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  1. (*steve*)

    impose current ceiling

    It was probably trying to dissipate 10W to 15W. That's waaaaay too much for a TO220 device all by itself. I would probably not use that mosfet for anything critical any more... Grab another one and fit it to a heatsink. You should be able to leave your finger resting on the mosfet at this...
  2. (*steve*)

    Buck convertors

    I have no idea how accurate the 5 digit current meter is, but the 3 digit one only has a resolution of 100mA, so that won't work for you. If you have a 3A meter, I'd not try to put more than 3A through it. If it comes to that, just make your variable current limit top out at 3A. 68 degrees is...
  3. (*steve*)

    RE-Maplin Electronics in the USA.

    It's the export regulations that are restrictive. Why concern yourself with maplins when there's so many US retailers with better range, prices, and shipping?
  4. (*steve*)

    impose current ceiling

    Not really, but you may not maximise your power, especially if one panel is slightly shaded.
  5. (*steve*)

    Modified meter lead for breadboards.

    I want an IC with an ∞ pin!
  6. (*steve*)

    Relay switching

    Try this: R1 and R2 about 1k, D1 1N4001, Q1 and Q2 BC548 or similar. Note that this driver (like many simple drivers) will invert the signal from your microcontroller. Program it to operate the output the reverse to how it does now.
  7. (*steve*)

    PIR and LDR light circuit

    50mA should be fine for those transistors.
  8. (*steve*)

    Voltage on a white LED.

    For those who don't know the difference, lumens are a measure of total light output, candella are a measure of brightness. LEDs are generally made brighter by focusing them (you'll note they have a smaller half-angle). LED efficiency (measured as lumens per watt) has been increasing since LEDs...
  9. (*steve*)

    LEDs

    It means that at 15 degrees from the axis, the apparent intensity falls to half. So yeah, that's 15 degrees on both sides. However it will be visible (just dimmer) as you move further and further off-axis. Oh, and it's "angle", not "angel" (unless it comes with an imaginary winged being to...
  10. (*steve*)

    Simp.e romote control

    I use the RF24Network library for the stuff I do. Both it and the RF24 library come with a heap of examples. Have you got them working? The "GettingStarted" sketch is probably the place to start.
  11. (*steve*)

    Buck convertors

    The maximum current you can safely draw from this DC source is about 6.25A You will need to place the ammeter and voltmeter after the regulator (ammeter in series and voltmeter after it across the output terminals). Because the ammeter will drop some voltage, you will see a slight drop (maybe...
  12. (*steve*)

    PIR and LDR light circuit

    If you can leave your finger on either/both of those transistors indefinitely, they're not too hot. The current through the LEDs vary exponentially with voltage, so a higher voltage drop across the transistors will probably cause a disproportionately lower current. This will tend to be...
  13. (*steve*)

    Modified meter lead for breadboards.

    Don't hold back! Photos!!! :)
  14. (*steve*)

    PIR and LDR light circuit

    There's lots of possible problems, but does it work ok? At the very least we need to know more about the light panel and the pir. Slowly changing light levels could easily make the middle transistor get quite hot when the LDR is triggered on. The voltage drop across the two transistors on the...
  15. (*steve*)

    Buck convertors

    Your question is not very clear. Sure, you can run 2 buck converters from a single power source. However, from here on your explanation gets very hard to follow. What is your "transformer"? Is it literally a transformer, or is it some sort of DC power supply? If it is the former, you will...
  16. (*steve*)

    Simple transistor / LED circuit problem

    With the collector and emitter connected backwards in this circuit you will have significantly damaged the transistor. If you have spares, throw this one out and use another one. If not, get a new one and replace this one. Oh, without a series resistance for your LED, you've probably damaged...
  17. (*steve*)

    Secure Brief Case - Electronically activated lock

    Craig, are you looking for an already made device, our are you wanting to build one? How are your programming skills? Any connection by accessible USB ports is going to be very insecure. External charging points can also be problematic. How secure does this have to be? Is it being used in a...
  18. (*steve*)

    Secure Brief Case - Electronically activated lock

    This isn't like email. You don't have to send the same message to different people.
  19. (*steve*)

    impose current ceiling

    Remember that those breadboards are not good for high currents
  20. (*steve*)

    Simp.e romote control

    I'd always use a separate 3v3 regulator. I'm also sure there is sample code for those libraries. Have you tried it? If I remember I'll pull out the code I've used to get these devices to talk to each other.
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