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  1. KrisBlueNZ

    Ring detector circuit, transistors not fully activating

    Why is Cnotsure connected to pin 5 of the 555? That side of that cap is supposed to be grounded.
  2. KrisBlueNZ

    Amplifier power supply capacitor removal advice needed!

    Re the pots, the fourth pin could be a tap for loudness compensation. Can you take closeups of the area around the pots from both sides? (Component side and underneath.) Use plenty of illumination (natural light is best) but no direct sunlight, to avoid reflections. Take the component side...
  3. KrisBlueNZ

    help with a small project - precise 1rpm motor & circut

    It looks pretty cool but it doesn't generate the control signals entirely by itself - it needs a "step" signal which would have to be generated by a crystal-controlled oscillator with frequency division. Its focus is on microstepping, i.e. stepping a stepper motor less than one complete step...
  4. KrisBlueNZ

    Amplifier power supply capacitor removal advice needed!

    You can replace axial caps with radial caps or vice versa, as long as they're the same capacitance and voltage (or you can use a higher voltage), and in some cases, the same type. Post a photo and/or description of the caps you want to replace and we can advise. You can remove the pots...
  5. KrisBlueNZ

    help with a small project - precise 1rpm motor & circut

    BobK, thanks for doing the research. I thought maybe a board with a motor driver and an accurate configurable digital control circuit might be used in robotics, but I guess not. So you (the OP) will need a "dumb" driver board and a circuit to generate the required control signals from an...
  6. KrisBlueNZ

    Component help

    That's a linear current regulator, controlled by a PWM signal. I mentioned this option in my earlier posts. It will work, but Q2 will dissipate heat and waste power. The power dissipated in any component can be calculated from the Power Law: P = V I, where P is power in watts, V is voltage...
  7. KrisBlueNZ

    Amplifier power supply capacitor removal advice needed!

    That's a point duke37. With the pots turned to maximum, check for any DC voltage across each pot. That is, between one end and the other. This would indicate failure of one or both of the DC blocking capacitors connected to the pot.
  8. KrisBlueNZ

    supply voltage for the sensor

    It might also be feasible to use a solar cell to power the transducer, with a light bulb to supply the light energy to the solar cell. This will give a very clean supply voltage with no common-mode noise. You would need a regulator on the solar cell output; use a low-dropout (LDO) 5V regulator...
  9. KrisBlueNZ

    Amplifier power supply capacitor removal advice needed!

    Thanks for the PDF. It's really helpful to have some idea of what we're talking about; there are so many different audio amplifiers around. If the noises happen as you turn the volume pots, and come from the speaker that's associated with the pot you're turning, it's probably bad spots on the...
  10. KrisBlueNZ

    help with a small project - precise 1rpm motor & circut

    I don't think the Jaycar kit is what you want. I think when they say "manually" they mean that you can step the motor by pressing keys on the PC. I don't think there is any kind of controller on the board. I could be wrong. There isn't enough documentation on the Jaycar site to be sure. I...
  11. KrisBlueNZ

    Amplifier power supply capacitor removal advice needed!

    Nothing comes to mind from your brief description. Can you tell us the brand and model number of the amplifier? Do you have a link to its circuit diagram? Does this noise happen even with the inputs disconnected? Does the position of the volume control make any difference? Does the...
  12. KrisBlueNZ

    supply voltage for the sensor

    Those are cute little power supplies. The output ripple is pretty high though. Harald addressed this earlier in this thread, in post #4. These are switching converters and they produce a lot of output ripple. You'll need a filter - either inductor-capacitor or resistor-capacitor - between the...
  13. KrisBlueNZ

    Component help

    I don't know what you're asking me. You suggested using multiple LEDs, not me. As Steve explained, two LEDs don't look twice as bright as one LED (assuming the currents are the same). This is a big reason why using one, two or three LEDs for different brightness levels is not a good idea. The...
  14. KrisBlueNZ

    How UC3845 Control Pin work?

    I don't think there are any substitutes for the UC3845 (apart from UC1845 and 2845 which are the same but in different temperature grades). It's still readily available AFAIK.
  15. KrisBlueNZ

    Component help

    I don't think it's a good idea to use extra LEDs to get different brightness levels. A boost converter with current regulation is not large. The largest part is the inductor. And there are lots of ICs that do all, or most, of the work. You would still be best to use a micro to read the...
  16. KrisBlueNZ

    help with a small project - precise 1rpm motor & circut

    That's the kind of board you need, yes. But I wouldn't search on eBay because the information you get is too brief. Look for web sites of companies that design and make stepper motor control boards. These will have detailed descriptions of what the board is capable of doing, and should have...
  17. KrisBlueNZ

    help with coupling components

    That's great jrb. Thanks for posting a follow-up.
  18. KrisBlueNZ

    Component help

    No, running them in series would require 900 mA. When they're in series, the same electrons flow through both of them. The voltages add, so you would be supplying 900 mA at twice the LED forward voltage. The alternative, with the LEDs in parallel (though you mustn't connect them directly in...
  19. KrisBlueNZ

    Mysterious diode identification help!

    I don't know of anywhere you could salvage a big resistor from. No doubt there are types of equipment that have them, but nothing I know of, and no consumer product that I know of. Have a look at http://www.digikey.com/product-detail/en/HL05006Z100R0JJ/HLB-100-ND/713668. It's a 50W, 100 ohm...
  20. KrisBlueNZ

    help with a small project - precise 1rpm motor & circut

    Bob, I agree it would be too much for a beginner if he had to design it all, but I imagine there are stepper motor driver boards available with documentation on models of stepper motors they can drive, and how to get a particular speed, etc, so maybe there wouldn't be much design involved. Some...
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