistor, would be like a short. Where as the mosfet just has voltage applied to its gate, with no current flow after the initial gate capacitance charge factor is gone, which is in micro seconds or less with no gate resistor.


  • Advertisement
  • Options
    #52
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    leeomurchu wrote: »
    Hey sorry.

    Bath night for the rug rats. right so clearly you guys know your relay so go easy on me :)

    I was using the solid state relays but they seemed to work intermittently depending on the load being switched through the contactor.

    I've no idea of the reasoning for this.

    I'm just gonna have a read back through the posts I see a couple of solutions thrown out there.

    Thanks everyone for their input.

    Exactly what is it you use to switch on the contactor? Is it a low voltage switch somewhere?

    Is it simply a fully manual switching on of the contactor you are doing? I mean a 5v relay switched on from a 5v supply can easily be setup to switch on a relay to switch on a contactor.

    Why not a 12v relay? 5v suggests a logic circuit of some kind. Where have you come up with 5v from?

    What im sort of asking is, exactly what is the setup, which maybe the drawing
    will help with.

    Is it a remote switching setup? Wireless?

    What is it you do to bring on the contactor?


  • Options
    #53
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    2011 wrote: »
    As I said, it would be nice to change the unit out to see if it is simply a faulty component.

    It would be even nicer to know what the user actually does to switch on and off the item being switched on and off. What is the normal action required.

    We have no clue about that.


    Why would the 5v relay be failing to close when the contactor is switching low loads, but not high ones? As if the 5v relay is controlled by a current sensing circuit. Is this the case? Again that has not been made clear.

    The first post asked for 40ma switched 5v relays, where as the ones they seen and later linked to were 100ma. This sounds like the relay coil current, where did those figures come into it?

    If in fact a 40ma coil relay would work, but a 100ma wouldnt, it would be a simple matter of using a general purpose npn tranasistor to switch the 100ma relay, and the transistor would only need 5 to 10ma to its base from the 5v signal, using a 1k resistor for the 5ma.

    But it is all very vague.


  • Options
    #54
    DublinDilbert
    Registered Users Posts: 5,379 ✭✭✭DublinDilbert


    Bruthal wrote: »
    I had a mosfet overheating last week when switching at 1khz. I noticed input capacitance in the mosfet gate in the data sheet. With the 1k resistor, and continuous rapid switching, id say the delay to full on due to the reisitor-capacitor time on the gate was causing it. No problem for switching on and off like a manual switch, but seems significant for high rate switching.

    I got a transistor to directly switch the gate with no resistor, and it worked perfect then, and put the 1k resistor between gate and 0v as a pull down. It was all just experimental, but interesting enough.

    Yea the gates on them mosfets are just a cap that needs charging. With 1K in there if you PWM your switching losses would be large, cause at turn on you'd have the voltage dropping on the device and current rising in it. The power loss is the two multiplied together. Something similar will happen at turn off.

    Often with mosfets 10 Ohm in the gate works well. You don't want to turn on a mosfet (or igbt) too quickly as you'll get ringing across it.


  • Options
    #55
    whizbang
    Registered Users Posts: 1,935 ✭✭✭whizbang


    Leeo, AC contactors are huge unrestrained industrial beasts as far as electronic components are concerned.

    The switching transients can be massive, and it may be simply your 5v relay is arcing/bouncing/flashing (insert appropriate word here)

    However it may be something simpler. electrical noise? is the ac load affecting your dc control voltage?

    Use an industrial type snubber across the contactor, and think about changing the 5v relay to SSR. packages are much smaller if this is a concern. i.e.http://radionics.rs-online.com/web/p/solid-state-relays/6241910/


Advertisement