Search results

Search Forums New Posts
  1. KrisBlueNZ

    Negative Thermal Resistance?!?!?

    Only if you're not taking any power out of the power supply! The total power dissipation in all the components will be equal to the input power minus the output power.
  2. KrisBlueNZ

    Trail Camera No Flash Troubleshooting

    If the output diode in a camera flash is shorted, the oscillator won't even run - so you won't hear the squeal. And obviously the output capacitor won't charge up.
  3. KrisBlueNZ

    replace triggering with switching

    I'm not sure what you're asking. Do you want the first 555 to trigger when you first press the switch, but not remain triggered while the switch is held down? If so, you can modify the trigger circuit like this: (image found on the net somewhere...) Keep the rest of your circuit the same; just...
  4. KrisBlueNZ

    Negative Thermal Resistance?!?!?

    I agree with Harald and Bob. If you really truly need to dissipate 150W you'll need several TO-220-package devices in parallel, or a device in a package with a much lower θjc. And a big heatsink, probably with forced air cooling.
  5. KrisBlueNZ

    EMITTER DETECTOR SENSOR

    You should run the IR LED at the current recommended in the data sheet. If in doubt, try 20 mA. IR LEDs have a forward voltage of around 1V so calculate your series resistor using Ohm's Law to give the desired current with (power supply voltage minus 1 volt) across it. For example if your power...
  6. KrisBlueNZ

    decoder for 8051

    OK, I'm going to have another go. I don't think you have grasped even the basics of how an MCU core executes code. I want to take one example case and go through the process that the core uses execute it, step by step, in detail, to see if you can understand it. I want you to read this...
  7. KrisBlueNZ

    Designing a Time Delayed Relay

    I think Digi-Key's best option is http://www.digikey.com/product-detail/en/F20-120-C2-B/237-1491-ND/3986400 which is 35 × 29 mm and 30 mm high. Mouser have a similar range. That one has a secondary voltage of 10V AC. Maximum load current will be about 120 mA (80 mA for the relay coil, 30 mA for...
  8. KrisBlueNZ

    Designing a Time Delayed Relay

    You mean use a transformer to supply the micro, etc? Well, considering how big the circuit has become, that would probably be a reasonable option. Back in the beginning, the whole design was going to be quite small and simple, and I thought it would be worthwhile to use a capacitor-fed power...
  9. KrisBlueNZ

    relay driver

    What is driving the base resistor? If it's a microcontroller or a logic gate, it will pull its output down to 0V when the transistor should be OFF, so there will be no current flowing into the base, and the transistor will not conduct. Therefore you don't need a base-emitter pulldown resistor...
  10. KrisBlueNZ

    Help with RS485

    You should look into the 1-wire devices that Fish mentioned. https://en.wikipedia.org/wiki/1-Wire http://www.maximintegrated.com/en/app-notes/index.mvp/id/1796
  11. KrisBlueNZ

    MOSFET mystery

    Hi there and welcome to Electronics Point :-) Thanks for the clear problem description! Are the mounting tabs of the two MOSFETs electrically isolated from each other? The tabs are connected to the drains and if heatsinking is required, the two MOSFETs must either have separate heatsinks, or...
  12. KrisBlueNZ

    Capacitive Reactance Circuit

    I haven't received mine yet. It's overdue. They said if I don't receive it within a week, to let them know and they'll credit me back. I would rather they tried again :-/
  13. KrisBlueNZ

    Ribbon cable length causes noise for displays why?

    Go ahead and start a new thread, Simmon
  14. KrisBlueNZ

    Designing a Time Delayed Relay

    Sorry for the slow reply! Yes, nice! The catch diode isn't needed with the TPS54062 because the IC contains a second MOSFET that performs the same function. This is called a synchronous converter. When the pass MOSFET turns OFF and the back EMF from the inductor tries to drive the "PH" pin...
  15. KrisBlueNZ

    Basic toy ski lift.

    Hi there and welcome to Electronics Point :-) I think you would be better to switch the motor direction by detecting the position of the cord, rather than relying on a timer, because there will be variations in how far the cord will move for a given run duration and it would be difficult to get...
  16. KrisBlueNZ

    design buck converter with arduino controlling pwm

    I think I would stick with the N-channel MOSFET. Once you have the driver with its bootstrap circuit running, it will give good results. P-channel MOSFETs have higher ON-resistance and poorer performance generally, compared to N-channel MOSFETs, and some kind of non-standard driver would be...
  17. KrisBlueNZ

    XTR116 18F46K22-DAC

    I think your general design is OK. Assuming U1's DAC uses a reference voltage of 5V, R1 should be 5 / (0.016 / 100) which is 31.25 kΩ, not 32kΩ. R1 (100k) provides your 4 mA base output current, but it will actually be 4.096 mA because VREF is 4.096V. R1 should really be 102.4 kΩ, or you could...
  18. KrisBlueNZ

    design buck converter with arduino controlling pwm

    Are you using an IRF540 as you say in your text, or an IRF510 as shown on your schematic? In either case, it's an N-channel MOSFET. To turn it ON strongly, you need to bring the gate about 10V more positive than the source. But when the MOSFET is ON, its source will be at +24V. So you need a...
  19. KrisBlueNZ

    Can you help me indetifying the components? (LED Hourglass)

    Why do you "have to" make your own board? If you buy the kit, you will probably save money overall because the company that makes it will get the boards manufactured in quantity which makes them cheaper. They provide a "manual" for the kit at http://www.electrokit.com/productFile/download/335...
  20. KrisBlueNZ

    12V ride on car help needed

    I haven't figured out what it is. I found a discussion on a Polish electronics forum but there was no clear answer on whether it was just a fuse, or some kind of resettable thermal fuse. It could be some kind of switch as you say. The manufacturer could be a company called Champion who...
Top