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  1. audioguru2

    0-30 Vdc Stabilized Power Supply

    You will have a lot more than only 0.6V on a diode carrying 3A, unless it is a Schottly. If it is external to the circuit then it will ruin the superb voltage regulation. You could protect the supply with a diode inside the feedback loop like this: EDIT -
  2. audioguru2

    0-30 Vdc Stabilized Power Supply

    My Energizer Ni-MH cells reach 1.4V when I think they are fully charged and the voltage keeps climbing. In the case for your 4.8V battery it will be about 5.6V.
  3. audioguru2

    0-30 Vdc Stabilized Power Supply

    I just use a wall-wart DC supply and a resistor to charge my batteries overnight. A regulator's current remains constant even when the battery is fully charged, causing overcharging. My resistor has less voltage across it as the battery reaches full charge so overcharging isn't as much a problem.
  4. audioguru2

    Troubleshooting for SLA battery charger

    Hi Harry, VR1 sets the max voltage, and VR2 sets the current of that project. IC2 is made to be a constant current source so its output voltage equals the battery's voltage. You would need to ask the battery's maunufacturer about the battery's fully-charged voltage. Some older lead-acid...
  5. audioguru2

    Design and construction of 3kVA inverter incorporating a 200Ah battery

    There isn't much to understand about an inverter. It is a power oscillator driving a step-up transformer. The input power is more than its output power. Power equals Volts times Amps, so to get a high power from a low voltage battery you are going to need many Amps. ;D
  6. audioguru2

    Inverter Circuit 12V DC to 230VAC Sine Wave

    Hi Musty, That project has corrections to make it work properly, and its output is a simple square-wave, not a complicated and expensive-to-make sine wave.
  7. audioguru2

    0-30 Vdc Stabilized Power Supply

    C3 is only 47uF and will discharge a lot quicker than the huge main positive filter cap. The problem is caused when the negative supply disappears then U2 loses its negative supply, causing its output voltage to rise if it was fairly low.
  8. audioguru2

    query abt plant watering watcher I

    Hi Meshal, In the Plants Watering Watcher I project: 1) IC1d is a Schmitt-trigger oscillator and uses D1 and R2 to quickly charge C1 which causes its duty-cycle to be so that its output is low for most of each cycle. 2) IC1a is an inverter. 3) IC1b and c are paralleled NAND gates which drive the...
  9. audioguru2

    LM317 Variable power supply

    No way, Alun. Your 18V/2.5A transformer has a 230V max primary current of 196mA. If it was 1k then it would drop 196V at full power and nearly double its output voltage without a load. Definately. It shows 1k for about a 60 ohms resistance. I hope you used a diode to discharge the cap at...
  10. audioguru2

    0-30 Vdc Stabilized Power Supply

    I am sorry that I made an error with the emitter of Q1. The original schematic is correct. I corrected my mistake in a post a while ago. It is not a serious error. The connection location for the emitter could be at the output's 0V terminal without harm and Q1 will still do its job of shorting...
  11. audioguru2

    LM317 Variable power supply

    Hi Alun, Your 18V transformer is rated to produce 18VAC at its rated current. It isn't a little 200mA wall-wart whose voltage doubles without a load, so its internal resistance is extremely low. So low that its voltage doesn't drop much when the rectifiers conduct their massive current. The main...
  12. audioguru2

    0-30 Vdc Stabilized Power Supply

    42VDC when loaded is normal for your 32V transformer. The 30V transformer that we recommend would produce 40VDC and reduce max heating in the output transistor by only 6W. Measure the current-regulator's pot. Your 4.8A max output indicates that its value is more than 14k, or the resistance of R7...
  13. audioguru2

    high voltages

    Ridiculous! I create more than only 30,000V of static electricity each time I comb my hair or walk across a carpet in winter. I don't set anything on fire because the current when I touch anything grounded is so low. The few hundred pF of my body's capacitance to ground holds only a tiny charge...
  14. audioguru2

    LM317 Variable power supply

    Hi Alun, My math shows a 25.4V peak from your transformer. The rectifiers drop it to about 23.4V. Subtracting the 1.2V output leaves 22.2V. At 2.5A then 22.2V produces 55.5W in the regulator. The TO-220 plastic case has a 4 degrees C/W rating. Mounting the regulator to a very big heatsink...
  15. audioguru2

    0-30 Vdc Stabilized Power Supply

    There is your problem. With your 46V supply (your transformer's voltage is too high) and 11V output at 4.8A, the power dissipated in the 2N3055 is 157W! The pot shouldn't give 4.8A anyway. The 11.2V reference at the output of U1 is applied to the voltage divider of R18 (56k), P2 (10k) and R17...
  16. audioguru2

    Re: what is trimmer

    Hi Staigen, The project's http://www.electronics-lab.com/projects/sensors/016/index.html IR photodiode and opamp circuit is interesting. At first I thought: 1)Where is the reverse bias voltage for its IR photo-diode, so it can leak current (conduct) when it receives radiation? 2) Where is the...
  17. audioguru2

    0-30 Vdc Stabilized Power Supply

    How can a 2N3055 in a metal TO-3 case split? ??? Maybe you are using a 2N3055 in a plastic case, that can't dissipate up to 60W like one in a metal case. It failed very quickly. I expected it to take a few seconds to overheat before failing. Don't you have the 2N3055 bolted to a huge heatsink...
  18. audioguru2

    LM317 Variable power supply

    A blow-torch de-solders parts quickly!  ;D ;D
  19. audioguru2

    LM317 Variable power supply

    The output voltage would jump lower when the LM317 goes into thermal shut-down. The TO-220 plastic package with a metal heatsink tab can't dissipate much power, about only 25W with an infinite heatsink and about 20W with a pretty big heatsink. Alun, the chip in your LM217 must have been way...
  20. audioguru2

    help me please??? table hockey game...

    Where on earth (?) are you? There are lots of ways to make a timer with difficult to find logic ICs, but 555 timer and LM3914 bar-graph ICs are pretty common nearly everywhere. Have a look at the datasheet for the LM555 timer. It shows it with a constant current source transistor producing a...
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