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31  Using Arduino / General Electronics / Re: Line voltage (0-177v) variable power supply, feasible? on: March 10, 2014, 12:21:52 pm
Who's arguing ?   smiley-confuse

You asked a question - I gave an answer that I felt offered the best chance of success with minimal risk - a colleague offered a helpful and realistic cautionary comment - end of story.  No-one is obliged to give answers that answer your problem, merely offer suggestions that, hopefully might be useful.  You are at liberty to either accept or reject as you see fit.

The fact that you haven't got a favourable response from other readers might indicate that other contributors feel you are aiming for a target out-with the capability of a typical amateur.   Switch-mode supplies are a complex subject, the complexity of which probably increases exponentially with power demand.
32  Using Arduino / Motors, Mechanics, and Power / Re: solenoid controlled pilot on: March 09, 2014, 04:19:15 am
You've been given this project as a training assignment.  Such assignments are not always feasible or practical, the purpose is to see how YOU progress.  The basis of the project is to identify how you research and develop an experimental rig.  So far you've asked questions and been given feedback.  What reading (research have you done).  Perhaps it's now time you started making metal and build a rig to see if your ideas are feasible.   Bear in mind that physical experiments do not have to be practical, the objective is to prove a principal.  If this succeeds you then look at the practicality of the design. 
33  Using Arduino / Motors, Mechanics, and Power / Re: solenoid controlled pilot on: March 08, 2014, 12:52:44 pm
You need to give serious consideration to the mass of the moving parts.  Using very simple thinking : If the 2-stroke is running at 3000RPM (50 RPS) you'll be looking to open and close the valve 50 times a second and require fully open to full closed in say 6 degrees of revolution (1/60th of a rev).  In other words the valve is doing the equivalent of (50 x 60)   3000 cycles per second.  I'd say that's just about impossible using a solenoid operated system.   
34  Using Arduino / General Electronics / Re: How to sample AC input? on: March 08, 2014, 12:42:13 pm
And you also need to consider system power factor since VA does not equal watts in AC circuits (unity PF excepted)
What is the purpose of the energy meter.  Do you simply want power generated/consumed or are you requiring instantaneous power per millisecond.  If the latter and you want to store the data, you'll be filling your memory like there is no tomorrow.
35  Using Arduino / General Electronics / Re: Line voltage (0-177v) variable power supply, feasible? on: March 07, 2014, 12:59:42 pm
I did not imply that 117 from an isolation wasn't potentially deadly (no pun intended).  But any voltage source pushing current through the body in order to do harm requires a return path and an isolated output offers no return path, via the body, to ground if neither terminal is grounded (isolated output) - as is the case with a utility mains supply (neutral grounded).  So, in that respect an isolation transformer offers a degree of protection that an autotransformer does not.
36  Using Arduino / General Electronics / Re: Line voltage (0-177v) variable power supply, feasible? on: March 07, 2014, 12:47:46 pm
If I had limited knowledge of building large power inverters and wanted a continuously variable value of the mains supply, I'd opt for a variable transformer configuration.  But why would I want such facilities if all I was playing with was an Arduino and PICs

177v at 10a is 1.77kVA so you're looking at something like 2kW input.   That's a massive (and complex) device for a novice to attempt to build.

I think your best bet is a 2kW isolation transformer followed by a Variac type variable transformer (also rated at 2kW) which offers 0-110% fully variable output.  Note that these are usually rated as x Amps so in your case 10A.  But this value remains a constant limit, irrespective of the voltage output, so for example you still get just 10A with an output of 20volts.

I specified an isolation transformer as the input device because variable transformers are usually autotransformer devices which means they offer no isolation from the potentially lethal mains system.
37  Using Arduino / Motors, Mechanics, and Power / Re: vibration motor cannot stop! on: March 07, 2014, 11:06:19 am
Your motor with weight will have a fair amount of inertia (tendency to continue to do what it was doing before you turned the power off)  Motors also act as generators when they are turned with no power supply.

What is possibly happening in your case is that when you de-energise the relay, it opens the motor contacts and disconnects the power to the motor, but the motor then acts as a generator and produces sufficient voltage to somehow hold in the relay which then re-applies power to the motor.

Obviously this isn't meant to happen if your circuit is wired up correctly so either you have a mis-wired circuit or the actual circuit design is flawed.  can you therefore please supply either the circuit or an EXACT drawing of what you have built.
38  Using Arduino / General Electronics / Re: Voltage regulator LM7805 on: March 06, 2014, 02:07:11 pm
Most 3.5 digit meters are range 1.999, 19.99 and 199.9 volts.  (the "1" is what is called the half digit) So  if you are measuring 5 volts you are probably using the 20 volt range.  
Calibration tolerance is usually (almost always) referenced to full scale so the 0.5% error is actually referenced to 20 volts which equates to +-  0.1 volts
Hence your 5 volts could actually display as anywhere between 4.900 and 5.100 volts
Then there is the +- 1 digit tolerance of the ADC that drives the display so we now get anywhere from 4.899 to 5.101
The 1 digit flicker you see is probably the 1 digit tolerance of the ADC
So with the best will in the world, measurement is at best a "near enough" science.

If your meter is reading anywhere in the range 4.899 to 5.101 you can be reasonably confident that the 7805 output is to spec.
39  Using Arduino / General Electronics / Re: Using a battery eliminator with rating 500mA to power analog sensor. on: March 06, 2014, 07:01:29 am
All you need to know, in answer to your question, is that 500mA is what the supply is capable of delivering, not what the connected device demands

40  Using Arduino / General Electronics / Re: Using trimpots as series resistors on: March 05, 2014, 02:00:12 pm
Never mind the olden days, it's still good practice when using a pot' as a rheostat to connect the wiper to one end of the pot.  As you rightly suggest, if the wiper should lift or be noisy the maximum resistance is the end-to-end value of the pot rather than an open circuit.
41  Using Arduino / General Electronics / Re: Alternative to reed switches in camera control project on: March 05, 2014, 08:07:57 am
Quote
I do understand that they are NOT working in that diagram -

I may be totally wrong here (shoot me down if I am - please), but isn't the original designer intending for the wire laid alongside the reed switch to supply the magnetic field to switch the reed switch when the relevant Arduino pin is made high?

Bernie

Getting enough amps from the national grid for that to happen will be a problem.  Reed switches need quite a few ampere-turns (10 to 50) to operate so expecting to get that amount of magnetic field from only a part turn (straight wire) will take an amazing amount of current
42  Using Arduino / Motors, Mechanics, and Power / Re: high frequency linear actuator on: March 04, 2014, 03:11:10 am
"Failure is merely recognition that a solution has yet to be found"    smiley-mr-green   That should ward him off
43  Using Arduino / Motors, Mechanics, and Power / Re: electronically controlled reed valve ? on: March 03, 2014, 05:34:06 pm
How about a rotary gate shutter driven round by a servo motor.  Something like the device used on the old style cinema projectors. See here for a cartoon of one  http://en.wikipedia.org/wiki/Rotary_disc_shutter
44  Using Arduino / Motors, Mechanics, and Power / Re: ideas for mini garage door opener on: March 02, 2014, 05:42:50 pm
Might be better with a winch rather than a wench, though a wench would probably be more fun
45  Using Arduino / Motors, Mechanics, and Power / Re: ideas for mini garage door opener on: March 02, 2014, 04:23:14 pm
A continuous rotating RC servo motor driving a spool drum should fit the bill.  You can either drive it for a fixed period of time (a known number of revs)  to control the movement range or fit some small micro switches at top and bottom to manage the servo controller.
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