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16  Using Arduino / General Electronics / Is there such a thing as nonconductive insulating putty? Or something similar. on: June 28, 2013, 01:56:38 pm
I have some electrical connections I'd like to temporarily protect.  They are about 14ga wire, soldered to large pads on a PCB.  Obviously shrink tube or electrical tape won't really work.  I could use some liquid electrical tape, or silicone, or epoxy but those are too permanent, will be a pain to get off if/when I need to desolder, and resolder the connection.

I'm wondering if there is anything out there, that works well and has been proven, that sort of has a consistency similar to silly putty (but a little thicker, and less prone to sagging).  Something that can be smeared/pressed around the connection, and will adhere and stay put well, but when it is time to remove, it can pull right off with zero residue.

Does such a solution exist.  Or is there a better solution I'm not thinking of?
17  Using Arduino / General Electronics / Re: Recommendations on affordable lead free solder? Confused by all the formulas. on: April 06, 2013, 09:03:23 pm
Awesome, thanks for the replies.

The link to the kester website was great, providing a description of what the formulations are actually used for.  Now I feel comfortable buying SAC solder.  Either SnAg3.0Cu0.5  or SnAg3.5Cu0.7

And the link to the MG chemicals solder is just the type of quantity I've had a hard time finding, about a $25 spool.

As far as using leaded solder, I have in the past, however I'd like to stick with the less toxic lead free, and although people claim its hard to solder with, I'm able to just fine.

My only last question, is there any vast quality differences between brands, or are they basically the same as long as the formulas are the same.  For example, I found a "Chip Quik" brand, that seems roughly identical to the MG chemicals brand, specs wise, both conforming to rohs for purity, and similar price.  Think anyone would ever see a difference brand wise, or best to go for whichever is cheaper, or less shipping, etc?
18  Using Arduino / General Electronics / Recommendations on affordable lead free solder? Confused by all the formulas. on: April 05, 2013, 09:21:34 pm
I've been soldering for many years, first using the radio shack 96sn/4ag lead free solder, and more recently the harbor freight 96sn/4ag solder, .031 in size.  Problem is it comes in such tiny little tubes, I've gone through about 100.  Its got to be cheaper buying a spool, but heres the biggest problems I'm running into.

1.  All the different formulations, and ratios.  Some with "no clean flux", others make no mention of the flux.  Kester has some SN96.3AG3.7 .031 that has my interest a little bit, seems almost the same as what I'm using.  But then I also hear of SAC solder which has mostly tin with a little silver and copper, perhaps its better?  As well as many other formulas.
2. I can't ever find a reasonable size like 1/4 or 1/2 pound.  Its all either super expensive 1lb rolls which I hesitate to buy not knowing if Its right, or else tiny tubes which aren't worth shipping.

I'm not that picky, just want it to work as well or better than the harbor freight stuff, but buy it in slightly bigger amounts to hopefully save money.  But all the different choices are just confusing me.  Any advice?
19  Using Arduino / LEDs and Multiplexing / Beginner question on Individually Addressible LED strips. on: January 26, 2013, 02:37:15 pm
So I decided the other day to start to get my feet wet in the world of individually addressible LED strips.  However I guess I didn't quite know enough to get everything compatible, and may have bought a couple wrong things. 

Heres what I bought......
A 5 meter strip of "Dream Color" LED's with IR controller.
http://www.ebay.com/itm/251168140405?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

And also this RF controller (since it seems like it has more programs than the IR one, had seen it in some youtube videos)
http://www.ebay.com/itm/170859665962?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

The problems I'm having are...
1) Apparently these "Dream Color" Led's that i thought were individually addressible, really appear to only be addressible in groups of 3's.
2) The RF controller doesn't seem to work with this strip, or at least has different connectors.  The led strip uses a 10 pin connection, whereas this rf controller seems to have a 4 pin output.

Can anyone tell me if there is a way to make them work together, or else what type of individually addressible led's should I shop for to work with that RF controller, and also in the future, work with arduino if I want more advanced functinality than the controller provides?

Thanks.





I may eventually integrate arduino, but right now I just want a good controller with tons of functions.
20  Using Arduino / General Electronics / Re: How do I drive 3 or more Cree XML-T6 LED's? on: December 01, 2012, 03:23:18 pm
I'm a little confused about the incandescent bulb idea. Seems to defeat the purpose of the LED's being small and efficient.  Putting an ugly old incandescent bulb in there.  And also confused why use an incandescent bulb rather than a resistor of the same value?  Afterall, isn't a incandescent bulb just a resistor?

I know they make single led drivers.  There is a abundant supply of cheap and compact drivers, that are about the size of a nickel, and cost $10 or less, to drive single XML-T6 leds.  Looking for something similar, but to be able to drive 3 or more of them.  Can't find this anywhere.
21  Using Arduino / General Electronics / How do I drive 3 or more Cree XML-T6 LED's? on: November 30, 2012, 11:39:20 pm
This seems like the type of question a that could have been answered by a simple google search, however I must be searching wrong, because I've spent a lot of time looking with no luck.

