our city is going green

Discussion in 'General Electronics Chat' started by willy2, Jul 28, 2008.

  1. willy2

    Thread Starter New Member

    Jul 28, 2008
    solar project// 1: how do I convert 12 volts dc to 24 volts ac ? i have a 12 v.d.c. plug in inverter to 120 v.a.c. and a 120 to 24 volt ac transformer which works but uses to much power 2: can I convert 12 volt dc. to 12 volt ac. to operate a photocell I found. 3: where do i find a 12volt ac or dc 7 day / week timer. all of my ideas are to conserve battery & reserve time to allow the solar panel to recharge the battery sufficiently for continual use. My circuit load is 12 volts dc and 7 watts. Thank you :confused: ;)
    Last edited: Jul 28, 2008
  2. Wendy


    Mar 24, 2008
    I've seen 120VAC timers that fit most of your description, but none that were low voltage.
  3. SgtWookie


    Jul 17, 2007
    Well, what's the efficiency rating of the inverter, and the transformer? I suspect the inverter is in the realm of 90% efficient, and the transformer is perhaps 97% efficient. If you think that you can improve upon that, I'll encourage you to try. But we don't have the facts about the load on your 24VAC transformer, nor what your inverter is using.
    Sure. What frequency AC do you need? At a minimum, you'll need to build an oscillator (or bistable multivibrator circuit) to drive the primary side of a transformer. You could even use a 120v isolation transformer rated at just a couple of Watts.
    No clue; never looked for one.

    A noble cause, to be sure.
    Do you mean to say that you have a solar panel capable of only 7 Watts?
    If so, you're generating about enough power to keep a single old-fashioned Christmas tree bulb (or night-light) lit for slightly less time that your solar cell is charging the battery for.

    You really don't have enough power generation capacity for any kind of serious application. Once you get up in the 500 Watt plus range, then you really have something you can work with.

    But with only 7 Watts - you're crippled. You're hardly supplying enough current to keep a normal lead/acid battery charged.
  4. willy2

    Thread Starter New Member

    Jul 28, 2008
    Hello & thanx for your answers, The job I installed was from a city blueprint that I believe some person designed by throwing it together.Since then we have redesigned the solar package to "known" wattage figures.I am trying to help the battery recovery more by allowing less usage incorporating a photocell & or timer but 12 volt dc components are alluding me' I have a 12 volt ac photocell from a landscape catalog but I need to convert it to dc. any ideas? Ps. I'll repost my ?'s since my details are foggy

    thanx again, willy2 :confused::)
  5. Norfindel

    Active Member

    Mar 6, 2008
    You could build a circuit to do the same thing with 12v dc... but wait a second, you have a solar panel! Just sense if the panel is delivering voltage, and use that to trigger a relay to activate the load. Of course, relay coils need some power, but you can probably replace the relay for an SCR, or something like that, and use less power.
  6. gerty

    AAC Fanatic!

    Aug 30, 2007
    Here's a 7 day 24 hour timer that runs off of 12v. It's programmable for several events daily and its output is either momentary or latched. It also has a battery backup to retain the time and program during power failure.
    I just installed one of these on a pa system to sound break whistles, works great.