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Christmas Tree Light Controller — Parallax Forums

Christmas Tree Light Controller

jsaddictionjsaddiction Posts: 84
edited 2011-11-27 11:57 in BASIC Stamp
Ok so here is my latest project. I have 6 dip switch packs that enable or disable certain sub routines each subroutine is a pattern for the lights. I have a trim pot and an rctime command to controll the overall speed of the patterns and then i have 8 outputs that bias transistors and have leds on the output of the transistors so i know what chanel is active (to help troubleshooing code) the SSRs i currently have are ones found lying around. They are kindof big but do the job... kind of.

here is my question. The minimum on current for these SSRs is 100ma. I am using LED lights at strand of 100 of them only draw 50ma for on half of the cycle. I currently have a 1kohm resistor to get 120ma load continuously. The resistors are 15w and get significanly hot. At this point of the circuit the efficientcy is completely thrown out the window. I suppose i need to rework this. I need to know if there are any SSRs that would supply around an amp or two of current that are maybe a lot lower in minimum current requirements. I looked at the sharp SSRs on parallax website but no specification is mentioned of minimum current. I want to be as efficient as possible so i was thinking a 10ma or lower minimum current and then maybe a resistor and a diode to keep the current going on the oposite side of the waveform.

What should i use? Circuit ideas?

Comments

  • $WMc%$WMc% Posts: 1,884
    edited 2011-11-27 10:12
    I think the SSR's would work.Heres a link to the data sheet.
    '
    You could also look at the IRL510 FET...Its fully on with 5volts at the gate.
    '
    http://www.sharpsma.com/webfm_send/304
    '
    http://www.vishay.com/docs/91297/91297.pdf
  • jsaddictionjsaddiction Posts: 84
    edited 2011-11-27 11:57
    My concern here is minimum current required to effectivly control the output of the SSR isn't mentioned as Minimum output current. I think Sharp calls it "holding Current" which is stated as 50ma. With that in mind and that leds pass current in one direction only then wouldn't i need a resistive load connected in parallel with the output to acheive the "minimum required current"? Assuming i do then i would need a 2.4k resistor rated at say 15w to keep things cool (acctual disipated power is around 6 watts) I am trying to stay away from big bulky resistors dissipating high ammounts of power. This is why i think i should be looking for an SSR with very low minimum current.

    Any insight to this ???
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