Atlas signals

Discussion in 'Getting Started' started by Gary Pfeil, Nov 7, 2007.

  1. Gary Pfeil

    Gary Pfeil Active Member

    I bought an Atlas signal recently, I have no intention of installing a comprehensive signalling system anytime soon, but am working on a scene in which I wanted a siganl more for scenery than any other reason. I thought I'd use the Atlas one as it would be possible to use it as part of an integrated system later.

    All I wanted for now was to be able to turn a red or green light on for photography purposes. The Atlas signal comes with the four leads (one each for red, yellow, green and a common) terminated in a connector, made to fit their pcb. I did not buy the pcb, no need to spend that cash, I figured I'd wire it to a switch and change it manually for now. So I clipped the wires before the connectors, saved them for future reinstallment, solderd on extended leads and applied power, from a AA battery. The 1 1/2 volts did nothing. So I tried two batteries, 3 volts. The green is great, nice and bright. The amber is dim. The red, unfortunately, lit for an instant and is dead. I don't remember if I had tried the red on 1 1/2 volts, or just one of the others.

    It seems odd to me, but is it possible that Atlas provides different voltages to the leds? Per the instructions, the power supply to their pcb should be between 6 and 22 volts. Of course there is no schematic, as I'm sure Atlas just wants you to buy their components.

    My signal is now useless, I can't see changing the led. I must say the signal is gorgeous. The signal head with the three leds is molded with the leads coming out of the head and into the pole I'm pretty sure I would destroy the head attempting to replace the led.

    BTW, the leads I cut were in red, green, yellow and black, and yes they worked for the led of that color. But the 4 wires are larger than the wires that go up the pole, they are soldered to what appears to be varnished wire of small size where they enter the bottom of the signal. When I cut back the shrink tube I initially thought I had accidently stripped the wires but I suppose they used the varnished wire to reduce the diameter.

    Just thought I'd mention my problem in case anyone else is tempted to do the same.
  2. baldwinjl

    baldwinjl Member

    It's not the voltage, it's the current. A resistor in series would have protected it.
  3. Gary Pfeil

    Gary Pfeil Active Member

    I guess batteries have the capability of delivering quite a bit of current. Any idea why only the red one blew out? And why the green looked nice and bright (and was on for maybe 10 seconds with no problem) while the amber was dim? Any suggestion on value for a resistor?

  4. baldwinjl

    baldwinjl Member

    If I am not mistaken, the red has the smallest drop over the diode, and may have led to the battery having the most current for outblowing. Quick, back of the envelope calculation coming up.....
    3 Volts from the batteries, a little over 2 across the LED, 15 ma, 1 Volt to drop, V=IR, R=V/I, R=1/15mA=almost .09 kOhm

    So, try 100 Ohms or so with two batteries.

  5. Gary Pfeil

    Gary Pfeil Active Member

    Thanks Jeff. I'm not decided on what course I will now follow, but the info will apply regardless. The amber was very dim, would increasing voltage to say 4.5 volts and installing appropriate resistors on red and green leads brighten the amber?
  6. baldwinjl

    baldwinjl Member

    If the amber was dim then you could go to 4.5V, try 100 Ohms on the amber, 270 on the green and 330 on the red. (You might start a bit higher, and work down to it, maybe get some 100s and 47s and put them in series til you get what you want, light wise).
  7. Gary Pfeil

    Gary Pfeil Active Member

    Thanks again Jeff, I really appreciate your help.

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