I'm trying to figure out what sort of cheap and simple driver I can use to drive 3 or more Cree XML T6 LED's.  They have a max current of 3000ma, and I believe a maximum voltage of around 3.35 volts.  So if I'm not mistaken, that means that I am to wire the led's in series (I hear this is the best way), that would need a driver that can deliver 3000ma at 10.05 volts.  I'm thinking I'd likely use a 3 cell lipo battery to power it, which are around 12 volts.  Where could I find a driver for this application?

And how about if I wanted to wire say 6 of the LED's in series.  I'd need 3000ma at 20.1 volts.  How could I find a driver to step up the 12 volts into 20.1 and 300ma?
22  Using Arduino / General Electronics / Re: How can I make this static electricity device stronger? on: November 24, 2012, 01:39:36 am
Ion generators use corona discharge, there's not much more voltage you can get once discharge starts!

Quote
It works pretty decent, and can allow someone to generate a pretty constant stream of 1/8 - 1/4 sparks from their fingers to any grounded metal.  But I want to see if I can make it stronger.

Why do you want to go higher?  Sounds painful.  Unless the air is dry you won't get much higher anyway.

To get more voltage the Van-def-Graff is the way to go, and there are _serious_ safety considerations with larger VdGG's.


No, not really painful, just about like touching a doorknob.  Reason I want to make it stronger is simply more fun, and more impressive.  As a kid I remember this one slide I'd go up and down over and over without touching the ground, and could build up to 1" sparks. so I feel like there has got to be some untapped potential.

A van def graff generator is definetly something awesome, however for this project I'm really looking for something that can be worn right on the body (unless I found a good way to make some sort of wearable one)

So anyone know exactly what is the limiting factor on the current design?  Is it the "corona discharge" (I'll have to read more about this)?  Is it perhaps the body simply can't hold more charge (a possiblity, it is a bit humid, however I don't think its the case since I've built up higher charges before the natural way).  Is the output of the ionizer module somehow too low?  Something else?
23  Using Arduino / General Electronics / Re: How can I make this static electricity device stronger? on: November 22, 2012, 02:08:27 pm
Increasing the voltage definitely makes sense, although I'm a little bit confused about how to do so in the example of static electricity, since doesn't it behave differently than typical current?

Its my understanding (and I could be wrong about some of this, so correct me if I'm mistaken on anything) that voltage boils down to one object having more negative electrons than the other.  In the sake of the static electricity I'm going for with this device, the body collects more negative electrons than its surroundings.   Its my understanding that the negative ion generator, to be simplified, constantly floods the body with negative electrons.  So isn't voltage constantly increasing, simply by more and more negative electrons flowing from the device onto the body, before they are discharged?  Basically making the body like a capacitor.

Thats why I was figuring 3 in parallel would work, is because they would all 3 be flooding the body with negative electrons 3 times as fast, and building voltage 3 times as fast.  But apparently not.  But then is it even possible to somehow increase this with a transformer instead?  And if so, how?

Here is a link to the ion generators I'm using http://www.allelectronics.com/make-a-store/item/SW-750/IONIZER/1.html .

24  Using Arduino / General Electronics / How can I make this static electricity device stronger? on: November 22, 2012, 11:53:02 am
I recently made a pretty simple device to constantly and rapidly charge a person up with static electricity.

The main part of the device is simply a cheap component called a "Negative Ion Generator".  Which runs off of AC, so I'm using a cheap inverter to convert the DC from a typical 9v battery, or 12v lipo, into usable current for the device.  The main wire off the Ion generator attaches to a piece of aluminum that is put against the skin, and another ground wire attaches to the bottom of the shoe.

It works pretty decent, and can allow someone to generate a pretty constant stream of 1/8 - 1/4 sparks from their fingers to any grounded metal.  But I want to see if I can make it stronger.

I tried ordering more Ion generators, and actually hooked 3 of them up in parallel, thinking this would drastically increase my output, however to my surprise, I saw absolutely no increase at all, in fact, it was possibly even a little weaker.  I know the lipo battery can supply more than enough power, and the inverter is rated for more current than all 3 of these things draw.

Can anyone explain why this didn't work the way I expected, or offer any advice how to make it stronger.  Would like to increase my spark length as long as possible.
25  Using Arduino / General Electronics / Re: Best 5v and 12v batteries good for high capacity and low cost? on: November 04, 2012, 12:52:56 pm
I like the sla + usb adapter idea.  Just ordered a combo.  That way I can have nominal 12v and regulated 5v, and pretty cheap for the capacity. 
26  Using Arduino / General Electronics / Re: Best 5v and 12v batteries good for high capacity and low cost? on: November 03, 2012, 05:29:23 pm
I'm sure a slight variation could be fine.  It will be powering things such as arduinos, servos, motors, a camera, etc.  Most of which shouldn't be super picky.  Even the camera I'm guessing would still probably run on slightly higher or lower voltage.
27  Using Arduino / General Electronics / Best 5v and 12v batteries good for high capacity and low cost? on: November 03, 2012, 04:33:15 pm
I have a couple projects in mind that will need a 5v power source, and another that may need a 12v power source.  I'm looking for some battery recomendations.  They will mainly be things that will use a pretty low draw over a period of time, and sometimes be outdoors (sheltered from weather), so I'd like a battery that could survive a low draw application for a few days between charging? 

