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Terminal Block to LED Leads

Discussion in 'Project Construction Technologies' started by allenpitts, Jul 7, 2019.

  1. allenpitts

    allenpitts

    2
    0
    Jul 7, 2019
    Hello Electronics Point,

    Working on a motion detector (PIR) actuated LED display
    w 300 lights. Using 3 mm LED Mouser #: 604-WP710A10PGT
    mounted in plexiglas operated by Maxim 7129 IC in
    a custom designed PCB.

    The question is how to connect the PCB to the LEDs.

    At the PCB using Mouser 571_282834-8, TE Connectivity
    Fixed terminal blocks. The terminal blocks
    https://www.mouser.com/ProductDetai...cu6/tyhQV/GlIyync%2BR5zJOVGuWWFlMGm6TZ9uXIA==
    while a bit expensive
    work great because the connector screws down onto
    the wire and provides good, firm connections.

    The issue is the connection to the LEDs.

    Have received :

    Mouser #: 593-CNXBE4112
    Mfr. #: CNX_B_E_4_1_12
    Desc.: VCC Lighting Cables Lighting Cables 3MM PNL CNXBE4112
    https://www.mouser.com/ProductDetai...Ikqup3QUmz/Q8k7gBr/4sqzV6M1gjuel%2B5IRrbvjg==
    and
    Mouser #: 523-SSL11J2LJ0B22A04
    Mfr. #: SSL11-J2LJ0-B22A04
    Desc.: Amphenol Lighting Cables Lighting Cables SSL1.1WIRE ASSY,WITH W2B LOCK
    https://www.mouser.com/ProductDetai...a2WeR3g4GXWcnccVVD3Vb3JJEFGSvolicLooHaVVZ2WTA

    Using the VCC CNXBX4112 it is often difficult to get the
    LED leads to fit down into the header. See attached photo
    marked 'LED One'.
    [​IMG]

    In that photo the header marked 2.2.2 sits
    down properly on the LED leads. The other two headers on the
    right, like many others, even after fitting and refitting for
    five or ten minutes will not go down onto the LED leads.

    When the leads won't go all the way down on the LED lead,
    if even touched slightly, will some times disconnect.

    The wire coming out of the terminal block could be soldered to the
    LED lead but that would be 600 solders. Will avoid if possible.

    So purchased the Amphenol hoping to get an easier more, solid
    connection at the LED, like the connx at the terminal blocks,
    which are pretty easy, and very stable.
    [​IMG]

    Hoped the Amphenol would solved the problem with fitting the header onto
    the LED lead. But although the leads go into the header easier, the header
    does not conduct through the LED to make the LED light.
    See GIF marked LED Three.
    [​IMG]

    Is there another lighting cable that would go from the
    terminal blocks to the LED leads?
    [​IMG]

    Thanks.

    Allen Pitts, Dallas Texas
     
  2. dave9

    dave9

    708
    159
    Mar 5, 2017
    I don't quite follow why you're doing what you're doing, but it makes no sense to me to use terminal blocks unless you're driving the LEDs so hard that you expect failure.

    Otherwise, how does it save time to solder wire to a connector then plug an LED into that, than to just solder wire to the LED?

    Again I don't know what you're doing but I would have a PCB all the LEDs are soldered to, with traces going over to a pin header if you must have a way to disconnect it, otherwise solder the wires in a row there or right next to each LED.

    Why do you even need the LEDs mounted on a different board or plane than the rest of the circuit?
     
    davenn likes this.
  3. hevans1944

    hevans1944 Hop - AC8NS

    4,148
    1,967
    Jun 21, 2012
    Did you check the polarity of the connections to the LEDs? Well, of course you did! This is a mechanical problem is it not? For how many of the green LEDs does your header identified as "2.2.2" actually "sit down properly on the LED leads?" Is it just the one LED that you show that seated properly? Or do other LEDs you ordered also fit while others do not?

    From what I have read at the vendor's website, your LEDs are designed for a panel mount with plug-in, mass-terminated connections to the LEDs. Assuming you have purchased the correct connector hardware (verify this with Mouser), perhaps you should be in a conversation with Mouser, or the manufacturer of the LED connectors, to see if one of them can solve your interface problem without too much finger pointing. This may be something as simple as a quality control problem in the manufacture of the LEDs or the connectors. Either way, Mouser should make it right or carefully explain why you ordered or they sent the wrong parts.

