Search results

Search Forums New Posts
  1. KrisBlueNZ

    Boiling capacitor!

    Well I'm glad you think that, since overunity devices don't exist! BTW any "device" that claims to be a magnet-only motor also doesn't exist. Its only practical application is to part gullible, scientifically uneducated investors from their money. High voltage spikes at low current is a...
  2. KrisBlueNZ

    How this circuit works ?

    You're welcome. I hope you followed it and found it interesting. Different types of circuits can be explained in different ways. In this case, the circuit is fairly straightforward and switches between two clear states, so I described the states and what causes the state changes, and went into...
  3. KrisBlueNZ

    How this circuit works ?

    Two-transistor relaxation oscillator - description This circuit is called a "relaxation oscillator". To understand how the circuit works, you need to consider the voltages on Q1 base and Q2 collector, and the OFF/ON states of Q1 and Q2. Start with both transistors OFF and C1 discharged. In this...
  4. KrisBlueNZ

    Automated Volage Slector

    Perhaps a USB sound card, or a chip that integrates a DAC and a USB interface? I googled "USB DAC" but mostly found pretentious and elitist audio company sites advertising overpriced products using meaningless jargon and unsubstantiated claims with the hope of parting gullible audiophiles from...
  5. KrisBlueNZ

    Automated Volage Slector

    As usual there is almost no information in this question from which to make any useful suggestions. Please give a lot more information about what you're trying to do, what existing circuit design (if any) you have, what hardware you are using to interface with the computer, what software you are...
  6. KrisBlueNZ

    animal repeller

    The repeller presumably uses an ultrasonic signal to repel dogs. Normal loudspeakers don't reproduce ultrasonic frequencies. Some tweeters have a bandwidth that extends into the ultrasonic range. If you want to make the signal louder, you obviously need a more powerful transducer, probably with...
  7. KrisBlueNZ

    This Is What's Really Needed!

    I agree, Digikey are a great first port of call when looking for possible components for a design. They know about manufacturers that I didn't know about. They sometimes know about new or special types of components that I didn't know about. They have parametric searches. They have direct links...
  8. KrisBlueNZ

    Tachometer Signal Modification Circuit Help

    What information do you have on the sensor? If it's powered from a DC supply it is probably a hall effect sensor with a digital output. These are usually 5V-powered; are you sure the controller is providing 12V? Are you sure the sensor is supposed to operate from 12V? Is it possible the sensor...
  9. KrisBlueNZ

    Need Advice 110 to 24v

    One thing you could try... "Borrow" a couple of fully charged 12V batteries from cars, connect them in series to get your 24V, connect a DC ammeter in series and power up the patient lift, to see how much current it draws. You'll need to test it under all conditions, and under load (with a...
  10. KrisBlueNZ

    tachometer

    Thanks for the explanation. It's still short on detail but it gives us somewhere to start. So you're talking about implementing an automatic gearbox. I've never done anything like this but I'll try to make some suggestions. What is the application? What is the output being used for? An automatic...
  11. KrisBlueNZ

    Power supply failure alarm

    The diode is needed because the circuit's input voltage goes to zero when the power supply fails; if this was connected directly to pins 2 and 6 of the 555, the 555 wouldn't be able to oscillate because pins 2 and 6 would be being held at ground potential. The diode allows the incoming voltage...
  12. KrisBlueNZ

    Coin counter photo-detector

    Raven, I think you're right. In that case the detectors are more likely to be active devices like the OPL550/551 http://www.optekinc.com/datasheets/OPL550.PDF since there don't seem to be any pullup resistors on the board so there is no need for a supply rail on the board if the devices are just...
  13. KrisBlueNZ

    Power supply failure alarm

    The 555's oscillation is controlled by the capacitor from pins 2 and 6 to ground, and the resistor that comes from pin 3. When it is oscillating, the voltage on pins 2 and 6 swings between two voltage thresholds, that are set at 2/3 and 1/3 of the supply voltage by an internal voltage divider...
  14. KrisBlueNZ

    Coin counter photo-detector

    You could try Element14, Mouser, Fry’s Electronics, RS Components, and maybe Jameco if they still exist? I would like to know whether all three pins on the devices are used, or just two. It would be useful to have a circuit diagram of that board. Are there any other components? Perhaps...
  15. KrisBlueNZ

    Coin counter photo-detector

    Knowing the LED part number will tell you the wavelength you should aim for, but there are several other characteristics of the phototransistor/photodiode that need to be right as well. Radial and axial refer to whether the leads come out the same side/end of the device (radial) or whether they...
  16. KrisBlueNZ

    Coin counter photo-detector

    Hi PWood, welcome to Electronics Point and thanks for explaining your question so clearly. As Raven Luni says, they're probably photo-transistors (or perhaps photodiodes). Can you lift one up to see if there's a part number printed on the back? You can look on Digi-Key...
  17. KrisBlueNZ

    tachometer

    Your question is VERY short on detail. You need to describe everything in MUCH more detail. Obvious questions that arise in my mind as I read the post are: What is the shaft connected to? How fast is it expected to turn? Do you have any ideas on how to detect its rotation? Can you attach a...
  18. KrisBlueNZ

    Connecting 20 3v LEDs in series?

    If it's going to be near a swimming pool, definitely keep the voltage as low as possible, for safety. There's NO WAY I would put 60V anywhere near a swimming pool; even 15V could be dangerous. I think Steve's suggestion would be best - a two-wire bus carrying around 3-4V, with an individual...
  19. KrisBlueNZ

    Power supply failure alarm

    You're welcome. That's great :-)
  20. KrisBlueNZ

    Connecting 20 3v LEDs in series?

    Connecting LEDs directly in parallel without individual resistors is not recommended because there are variations in forward voltage between LEDs, even LEDs from the same batch, that will cause some LEDs to draw more current than others and therefore glow brighter. Also the temperature of the...
Top