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  1. KrisBlueNZ

    Magnetic gearing system!

    Hi Moha, I got your PM asking me to comment on this thread. I don't think I can help much but here goes. I guess it should be possible to use magnets on discs to transfer rotation from one disc to the other. I don't think magnetic coupling will have any benefits over mechanical coupling in the...
  2. KrisBlueNZ

    RS-485 (MAX487 / MAX485) - On-chip fail-safe feature

    I'll try to help, but don't take this as gospel. 1. No, I don't think so. The "fail-safe" feature works by guaranteeing that if the data lines are at the same voltage, the receiver output is high. So, they have changed the behaviour whereby |VA-VB| < 200mV gives an undefined output, because the...
  3. KrisBlueNZ

    3V 2 LED flash circuit

    With a 3V supply your options are a bit limited. There was a device called the LM3909 but it only flashes a single LED. A monostable multivibrator using two transistors will work at 3V. Put an LED in series with a current limiting resistor across each collector resistor. Personally I would...
  4. KrisBlueNZ

    Help please- in making a midi to d-sub cable

    Oh! I assumed that the 9-pin D-sub you were connecting to was a standard RS-232 serial port, but obviously it's not. It's a combined MIDI and SPDIF connector so it will have a proprietary pinout. The cable most likely contains no components; it's just a breakout cable with the appropriate type...
  5. KrisBlueNZ

    Help please- in making a midi to d-sub cable

    Hi Johnny. It may be possible to do what you want. You need to understand that MIDI and RS-232 are not exactly the same, electrically, but can be made compatible. RS-232 uses a common ground and signals are bipolar (positive and negative) with respect to this common ground rail. MIDI uses...
  6. KrisBlueNZ

    C programming code question!

    jackorocko, sorry, my mistake. The | operator is a BITWISE OR, not LOGICAL. You're right, logical operations are two characters. I've corrected my previous posting.
  7. KrisBlueNZ

    C programming code question!

    The vertical bar is a bitwise OR. The two constants defined in the header file, RANGE_0 and RANGE_1, are: RANGE_0 00000001 binary (from 1 << 0 which means 1 shifted left by zero bits) RANGE_1 00000010 binary (from 1 << 1 which means 1 shifted left by 1 bit). The bottom two bits in the data...
  8. KrisBlueNZ

    Oh what to do with a Tetrode tube????

    None of those numbers mean anything to me, but I'm not widely experienced with tubes. No results from googling "5187LL tetrode", nor from "5187L tetrode". I think I've made a few assumptions here. Can you tell us more? Are you SURE they're identical? How big and how heavy are they, roughly? Do...
  9. KrisBlueNZ

    C programming code question!

    RANGE_0 and RANGE_1 correspond to bits 0 and 1 of the data register, which, between them, select the measurement range. Each bit can be 1 or 0, so with two bits, there are four ranges. Before you read the accelerometer, you write a value to the data format register using adxl345_write(). The...
  10. KrisBlueNZ

    Oh what to do with a Tetrode tube????

    Sounds like an opportunity to make a push-pull amplifier. You should get the part numbers though. You connect the anodes of the two tetrodes to opposite ends of the centre-tapped winding on the output transformer, and connect the centre tap to HT. You will need a phase splitter to provide...
  11. KrisBlueNZ

    Woo-Woo Why are there countless attempts to make magnets power generators..

    I see. Physics textbooks, perhaps? Search Amazon for "magnet"? But be sure to avoid the ones that talk about magnetic healing and the power of crystals. Unfortunately, it's STILL not illegal to sell that sort of BS. Well, I think you have elegantly answered the question that is the title of...
  12. KrisBlueNZ

    Woo-Woo Why are there countless attempts to make magnets power generators..

    Any pro-rotational force the static magnets supply at some part of the rotational cycle will be at least equalled by the counter-rotational force they supply at other parts of the rotational cycle. Force is not the same as energy. Adding magnets will never help the wheel to turn faster. Only...
  13. KrisBlueNZ

    How can rotate stepper motor?

    Right, the D suffix device doesn't need the external diodes. Steve didn't notice this initially, but we know now. You don't need external diodes.
  14. KrisBlueNZ

    How can rotate stepper motor?

    Hmm, yes. I'd suggest connecting a 2-pin bicolour LED (with series resistor) acoss each stepper motor winding, and yes, check the voltages on the VCC and Enable pins. He doesn't say whether the motor moves *at all*. If the sequence was wrong, you'd expect it would at least shudder a bit. A bit...
  15. KrisBlueNZ

    How can rotate stepper motor?

    (*steve*), the data sheet says that the D-suffix version of the L293 has the protection diodes built in. I think you have the sequence wrong. If your sequence numbers on the four control signals are right, you will have the following sequence of signals on the stepper motor windings: 1. Gap...
  16. KrisBlueNZ

    Woo-Woo Why are there countless attempts to make magnets power generators..

    I don't want to seem like a wet blanket, but I'm trying to save you from wasting your time and being disappointed in the end, which is always how these experiments work out. Unless you get tricky and make misleading YouTube videos in the hope of getting "investors"... who you then have to feed...
  17. KrisBlueNZ

    Woo-Woo Why are there countless attempts to make magnets power generators..

    Okay... No. In a perfect (frictionless) system, they will neither speed up the wheel, nor slow it down. The reason is simple: the repulsive force acts as much AGAINST the rotation of the wheel when the magnet on the wheel is APPROACHING the static magnet, as FOR the rotation of the wheel when...
  18. KrisBlueNZ

    Woo-Woo Why are there countless attempts to make magnets power generators..

    Sure, you can use moving magnets, or stationary electromagnets, to make a wheel rotate. It's called a motor.
  19. KrisBlueNZ

    Woo-Woo Why are there countless attempts to make magnets power generators..

    No, you're missing the point. Magnets can never add speed to a system. The closest you'll get is when you turn the wheel just past the point of maximum repulsion. Then, the repulsive force will give the wheel a "kick". But to GET the wheel to that point, you needed to provide MORE energy...
  20. KrisBlueNZ

    Woo-Woo Why are there countless attempts to make magnets power generators..

    It's tempting to imagine that there's a special position, or combination of positions, where statically positioned magnets could make a wheel spin; this is exactly the temptation that's being exploited by the creator of the "magnet motor" video you pointed us to, but it's not true, as BobK...
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