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Light Controller Suggestions — Parallax Forums

Light Controller Suggestions

Agent CobaltAgent Cobalt Posts: 88
edited 2005-07-06 10:23 in General Discussion
I am currently making a light controller using the BASIC Stamp 2 as the brains. I need to drive 14 lights (individually). I have read about triacs, SSRs, etc, but I need to keep the external components to a minimum to conserve board space plus the parts need to be inexpensive. I don't need to be able to dim the lights, all I need to do is turn them on with a simple HIGH statement from the Stamp and have the light stay on until I issue a LOW statement. Any help would be appreciated (schematics, places to get parts, etc). Thank you in advance.

Comments

  • Eric REric R Posts: 225
    edited 2005-07-03 20:15
    I assume you are talking AC current



    I use the Crydom SDV2415. It fits a 16 pin dip and has worked well for my light displays.
  • Agent CobaltAgent Cobalt Posts: 88
    edited 2005-07-03 20:28
    Yes, the lights are 120VAC.

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    Truth can be dangerous... Trust can be deadly.
  • Agent CobaltAgent Cobalt Posts: 88
    edited 2005-07-04 05:50
    I got a chance to look at the part you suggested. The only problem is that for my project I would need 14 of these on the PCB which would take up a lot of space.

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    Truth can be dangerous... Trust can be deadly.
  • OrionOrion Posts: 236
    edited 2005-07-04 06:27
    You could roll your own ssr, but it would take up the same space unless you use smd parts. Even with smd it would be hard.
  • Agent CobaltAgent Cobalt Posts: 88
    edited 2005-07-04 06:54
    When I was looking at Crydom's site, I came across a triac that seems like it might work in this situation. Here is some minimal information: Triac: 8A, 600V, Isolated, TO-220AB; Type:Logic Level Triac. I noticed that it mentioned isolation and figured it might protect the stamp from the high voltage. I'm not sure how to wire any of these things as I'm not that advanced with electronics and this is the first time trying to drive AC loads.

    The datasheet for the part I mentioned is at the following address: www.crydom.com/userResources/productFamilies/110/crydom_CT08.pdf (It's the CTA08-600SW that I was looking at)

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    Truth can be dangerous... Trust can be deadly.
  • OrionOrion Posts: 236
    edited 2005-07-04 14:48
    The isolation they talk about is the metal tab for the heat sink. It will not be connected to the mains voltage. Someone may prove me wrong but I don't think there is a smokeless way to directly drive a triac from a stamp pin. Look for an opto triac driver like the moc3042. http://www.fairchildsemi.com/ds/MO/MOC3042-M.pdf
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-07-04 19:41
    This circuit shows how to control 120 VAC through an optically-coupled triac interface: http://www.interq.or.jp/japan/se-inoue/e_pic6_c1.htm

    BE VERY CAREFUL if you build this kind of circuit.

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    Jon Williams
    Applications Engineer, Parallax
  • Eric REric R Posts: 225
    edited 2005-07-04 20:44
    Agent Cobalt said...
    I got a chance to look at the part you suggested. The only problem is that for my project I would need 14 of these on the PCB which would take up a lot of space.

    If you locate a smaller footprint then let me know as I think it will be tough to find anything smaller. It is good practice to run a ground trace between the 110vac and low level logic also. This way if you do get an arc it will ground rather than taking out your stamp.
  • Agent CobaltAgent Cobalt Posts: 88
    edited 2005-07-05 00:53
    Now when I connect the optically-coupled triac interface to the basic stamp, will I need to pulse the line at a specific interval? Or can I just drive the line high and have the stamp continue on with it's processing?

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    Truth can be dangerous... Trust can be deadly.
  • OrionOrion Posts: 236
    edited 2005-07-05 01:31
    It will operate just like a led would on a stamp pin.

    So yes.... just drive the line high and have the stamp continue on..
  • Agent CobaltAgent Cobalt Posts: 88
    edited 2005-07-05 07:35
    I was looking at a site that offers a product that is similar to what I'm designing (a traffic light controller; only mine is on a larger scale) and I found an image of their controller. The only thing is, it looks like there are 3 triacs, a fuse, a couple of resistors and capacitors, and one IC chip. Obviously they know some way of driving triacs from a logic level IC without the need for an opto-isolator yet I can't figure out how it can be done. I've been reading on triacs and it seems like there needs to be some isolation. So if anyone can help me figure this out, it'd be much appreciated.

    Picture of the controller:
    T3_photos.jpg

    Here is the link for the image: trafficlights.com/images/T3_photos.jpg

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    Truth can be dangerous... Trust can be deadly.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-07-05 15:14
    Are those TRIACS or MOSFETs?

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • Agent CobaltAgent Cobalt Posts: 88
    edited 2005-07-05 15:32
    I'm assuming that they are triacs because in the description on their site, this is what it says: 3 full AC TRIAC output channels.

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    Truth can be dangerous... Trust can be deadly.
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-07-05 15:48
    Okay,

    ·· I didn't go to the website, but thought I would ask.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
  • Agent CobaltAgent Cobalt Posts: 88
    edited 2005-07-06 01:13
    Yeah, I don't know how they did it or who's parts they used but they were able to accomplish driving a triac without any isolation of the AC power and the stamp's pin.

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    Truth can be dangerous... Trust can be deadly.
  • OrionOrion Posts: 236
    edited 2005-07-06 03:14
    Who to say they don't have isolation without a parts list. What is the black part labed blx-a? That size would be easy to beat with 4 triacs, some smd resistors and a 4 channel smd opto, ditch the screw connectors for wires right to the pcb or .100 headers.
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2005-07-06 03:44
    Here is something that I came across...

    http://khalus.com.ua/data/components/teccor/an1003.pdf

    (page 7)


    As spoken in the immortal words of "Jon Williams"...

    BE VERY CAREFUL if you build this kind of circuit.

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    Beau Schwabe

    IC Layout Engineer
    Parallax, Inc.

    Post Edited (Beau Schwabe (Parallax)) : 7/6/2005 3:47:25 AM GMT
    triac.jpg
    439 x 469 - 72K
  • Agent CobaltAgent Cobalt Posts: 88
    edited 2005-07-06 04:51
    I think this gives me the information I need now. Thanks for all the help. If I run into any problems, I'll let you guys know.

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    Truth can be dangerous... Trust can be deadly.
  • pjvpjv Posts: 1,903
    edited 2005-07-06 04:58
    Indeed, you say trust can be deadly.

    In particular if you have no isolation in your circuitry and where your unit is plugged in, you TRUST that Line and Neutral are not reversed!

    This is a lethal disaster waiting to happen, especially with the inexperienced.

    Please, grab some sense, and INSIST on isolation.

    Peter (pjv)
  • Agent CobaltAgent Cobalt Posts: 88
    edited 2005-07-06 05:08
    I understand what you're getting at there and I do agree, but I have found triacs that are electrically isolated (the gate is isolated from the terminals). Though having the line and neutral reversed would probably not be a good thing.

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    Truth can be dangerous... Trust can be deadly.
  • pjvpjv Posts: 1,903
    edited 2005-07-06 10:23
    No Agent, it would not.

    Please remember that lots of extension cords are unpolarized, and can be plugged in EITHER way; a DEADLY situation.

    Peter (pjv)
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