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16  Using Arduino / General Electronics / Re: Why do I need to calibrate servos? on: April 03, 2014, 03:20:09 am
Perhaps it's to establish the end points of your desired movement.  Not everyone wants or needs 90 or 180 degrees of movement.
17  Using Arduino / General Electronics / Re: Light Bulb 120vac to DC on: March 31, 2014, 02:40:11 am
You show your LEDs wired in parallel.  Each LED requires a means of controlling its current so LEDs in parallel with no individual current control will not work.  If you wire the LEDs in series a single current controller will suffice but any LED failing will stop all the rest operating.   Might I suggest you cheat slightly by dismantling and looking at how an existing LED mains light is constructed and then redesign from there. 
18  Using Arduino / Motors, Mechanics, and Power / Re: how to control high speed switching of a 12v ignition coil? on: March 24, 2014, 05:18:47 pm
What I was getting at was "What something can be forced to do is not necessarily the same what it is designed to do".
I appreciate the pulse capability is greater than its continuous rating but in this case the OP has not indicated the duty cycle.
Specified rated current for the unit is 18A and prudent circuit design should work on the basis of a lower value.
19  Using Arduino / Motors, Mechanics, and Power / Re: how to control high speed switching of a 12v ignition coil? on: March 24, 2014, 06:54:53 am
With that one a gate voltage of 5V can drive about 40A.
Out of curiosity, which part of the data sheet did you get that from ?
20  Using Arduino / Motors, Mechanics, and Power / Re: how to control high speed switching of a 12v ignition coil? on: March 22, 2014, 03:14:22 am
The back emf from such a coil could be in the order of 200volts or so.  The switching device should be rated to handle this.  Your best bet would be to google "electronic ignition circuit" and get a few images such as these http://uk.images.search.yahoo.com/search/images;_ylt=A7x9QXgXRy1ThmYAHThLBQx.;_ylu=X3oDMTB1bWoxZmFkBHNlYwNzYwRjb2xvA2lyZAR2dGlkA1VLQzAwMl83Mg--?_adv_prop=image&fr=spigot-nt-gcmac&va=electronic+ignition+circuit

You will see that several use a capacitor in the primary circuit, used to produce an LC ring when the "switch" opens.

Also bear in mind that an ignition spark performance is totally different when under pressure so what appears to work on the bench may not do so when installed in an engine.  I learned this fact some 50 years ago when experimenting with the building of an electronic system for a colleagues 2-stroke car.
21  Using Arduino / General Electronics / Re: BATTERY CHARGING WITH CONSTANT VOLTAGE on: March 19, 2014, 03:22:59 am
Basically yes, but it will not be capable of fully charging the battery.  You need somewhere between 13.8 and 14.4 to fully charge - depends upon battery chemistry.

Apart from that, it's improbable that your source is a true constant voltage - it will have an output impedance which will cause some voltage droop as the load increases.
22  Using Arduino / General Electronics / Re: Voltage regulator Batt Capacity Question on: March 17, 2014, 01:56:11 pm
You better of using either a DC-DC converter. There are nice compact ones in the market. or use a simple buck converter.  Both make more effective use of your battery capacity

I agree, but it doesn't answer the question
23  Using Arduino / General Electronics / Re: Parts for battery measuring? on: March 17, 2014, 11:16:02 am
OK, let's look at it in basic terms and see how my original calculations evolved.

Battery voltage is 32 (my figure) and you want to feed the Arduino with only 5 volts so divisor ratio is basically 32/5 = 6.4

Now, let us say we have a resistor divider chain with R1 coming from the battery positive terminal coupled to a second resistor R2, the free end of which is coupled to the battery negative terminal (and the arduino ground terminal).  The junction of the two resistors is connected to the arduino input terminal.  Let us say the value of R2 is 2.2k.  We know this has to develop 5 volts across it so the current flowing through it must be 5/2200 = 2.273mA.  The input impedance of the arduino is very high so we can assume no current flows into that point.  So 2.273mA also flows through R1 and this resistor has to drop (32-5) = 27volts.  So the value of R1 = 27 /2.273 = 11.88k. 

