1. Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
    Dismiss Notice

help with building an ssr to drive main line lamp

Discussion in 'High Voltage' started by shosh, Nov 18, 2011.

  1. shosh

    shosh Member

    Joined:
    Nov 18, 2011
    Messages:
    35
    Likes:
    0
    Hi

    so i need help with an ssr driving 120vac to a light bulb. I have the design of the ssr down, using an optoisolator and a triac to drive the bulb. My problem is working with main line current. I am no way a electrician so i need some help with creating a lamp, and how much current a triac can handle. i need some help to safely implement this lamp into my designed ssr.
     
  2. Sceadwian

    Sceadwian Banned

    Joined:
    Oct 27, 2006
    Messages:
    14,047
    Likes:
    141
    Location:
    Rochester, US
    You could start by reading the PDF sheet for the triac you're planning on using which you have not named. Or use the parametric search of a site like Digikey to select a triac in the first place.

    Even if you don't buy from them Digikey has a great parametric search. Go to their website, type in Triac in the search. Select the Triac option in discrete semi conductors, and it will open a new window with all the various parameters of a triac to filter by.

    Sort by off state voltage of your mains level (120VAC) and up. Which is pretty much everything. Assuming a 100 watt lightbulb that's 1 amp, Apply the selection and scroll down and you'll see every triac that can meet your needs, or your can further refine your options.
     
    Last edited: Nov 18, 2011
  3. shosh

    shosh Member

    Joined:
    Nov 18, 2011
    Messages:
    35
    Likes:
    0
    well my triac is an NTE 56006. I believe this should be able to handle it.

    So my main problem is incorporating a circuit using main line to the ssr. Im planning on using a breadboard (so i use something different?) and am not sure if its safe to hook it up to main line. What kind of terminals do you use etc.
     
  4. dave

    Dave New Member

    Joined:
    Jan 12, 1997
    Messages:
    -
    Likes:
    0


     
  5. alec_t

    alec_t Well-Known Member Most Helpful Member

    Joined:
    Jul 10, 2011
    Messages:
    9,253
    Likes:
    1,218
    Location:
    Cardiff, Wales

    If your breadboard is of the usual hobby type it probably won't be suitable for carrying the current your lamp (unknown wattage) will draw, and may not be suitable for 120VAC working either. Better to use chocolate-block type (or similar) terminals to connect your mains-rated components, including the triac.
     
  6. shosh

    shosh Member

    Joined:
    Nov 18, 2011
    Messages:
    35
    Likes:
    0
    should i use a wire to board block? or do i need to work on a general purpose PCB. I have not pcb experience, solely breadboards to prototype.
     
  7. alec_t

    alec_t Well-Known Member Most Helpful Member

    Joined:
    Jul 10, 2011
    Messages:
    9,253
    Likes:
    1,218
    Location:
    Cardiff, Wales
    Not sure what that is. Stripboard (Veroboard) would do if you don't want to make a custom pcb.
     
  8. Sceadwian

    Sceadwian Banned

    Joined:
    Oct 27, 2006
    Messages:
    14,047
    Likes:
    141
    Location:
    Rochester, US
    Simple perfboard and heavy gauge wire. Flesh out the design and solder the connections. If you absolutely need removable connections for part of the circuit, use terminal blocks rated for the current/voltage you'll need. It's not that complicated.
     
  9. shosh

    shosh Member

    Joined:
    Nov 18, 2011
    Messages:
    35
    Likes:
    0
    thanks for the replies.

    another thing is, I'm building the ssr with an optoisolator feeding into the traic gate. how do i determine what resistor values to use. there will be an Rin resistor fed the the anode of the optoisolator. then i was going to feed a mainline terminal hooked up to one side of the output terminals of the optoisolator and the other pin of the output of the isolator into the triac gate. in general terms, how do i compute the values of resistance i need. the circuit is similar to this http://computerchristmas.com/christmas/link-how_to/HowToId-7/FullSize-true/LowLimit-0/StepId-2

    i have this type of data of the isolator
    Viso = 7500v
    Pt - 330mW
    If - 50mA max
    Vf - 1.5v Max
    Vr 3v Max
    Vdrm - 250v
    Ift - 15ma
    Ihold - 100uA

    and the triac
    Vrrm - 400v
    It RMS - 15A
    Igt - 40/75mA Max
    Vgt - 2.5v
    Vf(on) - 1.6v Max
    Isurg - 150A
    I hold - 40mA Max
     
