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  1. KrisBlueNZ

    Boost converter 12V to 36V (25 mA load) using 555

    Another option is to use a voltage regulator (switching, preferably, for best efficiency) to convert the 36V down to 12V for circuit B so both circuits draw from the three batteries combined. Edit: Or use only one battery and step it up to 36V for circuit A.
  2. KrisBlueNZ

    Which type of large decoupling capacitor for amplifier audio output?

    It's hard to say accurately, because the loudspeaker is a complex load - it consists of resistance, inductance, and motional inductance, due to the movement of the cone, which is affected by the enclosure and environment, and it contains an impedance peak at the natural resonant frequency of the...
  3. KrisBlueNZ

    Which type of large decoupling capacitor for amplifier audio output?

    All components "have an effect on audio quality" but the question is whether it's detectable by anyone's ears. In many cases this question would be answered by double blind testing, but folks who claim to be able to hear subtle differences are very resistant to testing themselves in any reliable...
  4. KrisBlueNZ

    A few beginners questions

    Hi there and welcome to the Electronics Point forums :) Yes, that's pretty much right. There's quite a bit of variation between adapters - a specification of 6V, 350 mA doesn't really tell us a lot about its characteristics. But connecting it to a series group of four 1.2V NiCd cells...
  5. KrisBlueNZ

    Which type of large decoupling capacitor for amplifier audio output?

    It's a standard polarised electrolytic capacitor. The polarity is not marked on the diagram, but the side that connects to the TDA2003 is the positive plate, and the speaker side is the negative plate.
  6. KrisBlueNZ

    Help understanding slow start circuit and tracking circuit in simple dual rail power supply

    You're welcome :-)
  7. KrisBlueNZ

    hello everybody

    Hi there and welcome to Electronics Point :-)
  8. KrisBlueNZ

    Pulsed Output From 8 Data Lines To Drive A Solenoid

    If your loads are really drawing about 500 mA each, you may want to reconsider how you drive them. I assume you were planning to use a ULN2803 or similar. This is really convenient, especially with the built-in diodes, but because they're Darlington transistors, you can expect to lose 1.5~2.0V...
  9. KrisBlueNZ

    Choosing an Opto Isolator

    Yes, that looks right. Here's a schematic I found by Googling those keywords: (http://jumperone.com/images/2011/10/using-relays/002.png) The relay coil is represented by the box with the diagonal line in it. Of course! (Bloody silly Euro schematic symbols...)
  10. KrisBlueNZ

    Could use some guidance with resistors

    22 ohms is a standard ("preferred") value for resistors. If Radio Shack doesn't have it, that's because they're crap. If you use a higher resistor value, the LED current will be lower than you intended. This is a good idea if you were planning to run the LEDs near their maximum current. If you...
  11. KrisBlueNZ

    interfacing gsm to avr atmega 8

    You haven't given us enough information to tell what you're doing wrong. Does the modem need an initialisation string? Does it require delays between commands? What is "cp2100" that you mentioned? Upload a schematic showing exactly how you have connected the microcontroller to the modem...
  12. KrisBlueNZ

    Resistance range to output voltage range

    I don't think that will be an issue in the big scheme of things; it's only a fuel level meter. But I did consider the possibility:
  13. KrisBlueNZ

    Choosing an Opto Isolator

    You connected the zener in series with the diode that's connected across the solenoid, right? The current in an inductor changes only in response to voltage across it, and at a rate proportional to that voltage. When the SSR turns ON, the current builds from zero to a level where it is limited...
  14. KrisBlueNZ

    transistor and speaker help

    Running a constant current through the speaker will displace the cone and halve (or worse) the available movement distance. Using a single bias resistor will make the operating point dependent on the gain of the transistor. The circuit is fundamentlly flawed.
  15. KrisBlueNZ

    Maintaining DC voltage across capacitor with signal?

    I don't think you have a plan to conquer the world. It seems that you don't really have any plan at all. You can't prove a concept if you can't even define that concept meaningfully, and you need to ask meaningful questions if you want meaningful answers. Have fun mucking around :-)
  16. KrisBlueNZ

    5channel fan controller with one control knob

    Your simplest option is a PWM circuit driving all five fans in parallel. Here's a diagram I found: (from http://electronics.stackexchange.com/questions/96776/555-to-drive-a-mosfet) This circuit will emit some interference. This can be minimised by inserting an inductor, e.g. 100 μH and rated...
  17. KrisBlueNZ

    Maintaining DC voltage across capacitor with signal?

    Can you explain to us what you think the difference is between a "DC pulse" and an "AC pulse"? You still haven't told us what you hope to achieve by doing this.
  18. KrisBlueNZ

    Resistance range to output voltage range

    OK, here's what I suggest. There's a complete list of Jaycar parts there. The total cost is about AUD 21. You will also need solder, soldering iron, enclosure, wire, etc. The circuit is a "non-inverting amplifier" using an LMC6482 dual op-amp. This is the most suitable device that Jaycar...
  19. KrisBlueNZ

    High Frequency Amplifier

    If the three-terminal regulator mounts on the same side as the components, then it's drawn backwards. When you view a positive three-terminal regulator (78xx) looking at the markings with the leads pointing down, the input is on the left. Your Q1 and Q2 markings seem to be swapped (compared to...
  20. KrisBlueNZ

    interfacing gsm to avr atmega 8

    Does that modem connect directly to an RS-232 port? If so, you need to use an RS-232 transceiver (e.g. MAX232) between your microcontroller and the modem.
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