    You definitely should not want to be stripping 300 pairs of wires for insertion in your terminal blocks, but it appears to me that is exactly what you have set yourself up to do. If you are going to go to that much trouble, please consider using a crimp tool and a terminal ferrule on each wire. A label making kit to identify each wire would also be prudent. I used to print labels using mouse-print font sizes and secured them to the wire with clear shrink tubing. Well, I did that just once because our wire marking machine wasn't working. I just recently added crimped ferrules to connect a Superior Electric Slo-Syn stepper motor to a STEPPERONLINE DM556N Digital Microstep Driver and it works great. Kit with crimp tool and assorted terminals was less than thirty bux. Purchased everything online from Amazon, but you may find better prices elsewhere.
     
  4. allenpitts

    allenpitts

    2
    0
    Jul 7, 2019
    Hello EP forum,

    In the GIF marked 'LED Two' above, the terminal blocks are on the PCB on the left. The 3mm LEDs are superglued into 1/8" holes in the Plexiglas. The cable between the terminal block and the LED is
    https://www.mouser.com/datasheet/2/423/CNXB-3mm-bi-lead-connector-drawing-1064622.pdf
    purchased w one end stripped. Thought that the female Dupont style connector would go onto the LED lead easily. But having problems. The LED leads won't fit down onto the LED lead. In the GIF marked LED One shows the connector marked 2.2.2 fits down onto the LED leads. The two connectors on the right will not receive the LED leads. So trying to figure out an alternative to the Dupont connectors.
    Again I could snip the Dupont connector off, strip the wires and solder the bare wire to the LED lead, 600 times. But I was hoping someone could suggest a mechanical connector. Looked at the Sopoby crimp kit. I guess a sleeve would prevent the LEDs from touching each other and shorting out.
    Will give it a try.
    Thanks.

    Allen in Dallas
     
  5. hevans1944

    hevans1944 Hop - AC8NS

    4,148
    1,967
    Jun 21, 2012
    The connector you ordered and received should work!

    It appears to me, from way over here and not where you are, that the LEDs you have purchased (maybe el-cheapo Chinese parts?) have leads that are out of tolerance specs... some being too large to fit into the VCC connector, and perhaps others too small to make good mechanical contact with the tin-plated phosphor-bronze contacts inside the connector. The FACT that ONE of your LEDs fits the connector properly and lights up, leads me to believe that there are others that will also fit. You just didn't purchase them. Which is why I asked the question you did not answer: out of ALL the LEDs you purchased, is there ONLY ONE that fits the connector properly? Have you tried fitting all of the LEDs?

    Perhaps you should consider preparing a GO/NO-GO test gauge for your LEDs. This would be a small piece of aluminum stock with two holes drilled in it. Size the holes for the diagonal dimension of the square cross-section LED leads. Space the holes according to specs for 3 mm LEDs. Add a slight chamfer to each of the two holes to help guide the LED leads into the holes. Make sure the one LED you have that does fit the LED connector slides easily into the holes of the GO/NO-GO test gauge. If it does, try inserting each of the remaining LEDs into the holes of the test gauge. All should slide in and fit snugly. None should fall out. Those that fit the test gauge should also fit the connector.

    The purpose of the ferrules is not to insulate adjacent wires but to provide a sturdy mechanical connection to stranded wires. Unless you are using solid wires in your PCB terminal blocks, repeated loosening and tightning of the terminal screws on stranded wire will eventually cause broken strands of wire and lead to early failure of the wire-to-terminal-block connection. Even if you only intend to insert each wire just one time and then tighten the terminal screw, ferrules make this task a lot simpler and the final appearance is much neater.

    Back in the day, when we were building panels with hundreds of wires, we kept a solder pot hot and filled with 60/40 tin/lead solder. Each wire in the cable bundle was stripped and dipped in the solder pot. This was in the 1960s, but it wasn't until many years later that I "discovered" ferrules and how professional panel builders use them. The crimp tools were initially very expensive "star" crimps, and you can still purchase those, but the least expensive is a four-jaw rectangular crimp, which seems to work just as well and does not cost nearly as much as a star crimp tool.
     
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