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61  Using Arduino / General Electronics / Re: Are these variable capacitors? on: October 21, 2013, 10:25:07 am
Side Note:  the big square item in clear plastic (almost not shown at the top of the first picture) which is above the tunable transformers/coils colored red and yellow..,. is actually what a variable capacitor looks like... because that is what that is.
62  Using Arduino / General Electronics / Re: Sub-zero temperature arduino and capacitors on: October 19, 2013, 08:24:14 pm
There are conformal coatings that are designed to be sprayed (or applied how you see fit) that will seal the board and electronics from the moisture...   not doing so can only lead to additional issues.

An example:  Probably not the best choice... http://www.amazon.com/CRC-Urethane-Viscous-Coating-Temperature/dp/B000IC7ZQ2/ref=pd_sim_sbs_indust_1
63  Using Arduino / General Electronics / Re: Capacitance Meter (Help) on: October 18, 2013, 12:37:56 pm
Commented on drawing...

NOTE:   Not 180K but 1.8K  not 330K but 3.1K
64  Using Arduino / General Electronics / Re: Capacitance Meter (Help) on: October 18, 2013, 10:42:42 am
Learning how to read and draw circuit schematic diagrams means that you will be able to speak the common language of electronics engineers.  It's worth it to spend some time learning how to get beyond pictorial representations. 
65  Topics / Science and Measurement / Re: Acoustic Rain Gauge (Loudness to Rain Rate) on: October 16, 2013, 07:32:50 am
While I have not tried this,  I would assume 2 things.  1) the piezo sensor will help you generate spikes that you can capture since it is more unlikely that you get simultaneous drops  2) bigger drops (or combined drops) means louder volume.  The way I would approach it is to measure the low(ish) frequency of spikes  and then measure the overall strength of the signal (size/quantity of water).  Only with both those values, in my opinion, it is possible to make a gauge.  The frequency of spikes measurement is more about "is it raining light or heavy or not at all" and volume intensity can only give a rough idea about how much water "weight" is hitting the sensor.  (IE assuming  you are using Piezo glued to the underside of a sheet of glass, for example).

Personally, I would start experiments on this using a quick and dirty pre-amp with DC output  and feed DC to a digital pin  using the frequency measure library from PJRC...
http://www.pjrc.com/teensy/td_libs_FreqMeasure.html

and to an Analog input for relative volume.


http://lowvoltage.wordpress.com/2011/05/15/lm386-mic-amp/
66  Using Arduino / General Electronics / Re: Controlling a 5V Solenoid with a Mosfet irf540 on: October 14, 2013, 07:17:59 am
Controlling a 12V motor (Like a PC fan)  with an IRF540 is more likely the intended reason you have one in your kit... but, the fact  remains that to use it properly, you really need to get the gate voltage closer to 10V. The 5V from the arduino pin will seriously under drive the part.  

How to solve?

Personally, I do it with a 74HCT06 (since I have a  lot of 7400 IC's handy for glue logic).  The 7406 is an open collector part which means that the output can be tied to circuits where voltages above 5V exist.  (the part can only SINK, not SOURCE).  NOTE: SINK means "provide a circuit path to ground".  

The input of the 7406 goes to an Arduino pin... the output goes to the MOSFET GATE and that connection ALSO is "pulled up" to 12V using a 10K resistor.  

So, you need 2 extra parts... but you can make your IRF540 useful IF you are working with a 10V or higher load voltage.
67  Using Arduino / Sensors / Re: Thermostat relay output with Dallas temp sensor ds18b20 sensor, arduino, on: October 11, 2013, 08:45:05 am
Have you considered using the PID library?

https://github.com/br3ttb/Arduino-PID-Library

http://brettbeauregard.com/blog/2011/04/improving-the-beginners-pid-introduction/
68  Using Arduino / General Electronics / Re: Solder possible with yellow resin around. [Solved] on: October 10, 2013, 06:41:48 pm
Even VODKA has been used with no bad results.
69  Using Arduino / General Electronics / Re: Electrical Help for a Push-pull solenoid on: October 10, 2013, 09:25:56 am
It was recommended that you try:
Quote
Use a logic level N-channel power mosfet instead

What made you decide on P channel?  Your solution will become more complicated with that device.
70  Using Arduino / General Electronics / Re: Ordering Arduino DIY parts, can't see forest through trees :-( on: October 10, 2013, 09:17:47 am
I think it is good to realize that many "instructions" on the web are created by those with not much more knowledge than yours... and for some reason, they like to omit things like capacitors and resistors because they don't "understand" them.

It's human nature to think "well it works without *it*... so it must be OK" and then not realize your design is suffering. 

It's sort of like the "Hey, if I don't get caught, it's not illegal" kind of logic.  There is a flaw in the somewhere... it will bite you.

71  Using Arduino / General Electronics / Re: NTE7426 NAND gate IC won't work on: October 09, 2013, 09:53:53 am
And really, you paid way too much for that part.  Like almost  a $1.00 more than you needed to.  Friends don't let friends by NTE parts.
72  Using Arduino / General Electronics / Re: SMPS Connection. on: October 07, 2013, 06:34:15 am
Your  "Europlug"  wall plug does not include a GND wire (green or AC GND).  All "europlug" type that I know about are unearthed except the one that the Swiss use  (well, my experience, being American is somewhat limited too...).  The Swiss one is basically a Europlug with an extra off center "earth" pin.

It is considered "less safe" to *not* have a chassis earth ground on a metal frame enclosure.
73  Using Arduino / General Electronics / Re: Time delay relay circuit? on: October 05, 2013, 08:14:33 pm
Hint.  A relay is certainly a discharge path... this is where you need to insert a device that will not try to discharge the cap faster than you can charge it...   you need to replace the low impedance load with a high impedance load.  A semiconductor or IC could help with that.

http://www.talkingelectronics.com/projects/200TrCcts/101-200TrCcts.html#16AB
74  Using Arduino / General Electronics / Re: Latching Circuit/ Auto off on: October 04, 2013, 06:18:44 am
There are many variation of the power button design you shared.

A nice explanation of "how they work" is done here: http://www.eevblog.com/2012/03/30/eevblog-262-worlds-simplest-soft-latching-power-switch-circuit/

Though, he does not share much about using a signal to turn it off.

Simplest one I know of:
http://img36.imageshack.us/img36/420/davidlw.png


For me personally, it's just simpler to buy one of these. http://www.pololu.com/catalog/product/750

It meets your requirements since it has a logic level shutoff pin.
75  Using Arduino / General Electronics / Re: Transistor array to go between 5v and load? on: October 03, 2013, 12:44:29 pm
TLC59213IN needs a 5V supply to the IC... but it does look like 3V logic will drive the input pins correctly.
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