Search results

Search Forums New Posts
  1. Alec_t

    contact sensor based on soft dance pad sensor

    A simple CMOS inverter oscillator (power pins not shown) is like this :- R1 would be chosen according to the no-load capacitance of the home-made sensor, so as to give a convenient oscillator frequency (a few kHz). There are various ways a micro could measure the frequency. One would be...
  2. Alec_t

    Protection circuit for Li-ion batteries

    Agreed. But the OP said in post #1, "I've got a bunch of 18650 3.7V li-ion batteries lying around", which to me suggests they could be of mixed heritage and perhaps badly matched.
  3. Alec_t

    Protection circuit for Li-ion batteries

    Safer, but still not safe enough IMO :(.
  4. Alec_t

    Help on how to test this device

    The transformer core looks to have split. One leg isn't vertical. There's a distinct shadow by the gap in the tape in IMG-0927.
  5. Alec_t

    Protection circuit for Li-ion batteries

    In that case you will need a separate voltage monitor for each battery (cell), because no two batteries are identical and the one that drops to 3V first will die if you only monitor the combined '6V' voltage.
  6. Alec_t

    AC Compressor blowing fuse

    Actually the reverse voltage rating of a freewheel diode isn't very important (provided it exceeds the supply voltage), since when it is supressing a spike it is forward biased. Here's a sim showing the voltage Vab across the diode when a 1A current through a 100mH coil is switched on and off.
  7. Alec_t

    What Potentiometer should I get to control the speed of a computer fan?

    Digikey's price for a 100Ω 12W wirewound pot is £77 :eek:. So PWM is the way to go! If a conventional PWM control conflicts with the internal commutation of the fan you could try my 'Synchronous Pulse Delay' method as described in this article.
  8. Alec_t

    Adjustable Schmitt Trigger Circuit Help

    To modify the voltage while retaining threshold independence would need two buffer amplifier stages in addition to the 555. Simpler just to use the two comparators as Steve suggested in post #2.
  9. Alec_t

    What power supply would I need for this and how would my circuit look like?

    What is the purpose of the potentiometer? A standard pot will burn out if you try to pass 0.32A through it. A pot able to handle that sort of current will be expensive.
  10. Alec_t

    contact sensor based on soft dance pad sensor

    Have you considered using thin sheet rubber/plastic foam sandwiched between aluminized-plastic sheets? That would make a capacitor which could be used as a frequency-determining element in a simple CMOS-Schmitt-inverter-gate oscillator. The micro would then get a logic-level square wave and...
  11. Alec_t

    Giant newbie, needs help regarding transmitter

    Without knowing what the receiver is, whether the data carrier is optical or radio or gravitational or ..... it is impossible to say. And by 'you', do you mean yourself, or an electronics expert, or a micro-manipulation robot, or ..... ?
  12. Alec_t

    4 state illumination controller

    Personally I wouldn't use relays at all. The linked driver can accept an analogue or digital input signal to control LED current (hence brightness) and all 4 LEDs can be connected in series with the one driver. A CD4017 as Colin mentions could be used to provide a 4-level analogue control signal...
  13. Alec_t

    HOME THEATER AUDIO CUTS OFF

    Some amplifiers (I don't know about yours) have an anti-thump muting circuit to protect the speakers at power-on. This often involves a high value capacitor charging up over a second or two during power-up. Clutching at straws here, but if this cap has gone leaky perhaps it subsequently...
  14. Alec_t

    AC Compressor blowing fuse

    Wire it in parallel with the coil. The diode must be reverse-biased, i.e. its cathode (usually marked with a coloured band) should be more positive than its anode. Edit: Martaine beat me to it. Reverse-biased = antiparallel.
  15. Alec_t

    Spice Circuit

    Here you go
  16. Alec_t

    Protection circuit for Li-ion batteries

    If Vbat drops to 3V, what will the regulator output do? Is it a low drop-out type? The supply for the LM358 and the pot will, of course, drop too.
  17. Alec_t

    AC plug for DC purpose?

    What was the failure mode? If solder joint melted then the connector is overloaded. If wire fractured then proper cable support (e.g. a rigid splint) at and near the joint is needed.
  18. Alec_t

    Reviving an LED Lantern

    If you're new to electronics I'd caution against using the lithium batteries for this or any other project. Unless their charging and discharging are properly controlled they can catch fire or EXPLODE. Take a trip to www.batteryuniversity.com and check out battery charging arrangements for SLA...
  19. Alec_t

    Power amp fan trouble

    I'd guess the base of the driver Darlington transistor is floating instead of properly connected to the temperature amplifier. Check for dry solder joints and hairline cracks in traces in that area.
  20. Alec_t

    Electronic supply, help.

    If you're building gizmos for sale, don't forget to factor in the huge costs of 1) obtaining the necessary approvals for compliance with various national standards and 2) product liability insurance.
View older results
Top