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  1. Alec_t

    Proper home for school/college 'projects'?

    Thanks guys. Hope that will divert at least some posts appropriately :).
  2. Alec_t

    Can you make my 12v LED light up?

    The 'working voltage' of C1 needs to be >12V, so I'd suggest 25V or so. Observe correct polarity when you connect it. Almost any small signal (low power) NPN and PNP silicon transistors are appropriate. Common types are 2N3904 (NPN) and 2N3906 (PNP). Any general purpose silicon diode will do for...
  3. Alec_t

    Proper home for school/college 'projects'?

    Too many students, assigned a project to do, post their requests for help to the 'Electronics Projects' forum instead of to the 'Homework Help' forum. Can the Projects forum header be clarified to make it clear that assigned student projects should be posted to the Homework forum only? (If they...
  4. Alec_t

    Automatic object tracing system

    With all the necessary bits that Kelly pointed out, the cost is mounting, just for one goat!. Might be cheaper to employ a goat-herd :).
  5. Alec_t

    Faraday cage?

    Any metal would work for electrical screening. For magnetic screening you would need ferromagnetic material, e.g. common steel. IIRC, some stainless steels are ferromagnetic; others are not.
  6. Alec_t

    Encrypt tv

    Welcome to EP! Presumably you would need to plug the TV into a set-top box which decrypts the channels. Are such boxes available in your country?
  7. Alec_t

    Mobility scooter

    If you increase the motor size it will draw more current, so you may also have to replace the controller (to handle the higher current) and replace the batteries with higher Ah ones (to get the same duration between charges). Check with your insurer if they would provide cover for a faster...
  8. Alec_t

    Mobility scooter

    If the torque stays the same you won't get any speed increase. Is increased speed legal in your area? In some jurisdictions, scooter speed is restricted.
  9. Alec_t

    5second dark triggered timer

    Is this a school/college task?
  10. Alec_t

    DC-DC Isolator

    Why is the 741 getting its +ve supply via R2?
  11. Alec_t

    Is this circuit fit for purpose if used on a 12vdc pump?

    The diode is rated for 15A continuous, so should be fine, even allowing for pump switch-on surges.
  12. Alec_t

    4-20mA splitter

    Good move. The cap introduces some delay in the input response, but presumably the loop current isn't meant to change rapidly? If so, might be an idea to add similar filtering to the other loop(s).
  13. Alec_t

    Hall switch magnets.

    Couldn't you fit a toothed wheel (with a square central hole) around the cam? Or wouldn't Bluejets' suggested alternative method work simply using the original cam?
  14. Alec_t

    4-20mA splitter

    If the IA is disconnected from the circuit and its output is instead connected to the 0V rail by a 100Ω resistor, what voltage do you read at the IA output?
  15. Alec_t

    Meaning of some german words on the front of a radio

    The push buttons are known as 'radio buttons'. Press in any one and the others should pop out. These are station selectors. Each one presets the tuner to a chosen frequency, which can be adjusted by rotating its black sleeve. So, they are a sort of memory. 'afc' denotes 'automatic frequency...
  16. Alec_t

    4-20mA splitter

    Sounds correct to me. R1 completes the circuit if you're simply connecting the injector across it. What value R1 are you using? 100Meg won't work :D.
  17. Alec_t

    4-20mA splitter

    Here's another way of looking at the current loops ....
  18. Alec_t

    4-20mA splitter

    Is the IA 4mA current flowing through R1 with the correct polarity? If so, you should see +0.4V at the non-inverting input. Do you?
  19. Alec_t

    Help, audio mixer!!

    ..... in the meantime, try reducing the 100k bias resistor to 33k, or (to draw less battery current) increasing the 15k bias resistor to 33k. Simulation shows the transistor is incorrectly biased in the circuit as shown.
  20. Alec_t

    Help, audio mixer!!

    Welcome to EP! The potentiometers may or may not be necessary, depending on the two signal sources. In the posted circuit, R1 and R2 allow the input levels from the two audio sources to be individually adjusted (preset). This might be necessary for high level inputs, to avoid over-loading the...
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