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  1. Alec_t

    Need of component detail

    Welcome to EP! The component is a resistive element exposed to the wind, so that its temperature will be dependent on the wind speed. Its resistance, Rx, would be given approximately by the relationship Rx/R3 = R5/R4 and it would have a positive temperature coefficient of resistance. These...
  2. Alec_t

    Can you make my 12v LED light up?

    Ta-da! You've got there! Now connect up D4 and check that a simulated AC switch turns the green LED off.
  3. Alec_t

    Can you make my 12v LED light up?

    Good info again. We were wrong about only one track break being necessary :rolleyes:. I've just noticed there is a possible short between the trimmer and Q1 collector. Make sure there is a track break between trimmer and collector. A short there explains the odd symptoms you've got.
  4. Alec_t

    Can you make my 12v LED light up?

    Good info. Hmm, no obvious problem there. Try reducing R4 from 47k to 10k. Connect up the 12V supply and see what happens when the PWM input is (a) left unconnected, (b) grounded, (c) connected to +12V.
  5. Alec_t

    Have been given a disassembled Whirlpool grill-microwave oven with missing decals & fuses?

    Electrical power is applied to a magnetron to generate microwave radiation, This is then guided to the oven cavity where it heats the contents. The power supply is switched on and off repeatedly to control the average microwave power. This explains the magnetron operation.
  6. Alec_t

    Can you make my 12v LED light up?

    Nice pics. Right. Both look ok to me. So, the wiring seems fine. If earthing the PWM pin increases green LED brightness, that suggests Q1 collector-base junction is leaky and perhaps Q1 or Q2 has a very high gain. With the circuit powered off, use your Ohmmeter to measure the collector-to-base...
  7. Alec_t

    Looking for help with some projects that require electrical expertise

    Who are "we"? Students? Mechanical power sources are usually quite bulky. What are your size limits (in mm, cm or whatever)? "Super tight" doesn't mean much.
  8. Alec_t

    Can you make my 12v LED light up?

    Use 12V. With nothing connected to the PWM input the green LED should be off, regardless of the setting of the trimmer. If that doesn't happen, try shorting the PWM input to ground. If the green LED is still on there is a wiring error or a faulty component. Don't connect the fan or the...
  9. Alec_t

    4P3T rotary selector switch for guitar

    Welcome to EP! Not all 4P3T switches are the same. Post a sharply-focussed close pic or two of yours. If all the pickups share a common ground, that would not need to go to the switch, although the switch mounting boss would make a good anchor point.
  10. Alec_t

    6V battery charger

    Have a read of this, regarding recommended charging procedure. Welcome to EP!
  11. Alec_t

    Remote observatory power... amperage reading is not what I expected

    If one of the diodes in the two bridges were leaky and if the two power supplies were of different voltage then the higher voltage supply might be driving reverse current through the other, affecting the current readings. Depending where your current probes are located, if bus currents share a...
  12. Alec_t

    Remote observatory power... amperage reading is not what I expected

    Why do you have your DC-DC converter getting its power from both bus A and bus B? That may account for the odd current readings. Is it a supply back-up arrangement? Why the bridges?
  13. Alec_t

    LED dimming module

    Why does one light need two driver modules? Looks to me, judging by the two sockets (connectors) in post #1, that one dimmer controls both LED driver modules. Can you confirm? If so, does swapping the plugs over affect which driver module is/isn't dimming?
  14. Alec_t

    Can you make my 12v LED light up?

    Yup. Correct. Correct. Just depends whether you prefer clockwise or counter-clockwise adjustment to increase the turn-on threshold for the green LED. D4 is still optional. But get the green LED working before adding it and before trying the circuit with the PWM from the controller.
  15. Alec_t

    Can you make my 12v LED light up?

    That's a good start :). Just ensure you have a 3906 at Q2.
  16. Alec_t

    Can you make my 12v LED light up?

    That sounds like you have a PNP transistor for Q1 instead of a NPN transistor. Makes no difference. Oh dear! If R1 was shorted like that and the input pot wiper happened to be set at/near the top then there would be little or nor resistance to limit the current through the pot wiper and the Q1...
  17. Alec_t

    One wire light bulb?

    Welcome to EP! The path for the current would have been completed via your body.
  18. Alec_t

    Garmin GPS120

    Good luck with that. I'd be looking for a replacement connector, since the contacts are likely corroded.
  19. Alec_t

    HS540 DC motor circuit

    For a 100-300 rpm speed you will need a gear-motor. Datasheets for those should state the available torque at the rated speed.
  20. Alec_t

    Garmin GPS120

    Can you see any fine lines in the plastic to suggest if it's a 2-part connector, or is it definitely a single-part plastic moulding?
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