Remote controlled window blind

Discussion in 'The Projects Forum' started by tracecom, Dec 17, 2012.

  1. tracecom

    Thread Starter AAC Fanatic!

    Apr 16, 2010
    I have a motorized blind in a window that is reachable only with an extension ladder. The blind is powered by a 12 VDC motor running from 8 AA batteries, except it's not running because the batteries died. I am thinking about a small solar panel to charge the batteries. What is the cheapest, easiest way to implement this? I don't adjust the blinds very often, so the recharging system can be very small.

  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    Is it possible to use a mains psu instead of batteries?
  3. John P

    AAC Fanatic!

    Oct 14, 2008
    I wonder if this is at all worth doing. An alkaline battery lasts for several years, so with very occasional use, I'd guess that you'd see the batteries die from old age, not exhaustion. But then again--is there a remote control receiver that runs all the time, and depletes the batteries faster?

    If you want to get something, this sort of product might be right, but there are questions about its quality:

    However, all the trickle chargers I saw online seem to be for lead-acid batteries, not a bank of AA cells. This site:

    suggests that the best way to keep a NiCd battery charged is to run a charger for half an hour a day. But I wonder how well a NiCd battery that's kept charged would last, compared with an alkaline battery that just sat for a few years.
  4. wayneh


    Sep 9, 2010
    You'll need about 24V at the solar panel, but only a few square inches. Just about every solar charger system I see uses a panel that can make about double the battery voltage. Will 18V work? Probably. Forget about anything less than 16V.

    At the very least, you will need a blocking diode between your panel and the batteries to prevent reverse current during dark periods.

    Protecting the batteries against overcharge is a concern, and there are many different approaches. If you use nicads and the panel is small enough, you may not need to protect against overcharge. Nicads can tolerate a constant trickle without damage from overcharge. That's why they are used in those solar lights you see everywhere. Supposedly, other rechargeables are getting better in this regard but I believe nicads are still the most tolerant.

    Some circuits use a current dumping arrangement, where excess current is shunted when the battery pack voltage reaches some preset level.

    The highest level of tech is to use a battery charging IC meant for your specific battery chemistry. This will optimize charging and battery life.

    [ADD] There are plenty of commercial solutions out there for 12v chargers - you can probably get something off the shelf.
    Last edited: Dec 17, 2012
  5. tracecom

    Thread Starter AAC Fanatic!

    Apr 16, 2010
    Unfortunately, I didn't have the builder provide mains power at this window, and if I was going to run a wire up to it, I might as well just run a control wire as well.

    I can't remember what type of batteries were there, but they quit in a matter of a few months. They weren't alkaline, carbon zinc, or nicad; seems like they were lithium ion or similar. I'm not much good on ladders and haven't been up to check. Maybe you are correct, and I should just try a fresh set of alkalines.

    The remote is IR and there is an IR sensor at the window, but I don't know how much power it consumes just waiting for a signal.

    Maybe it's too complicated. The blind is just there to block the direct southern sun, and is closed now. There are times when I would like to open it however.

    Thanks for the replies.

    I have even thought of doing away with the motor and fabricating a long wand to use from the floor.
    Last edited: Dec 17, 2012
  6. ifixit

    Well-Known Member

    Nov 20, 2008
    Run some bell wire up there, then put power and control where you can get at it and maintain it easily. No batteries.

  7. tracecom

    Thread Starter AAC Fanatic!

    Apr 16, 2010
    That would work, and I wouldn't have to look at it either; I would be living in the garage. :)
  8. Zapstrap

    New Member

    Dec 17, 2012
    Thanks for the laugh...

    "Do you want it to work or do you want it to be pretty", asked the naive new husband...