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631  Using Arduino / General Electronics / Re: 3 wire solenoid on: July 21, 2012, 02:05:33 am
How long will the battery last
Measure the current, look up your battery AH rating, divide AH by current and there is your answer +- 50%
You don't have a meter ?  then why are you playing with electronics ?
632  Using Arduino / Sensors / Re: sensing mains power on: July 20, 2012, 09:27:31 am
1/4 watt is more than sufficient since you'll only be pulling  <1mA, but resistor must be rated for the supply voltage.  From memory somewhere between 220k and 470k are often used.  Note that, once the neon strikes the voltage across it will be fairly constant at somewhere between 60 and 90volts.  We used to use such devices as HV voltage stabilisers in the days of valves (tubes to you yanks).

You should be able to buy a neon+resistor combination off the shelf at the likes of Tandy, RS, Maplins etc
633  Using Arduino / Sensors / Re: Detect green (but not red) LED lighting up? on: July 20, 2012, 09:22:23 am
Put a filter over a photocell (green) then only the green light will excite the photocell which you use to trigger a transistor which, in turn, triggers the arduino input
634  Using Arduino / Project Guidance / Re: Drilling a hole - need help. on: July 19, 2012, 04:37:08 pm
Coping saw then a dremel drill with a round emery wheel installed to clean it up
635  Using Arduino / Sensors / Re: Accuracy on: July 19, 2012, 03:18:15 am
And stopped watch tells correct time twice per day

Now that may be obvious and a bit stupid but when a person glances at their watch to see the time, how do they know a) the watch is correct and b) it is actually going.  In this case accuracy is in the eye of the beholder.  My better half always has clocks running some 10 mintes ahead of "real" time.  Don't ask why  -  it's a woman thing !

Accuracy is a subjective criteria - unless you are comparing against a national standard.

For "in-house" use you do not need accuracy - you need repeatability
636  Using Arduino / Motors, Mechanics, and Power / Re: Faulhaber 141:1 6VDC Gearhead Motor on: July 19, 2012, 03:07:43 am
You sure it's an Allen socket (hex) and not a TorX
637  Using Arduino / Sensors / Re: sensing mains power on: July 18, 2012, 04:45:31 pm
Capacitor should have class X dielectric implying ti is suitable for use as a mains "dropper"
638  Using Arduino / Project Guidance / Re: Self Leveling Deck on: July 18, 2012, 01:46:38 pm
What sort of response time do you require.  How much overshoot can you tolerate.  What weight is the device that you want to level.  What size is it etc etc etc

A bit more information on your project would be helpful

Have you considered a simple gimballed device using gravity as the levelling force  -  seems to work pretty well on ships.
639  Using Arduino / Project Guidance / Re: dimming neon on: July 18, 2012, 01:39:13 pm
You could use a mechanical interface to drive the potentiometer on a dimmable ballast system.  Use the arduino to drive an RC servo which is attached to the spindle of the dimmer pot.  Crude ?, yes,  but a solution
640  Using Arduino / General Electronics / Re: Bodge wire glue on: July 18, 2012, 12:38:59 pm
Hot-melt glue ?
641  Using Arduino / General Electronics / Re: Constructing a high-voltage transformer for safety and ruggedness on: July 17, 2012, 03:05:21 pm
Before you go for HV output it might be an idea to wind an LV output coil so that you can establish the core operating conditions without too much effort.   From memory of my transformer days you also need to ensure the faces of the cores mate completely since any increase in reluctance ( a beautifully illustrative word) due to face separation has a major effect on performance.
642  Using Arduino / General Electronics / Re: Constructing a high-voltage transformer for safety and ruggedness on: July 17, 2012, 12:35:21 pm
Why not simply use the line transformer as it's already manufactured (by professionals who knew what they were doing) and control the excitation voltage to give the output you want.  Transformer ratio times the input voltage determines the output so a suitable inout voltage will give you whatever output you desire.  I take it you appreciate that ferrite cores require high frequency excitation (in the order of 10s of kilohertz)
643  Using Arduino / General Electronics / Re: Measuring conductivity in water on: July 16, 2012, 05:55:18 am
You might also need some sort of depolarizer (AC excitation ?) since DC applied to a pair of probes is bound to set up an electrolysis reaction.
644  Using Arduino / Sensors / Re: Termostat problems on: July 14, 2012, 02:28:02 pm
You don't show how you are powering the system.  USB, battery and if the latter what voltage, type and size.

There is a possibility (remote ?) that the pot wires are inducing noise into your temperature sensor input circuit.  Perhaps placing 0.1 capacitors between ground and each of your 2 inputs will dampen any noise.
645  Using Arduino / General Electronics / Re: dumb question: diode and relay on: July 14, 2012, 02:45:20 am
The reed coil, unlike a conventional relay has no iron core so is of very low inductance.  It will still give a negative kick when de-energised but is very much less than that from a metal cored coil.  Having said that, it should still have a clamping diode fitted.
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