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16  Using Arduino / General Electronics / Re: valley peak detector on: April 15, 2014, 02:31:40 am
What do you mean by "valleys"  Do you mean the maximum negative peak or the lowest voltage that the "rectified" signal fall to.
17  Using Arduino / Motors, Mechanics, and Power / Re: Failed to drive a CD Rom sled motor via Hall effect sensor. on: April 14, 2014, 12:24:23 pm
and then rotate it because it's also back to front
18  Using Arduino / General Electronics / Re: snubber circuit capacitor and resistor? on: April 14, 2014, 07:27:27 am
Hopefully this document tells you the technical story behind the snubber requirement / design

http://www.soloelectronica.net/triac/AN_3003.PDF
19  Using Arduino / General Electronics / Re: How can I find out why a small DC motor won't work? on: April 07, 2014, 02:47:46 am
If you simply wired the speaker to the car horn circuit then you will indeed have destroyed it. 
A car horn circuit is a simple 12V DC system which is either ON or OFF. 
A speaker operates from an AC signal source (amplifier) matched to the speaker impedance, usually 4, 8 or 16 ohms. 
If wired directly to DC, all that will happen is the cone will give a single click as it moves to a new fixed position and excess current will flow through the voice coil windings.
20  Using Arduino / General Electronics / Re: How can I find out why a small DC motor won't work? on: April 06, 2014, 06:25:31 am
Cut one of the motor leads to isolate the motor from the rest of the circuit, then apply voltage, 6 or so, to the motor terminals to see if it will run.  This will verify if the motor is defective or the motor drive circuit is defective.   Note that if the motor is defective its drive circuit might also be defective.
21  Using Arduino / General Electronics / Re: Take pictures with DRAM!!! on: April 05, 2014, 12:59:39 pm
and here's me thinking it involved taking photographs whilst supping at a glass of the "water of life"
22  Using Arduino / General Electronics / Re: Where can I buy an Electro-Permanent Magnet? on: April 05, 2014, 12:56:54 pm
Many thanks for the educational bite - never too old to learn - though at my age retention of yesterday's education is a problem  smiley-grin
23  Using Arduino / General Electronics / Re: Where can I buy an Electro-Permanent Magnet? on: April 05, 2014, 11:08:47 am
What's an "electro-permanent magnet"
Electro magnet = one that is magnetic when energised
Permanent magnet = one that is permanently magnetised

So what is it you are looking for ?
24  Using Arduino / General Electronics / Re: I need help understanding my adjustable power supply on: April 05, 2014, 03:40:09 am
I agree Mike, I misread the OP's text
25  Using Arduino / General Electronics / Re: I need help understanding my adjustable power supply on: April 05, 2014, 02:05:45 am
The metering switch is merely a display selector.  The meter can only display one value at a time and the 4-way slider switch selects the value to be displayed.

The output voltage is determined, when in independent mode by the setting of the voltage adjustments.  the output current is determined by the load that you apply to the terminals and the voltage appearing there.

In tracking mode, voltage B follows what A is set to, depending on how you have set the 2-way mode switch.

The 1.45 volts is the drive voltage that the supply provides with NO load.  When under load the output is drooping down to 1.36 which means the regulation is somewhat poor.  Perfect regulation would maintain the set voltage irrespective of the current load.

You say you are charging 3 cells in series and only getting a battery voltage (batteries are a collection of cells) of 1.3V.   It appears that your cells are either defective or extremely depleted and will need in excess of 10 hours of charge to recover.

The green terminal is probably attached to the casing and is used, if desired to connect the casing to the circuit you are working on to maintain an earth reference.  In normal circuitry work you can completely ignore it.  You might care to test to see if it is connected to any of the output terminals  -  it shouldn't be!
26  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.
27  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. 
28  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.
29  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 ?
30  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.
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