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  1. Alec_t

    Fine movement of 12v motor on pan/tilt head

    That suggests the supply to the motor is PWM (Pulse Width Modulated), with reversible polarity, to provide speed control.
  2. Alec_t

    Need help with FM transmitter "adaptation" in photo

    Even if a power-boosting modification were possible (and legal), the transmitter IC might well overheat and have a short life.
  3. Alec_t

    MOSFET replacement help

    Welcome to EP! The LU024N is widely advertised. HereHere's one sourceHere's one sourceFarnell stock them, for example.
  4. Alec_t

    Have a discontinued gadget, need Lithium Polymer battery

    Googling "3.7V 200mAh" gets several hits for cheaper online sources.
  5. Alec_t

    Fixing a Li-ion battery pack for a laptop

    What measurements do the other slots give?
  6. Alec_t

    Fixing a Li-ion battery pack for a laptop

    The BMS could have turned off an internal switch, requiring some resetting incantation known only to the OEM.
  7. Alec_t

    Fixing a Li-ion battery pack for a laptop

    Is it possible that removal of the battery has set some flag so that only a genuine OEM battery replacement will work?
  8. Alec_t

    Peak Power and Nominal power of motor

    The conditions, and the current, for peak power won't be the same as for continuous power.
  9. Alec_t

    Diode Characteristic Graph

    That was my intended meaning in post #8. Agreed. That arrangement is probably what the question-setter intended, but within the strict wording of the question the diode could be 'used' merely as, for example, a dummy load and play no part in the regulation. It seems to be a modern trend in...
  10. Alec_t

    Diode Characteristic Graph

    Unless we're missing some hidden background to the question there are no limits placed on how or where in the circuit that diode must be used. Clearly, from the graph, it is unsuitable as a reference voltage source, so an alternative, such as a Zener (which you've already tried), would be...
  11. Alec_t

    Diode Characteristic Graph

    That is the challenge; to consider how you could use the hypothetical characteristic shown to get 12V down to 5V.
  12. Alec_t

    Diode Characteristic Graph

    You're not being asked to build the circuit; just to design it. So diode selection shouldn't be an issue. Considering the graph linearity, that particular diode could be substituted by a resistor if the current is kept within the graph limits.
  13. Alec_t

    Diode Characteristic Graph

    Unless you know what the diode's construction is and semiconductor is (germanium, silicon, .....?) I don't see how it could give any clue as to size. Why do you want to know the size?
  14. Alec_t

    Diode Characteristic Graph

    The graph is telling you what the relationship is between the current through a particular diode and the voltage across the diode. To answer the question set you have to use that particular diode, so there is no 'changing diode sizes' or 'selecting a diode size'.
  15. Alec_t

    Can I attach a water pump (12v) to raspberry pi (3v)?

    If the pump is rated 5V 3W then the nominal running current is ~0.6A. AFAIK the Pi outputs can't provide that current, so a buffer stage between the Pi and pump will be needed. See post #2. Note that the start-up current of the pump will likely be several times the running current. The buffer...
  16. Alec_t

    how do i fix this pls

    Are the two broken wires part of a USB connection to CON1? I so, I'd guess they are the D+ and D- wires. Counting the CON1 terminals from the left, 4 and 5 appear to be marked D+ and D-. Googlng USB wire colours, not all USB connectors seem to use colours consistently. However, some show white...
  17. Alec_t

    Canon Camera battery help

    Edit the images to reduce the file size below 1Mpx (maybe smaller, to suit forum limits).
  18. Alec_t

    how do i fix this pls

    Welcome to EP! It looks as though there are wire remains in the two right-most terminals of CON1. Are the green and white wires the ones you need to re-attach? Please post a sharply-focussed picture. Do you have a multi-meter?
  19. Alec_t

    zero crossing transistor

    Your op-amp has no negative feedback so has a huge gain, resulting in the output being driven hard against the supply rails, i.e between nearly +5V and nearly -5V.
  20. Alec_t

    Power chair gel cell batteries

    Welcome to EP! If the chair when connected draws any current at all, which it probably will if in 'standby mode', then the batteries will have slowly discharged. Even non-connected batteries self-discharge in time. The instructions that came with the chair may have advice on battery usage and...
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