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  1. K

    SMPS question...

    Indulis, I figure you are partially right. A switch mode power supply may contain a switching voltage regulator as well. Maybe he wants a switching regulator for his application.
  2. K

    SMPS question...

    A switch mode supply takes a DC input, and of course mains is AC. There isn't many parts to a switch mode supply, but I wouldn't recommend you design one if all you need is a DC power supply.
  3. K

    Transformer question

    I attempted to construct a step down autotransformer one time with magnet wire. I figured that without a load, if I got the turns right, I would have a simple voltage divider. Being totally reactive for the most part, it would consume very little power. The primary reactance was about 1000...
  4. K

    Transformer question

    Gazza, that is the problem, the turns ratio should have stayed the same. A power transformer needs to transfer energy from the primary to the secondary. How are you going to get power in the primary if the reactance is so high that you don't get any current in the primary? Conversely, how are...
  5. K

    Free wheel rectifier

    I did a little calculation with turning on and off a relay. It doesn't seem like it would always be necessary to add the reverse bias diode. I've seen it used many times, but isn't it just a small precaution? It looks like most of the energy is just burnt up within the coil, and you shouldn't...
  6. K

    Audio Preamplifier Design Project

    I agree. Instrumentation amplifiers are used to rid large signal common mode noise from small signal single ended input information. I only know of airwave interference when it comes to common mode noise, or maybe crosstalk. I would certainly want to test my circuit to prove that my...
  7. K

    Audio Preamplifier Design Project

    Maybe you could use a noise generator to test how well it rejects noise. If you know the source of the noise in your particular application, you might incorporate a filter.
  8. K

    RC Circuit (How?)

    Just a parallel capacitor is what you want. But you need a relay with a 10Kohm coil to slow the relay down.
  9. K

    RC Circuit (How?)

    Probably what will happen is that it will cycle the relay very fast, wearing it out. A large capacitor will hold the voltage on the coil for a period, a larger capacitor might make a noticeable difference.
  10. K

    Automobile ignition power transistor

    Has anbody ever heard of these going bad? I want to replace mine, but it's too expensive. I just want to know if I might get better performance with a brand new ignition power transistor?
  11. K

    Transformer question

    There's not much information written on the transformer itself, just some numbers. But it came from a power supply that had a 120Vac 60Hz input. It weighs about as much as an AC adaptor 4.5V .8A output DC. The AC adaptor says 6W also. The 100ohm load with a 34Vac input stepped down 3:1, just...
  12. K

    Transformer question

    Alright. I took a 3:1 transformer, 34Vac input 10.3Vac output with 100 ohm load. That's 2.1 Watts peak power. I reduced the load to 25 Ohms. 34Vac input 6Vac output. That's 2.9 Watts peak power. The transformer is rated at 120Vac, and put's out 40Vac when plugged into the outlet. That's 3:1. A...
  13. K

    Transformer question

    Okay. All you need is turns ratio and resistance. They say use 60 Hz, but that's only a general rule of thumb. I use 120 Hz.
  14. K

    TV Signal Amplifier ?

    Correct me if I'm wrong, but reducing gain increases bandwith. A 741 can be operated up to about 1Mhz at very low gain. I would have opted for a high frequency opamp in this case, which they do make real high frequency opamps.
  15. K

    Transformer question

    I think the voltage might step down okay with a light load. A power transformer has an iron core to keep the inductance not so high, which makes the reactance lower, which makes the current high. 120Vac can't generate as much current. 1 Watt on the primary can't provide 2W on the secondary...
  16. K

    design square waveform oscillator circuit/ relaxation oscillator

    An opamp output can only be operated to about 15mA DC whether the current is going in or going out. A 5Vpp output into a 2Kohm load is 2.5mApp. A 2Kohm load is optimistic for an ordinary transistor load, however. I would use good size resistors to bias the transistor, with a very low transistor...
  17. K

    TV Signal Amplifier ?

    I wanted to convert my standard rabbit ear antenna into an amplifying antenna. Looking at the circuit, it's all impedance matching. I think trying to add an opamp would just screw things up.
  18. K

    The caps surrounding the LM7812 regulator?

    Okay. I think we weren't on the same page. About the design, the circuit values are chosen around an ideal circumstance. Do you think it was designed around an open load, or a mid value of about .75A. I wouldn't choose a 5A regulator over a 1.5A regulator for a 1A application.
  19. K

    The caps surrounding the LM7812 regulator?

    That's what I said. It regulates 5v with a 7.5V to 30V input. So this is what it must focus on because .... There is no load that can compete with that low of resistance. That means the load is nothing to the regulator up to 1.5A.
  20. K

    The caps surrounding the LM7812 regulator?

    So the regulator really needs to regulate against the fluctuating input, and not worry about the 5 ohm load because it's nothing? Passing 1A without affecting the regulator circuit at all seems farfetched. That is why I think that the regulator, which is a complicated DC circuit, directly...
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