Search results

Search Forums New Posts
  1. Alec_t

    How to make Toy Voice Changer (AA battery) Run on 12 Volt

    Nothing. Since "just want it a little louder" is subjective and we don't know the power the toy speaker handles it's hard to advise on what power rating would be best for your purpose. I'd guess a couple of Watts. Try googling for 1W, 2W or 5W audio amplifiers which can be run from 12V. What...
  2. Alec_t

    A means of closing a JFET switch with a postive voltage?

    Up to a point, yes. But unless you can get the voltage down again your circuit becomes just a peak detector. With the diode in circuit you couldn't measure a low voltage signal amplitude that follows a high voltage signal amplitude. It would prevent flow; which is why there would need to be an...
  3. Alec_t

    Site feature suggestion

    It would also be useful if .asc and .sym files were allowable, for those folk who use the LTspice simulator.
  4. Alec_t

    Simple way for LED to indicate at 2 different brightness's

    If I've understood what you're trying to do correctly, here's a sim of how I'd do it (only 3 diodes shown, but extendable as required). The HC4017 was chosen so as to provide enough drive current for the LEDs without the need for one transistor per LED. When Vgate is high the transistor turns...
  5. Alec_t

    How to make Toy Voice Changer (AA battery) Run on 12 Volt

    Would you be able to build a converter and an amplifier (e.g.from a kit), or are you looking for an off-the-shelf solution? How are you planning to identify the necessary connections to make to the toy in order to amplify its output?
  6. Alec_t

    A means of closing a JFET switch with a postive voltage?

    The diode in post #6 will prevent the flow of opamp input bias current to ground/negative rail (unless you have some other path for that), and will also prevent the sampling cap voltage from decaying. Have you considered using a CD4052 or similar?
  7. Alec_t

    Simple way for LED to indicate at 2 different brightness's

    As you show only a part of your circuit it's impossible to say. How's the 4017 couple up to what you show?
  8. Alec_t

    will this really give me a triangular wave?

    Do you have to use a converter to get from a square wave to a triangle wave? If not, a simple CMOS inverter Schmitt trigger oscillator will produce an output similar to that in post # 5, as well as a square wave of the same frequency (but not the same amplitude). The 'triangle' output amplitude...
  9. Alec_t

    A means of closing a JFET switch with a postive voltage?

    You need to make the gate negative with respect to the source to turn the FET off.
  10. Alec_t

    will this really give me a triangular wave?

    The 741 is a poor choice because of its limited output swing, bandwidth and slew rate. For a fixed input frequency square-wave, R4 and C2 determine the slope of the triangle wave and hence the peak-to-peak amplitude (up to the point where clipping occurs because of the poor performance of the 741).
  11. Alec_t

    Simple way for LED to indicate at 2 different brightness's

    When the 555 output is low you will be wasting energy by driving current into it via the left-hand resistor. Connect a diode in series with the 555 output (pin 3) to prevent that.
  12. Alec_t

    IR Temperature sensor -> Multicolored LED

    Welcome to EP! How remote is remote, what is the object? An elephant at 1metre would be simpler to measure than an ant at 10metres :).
  13. Alec_t

    Can a clock pendulum be slowed down by adding a resistor to the PSB?

    The period of oscillation of a pendulum is independent of the pendulum mass, but depends on the distance of the centre of mass from the pivot, which is shortened by that dual mass arrangement and, as Hop said, should reduce the period (increase the frequency).
  14. Alec_t

    Power for 12v water pump

    A transformer and a converter are not the same thing. A transformer provides an AC output only. A converter may provide AC or DC at its output: you need one with a DC output. If yours does have a DC output and is a switch mode type then perhaps it dislikes the start-up current surge which a...
  15. Alec_t

    How to make Toy Voice Changer (AA battery) Run on 12 Volt

    Something like that, though a lower power one would probably be adequate. Yes. One that can be run from 12V. Don't expect hi-fidelity sound: the amp will amplify any existing distortion.
  16. Alec_t

    Can we charge a battery using a power supply?

    Lots of info on safe charging to be found by visiting www.batteryuniversity.com .
  17. Alec_t

    Hovering Drone....W/Kg Calculation.....

    The background equations in this link give propellor thrust. Air exit velocity from the propellor would be calculated from the propellor diameter and blade pitch and the motor power.
  18. Alec_t

    How to make Toy Voice Changer (AA battery) Run on 12 Volt

    Welcome to EP! Go to your local dollar store and pick up an in-car USB charger (12V to 5V converter). The toy won't object to 5V, since 3 fresh AA cells supply about 4.8V.
  19. Alec_t

    Digital volt meter doesn't like a power supply?

    How do you know the 'homemade thing' is working properly?
  20. Alec_t

    Change a microwave dial into a keypad?

    Ah, that sort of dial :). Probably just a shaft encoder which the system micro reads. So your keypad scanner would have to emulate the encoder output.
Top