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61  Using Arduino / General Electronics / Re: measuring ON time and off Time of PWM pulse on: February 22, 2014, 08:00:20 am
As MarkT says, use a multimeter, but make sure it's an analogue one (with a moving pointer).   The mechanical inertia of the movement will even out the pulses and give a rough indication of duty cycle.
62  Using Arduino / Motors, Mechanics, and Power / Re: Putting three lead acid batteries in parallel on: February 21, 2014, 01:44:21 pm
But not how it's been shown.  B2 is the wrong way round for that technique. 
63  Using Arduino / General Electronics / Re: Component packaging. on: February 21, 2014, 01:40:01 pm
a few seconds in the microwave should sort out your concerns

ONLY JOKING  --  DO NOT DO THAT  !!!!!   smiley-twist smiley-twist smiley-twist

I really don't understand your concern.  The components, once removed from a packet (sealed or otherwise), are exposed to the humidity of your environment, irrespective of what that may be.    Unless the items are actually wet there should be no cause for concern.  The  component internals are hermetically sealed so external humidity only acts upon the leads.

I'm sure most reputable suppliers go to great lengths to ensure their products are not immersed prior to sale.
64  Using Arduino / Motors, Mechanics, and Power / Re: Putting three lead acid batteries in parallel on: February 20, 2014, 05:33:30 pm
There is no right answer; just wrong and wronger.  You pays your money and takes your pick.   smiley
65  Using Arduino / Motors, Mechanics, and Power / Re: Putting three lead acid batteries in parallel on: February 20, 2014, 01:44:49 pm
My grey cells were clearly in a spin when I made my comment about increased duration.  smiley-red smiley-red

What I was actually trying to convey was that system current would be reduced by a factor of three.

By placing batteries in parallel, the OP was endeavouring to increase battery capacity to 21AH at 12 volts, so total power available would be 252WH and he would be assuming that current load would be evenly distributed across all three batteries.
For example, say motor rating was 200W, then system current would be 200/12 = 16.67 amps.  Ignoring any loss of capacity due to discharge rate, the potential duration would be 1.26hours

However, if the motors were in series the battery system would be 36 volts at 7AH.  Again total power available would be 252WH.  However with the 200W motor, the load current would now be 5.56amps.  Duration would remain at 1.26 hours

There are benefits to be gained by having batteries in series (increased voltage)
a) the same discharge current flows through all three batteries so each gets discharged evenly
b) the same charge current flows through all three batteries so each gets an improved chance of being charged evenly
c) by reducing system current by a factor of 3, the I2R losses would be reduced by a factor of 9 so the system is electrically more efficient.

Apologies for any confusion caused.

66  Using Arduino / General Electronics / Re: Controlling the rotation of brushless motor by changing polarity on: February 20, 2014, 07:35:00 am
Mingki
They are quite useful for making systems idiot proof whereby it doesn't matter which way the battery is connected. 
But, as you say, that's not relevant to this topic.
67  Using Arduino / General Electronics / Re: Electric Fence Voltmeter on: February 19, 2014, 05:06:13 pm
8000v across 6 resistors.  That's around 1300volts per resistor.
Most "standard" resistors will tolerate a couple of hundred volts or so, certainly not voltage in excess of 1000.  It's nothing to do with power dissipation, it's all about voltage rating.
You will need to source "high voltage" resistors.
68  Using Arduino / General Electronics / Re: Controlling the rotation of brushless motor by changing polarity on: February 19, 2014, 03:51:44 pm
Welcome back

I've now given up  smiley-confuse smiley-confuse
69  Using Arduino / Motors, Mechanics, and Power / Re: Putting three lead acid batteries in parallel on: February 19, 2014, 03:03:26 pm
Quote
"so duration is increased by a factor of three."
forget this one, please. 

Sorry, don't quite get your point
70  Using Arduino / Motors, Mechanics, and Power / Re: Putting three lead acid batteries in parallel on: February 19, 2014, 03:50:30 am
Or you could use 36volt motors and put the batteries in series.  AH value remains the same at 7AH but current drawn is only one third (for the same motor power) so duration is increased by a factor of three.
71  Using Arduino / General Electronics / Re: Controlling the rotation of brushless motor by changing polarity on: February 18, 2014, 10:36:30 am
Zapro, you give in too easily.  I'm sure we can get in lots more head banging over this project before he decides to listen to reason. smiley-grin smiley-grin
72  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.
73  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.
74  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
75  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.
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