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  1. BGB

    Charging AGM batteries

    I understand this as being: he has an inverter that converts 24V to 120VAC (such as for running wall-powered electronics), which is run off of a pair of AGM batteries, and needs a charger for those batteries. basically, like a big UPS or something...
  2. BGB

    Charging AGM batteries

    errm... 14.4v per battery, with a limit of 50A, should be sufficient, and should get them "mostly" charged in 5 hours. this would mean 28.8v total, then maybe have a circuit to drop the voltage to 27v when the current drops below a certain point (say, 2A or so), at which point it will...
  3. BGB

    idle: driving steppers closed-loop?

    this is just what I had heard. apparently it is a patent on the use of a rotary encoder on a stepper motor for the use of absolute positioning, IIRC owned by Epson. had some random ideas for making custom motors partway between a 3-phase BLDC and a stepper motor, but this would not likely be...
  4. BGB

    idle: driving steppers closed-loop?

    yeah. I think most decent/big-name printers use optical encoders. AFAIK, some don't, partly due to cost, and partly due to there apparently being a patent on using optical encoders with steppers. this is apparently why most of the 3D printers and desktop CNC machines are driving their steppers...
  5. BGB

    idle: driving steppers closed-loop?

    overall price per unit?... and how many watts?... the goal here is minimization of cost per unit, not really that much about motor quality or accuracy. ( this in also not for my CNC project, which uses open-loop steppers, and seems to basically be working ok as-is. though I ended up using a...
  6. BGB

    idle: driving steppers closed-loop?

    yeah. I am mostly looking for the cheapest route here. say, spending $30 or so on an optical encoder is no-go (costs more than the motor). though, from what I have seen, NEMA-17 motors tend to be around 50-64 oz-in, and NEMA-23 around 250-300 oz-in. bigger is more torque and more power, and...
  7. BGB

    idle: driving steppers closed-loop?

    yes, in normal use, they are used open loop. this is good for positioning, but not necessarily a good option for variable-speed / variable-load applications (more typically where a BLDC motor is more popular). however, problem is mostly that BLDC's tend to cost a lot more than steppers of...
  8. BGB

    idle: driving steppers closed-loop?

    pots can work, but pose the difficulty of getting the analog signal back into a digital one. either need an MCU with analog input pins, or an ADC per motor (not free). selsyns seem to cost significantly more than the steppers I was looking at (would be cheaper just to buy more steppers and use...
  9. BGB

    idle: driving steppers closed-loop?

    ok, so this is one of several ideas that I have been thinking of recently. so, goal is to drive a stepper closed loop (similar to what can be done with a BLDC motor), preferably without any reliance on external sensors (IOW: preferably no encoders or similar), and ideally without modifying the...
  10. BGB

    NiCd batteries

    however... NiCd can generally provide more peak amperage than NiMH, and is cheaper than LiON. so, at least in the US, they aren't really dead yet. they are one of the more common battery types for lower-cost cordless power tools (with LiON being more typical for higher-end models). decided to...
  11. BGB

    12V DC motor with 12V battery getting hot

    yeah. though, some sparks may still be seen around the commutator. in some motors I have, at full speed it is a small blue spark. will add though: though that if the motor is salvaged from a 12v device, it is not necessarily a 12v motor. a lot of electronics devices and power-tools will use...
  12. BGB

    potential health hazard from electronics

    I have wondered some about this some. I have recently had issues with occasional slight eye twitch, and have been left to wonder if it is a potential adverse effect of soldering (fumes or similar, like getting fumes and smoke in the face). it has been a periodic annoyance for the past some-odd...
  13. BGB

    reflowing a board

    AFAIK: a lot of early semiconductors were heat-sensitive, so getting too hot could destroy them. most modern semiconductors are a lot more resistant to heat, and are typically soldered by them putting the entire PCB in a specialized oven (heats to a certain temperature for a certain amount of...
  14. BGB

    misc idea: small (3-phase BLDC) motors with built-in drivers.

    ok, cool. had to look it up, but pretty much all the motors I have seem to come from various companies located in China. some are pretty nice. others came filled with metal debris (metal chips, ...), where apparently metal chips had gotten stuck to the magnets at some point. better still would...
  15. BGB

    misc idea: small (3-phase BLDC) motors with built-in drivers.

    yep. they are more readily available for higher power ratings at lower costs than large PMDC motors. likewise, haven't seen a whole lot of PMDC motors much into the kW range. yeah. mine is made mostly of OSB, steel pipe, and hot-glue, not exactly high-end. I am not even really sure it will...
  16. BGB

    misc idea: small (3-phase BLDC) motors with built-in drivers.

    I have seen people use series motors, but yeah, not for servo. they seem to be fairly popular for things like DIY EVs though (although commercially-made EVs more often go for synchronous AC motors). the stepper motors I have seem to have around 3x the torque of the drill motors, but are roughly...
  17. BGB

    misc idea: small (3-phase BLDC) motors with built-in drivers.

    first one apparently can't drive the full per-phase current for the motors I have. the latter could work though. I can debate the cost, since I am still using reasonably cheap transistors for driving it (probably not using $2 worth of parts). not like I am throwing MOSFETs at the problem or...
  18. BGB

    misc idea: small (3-phase BLDC) motors with built-in drivers.

    in tests where I did use feedback, it was from a back-EMF sensor (a voltage divider and some transistors) which would watch one of the phases, and turn on a signal whenever the voltage went low enough to turn on a PNP (approx 2.5v). during part of the phase, this would be watched, and used to...
  19. BGB

    misc idea: small (3-phase BLDC) motors with built-in drivers.

    for my projects, a lot have used Raspberry Pi's, as they are pretty good in-general, and reasonably affordable, nevermind needing to do PWM/PDM in software (nor them not supporting analog IO). a lot of things could probably be also done on Cortex-M4 or ARM9 chips, which could be a cheaper...
  20. BGB

    misc idea: small (3-phase BLDC) motors with built-in drivers.

    dunno. at first I had considered using some BLDC motors out of old HDD's, but ended up getting some steppers instead, partly due to various reasons. the smoothest movement (and highest speeds) I got was when using sine-waves to drive them, but they didn't really move all that smoothly from one...
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