Size isn't too much of an issue, I mean I don't want it to be huge and cumbersome like a car battery, but doesn't need to be small either.  I do want it to be low cost, and simple to recharge (I have a very good lipo/nimh/nicd/pb charger)

Perhaps some sort of lead acid battery?  A large bank of AA nimh batteries in series/parallel?  Lipos could be nice, but I've never found a good cheap low voltage cutoff device for them before.

Any suggestions on a good type to look for?
28  Using Arduino / General Electronics / Re: Running high power led's without drivers. on: October 08, 2012, 10:03:14 pm
Am I really doing this the wrong way?  Do they need to be in series instead?

Yes, by having only one constant current driver, you then have no defined control mechanism for equal current flow to each parallel LED, your just assuming somehow that each will take its equal share, and while that may be your wish and desire that doesn't make it so. Kirchhoff has defined how current and voltage works in series and parallel circuits and is worth a review: http://physics.about.com/od/electromagnetics/f/KirchhoffRule.htm

 And if so, can anyone explain why they would need to be in series and parallel doesn't work?

Well according to one of Kirchhoff's rules in a series circuit the current flow is equal at all points in the circuit. So if three leds are wired in series and 700ma is the circuit current flow then of course 700ma is flowing into and out of each led, so they all operate at the same current. But of course as the desired LED current is 700ma for your LEDs, your constant current driver needs to run at 700ma output only, you can't use one that outputs a constant 2800ma output.

This whole explanation was very helpful, and a lot more things are starting to make sense now.  I think I must have been mistakenly assuming that there is current drop the same way there is voltage drop.  Mistakenly thinking I have to add up the current of each led in series, the same way you add up voltage, but I guess this is wrong.  If I understand correctly, there is voltage drop across each led, but no current drop, so if I have 700ma led's, and a 700ma driver, I can light up as many led's as I possibly want in series, as long as the driver is putting out enough voltage?  Example if i want 100 3.5v led's, I would need a driver that outputs 350V, but only 700ma of current?

So you say I cannot power a 700ma led with a 2800ma driver?  What would happen? I was thinking as long as the driver puts out equal or more that it is fine?  Same way you can use a 12v 1A ac adaptor to power things that only use 100ma, since they only take what they need.  Or how on RC motors I use, I can use a 30A speed controller on a motor that only draws 15A if I want, since the motor only takes what it needs.  Are you saying things work completely differently when it comes to led's and drivers?
29  Using Arduino / General Electronics / Re: Running high power led's without drivers. on: October 08, 2012, 03:09:13 pm
Well, the driver is designed for 18650 batteries, and says 4.2 input voltage.  So input voltage should be good.  Don't have a direct link, but its the same type typically used in flashlights to drive the 10w cree xml-t6 led's.

The battery does have protection on it, but when I experimented by hooking it directly up to a xml-t6 led, it pulled 1.6A and i'm guessing it can pull more, so its definetly capable of delivering more than the 700ma-1A that I was getting with the other led's.

Someone mentioned one of the weak led's taking all the current from the others.  However if they are all wired in parallel, I don't see how this could happen, each one should get as much current as it wants right?

Am I really doing this the wrong way?  Do they need to be in series instead?  And if so, can anyone explain why they would need to be in series and parallel doesn't work?  I don't exactly see why it would make a difference as long as they are being fed their correct voltage (for example say there are 4, 3.5 volt led's, either feed 3.5 volts to them all in parallel, or feed 14v to them in series, why would there be a difference).
30  Using Arduino / General Electronics / Re: Running high power led's without drivers. on: October 07, 2012, 09:30:05 pm
Thanks for all the replies.  I admit, some of the info in the debates was a little over my head, but I realize now theres not much point in running the LED's without a driver.

I'm still confused though why my numbers aren't adding up on this setup I made.  I have some 3w led's that say they are rated at 700ma max current.  I also bought a driver that is supposed to put out 2800ma.  Seems like a perfect fit, 4x 700 = 2800ma. I wired up the driver, and had 4 of these led's in parallel, and using a 18650 battery, which is a single cell lithium ion battery.  However, at full power, this setup  only seems to be drawing about 700ma for all 4 of them, not the 2800 I was expecting.  I read specs on the 18650 battery, brands vary, but they all seem to put out a minimum of 3 amps, many putting out 9 amps.

Out of frustration I did bypass the driver and hooked the battery directly up to the 4 led's in parallel, and they were only pulling 1A, again not the 2800 I was expecting. (note: one person claims i damaged the led's doing this, but I only did this AFTER already having hooked them up through the driver, and them only drawing 700ma)

PS: I was expecting these 4 led's to total 12w of power, and be a touch brighter than my cree xml-t6 flashlight which uses a single led which is 10w, but as is, they are nowhere near as bright.
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