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  1. KrisBlueNZ

    Valve (tube) amplifier schematic help

    Solidus, interesting comments. Yes, hard clipping sounds harsh because of all the harmonics generated by the sharp edges on the waveform. That's why some fuzz guitar sounds can be mixed quite low and still cut through. I'm interested in your comments about differences in 12A*7 valves. Have you...
  2. KrisBlueNZ

    resistor should be renamed lol

    Excellent advice and descriptions on this thread. Especially, I like Steve's summary. Personally I find that I don't need to think about the physics in my everyday electronics design process - when you're choosing between a 10K and a 22K pullup resistor, for example. I think of a resistor as a...
  3. KrisBlueNZ

    Valve (tube) amplifier schematic help

    I think (not certain) that the "valve distortion" ("tube distortion" for Americans) sound is only really achieved when you drive a valve output stage into clipping. Normally these output stages have one or more pairs of power pentodes (or beam tetrodes) driving both sides of a centre-tapped...
  4. KrisBlueNZ

    Motor control diy

    As long as the pulley on the motor is small enough I don't think he'll need gears or PWM. The 4500 RPM is unloaded; it'll be a bit less loaded. The shaft is around 3 mm diameter and I did calcs in an earlier post that worked out at 0.5~0.75 m/s using the motor shaft as a pulley. A steel cable...
  5. KrisBlueNZ

    heat switching relay

    "15K" isn't enough information. That's its resistance at a particular temperature, probably 25 degrees Celsius. It doesn't tell us how low its resistance will go at 100 degrees Celsius. Most likely its resistance won't drop too low at 100 degrees Celsius and there won't be a problem with either...
  6. KrisBlueNZ

    DC in series with AC

    If it's an analogue scope, make sure the "variable" vertical gain adjustment is turned fully clockwise. This is usually a little rotary control in the middle of the input range selector. It should click when it's fully clockwise.
  7. KrisBlueNZ

    heat switching relay

    Yeah, good idea. But there might be a problem with high current drain and possibly even self-heating of the thermistors if they thermistors are NTC and they get hot. I was going to suggest Steve's idea too, but with a single-supply op-amp or comparator, in case the thermistors get so hot that...
  8. KrisBlueNZ

    What value of resistors do I need and a sanity check

    It would help if I knew which country you were in. I'll assume you're in America and point you to the Digikey web site. Digikey and Mouser will sell you almost any electronic component you would ever want. Here's an updated schematic. Resistors in this application are not critical. For...
  9. KrisBlueNZ

    Motor control diy

    Thanks for the nice physical drawing Chris. That should work nicely. I should have included a fuse in my schematic, as you did. 1A should be plenty since the motor is specified as 6W i.e. 0.5A. Anti-surge would be desirable I think. In this case I think the motor pulley will need to be quite...
  10. KrisBlueNZ

    Motor control diy

    Here's a wiring drawing and description. It looks confusing at first glance but it isn't. I've marked the "away" and "back" circuits separately with arrows, which show the direction of current flow (conventional current - positive to negative). I've drawn the switch as it appears in real...
  11. KrisBlueNZ

    Bicycle Turn Signal Electronics needed.

    I think you're right Chris. I've always thought there was a deliberate association. The MOSFETs with 3055 in their number aren't part of any series - there are no MOSFETs with 3054 or 3056 in their number. Also, there are similar P-channel MOSFETs with 2955 in their number, so that's a dead...
  12. KrisBlueNZ

    Motor control diy

    Chris, that's a nice looking switch. And that's a good point about that style being much easier to mount. I guess the OP has to make the choice between a momentary (aka spring-loaded or centre-biased) switch, and a switch that stays in position. If there's no advantage to being able to walk...
  13. KrisBlueNZ

    Bicycle Turn Signal Electronics needed.

    Here's an updated version of the schematic. I've followed some of duke37's ideas and included a zener and series resistor to protect the 555 "just in case" (shouldn't be needed if you're using a dedicated battery), and I've shown the formula for calculating the flash frequency so you can vary...
  14. KrisBlueNZ

    Bicycle Turn Signal Electronics needed.

    Sure, you could mount the switch 12~18" away from the control box, as long as the wires are well insulated. But I wouldn't use 3.5" jacks - any outdoor exposure will quickly lead to corrosion. You really need a fully airtight and water-tight plug and socket arrangement for everything. If you...
  15. KrisBlueNZ

    1V/Oct Control for oscillator

    I haven't been able to find the article. I'll look again tomorrow. Have a look at http://www.midimplant.com/ for a compact MIDI-to-CV converter. There are several others available but they're big and expensive, and this one is probably all you need.
  16. KrisBlueNZ

    Motor control diy

    That motor is rated for 6W which is 0.5 amps at 12V. I would use a 12V DC power supply rated at 1A or more. Any type will be OK. A plug-in adapter would be fine. Both of those switches look OK. Personally I would go for one with a "paddle" that you can push or pull with your finger, but a...
  17. KrisBlueNZ

    1V/Oct Control for oscillator

    I think you may be able to find a better design for the MIDI to CV converter. I see a few problems with that one, including what looks like an error in the schematic and lots of design decisions that aren't good. The main problem is that the DAC only has 8 bits of resolution, which means the...
  18. KrisBlueNZ

    Diode help

    All good advice here. Here are a few specific pointers. All diodes drop SOME voltage. Standard diodes will drop about 0.8V or a bit more, depending on the current flowing through them. This means your 24V battery will be 23V at the camera. Schottky diodes drop about half as much voltage and...
  19. KrisBlueNZ

    1V/Oct Control for oscillator

    Steve has answered this. No, 1/4 watt resistors will be fine. Yes, but don't worry about it, it's not exactly going to be a big contributor to greenhouse gases! The oscillator has to keep running after the key is released, so you can hear the "release" part of the ADSR...
  20. KrisBlueNZ

    Motor control diy

    Shaft diameter is 3.7 mm which is circumference 10 mm (1 cm). Speed is 4500 RPM unloaded which is 75 revolutions per second. This equals 75 cm (3/4 metre) per second, assuming you don't use a pulley. Under load it will be somewhat slower; say 50 cm per second. That sounds reasonable to me. What...
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