    Last edited: Nov 21, 2011
  10. Reloadron

    Reloadron Well-Known Member Most Helpful Member

    Joined:
    Dec 23, 2009
    Messages:
    6,777
    Likes:
    281
    Location:
    Cleveland, Ohio USA
    Hi Shosh

    How much of a load is the lamp you plan to light? You have a 50 amp triac which is a pretty beefy triac. At 120 volts that would easily handle about 50 100 watt standard incandescent bulbs.

    The reason I ask is because somewhere around here I have several (like a pile of them) complete SSRs. Mostly 5 and 10 amps but some higher. They are complete and only require an input voltage of 3 to 32 VDC to work. It's like the entire triac and driver package in a small single package. If you are in the US (I saw 120 volts) I'll be happy to send you one. I don't want anything for it in return as in free including the postage. They were ripped from AC control systems. If all you want to do is light some incandescent lamps (light bulbs) they should do fine.

    Next to answer your question what you care about is If - 50mA max and Vf - 1.5v Max, however, you do not mention the DC voltage you plan to use? The max forward current is 50 mA but the opto would likely work fine with 20 mA. Let's assume 5 volts DC is what you have. It would look like this Vsupply - Vled / I forward so it would be 5 - 1.5 = 3.5 / .020 I led = 175 Ohms so a common 160 or 180 off the shelf would do fine. Again, not knowing the DC supply voltage that being just an example. In reality I would run with between 180 and 200 ohms in the example.

    Ron
     
    Last edited: Nov 21, 2011
  11. shosh

    shosh Member

    Joined:
    Nov 18, 2011
    Messages:
    35
    Likes:
    0
    sorry, i forgot.
    input voltage is at 3-30vdc

    and im driving 120vac,
    im just using a simple lamp circuit to test it
     
    Last edited: Nov 28, 2011
  12. Reloadron

    Reloadron Well-Known Member Most Helpful Member

    Joined:
    Dec 23, 2009
    Messages:
    6,777
    Likes:
    281
    Location:
    Cleveland, Ohio USA
    If the input voltage can vary that much you may want to think about adding a zener diode to protect your opto coupler LED and maybe a series 1K resistor. That 3 to 30 volts sounds like a typical DC Control SSR.

    Ron
     
  13. shosh

    shosh Member

    Joined:
    Nov 18, 2011
    Messages:
    35
    Likes:
    0
    thanks,

    so now what about the resistor hooked up to the main line? That was actually the resistor I had questions about
     
  14. Reloadron

    Reloadron Well-Known Member Most Helpful Member

    Joined:
    Dec 23, 2009
    Messages:
    6,777
    Likes:
    281
    Location:
    Cleveland, Ohio USA
    The 180 ohm resistor you see is based on the the maximum surge current of the MOC3010 as that value sets the resistor value, that and the line voltage. The maximum surge current rating of the MOC30xx series sets the minimum value of the resistor using the equation:

    R minimum = Vin pk / 1.2 amps as 1.2 amps is the maximum surge current so for 120 VAC RMS the Voltage peak would be 1.414 * 120 = 170 Vpk. So now we have 170 / 1.2 = 142 Ohms so we go over the minimum with a common 180 Ohm resistor. This is not a very exact science and in basic circuits like this using 120 volts you will see values like 150 or 180 ohms used.

    Also, keep in mind, the simple circuit you posted is fine for resistive loads on the triac like incandescent lamps. It would need modifications for an inductive load like a small motor or transformer load.

    Ron
     
  15. shosh

    shosh Member

    Joined:
    Nov 18, 2011
    Messages:
    35
    Likes:
    0
    pardon my ignorance, but can you clue me in on where you got 1.2amps from?
     
  16. Reloadron

    Reloadron Well-Known Member Most Helpful Member

    Joined:
    Dec 23, 2009
    Messages:
    6,777
    Likes:
    281
    Location:
    Cleveland, Ohio USA

Share This Page