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  1. KrisBlueNZ

    Basic beginner questions (voltage reading/resistors)

    Which resistor are you talking about? Yes, as Harald said, that is probably the reason. The USB supply voltage range is 4.5~5.5V. This is cutting it pretty fine when the laser LED's forward voltage could be as high as 3.41V. That leaves only 1.09V for the current regulator. If it's important...
  2. KrisBlueNZ

    need help identifing this diode,radar unit

    If it's a capacitor, "475K" means 0.47 µF ±10%. The "+20" may be a polarity indication and a 20V rating. If it's polarised it's probably a tantalum capacitor. Here's a 25V-rated one from Kemet: http://www.digikey.com/product-detail/en/T322A474K025AT/399-4580-ND/946598
  3. KrisBlueNZ

    Re-wiring a powered Subwoofer

    You can tell whether it's an earth loop or not by disconnecting the input connector. You can short the signal and ground connections at the signal connector as well. That should eliminate any hum. If it doesn't, it may be due to power supply ripple. If unplugging the input connector stops the...
  4. KrisBlueNZ

    does this seem right?

    Well, since you haven't given us any information on the servo controller you want to use, I can't be very specific! But as you can see, that control chip has two inputs: direction and PWM. The PWM input is the ON/OFF control. So if your servo controller provides an ON/OFF signal and a direction...
  5. KrisBlueNZ

    automatic doorbell

    Fixing the errors would take as long as redesigning the circuit, and I wouldn't be confident it would work. I'll design a new circuit. It may take a few days.
  6. KrisBlueNZ

    12V - 350V 200mA converter for motorcycle CDI

    I don't think those spikes are real Steve. Though adding the zener couldn't hurt.
  7. KrisBlueNZ

    Designing a Time Delayed Relay

    It's hard to be sure, but I think the track that runs northwards from R11 is connected to a via with tracks that run off to C3 and R9. That's definitely wrong - it should only go to C13 an pin 2 of the PIC. That track should not connect to the groundplane either. I can't see whether it does or...
  8. KrisBlueNZ

    Input/Process/Output

    Have you tried Googling how does a TV work?
  9. KrisBlueNZ

    Designing a Time Delayed Relay

    I wish LOL but thanks :-) One reason for going with the data sheet layout vs. the tidy-looking schematic would be that some components need to be physically close to the device - mainly the input and output capacitors, I think - and this may not be shown on the schematic. But post your layout...
  10. KrisBlueNZ

    Designing a Time Delayed Relay

    It's not "tied to" it; it's fed from it. That's to get the 50/60 Hz time base for measuring the turn-off time. You definitely wouldn't try to stick the soldering iron between the relay and the board on the top side, but you could raise the relay slightly off the board so you'll get a bit of a...
  11. KrisBlueNZ

    trigger adjustable converter

    I'll leave the details of the trigger up to you. For the ON/OFF control, you need a way to detect when the trigger resistance is higher than a certain amount. I can't think of any good way to detect this apart from using the trigger to generate a voltage, monitoring that voltage to detect...
  12. KrisBlueNZ

    trigger adjustable converter

    Most likely, yes. If the trigger includes a switch which is OFF when the trigger is fully released, then it's easy. If it doesn't, it should be possible to detect when the trigger is nearly fully released and turn the module OFF then. You need to focus on getting a suitable trigger controller.
  13. KrisBlueNZ

    does this seem right?

    Police and army have reasons to be using firearms. Civilians, not so much.
  14. KrisBlueNZ

    LM358 operating amlifier & Led

    I guess the zener is supposed to be the LED. An LED operates like a low-quality photodiode. So you need a photodiode amplifier. A photodiode can be operated in two modes: photovoltaic and photoconductive. Which is best depends on what characteristics are important - accuracy, speed, etc. Your...
  15. KrisBlueNZ

    does this seem right?

    Ah, yes. It's part of the NZ Government's policy to encourage immigration of gangsters and hitmen. They would be happy to know that their efforts are appreciated. :-/
  16. KrisBlueNZ

    trigger adjustable converter

    I understand. Do you not want to tell us how it will be used? Here are the relevant parts of the data sheet. So the output voltage is controlled by an external resistance that you connect between the TRIM+ and TRIM- pins (pins 1 and 5). The lower this resistance is, the higher the output...
  17. KrisBlueNZ

    does this seem right?

    Have a look at the Microchip TC4469 (http://www.digikey.com/product-detail/en/TC4469CPD/TC4469CPD-ND/115363 USD 3). As I said in post #9, it will drive your existing two P-channel and two N-channel MOSFETs. It includes logic to prevent cross-conduction (shoot-through). The data sheet includes a...
  18. KrisBlueNZ

    automatic doorbell

    Hi there and welcome to Electronics Point. It's helpful if you post the source of the design. I found it at http://www.electronicshub.org/automatic-doorbell-with-object-detection/ It's a pretty poor design. I can point out at least five significant problems with it. But it might work. The...
  19. KrisBlueNZ

    trigger adjustable converter

    Hi there and welcome to Electronics Point :-) There are eight models listed on that page. Which one do you have? Can you tell us about the application? It will make it easier to understand what you want to do. Do you have a trigger controller in mind?
  20. KrisBlueNZ

    Darlington Pair Touch Switch meets Edward Holmes' Toy Piano

    In case you're still looking, here's a design that should do what you want. I've only shown four keys - the bottom three, and the top one. The "JPn" items represent touch areas for fingers. I've used a 555 as the oscillator, against my better judgement, because a DIY electronic project just...
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