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  1. BGB

    Need help with battery power for my project

    probably not necessary as the TIP120 and 122 have an hFE of 10000 (they are already Darlington). any more than about 500 uA should reach saturation.
  2. BGB

    Stepper motor control

    IMHO, this seems like a better use-case for a small DC gearmotor than for a stepper. a 3 position switch (DP3T) can be wired up to the motor, which connects it as-appropriate to a battery. controlling a stepper is a bit more involved, and it isn't really obvious what if-any advantage it would...
  3. BGB

    Need help with battery power for my project

    I would think a TIP120 or TIP122 (Darlington NPN) would be cheaper than most MOSFETs I have seen, though the prices are pretty variable (depends on seller and quantity, ...).
  4. BGB

    Simulating electronics on a PC

    essentially, when the circuit is edited, the simulation would be essentially aborted and restarted in-place (though likely retaining the current operating state for some components). if things like an o-scope display were keyed to the grid, then they would quietly change over to the new IDs when...
  5. BGB

    Simulating electronics on a PC

    I also use LTspice. a few drawbacks though: does not support editing and simulating at the same time, ex, putting a switch in a circuit and seeing immediately what this switch will do, ... it generally lacks much ability to be all that useful for digital electronics nor supports emulated...
  6. BGB

    motor driving: sane?...

    ok, status update. added a bunch of 1/2 twist-tie ballast resistors, each having around 70 mOhm. 150mOhm / 2, losing ~ 5 mOhm in soldering the twist tie to pieces of copper wire to serve as leads (soldering to steel is ill-behaved). vague information about how I am driving the motors...
  7. BGB

    Solder terminal to breadboard

    or the cheapest spool of stranded 24 or 26 AWG wire you can find. better yet if you can find some of the stuff where the insulation melts off onto ones' hands the moment the wire gets sufficiently warm (but one may find luckily it also washes off in warm water).
  8. BGB

    motor driving: sane?...

    didn't have much space, so no. closest I have to applicable power resistors though is twist-ties, where I determined in a past experiment that each is about 0.15 ohm. could add 1/2 twist tie to each, which would add 0.075 ohm. not sure how critical it is. I did a water-cooled DC motor driver...
  9. BGB

    motor driving: sane?...

    so, had been working on boards to drive a motor. one is a triple half-bridge, with 12x MJE3055Ts, in turn driven with 3x TIP122 or TIP127 transistors. two 3055Ts are naively wired in parallel, which is theoretically a terrible way to do it, but in past tests it doesn't seem to blow up. this is...
  10. BGB

    back for now: PWM + Serial (single wire)

    no, it would actually be a fair bit different. the use of multiplexing data and PWM control is that the main control interface (say, a Raspberry Pi), only needs a single wire (from a GPIO pin), going to each motor-driver. the motor driver would be an MSP430 connected to an H-Bridge, possibly...
  11. BGB

    back for now: PWM + Serial (single wire)

    earlier, I wrote some code (for an MSP430) for implementing a 3 phase VFD, using both servo-style PWM and I2C for control inputs. then I was thinking, it is a little pointless, as the I2C and PWM are both partially redundant and also one ends up with the worst of both worlds. so, I had an idle...
  12. BGB

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

    though, one doesn't need to supply the energy to keep a boat floating, rather, gravity and the water do so, and the net energy is still roughly 0. more like two magnets stuck together. a lot of force may be present holding the magnets together, but they are neither being supplied this power...
  13. BGB

    Can we charge a battery using a power supply?

    as others have noted: no. rather, you limit charging current to a certain amount (say, 1A). if the battery wants more than this, then the voltage to the battery drops. when the battery nears being fully charged, then the voltage rises to match the charger voltage, and current drops off...
  14. BGB

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

    the way I had imagined it before (very informally) was that you have to provide enough power to accelerate the vehicle upwards at the same speed gravity tries to pull it downwards. so, to hover, you need about 9.8N for every kg. naively, this would imply about 9.8W per kg (since 1W and 1N are...
  15. BGB

    Real life dilemma: Help powering an AC device with DC

    yeah, could be. the contactor coils have resistances of around 7 and 12 ohms IIRC. probably not meant to pull a lot of current as they use fairly thin wire. one looks like 28 AWG, the other maybe 30 AWG (and uses a physically smaller coil). one will close at 5v, and the other closes at 7v...
  16. BGB

    Easiest/cheapest UPS for an arduino

    will add that you may want to use a few diodes to isolate the power supplies. for example, if you have batteries connected directly in parallel with a power-brick or similar, then the power-brick will try to charge the batteries. there is a risk of them overcharging and rupturing in this case...
  17. BGB

    Real life dilemma: Help powering an AC device with DC

    is that why a 24vAC contactor slams closed pretty hard with only 9v DC os so?... I had wondered about this (with a few contactors scavenged from a broken HVAC unit), namely they slam closed pretty hard and start getting rather warm well under the theoretical 24v (and seem to still work down to...
  18. BGB

    Car Battery Powered House Ideas, Questions

    PbAc AGM batteries tend to work reasonably well IME, and seem to have a lifespan somewhere between 5 and 10 years if treated well. adding water shouldn't really be necessary unless you are severely overcharging them. though, yes, if not actually supplying power to them, they will drain down...
  19. BGB

    Car Battery Powered House Ideas, Questions

    it would be nice to be able to live somewhere rural, but then there is a lot of hassles: no grid power or internet; need to drill a well; need to haul out/set-up a mobile-home or similar; long drives over dirt roads before reaching any paved roadways; ... or even just living slightly out of...
  20. BGB

    Battery charging- Float mode and boost mode

    typical battery charge rage for AGM is 0.3C, which is about 60A. 50A is pretty close to this. near the upper end, you can't really control the charge rate, since the battery will only take what it wants to take at a given voltage. at lower levels of charge, it will try to take a lot more, so it...
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