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  1. chromei386

    Car battery circuit design - comments, feedback?

    I've fixed up so they are common emitter, thanks for the tip: How would I find out the forward voltage drop over the lead acid battery while charging? I suppose that may not apply it's not an active device. Would it just a matter of measuring the battery's internal resistance and using Ohm's...
  2. chromei386

    LED driver

    From what voltage source? Batteries? Power supply unit? Wall wart? To get the right mA to your LEDs, use this formula: R = (Vs - Vl) / I where R = resistance Vs = power supply voltage Vl = sum of LED voltages (check, but probably 2v ea)   I = LED mA = 30mA you could hook them all up from a...
  3. chromei386

    My First Post And First Question

    My interpretation of that question would be:
  4. chromei386

    12v to 230 volts dc with voltage doubler circuit its possible?

    I picked up a 400W 12v to 240v inverter from Kmart (Aust.) for $30 AUD. It has a fan and a bunch of MOSFETs along with the usual transformers & capacitors. It works well and if it breaks down I refund it. I couldn't buy the parts separately and build one myself for that price. It's clean...
  5. chromei386

    Car battery circuit design - comments, feedback?

    As promised! I'm really pretty good about it but I'm sure I've missed something
  6. chromei386

    Car battery circuit design - comments, feedback?

    thank you very much audioguru, I have bought the LM339 IC and almost ready to test. but first I want to add a feature to auto stop charging battery once the LED goes on. it doesn't have to keep monitoring it would be satisfactory for it to completely shut off until reactivated manually via a...
  7. chromei386

    Car battery circuit design - comments, feedback?

    Thank you audioguru, I have gone back and done some calculations with the inputs, and have dramatically reduced the current. I don't understand the part about positive feedback but I am reading the datasheets now and wikipedia. my interpretation of that is: and I'm not sure on what...
  8. chromei386

    Car battery circuit design - comments, feedback?

    Thanks Audioguru, I have switched LM311 with LM339 which has a voltage range 2-36V: http://www.national.com/mpf/LM/LM339.html#Overview The 15V is regulated by a computer PSU. Is that what you mean? I have added a pullup resistor on LM339 output - value as per datasheet
  9. chromei386

    Car battery circuit design - comments, feedback?

    Hi, I have designed, based on another car battery charger (http://www.aaroncake.net/circuits/charger1.asp?showcomments=all), a circuit to charge a lead-acid battery to about 14.4V then auto-shut off and light an LED. I think it may need some work but will the concept work?? Am I crazy? The...
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