Help! building Regulated battery charger

Discussion in 'The Projects Forum' started by jgraham83, May 15, 2009.

  1. jgraham83

    Thread Starter New Member

    May 12, 2009
    In the process of building the circuit below for a project.

    Need help assembling, Im not sure about the pin 4 connection on the op-amp. It references "Z1" but unsure where to connect it. Also the 2.5 volt regulator (mc1403) is this required? can i just put 3 diodes in series to get the 2.1 volts or 4 for 2.8 volts reference. Im a complete noob and i need some assistance. Any help would be apprciated. Simply just need more detailed instructions on the connections.

    thanks in advance
  2. DonQ

    Active Member

    May 6, 2009
    In this case, Z1 is only the "name" given to the CA3140 amplifier (like calling a resistor R3).

    If you find the data-sheet for the CA3140, or any similar op-amp, you will see that pins 4 & 7 are the positive and negative power-supply connections. The positive supply is pin 7 that is connected to C1 & D4. Pin 4 should hook to ground for this single-sided circuit.

    Your regulator will only be as good as your voltage reference, but in this case, the regulator circuit is not of a high enough quality that using diodes instead will make much of a difference. This will only work if you supply them with a current by putting a resistor between them and the positive supply voltage. There are a number of other 2.5 V references you could use instead if the problem is finding this particular device.
  3. jgraham83

    Thread Starter New Member

    May 12, 2009
    thanks so much for the information. I now just need to pick up a better opamp. As i only have a couple 741's in my kit. I really appreciate the help.

    This is for my final project for my advanced electrical apprentiship. The curiculumn has recently changed here in ontario, maybe elsewhere. We have cut out some of the oldschool theory and focused more on electronics. Some of us are really struggling.

    As for this being somewhat of a simpler circuit than others, i was planning on putting this circuit into a 6x6x4 box and drilling 1/2 inch hold for 120 volt plug, and a hole for my 12v battery cables. Ill let you know how i make out. its due in 3 days.

    another thing/ if all goes well, would it be possible to put a couple leds in this circuit without modifying much. mybe a charging led, charged led, and a power on led. let me know what you think. i may be out of my league but if its somewhat simple ill try.