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1  Using Arduino / General Electronics / Re: Switching High Current Loads on: July 26, 2014, 06:29:03 pm
Don't buy a 10A relay from Ebay, they might melt with 5A.
Here are some good components:
Heavy relay: https://www.sparkfun.com/products/10924

That particular unit is made in China by BC Relay, AKA Shaanxi Qunli Electric Co., Lt.  BC stands for 'Best China'.  They are also made by Yueqing Hengwei Electronics, Zhejiang Zhonji Technology,  Zhejiang Asia Dragon Relay,  and other Chinese manufacturers.  if they carry the JQX designation, they all meet the same Chinese government controlled specifications.

I purchased 10 of these exact BC Relays from an eBay vendor last year for $9 including shipping.  None have melted.  Just saying.  But if you want to give the extra $ to SparkFun, hey, whatever.

http://www.bcrelays.com/Relay.JQX-15F.pdf



The gate of  a MOSFET is isolated.  I do not see why you would need an opto-isolator if proper grounding was unitized.  Even still, an opto-isolator is easy to use and this would be a good opportunity to learn how to use one.
2  Using Arduino / Project Guidance / Re: Arduino Uno + Ethernet Shield + MCP23S17 on: July 26, 2014, 05:40:53 pm
Why not use the MCP23017 instead?  It has a I2C interface and will not conflict with your Ethernet shield.
3  Using Arduino / Project Guidance / Re: Measure distance to water level within a cylinder on: July 26, 2014, 05:31:47 pm
Your going to get a ton of standing waves in that set-up.  They would be bouncing off everything like the water, the side of the main pipe, those conduits and even the wire and small pipe.  Depending on the level of the water, different echos could and would dominate.

I'd suggest you try to clear the 'view' of the HS-SR04.  Try to mount it as close to the center of the main pipe as possible, trim the corrugated conduit and strap everything else as closely to the sides of the main pipe as you can and keep them out of the field of view of the sensor.

One simple alternative might be  pressure sensor at the bottom of the tank.
4  Using Arduino / General Electronics / Re: Looking for a collection of schematics for learning on: July 24, 2014, 11:45:43 am
I have looked at the learning section, but didn't look like there were easily downloaded schematics there.

Hmm, I usually just right-click the schematic image and choose either 'Copy Image' or 'Save Image as'

Oh well.

Thanks for the search.
5  Using Arduino / Project Guidance / Re: DIY Rev Limiter using Inductive Pickup on 2 Stroke Carbureted Engine on: July 24, 2014, 11:38:01 am
You might be able to just use an N-channel MOSFET to short the output of the trigger coil to ground.

But 2k-4K RPM?  That engine does not even begin to make any power until about 8K-9K RPM.  Would the clutch even engage in that range?
6  Using Arduino / Project Guidance / Re: Weather Sensor Project on: July 24, 2014, 11:22:55 am
A DHT22 will give you both temperature and humidity and they are cheap and accurate.

What kind of precision do you need for the pyranometer?  Would a simple CDS photocell do the trick?  Dirt cheap and easy to interface.

I have no personal experience with IR distance sensors, but there are simple to use HC-SR04 based ultrasonic sensor modules available for about $4.  Lots of software examples too.  You just need to use a hood or something like that to keep it dry outside
7  Using Arduino / Project Guidance / Re: Relying on Arduino internal input protection against high voltages on: July 24, 2014, 11:08:21 am
I'll probably get trounced for this, but I'd say go for it and try it out.  The worst that can happen is you would damage a $3 chip.

Also, keep in mind that if your series resistor is too high, the input leakage current may affect your measurements, however you can probably compensate for that.

A better approach might be to use a simple voltage divider that brings the maximum expected voltage down to under 5V.
8  Using Arduino / General Electronics / Re: Looking for a collection of schematics for learning on: July 24, 2014, 10:57:38 am
There are schematics for a lot of the examples.  Plus everything I have looked at in the hardware section of the Playground has a schematic.

All in all, there are lots and lots of schematics in that section.
9  Using Arduino / General Electronics / Re: Looking for a collection of schematics for learning on: July 24, 2014, 10:46:59 am
Did you investigate the 'Learning' menu at the top of the forum page?
10  Using Arduino / General Electronics / Re: ENC28J60 not powering up on: July 05, 2014, 12:10:40 pm
The ENC28J60 requires far more current than will pass through that 10K resistor.  You need to add 3.3V LD regulator coming off the 5V.

If I am not mistaken, and ENC28J60 driving a standard magjack will draw over 300ma.
11  Using Arduino / General Electronics / Re: reason for no on/off switch on arduino? on: July 03, 2014, 10:51:21 pm
1) I don't see it that way, I just don't see the merit of using a shunt for a power switch (in this context or probably any other).
Why get so worked up? It's not as though the "Arduino gods" give a monkey's what I think and will pan your most excellent idea based on my comments.
It's simple, cheap and easy to use.  Of course, this does not cover Fungus' application of swapping it on and off for every wire or other change (ad minutia) you make.  However, I have boards that have the facility and it really is handy to cut the power when you need to.  No additions required.  If this is really confusing you and our Spanish compatriot, I could arrange a video on how the whole complicated and outrageously difficult to fathom thing works.

2) I don't get the inference. How does losing a shunt make anyone stupid?
Look up the word 'facetious'.  It applies to the comment.
12  Using Arduino / General Electronics / Re: reason for no on/off switch on arduino? on: July 03, 2014, 01:09:10 pm
A jumper placed at the right point in the circuit would cost $0.03.  Probably less in the quantities they make Arduinos.
Pulling a little jumper off the board then putting it back on every time I change a wire would annoy me intensely.

I could see you doing things that way.

So, unplugging your wall wart every time you change a wire, or reaching to toggle a soon to wear out switch every time you change a wire is a real improvement?

Okay, you win.
13  Using Arduino / General Electronics / Re: reason for no on/off switch on arduino? on: July 03, 2014, 01:01:52 pm
And that would lead to another question that would be asked over and over and over:
"I lost my little do-hickey. Anyone know where I can get more?"

Anybody who needs a switch can rig one up.

They can rig up a switch but they can't take care of a shorting block?

Oh, right.  I almost forgot 2-things:
 1) Thou shall never speak against the design of the Arduino gods, for it is flawless.
and
2) People who buy genuine Arduinos are really that stupid.

You know, I'm no genius (I'm sure you'll agree with that), but I've... a) never lost a jumper off the boards I have,  and b) Long ago I bought a big bag of them on eBay for about $2 for the time I should ever need one.
14  Using Arduino / General Electronics / Re: reason for no on/off switch on arduino? on: July 03, 2014, 06:12:53 am
A jumper placed at the right point in the circuit would cost $0.03.  Probably less in the quantities they make Arduinos.
15  Using Arduino / General Electronics / Re: type of board on: May 24, 2014, 08:26:13 am
RedBot uses an Optiboot bootloder, so choose Arduino Uno.
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