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61  Using Arduino / General Electronics / Re: Controlling the rotation of brushless motor by changing polarity on: February 17, 2014, 03:48:54 am
To answer your specific question - none of them
But all three offer directional change via a direction control port marked as CW/ACW
The first motor also possibly requires a 3phase supply so clearly outwith your scope
It's not possible to make out the connection detail of the third sample so cannot comment on what the exact supply requirements are

But none are suitable for your door application without a major speed reduction via a gearbox.
62  Using Arduino / General Electronics / Re: High Power Transistors on: February 16, 2014, 04:31:49 pm
For that type of application you may be better off looking at zero-crossing burst fire control module triggering a thyristor.    
PWM is a bit unpredictable when used to trigger an AC load as you cannot determine which point in the cycle the ON state exists.
63  Using Arduino / Motors, Mechanics, and Power / Re: Understanding relay wiring (of a relay salvaged from a UPS) on: February 15, 2014, 01:42:39 pm
Assuming the mains power comes from the right hand side and the UPS power is on the left.  By definition the UPS is "Uninterruptible" which means the system power oscillator is running in synchronous and in parallel with the mains supply.  Alternatively it must fire up and come on line in a minimum number of milliseconds, certainly less than 1 cycle of the mains (20 or 17mS).  That style of relay will not mechanically drop out in such a short time so it is still closed when the UPS comes on-line following mains failure.  Hence the UPS back-feeds the relay and holds it in the energised state.

That is why I state that particular circuit will not function as stated - unless there is some other form of "interrupter" system further to the left of the circuit you show.

But there again, I have been known to be wrong  smiley-lol smiley-lol
64  Using Arduino / Motors, Mechanics, and Power / Re: Linear bearing shaft on: February 15, 2014, 01:30:08 pm
If it fits neatly and it's round then the answer is yes
The only way you are really going to know is to try it.
65  Using Arduino / Motors, Mechanics, and Power / Re: Understanding relay wiring (of a relay salvaged from a UPS) on: February 15, 2014, 04:01:10 am
That relay circuit wired as shown won't provide that function.   
66  Using Arduino / Motors, Mechanics, and Power / Re: Mosfet capacitance? on: February 15, 2014, 03:58:29 am
At the sort of frequencies you're talking about the motor winding inductance will inhibit current flow so the available power will only be a fraction of it's rating.   
67  Using Arduino / Motors, Mechanics, and Power / Re: Mosfet capacitance? on: February 14, 2014, 01:12:53 pm
The C stands for Coulombs  which may be defined in terms of Amp-Seconds or Farad-Volts
68  Using Arduino / Motors, Mechanics, and Power / Re: Understanding relay wiring (of a relay salvaged from a UPS) on: February 14, 2014, 01:07:13 pm
As shown, the circuit is appears to be pointless.  When power is available the relay closes and power passes through to the output terminals.  When power is not available, the relay is de-energised and the contacts are open; but in this case there is no power, hence no power is or would be available to the output, irrespective of the relay state.  Hence the "pointless" nature of the circuit.

May I suggest you re-examine how the relay is actually connected and redraw your illustration.   Alternatively provide a photograph of the actual relay and its connections within the circuit.
69  Using Arduino / Motors, Mechanics, and Power / Re: Motor Help, PLEASE on: February 14, 2014, 11:34:43 am
If you want pulling power and speed I'd suggest you look at the 24volt motors that are fitted to electric scooters.  Something like one of these :

http://www.ebay.co.uk/itm/Electric-E-scooter-24-volt-150-wt-motor-brand-new-upgrade-X120-e10-x140-etc/231076950902?rt=nc&_trksid=p2047675.m1851&_trkparms=aid%3D222002%26algo%3DSIC.FIT%26ao%3D1%26asc%3D74%26meid%3D4833598195879507660%26pid%3D100005%26prg%3D1048%26rk%3D2%26rkt%3D4%26sd%3D231157329773%26

or visit your local wheelchair repair shop and see if you can pick up some motors from a scrapped wheelchair.  The advantage of these is that they generally come with a gearbox fitted.
70  Using Arduino / General Electronics / Re: Mitsubishi AC hacking on: February 13, 2014, 05:31:10 pm
Or whoever has wired it up has used a piece of "twin and earth" and is using the earth wire to carry a signal (5VDC or 230VAC? !!!)   smiley-eek-blue smiley-eek-blue

If that's a thermostat it's a mighty complicated one  incorporating a fully pblown processor
71  Using Arduino / General Electronics / Re: Capacitor Voltage on: February 12, 2014, 01:41:43 pm
If you are only working at arduino voltage levels then you may be worrying over nothing.  Virtually all capacitors will tolerate 5 volts (2volt super-capacitors excluded)
72  Using Arduino / General Electronics / Re: Controlling the rotation of brushless motor by changing polarity on: February 11, 2014, 04:57:22 am
I take it you realise that a motor designed to run at 2400RPM will require a substantial gear ratio to make it suitable as a door opener.  Say 90degrees rotation in 2 seconds = 0.125revs/second = 7.5RPM  So gear ratio required = 2400/7.5 = 320:1

The motor, by design, is fixed speed, so playing with the supply voltage to reduce speed is not a realistic option.  Then you have to arrange limit switching to prevent over-run.

I'd suggest you'd be far better looking at a stepper motor/gearbox arrangement whose position and speed can be fully controlled by the drive pulses.   However, if it's only a "small" door then a model aircraft R/C servo motor is probably the best option.

I appreciate you already have the BLDC motor but that's a poor reason to drive yourself down a route that may well be doomed to fail to meet your needs.
73  Using Arduino / General Electronics / Re: Electrical Safety on: February 10, 2014, 08:39:25 am
Irrespective of what EU documentation may state, when you stick your fingers onto 60VDC you are definitely going to feel it (based on personal experience).  Manufacture of any electrical apparatus liable to cause "excitement" subjects you to potential litigation, not only by the afflicted but also by relevant statutory bodies.  The response of the human body to electric shock is not only affected by the drive voltage or resultant current, but also the physiology of the recipient, his/her state of health at the time, the manner of connection etc etc etc.

First rule of construction  -  prevent hazard by physical separation
74  Using Arduino / General Electronics / Re: Controlling the rotation of brushless motor by changing polarity on: February 09, 2014, 08:33:52 am
""rotational direction should be controlled by switching of DC power polarity""

Can you please explain why you demand this particular criteria ?

To get reverse direction of a basic 3-phase BLDC you must be able to access the phase supplies (or at least 2 out of the three)  Alternatively you purchase a BLDC speed controller which has the facility for transposing the phases as part of its design and direction is controlled by a logic or analogue trigger input.
75  Using Arduino / General Electronics / Re: Controlling the rotation of brushless motor by changing polarity on: February 09, 2014, 04:03:05 am
Sorry, but CANNOT be done by simply switching the power line.  A BLDC is not the same as a conventional commutator motor.  You need access to the winding connections (2 out of any 3) and do the switching there.
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