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  1. KrisBlueNZ

    kernel and scheduling for RTOS

    vead, you've now wasted Gryd3's time. You are able to use Google and Wikipedia yourself, aren't you? You really have made a big deal out of a couple of straightforward questions on an assignment. Please stop posting questions that you can answer yourself and wasting our time. This is not the...
  2. KrisBlueNZ

    kernel and scheduling for RTOS

    That's not the kind of help we're here to provide. I suggest you submit your answers to your tutor. If they're wrong, your tutor is the best person to explain this to you.
  3. KrisBlueNZ

    741 as differential amplifier

    No problems. Yes, search for "high side current measurement". That's what you want to do. I also think you may need to increase your shunt resistance, as suggested by Adam in post #8.
  4. KrisBlueNZ

    A new dawn... programmable window blind

    If you're going to use an Arduino, you can probably ditch the idea of using a smartphone with an audio file to control things. You might as well do it all on the Arduino. You can get a real-time clock shield, I think, and a display to allow you to program in dates and times. Getting the Arduino...
  5. KrisBlueNZ

    Looking for a component marked "made in Austria"

    Should we be keeping an eye out for Dave's Mailbag segments, Steve? :-)
  6. KrisBlueNZ

    741 as differential amplifier

    No, few op-amps have rail-to-rail inputs. It's advertised prominently for op-amps that have it. Another problem with that design is resistor tolerances. If you do some calculations on the effect of resistor value variations you will see that even variations less than 1% will cause significant...
  7. KrisBlueNZ

    741 as differential amplifier

    Yes, you've drawn the LED backwards. You can't power the 741 from the same supply voltage that you're feeding into the inputs. Have a look at the 741 data sheet; you'll see that the inputs can't be higher than a few volts less than the positive supply pin. With the inputs so close to the...
  8. KrisBlueNZ

    Confusing Relay-Relay Connection .. pls help

    The only mistake is the lack of back EMF suppression on the coil of your 5A DPDT relay. This is unlikely to be a problem because these relays will not be activating very often, but I will mention it for completeness. When the contact closes on a receiver, a circuit is completed and 12V is...
  9. KrisBlueNZ

    Greetings from Paramaribo

    Hi Dario and welcome to Electronics Point :-) Here's a link to your thread in the Circuit Help forum. Steve, you may want to move the technical posts onto that thread. https://www.electronicspoint.com/threads/lets-opensource-zwave.269231/
  10. KrisBlueNZ

    A new dawn... programmable window blind

    I didn't mean that he would use the normal alarm system on the smartphone. I was thinking that it could be done either using an app that could either send commands to other apps at particular times of day (e.g. start the music player at a certain time) or by adding a long period of silence to...
  11. KrisBlueNZ

    A new dawn... programmable window blind

    Yes. Also, the sound file would give you complete control over the fade-up. You could use different sound files to give you different fade-up periods, different maximum brightness, or different "shape" to the brightness vs. time graph. That versatility was the reason I suggested it.
  12. KrisBlueNZ

    Isolation Transformer Potential to Earth Ground

    It's not grounded; it's not connected to anything at all. I don't know the rationale behind the choice between connecting or breaking the ground connection on the output socket. I found a couple of discussions on the subject though...
  13. KrisBlueNZ

    A new dawn... programmable window blind

    Hi Mat and welcome to the Electronics Point forums :-) Have you considered alternatives to natural light? LED technology is advancing all the time in terms of spectral accuracy and efficiency. See the blog at http://edn.com/electronics-blogs/4390303/LED-Zone and the article at...
  14. KrisBlueNZ

    Need help with analogue question

    Well, you worked out that you needed to change the source signal to have a period of 1 second to get a 1 Hz frequency. The calculation is very simple but the question asks you to show it, so you should.
  15. KrisBlueNZ

    Finding a replacement transistor for a theremin design

    OK. Digikey list the Fairchild 2N5486 but not in stock. They list one from Central Semiconductor as in stock for USD 1.00 (but Digikey add significant shipping charges outside USA in my experience): http://www.digikey.com/product-detail/en/2N5486/2N5486CS-ND/4806920 A US company called NTE...
  16. KrisBlueNZ

    Finding a replacement transistor for a theremin design

    Those devices are N-channel JFETs. They're used at audio frequency. The first is used as a variable resistor in a variable attenuator; the second is used as an audio signal buffer. Element 14 (formerly Farnell) have the Fairchild 2N5486 in stock; catalogue number 1387771. The price is NZD 0.61...
  17. KrisBlueNZ

    Parallel connection of 2 AC/DC converters

    Can you upload a diagram of how you have connected them? And/or a photograph?
  18. KrisBlueNZ

    Isolation Transformer Potential to Earth Ground

    The important characteristic of the isolated side of an isolation transformer is that the whole winding is completely isolated from everything. Voltage appears across the winding, i.e. between the Phase and Neutral inputs to the powered appliance, but this supply is fully floating relative to...
  19. KrisBlueNZ

    running a 240VAC led from 24VDC

    Hi Jared and welcome to Electronics Point. You can reduce the values of the resistors on the LED board to make it run from a lower voltage. At present the three on the underside are all 100 kilohm (marked "1003"). I can't make out the marking of the one on the other side. Adding a 12k...
  20. KrisBlueNZ

    electric leakage

    That's kind of like asking whether something gets hotter when its temperature increases. In other words, the unwanted current flow is the leakage; they're the same thing. If you increase the voltage across a leakage path, the current will increase; often the increase in current is greater...
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