These resistors have the ration of 11.88/2.2 = 5.4 which obviously does not correspond to the original divisor number of 6.4 but is actually the ratio of the two resistors required to create the desired input to the arduino

However, if we add the chain values 11.88k + 2.2k = 14.08k  (R1 +R2) and divide this number by the lower resistor 2.2k (R2) we have 14.08/2.2 = 6.4 which is the ratio of the input voltage to output voltage.

Confused ?  I'm not surprised.   
24  Using Arduino / General Electronics / Re: Voltage regulator Batt Capacity Question on: March 17, 2014, 10:51:14 am
Yep,  basically it's so many amps for so many hours  ie AH
25  Using Arduino / General Electronics / Re: Parts for battery measuring? on: March 17, 2014, 05:54:55 am
2.2k and 12k were based on using readily available resistors to produce a voltage drop ration of 6.45 :1      ie 32/6.45 = 4.96  (approx 5volts).  So with 5 volts input to the Arduino developed across the 2.2k resistor, the remainder of the 32 volts ie 27 volts will be dropped across the 12k resistor.  I chose 32 volts as a maximum charge voltage of your 24 volt battery.   Others might say these resistor values are a bit low and cause excessive current drain on the battery.  However consider that 14.2k places a 1.7mA load on the battery, which being rated at 100AH should be capable of feeding this for in excess of 7 years !!  I think self-discharge and other circuits will far exceed this trivial burden.
26  Using Arduino / General Electronics / Re: Parts for battery measuring? on: March 17, 2014, 03:38:33 am
Thank you, Chagrin.

Yes, those are averages. I've chosen those resistors in an attempt to reduce heat -

That equates to 0.5mW  ie one half of one thousandth of a watt.  Are you serious ?
27  Using Arduino / General Electronics / Re: How to charge Supercapacitor? on: March 17, 2014, 03:33:14 am
Or you could use a relay in the charging circuit.  Then by placing the NO contacts in series with a diode in the feed to the super capacitor, when power goes off the relay opens the contacts and absolutely none of the microscopic reverse current through the diode feeds back to the charge circuit.  Sometimes we are guilty of over-engineering.  A diode is all you need !
28  Using Arduino / General Electronics / Re: Understanding anti-parallel clipping diodes on: March 16, 2014, 04:10:32 am
Mark, are you saying they behave more like zeners in this combination?

Not at all, the zener effect is a totally different phenomena
See :  http://en.wikipedia.org/wiki/Zener_diode
29  Using Arduino / General Electronics / Re: Parts for battery measuring? on: March 14, 2014, 06:22:45 am
Digital volt meter and a thermometer   smiley

Or if you want the arduino to read the voltage a couple of resistors to suit an input voltage or around 32 volts (the battery exceeds 24 when being charged).  Say a ratio of 5.4 to 1,  so probably a 2k2 and a 12k.  These ratios do not give an exact 32volt range, but near enough using standard components to permit you to trim in the range in the algoritm. You will of course also need a means of powering the arduino.  This could come from the 24v supply but you would need something like a 36-to-5 volt DC power module.

If you want to also log temperature then I suggest you read the following for an example
http://learn.adafruit.com/tmp36-temperature-sensor/example-projects

I wonder why you want to read battery temperature if you are not reading battery acid SG.  Capacity is primarily electrolyte temperature and SG dependant, voltage being a secondary variable and not a good indication of capacity.
30  Using Arduino / General Electronics / Re: jammer 433 mhz arduino uno? on: March 13, 2014, 03:36:14 am
Could be a bit sticky but if pectin is modulated into the mixer circuit it should produce a stable base
I think this could be done using one of those new Pi micro-processors with a butterworth filter
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