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  1. Alec_t

    How do I reduce the speed of a 12v childrens car

    If a control voltage of 1-4V2 is used, I'm surprised that great lump of carbon is needed to adjust it. It does look robust though; which is no bad thing where kids are involved :).
  2. Alec_t

    How do I reduce the speed of a 12v childrens car

    Hard to imagine that being a variable resistor, yet alone one able to handle 30A or more. What are its dimensions (roughly)? How far does it slide? It doesn't seem to have any way of connecting to that 3-way plug/socket alongside.
  3. Alec_t

    Improve Biometric Lock

    A vandal-proof one. All that electronic kit will become a target for vandals and thieves. Is this a school/college assignment?
  4. Alec_t

    Current rise in 12v pump

    Can't you just modify the bit that actuates the switch? It's amazing what can be done with duct-tape, Blue-tak, hairpins, wire coat-hangers etc :).
  5. Alec_t

    How do I reduce the speed of a 12v childrens car

    Can you provide a clear picture of this variable resistor thing with the 'two halfs', and its connections?
  6. Alec_t

    Spike Generation

    That diode may not be fast enough to catch a sharp spike. If the relay coil current is less than ~150mA, try a 1N4148. Failing that, try a fast-recovery diode.
  7. Alec_t

    IR ne555 receiver

    The 555 circuit has a high shoot-through current when its output changes state. If your supply is not adequately decoupled its voltage can dip as a result and cause false operation of whatever it supplies. Try connecting respective 100uF caps across the supply terminals of each 555, as close as...
  8. Alec_t

    IR ne555 receiver

    Welcome to EP! The circuit in the link is a monostable, not bistable. The TSOP1736 is for a 36kHz IR signal. What is your IR modulation frequency?
  9. Alec_t

    Stabilizer for fridge, washing machine and Led TV

    Are you kidding? The TS Is in India :).
  10. Alec_t

    Reversing polarity on push of a button

    LTspice (a free download from Analog Devices).
  11. Alec_t

    Reversing polarity on push of a button

    If it really must be single-button operated and you don't want to go the micro-controller route, here's the basis for a circuit to do the job :- The relays are the common automotive type with contacts rated to handle the DC motor current. Depending on the relay coil current draw, N-channel...
  12. Alec_t

    Spike Generation

    Read up about Faraday's Law and Lenz's Law.
  13. Alec_t

    Reversing polarity on push of a button

    There is also the little matter of should the valve automatically return to the default state (presumably closed) when the ignition is turned off?
  14. Alec_t

    I need to charge a six volt SLA battery

    Welcome to EP! Your 12V charger is unsuitable. Buy a 6V SLA charger, such as one of these.
  15. Alec_t

    Op Amp Troubles

    The supply voltage and common-mode input range make the RC4558P unsuitable for your application. Look for an opamp specified as rail-to-rail input and output and which will work well with only a 5V supply.
  16. Alec_t

    Can you extend the leads on a fluorescent ballast (blown ballast?)

    Post deleted.
  17. Alec_t

    RF detector

    If your radio is feeding an external antenna efficiently, would there be enough energy 'close' to the radio to be detectable with an RF sniffer?
  18. Alec_t

    Halogen to LED

    Sounds more like an operating theatre than a kitchen :). Are you planning to have the same level of LED lighting, or will you be lowering the wattage somewhat? If the lamps are indeed all in parallel, then presumably there is a 16-way distribution block somehere, in addition to the chunky 800W...
  19. Alec_t

    Switching Polarity of Electro-magnet.

    Welcome to EP! What you are looking for is called an H-bridge, which uses four semiconductor switches. Power MOSFETs and IGBTs are available which can handle 120A, but great care is needed in controlling them to avoid them frying, especially if rapid reversal of the current is wanted. Why do you...
  20. Alec_t

    Solid State Musical Organ just hissing....

    Just a controllable hiss level suggests that at least the pre-amplifier and main amplifier sections are working. I'd start by checking any fuses, and the supply voltage(s) to the plug-in cards. The organ schematic and/or service manual would be handy.
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