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151  Using Arduino / General Electronics / Re: reading an ultrasonic sensor on: August 16, 2012, 12:31:27 pm
if by ridiculous price, you mean $29.99

http://www.parallax.com/Store/Sensors/ObjectDetection/tabid/176/ProductID/92/List/1/Default.aspx?SortField=ProductName,ProductName

how about $2.26
http://www.ebay.com/itm/1pcs-Ultrasonic-Module-HC-SR04-Distance-Measuring-Transducer-Sensor-for-Arduino-/261009210866?pt=LH_DefaultDomain_0&hash=item3cc55c7df2

or way less if you are not in a hurry and bid on auctions.
152  Using Arduino / General Electronics / Re: Help! unable to upload code in to the Arduino with specific conditions on: August 13, 2012, 02:17:42 am
in the 10 pin group, if you omit the ground from arduino, then you are isolating the arduino circuit from the relay circuit. you only need to connect the external supply +5 to jd-vcc and gnd. isolating would make the arduino circuit ground independent of the relay circuit ground.

153  Using Arduino / General Electronics / Re: Minimum input current for a reliable reading? on: August 10, 2012, 04:45:04 pm
good catch. I just tried getting a digikey shipping estimate and don't see anything for $8 overnight lol.
154  Using Arduino / General Electronics / Re: Minimum input current for a reliable reading? on: August 10, 2012, 01:05:10 pm
Well seeing as my patience is exceedingly low, I can rarely wait 2 and a half weeks for a Tayda delivery (even though it's cheaper overall) when digikey can ship overnight for $8. Never tried dipmicro though, I'll have to check them out.

it's always a tradeoff between time and money.
it can get quite expensive though if you order 1 or 2 parts at a time and have it shipped overnight.
if possible to plan ahead like crossroads, you can save money and at the same time use a lot less packaging material for shipping. (digikey use the same box packed with the shredded brown paper even if I order just 1 smd part that is as small as a dot)
155  Using Arduino / General Electronics / Re: ESC power supply on: August 10, 2012, 12:41:32 pm

The questions are:
1.Along the signal pin from the Arduino, there are those other 2 pins for supplying. What should I do with them? Connect them to the Arduino? Leave them alone?
2.What should be the voltage for the signal pin coming from Arduino? (I have a 3S battery for the motors, and a 2S battery for the platform)


1. connect signal and at least one ground (if you have multiple ESC). The supply line is unconnected, assuming you are powering the arduino separately.
2. use the signal pin as it is coming from arduino to the ESC. no need to level shift.
156  Using Arduino / General Electronics / Re: Help! unable to upload code in to the Arduino with specific conditions on: August 10, 2012, 12:33:58 pm
No, Arduino is powered with a external 12V power supply and every relay group has it's own 5V power supply.


I take it that you disconnected that blue jumper on the relay board and attached its own 5V power supply there (make sure you connect to the correct pin).

You can completely isolate the arduino signal from the relay by only connecting the +5 from arduino and the signal pin (no ground) since the relay boards are designed to be optically isolated and active low..
157  Using Arduino / General Electronics / Re: Resistors and application usage... on: August 08, 2012, 11:34:29 am
I can explain the LED part.

as in your example, LED is rated 2.6v forward voltage and 28ma.
If you apply 5V, that means the 2.4v must go somewhere (2.4+2.6=5).  That's where the resistor comes in.
To calculate the resistor value, you know the voltage (2.4) and the current (28ma), so R= 2.4/0.028 = 84.71 ohms.  
158  Using Arduino / General Electronics / Re: Problem with relay wiring on: August 07, 2012, 11:36:30 am
I initially got a 5v relay board also and it just takes too much current to activate the relays. So I switched to 12v relay board.
If you are stuck with the 5v relay, instead of getting a 7v power supply, you can get a dc-dc buck converter for like $1 shipped (I got 2 for $1) and it can step down 12 to 5 v very efficiently (without getting hot) compared to using the linear regulator. Search ebay for LM2596.
159  Using Arduino / General Electronics / Re: Time for a new iron on: August 01, 2012, 02:52:59 pm
That is a Hakko 936 clone from China.

That model is a retired product  It's not for sale any more...

This is it's replacement Hakko 926 clone from China, perhaps you meant this: http://www.sparkfun.com/products/10707

Sorry, that's the one I meant. I'll probably pick one up next week.

It seems to be have good reviews.

I got that one from sparkfun and been using it for a couple months and it works very well.
160  Using Arduino / General Electronics / Re: Where can I purchase a 120ac in isolated transformer? on: July 30, 2012, 03:15:13 pm
The learning objective is just that, "learning." The final outcome of this project
is to have a functioning benchtop variable AC to DC transformer from 1volts to maybe 24volts. I know I can purchase one on Amazon for a relatively low price, but I want to build one to learn the theory and the functionality.

no objections to the learning part. just merely suggesting that there might be more beneficial areas to spend your resource on (perhaps build a switching power supply?). as it is like learning vacuum tubes circuit. its a bit outdated.
161  Using Arduino / General Electronics / Re: Where can I purchase a 120ac in isolated transformer? on: July 30, 2012, 01:34:06 pm
what exactly is your learning objective?

I did a benchtop power supply project like 30 years ago and I can't imagine that will have the same learning value nowadays.
162  Using Arduino / General Electronics / Re: Will this ethernet module work for Arduino UNO? on: July 26, 2012, 06:07:43 pm
Well, I'm thinking about just getting the official arduino ethernet shield... Though the price is quite wack ($50, with shipping)

I highly recommend this
http://www.ebay.com/itm/New-SainSmart-Ethernet-Shield-W5l00-for-Arduino-UNO-MEGA-2560-R3-Duemilanove-/270998590388?pt=BI_Electrical_Equipment_Tools&hash=item3f18c653b4

if they have one on auction, you can usually get it for almost half that price.  they ship via their amazon store so you get it in a week.
163  Using Arduino / General Electronics / Re: Will this ethernet module work for Arduino UNO? on: July 26, 2012, 11:53:10 am
you can get w5100 based ethernet modules (with micro SD) now for $10-$12. IMHO, not worth saving $5 to go though all the trouble and headache to make the $5 module to work.
164  Using Arduino / General Electronics / Re: Arduino Uno Referance Design Query on: July 26, 2012, 11:49:33 am
This is just a personal belief:  I believe subtle errors like this one are present in the reference design to throw off clone makers who just take the files and produce them verbatim.  Maybe it was just a mistake, maybe it was intentional.

that's why there is a  fineprint saying "subject to change without notice".
there is a similar situation with the ethernet shield, the eagle file  left in a resistor that makes auto reset to not work.
I would not go as far as calling them "clone" makers. after all, this is supposed to be "open source".  cloning implies copying without authorization.  True there are some projects out there that pretend to be open source by doing things like leaving key component values out, extra component added or removed, etc. arduino's case is certainly not as the above post is implying, as you can email Massimo directly can he will tell you exactly what the correct circuit should be.
165  Using Arduino / Networking, Protocols, and Devices / Re: HTTP Server running with Ethernet library =] on: June 08, 2012, 02:06:56 pm
ajax support would be nice. useful for updating the value for a few fields without refreshing the entire page.
can you elaborate on iphone compatibility? is it for things like supporting the apple-touch-icon used by safari browser client? jquery?

I imagine this would barely fit on an UNO and a mega would be required right?
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