Search results

  1. S

    LEDs in parallel don't consume sum of individual currents??

    I checked the currents that passed through several LEDs at a particular voltage. They varied from 12.0 to 15.1 mA at 3.0 V. I then connected them all in parallel and the current running through them was about 22 mA. How can this be? I thought it would be the sum of the currents that passed...
  2. S

    Multimeter giving bad voltage readings

    I've had a cheap Precision Gold Academy PG 10B multimeter since I was a kid (so it's about 20 years old) but just recently I've got reason to suspect the voltage readings. For my computer PSU it gives the 5 V rail as 5.8 V and the 12 V rail as 13.9 V. For my variable power supply it gives any...
  3. S

    What do people stick their self-adhesive breadboards to?

    I have a couple of breadboards and they both have spongy self-adhesive backings. Searching the Internet suggests to me this might be more common than not. What are people sticking their breadboards to?
  4. S

    Electronics modules names and why there are so many manufacturers of the same thing

    It seems like there are many different manufacturers of the PIR module HC-SR501 and this confuses me somewhat. What is the name "HC-SR501"? There's only one manufacturer of the Galaxy S7 and that's Samsung. Why is it different for the HC-SR501? Did the originator not patent it or is the patent...
  5. S

    That kind of photodiode to use for HC-SR501 PIR module.

    I meant "What kind of photodiode..."
  6. S

    That kind of photodiode to use for HC-SR501 PIR module.

    I'm using a "HC-SR501" PIR module to control a lamp I'm making for my hallway. As well as being motion-activated, I want to use a light sensor to only allow activation after dusk. The HC-SR501 comes with this functionality - you just need to add a suitable component at the right place on the...
  7. S

    Flickering flame simulation with PIR motion sensor - mostly need help with transistor, I think

    I've more or less built the circuit on breadboard and it works! I just need to tweak some things and then transfer to stripboard. I'll post some pictures or video in the next week or so. Thanks again!
  8. S

    Decorative wiring: enamelled copper?

    I'm intent on glueing the wires to the surface of the candelabra once I confirm that there are no short circuits. I may have to strategize a way to protect the wire whilst its pulled into place before removing the protection and glueing the wires down. Grommets probably aren't suitable due to...
  9. S

    Decorative wiring: enamelled copper?

    I'm making an LED candelabra and the wiring has to be visible because it's running along the outside of the candelabra. Is it a totally mad idea to use polyester enamelled copper for the wiring? I think it's the least aesthetically unpleasant option. Are there different thicknesses of enamel...
  10. S

    3.85 V li-ion battery to replace 3 V lithium cell in bathroom scales?

    But then when the potential drops to nominal voltage, it will be too low. I think a voltage regulator is the only way but I can only find them for 3.3 V except a few SMD packages. I think I can work out a resistor to use by measuring current consumption at the rated voltage. Is a regulator dead...
  11. S

    3.85 V li-ion battery to replace 3 V lithium cell in bathroom scales?

    Thanks, Harald. I already have some diodes so I guess I'll just use one of those.
  12. S

    3.85 V li-ion battery to replace 3 V lithium cell in bathroom scales?

    I have a couple of old phone batteries which I would like to put to use and I have bathroom scales which use a single 3 V lithium coin cell. Would the electronics in the scales be likely to be damaged if connected to a lithium-ion battery? The scales have an LCD screen in case that helps.
  13. S

    Flickering flame simulation with PIR motion sensor - mostly need help with transistor, I think

    I added an extra transistor to increase the current I could get through more strings of LEDs. I will probably use 15-18 LEDs. I just need to order the PNP transistor and I'll be set. Thanks again. I'll post some videos in a few weeks if I get it working. Edit: Damn, I just noticed that adding...
  14. S

    Flickering flame simulation with PIR motion sensor - mostly need help with transistor, I think

    Thanks a lot, cjdelphi! The voltage increase is fine - I can just get a different power supply or, the one I'm thinking of getting lets you set it at various voltages including 6, 7.5 and 9. Can you tell me whether 2N2222 or BC337 is suitable for the NPN transistors? And what about the PNP...
  15. S

    Flickering flame simulation with PIR motion sensor - mostly need help with transistor, I think

    Sorry about that. I thought the circuits would be shareable across platforms. The second switch on this circuit is just to reset it without having to wait for the slow fade. The first switch simulates the PIR sensor circuit. When I add more sets of LEDs in parallel, the current gets shared...
  16. S

    Flickering flame simulation with PIR motion sensor - mostly need help with transistor, I think

    If I keep the capacitor precharged using a potential divider on the 6 V supply then I can eliminate the lag before lighting occurs. It means that the fade off takes quite a bit longer but that's acceptable to me. Do you think it's a stupid idea? http://everycircuit.com/circuit/6450830268432384
  17. S

    Flickering flame simulation with PIR motion sensor - mostly need help with transistor, I think

    Here's my circuit which uses a lower voltage to represent the PIR output. It's 2.6 V after 0.7 V drops on the diodes. The problem is that the light takes about six seconds to start coming on and once it starts, it's at full brightness in about a second. Also, do you know how different the Every...
  18. S

    Flickering flame simulation with PIR motion sensor - mostly need help with transistor, I think

    Oh I see. I was not aware of this either. I made a modification to your circuit which you can see here: http://everycircuit.com/circuit/6111272301494272 - I added a resistor to make the capacitor charge more slowly but it does not affect the speed that the LED turns on. Can you tell why? Edit...
  19. S

    Flickering flame simulation with PIR motion sensor - mostly need help with transistor, I think

    In this screenshot, when I lowered the voltage to the base of the transistor, the LEDs light up more instead of less. That makes no sense!:
  20. S

    Flickering flame simulation with PIR motion sensor - mostly need help with transistor, I think

    But it doesn't make sense - a low voltage means a smaller current yet the LEDs are lighting up more. It's backwards!
Top