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  1. Alec_t

    Whatever happened to the Speech recognition chip?

    Makes you wonder how accurate the chips were. The slightest error in recognition could be disastrous in many uses, so perhaps the chips didn't sell well?
  2. Alec_t

    I Need Some Help With a Level Indicator Project

    If you want dirt-cheap/simple, how about a 2-axis spirit level on the motor housing, and a 45 degree mirror above to view it? Edit: Or one of these might be easier to mount.
  3. Alec_t

    self-walking legs

    The mechanism for powered legs would need a LOT of energy to power it. Try doing the maths to see just how much. I envision you having to lug the eqivalent of a couple of car batteries around with you to cover more than a few hundred yards :(.
  4. Alec_t

    Testing capacity of a battery..

    It probably won't be a 'cheap and cheerful' solution. It will need an adjustable constant-current source able to dissipate ~44W, hence a high-power-handling FET on a BIG heatsink, plus current-monitoring and control circuitry and, importantly, voltage monitoring circuitry to provide automatic...
  5. Alec_t

    Need Help on semi automatic water level controller using 555 in bistable mode

    Aren't you happy with the replies you had over at the AAC forum?
  6. Alec_t

    Help! Arduino based car not working when touching ground.

    The linked shield uses L293D chips, which according to the datasheet can provide up to 600mA per motor and have in-built back-emf protection diodes.
  7. Alec_t

    High Precision LED Absorbance Measurement

    I would guess due to thermal effects? The diode forward voltage is temperature dependent, and the spacing between emitter and detector could be varying (probably negligibly) due to temperature change.
  8. Alec_t

    Simple solar powered lights with a battery

    Is that the open-ciruit (no load) voltage, or when the cell is powering a load?
  9. Alec_t

    Help, Newbie Question - Wall Dimmer to LED Driver

    The linked LED driver is a 300mA constant-current type, so a dimmer won't work with it. You need to get a driver that is designed to be dimmable..
  10. Alec_t

    Simple solar powered lights with a battery

    White LEDs have a forward voltage of at least 3V, so you'd need 3 or 4 AA cells in series to drive them directly. Alternatively a DC-to-DC converter could step up the voltage of a single cell (as is done in most garden lights). Your solar cell rating is probably an optimistic one for full sun at...
  11. Alec_t

    Help! Arduino based car not working when touching ground.

    You don't show any connections to the Dir and PWM inputs of the shield. How are you controlling the motors?
  12. Alec_t

    12vMM..what does it mean?

    12VMM is shown top right of the schematic, but there is no connection shown to Plug 2. It is a crude full-wave rectified, unsmoothed mains-waveform. Perhaps 'MM' denotes 'mains'? I agree with Minder, post #2.
  13. Alec_t

    Replacing triple a batteries

    Welcome to EP! How much current does the headset require?
  14. Alec_t

    Simple stall over current 12v dc motor protection?

    Here you go:
  15. Alec_t

    Simple stall over current 12v dc motor protection?

    You're probably right. Add a latch to keep the tripped state?
  16. Alec_t

    Ultrasonic Metronome, or rangefinder transmitter

    Readily-available transducers generally operate at around 40kHz. For maximum efficiency it is better to let the transducer dictate (control) the operating frequency, rather than try to force it to vibrate at some frequency you determine. Try googling 'self-resonant ultrasonic' for a suitable...
  17. Alec_t

    Simple stall over current 12v dc motor protection?

    How about this? The current trip is adjustable. The higher the stall current the shorter the delay before the trip. Automatically resets after a further delay when current drops. R3,C2 determine the delays.
  18. Alec_t

    Transformer output

    Yes (approximately). If you put in X Volts you should get about X*220/12 Volts out.
  19. Alec_t

    Loss of voltage with MOSFET

    That is the rated value when Vgs=10V, but your FET has Vgs <=5V so Rds(on) will be in the 0.025-0.035 Ohm range so will drop more voltage. What gauge interconnecting wire are you using? Thin gauge and poor battery connections would add significant resistance.
  20. Alec_t

    SUPERCAPACITORS

    In brief: a supercap gets charged to a low DC voltage, whereas the grid is an AC high-voltage system. Do you see the problem? AnalogKid's post sets things out in more detail.
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