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1  Using Arduino / General Electronics / Re: built these optocoupled circuits to drive a 12v light from arduino uno on: October 26, 2012, 01:08:28 pm
Crossroads - sorry to be such a "newbie" but if you could give me a laymans' idea of what you are saying (i.e. standard resistor values, connect x to y, etc.) certainly I'll understand. I'm pretty quick on the uptake and really need to see cookbook/textbook examples once to get the general principle. But as for the isolation - I just want to use a standard configuration across a board that will have multiples of this same circuit for switching, in some cases, devices that could have inductive loads and such. I am just overly cautious!

About the Fritzing schematic creation - let me say one thing.

Three different views in Fritzing - breadboard, schematic, and PCB. Once you breadboard something, on the schematic page (and the PCB page) Fritzing tosses everything into a giant ratsnest of wires / traces and then you gotta go about sorting it all out and making it "pretty."

Like most software it's just a tool and a lot of folks just double-click connections and - wham - you have ground in the upper right corner, an LED array diagonal across the screen, and somewhere half off the screen you have source voltage. It's about laying things out nice!

I don't like to create schematics unless they're clear - and the whole fritzing thing has really enabled me to start thinking in terms of hardware better than I ever have  before. Without having to use my clumbsy fingers I can build, rip out (no static issues!) and rebuild things until I get them right. My idea is to train on fritzing and advance to eagle so to speak.

DHenry - thanks for the advice! Greatly appreciated. I'll keep that in mind. I have so much stuff sitting around here - I bought a monster package of IC's and all sorts of stuff from an online retailer (a rather nice assortment for a good price from a guy working out of Vermont and Asia). I just want to put this veritable potpourri of MOSFETs and IC's to good use while learning what I have!
2  Using Arduino / General Electronics / built these optocoupled circuits to drive a 12v light from arduino uno on: October 26, 2012, 09:15:52 am
Hello all! I am relatively new to electronics and not too new to coding - so I would like some feedback on my schematic that I've generated from Fritzing.

In short what I am looking to do is drive a power FET with an Arduino digital signal. I have a basket of 4N35 optocouplers, and IRF540 MOSFET - N channel MOSFETS. I know that N-channel mosfets source current from ground, and that's how they turn on and off by switching off and on the N-channel. I hope my terminology is correct! So I put together - based on other projects and products I've seen - a schematic that I'm trying to turn into a PCB to control 12v lighting. The IRF540 with heatsink can handle some pretty high current loads!!!

So what I have here are two circuits intersecting at the 4N35. This is a 5v Arduino circuit for the digital signals, and a 12v power circuit to drive the load (s). Both go back to their respective battery grounds because of the opto-isolation. That said - anything I could do to prevent say a voltage spike on the 12v side or overcurrent would be helpful. Also if I did anything wrong - or something is represented incorrectly, it would be greatly appreciated if the experts out there could provide some feedback. This is my first shot at a schematic - so bear with me!!!

3  Using Arduino / Motors, Mechanics, and Power / Re: A sample Power FET Circuit using IRF540 and the 4N35M - any comments on: October 25, 2012, 07:26:33 pm
Here's a link to a re-worked schematic. Worked backwards from a circuit I saw that works on a power fet board I bought. Combo of looking @ the schematic and reading the board.

The picasa web albums site allows you to zoom and pan and such. seriously this my first i've worked up - i mean i've made LED boards and such in fritzing so i can practice coding for pin outputs on a little shield - but this is something a little bigger.
4  Using Arduino / Motors, Mechanics, and Power / A sample Power FET Circuit using IRF540 and the 4N35M - any comments on: October 24, 2012, 09:22:48 pm
The first proper schematic I have ever drawn of a circuit - and I hungry for any feedback that the experts out there may have.

Briefly, I am driving accessory foglights in my car. I want them only to turn on and off with the microcontroller running the circuit. I have sets of three-wire pins that snap into a fitting on the circuit board, so the VCC / Battery 5v Arduino represents the three pins from Arduino (signal, voltage, ground) to drive the opto-isolated circuit. The 5V in may be expanded to do other things than just this on the board, but I've left it there for my own reference. Based on my research this setup should work fine - any input on, say, diode protection or other for running more inductive loads would also be appreciated.

I did not label the capacitor - but it's a 10nf ceramic capacitor. I did some research and with a proper heatsink the IRF540 will be fine for the amperage on my 12v lighting - for each light. In fact more than adequate.

Thanks so much! I hope I did a decent job!
5  Topics / Education and Teaching / Starting an Elementary Electronics Circuits Class Locally on: August 11, 2012, 09:07:20 pm
I am considering starting a local "elementary" class in electronic circuits (simple low voltage DC, our favorite here). Has anyone had any experience with this?

I am thinking of integrating Arduino in the Forrest Mimms Intro to electronics and then working through the two books available regarding the electronics learning lab - with, of course, the lab itself.

Target audience are boys 8 and up - but it would start small with some friends children to see how they take to the idea.

Has anyone had any experience in this, any support materials available, and are there Arduino specific programs that any of you have worked through with similar audiences?
6  Community / Exhibition / Gallery / Modified Prototyping Board (Radio Shack Electronics Board / Arduino Uno R3) on: August 02, 2012, 06:55:11 pm
Forrest Mimms could go a step further - or maybe the "Shack" could catch on to this sort of thing.

Anyhow, I just wanted to share.

I also have more detailed pictures if you click on the user photos on Amazon for the Radio Shack Electronics Learning Lab.

In a rather simple manner I affixed my Uno R3 to my Radio Shack Electronics Learning Lab over the transformer, which I am not likely to use. I am also considering replacing the rather pitiful ammeter with something more useful - like a Harbor Freight digital multimeter and solder the test probe terminals to the spring terminals on the board.

Also I am going to go ahead and convert the system to a regulated, wired power supply as currently the board only has batteries. In short, I wanted a budget Arduino development board with pots and LEDs and everything else integrated so I can work more quickly. It will also help when I get my QFP to DIP converter!

In short I just want to share what has made my Arduino experience more comfortable - and easier to learn on. I've resurrected old Physics textbooks from Amazon, ordered a few books on C++, and I'm trying to most effectively work myself through the Mimms material, then onto more advanced things to take things further. As a neophyte microcontroller hobbyist it takes some creativity  - even just a tiny bit of hacking - to get yourself comfortable with the medium. And this is the result of asking, "why not," and then doing.

I hope that others do the same thing -or similar. You can find these learning labs on craigslist for no more than a song sometimes!
7  Using Arduino / Motors, Mechanics, and Power / Re: Mosfet question on: July 01, 2012, 01:22:48 am
Why specifically a transistor? And which sort of transistors would be best for this application? Again, this is a project I've taken on as an educational endeavor - but if a MOSFET configuration would be possible I'd like to proceed in that direction. I have just grown comfortable with pre-coding most of my project using MOSFET's so far - and I just haven't jumped into utilizing transistors for this application.
8  Using Arduino / Motors, Mechanics, and Power / Mosfet question on: July 01, 2012, 12:42:46 am
I am looking to drive a number of 1157 automotive bulbs utilizing a 12v DC MOSFET configuration paired / breadboarded to my Uno.

1157 bulbs are typically used in automotive applications - you know, night time lights when you're driving and then they brighten and become brake lights.

In my application I need to creatre a functional circuit controlled by a switch that mirrors this wattage brightening effect - I am assuming that MOSFET controlled would work best here.

Like in automotive night time mode, I need the bulbs to run at the standard luminescence that is effected at 10W, the brightened mode at 27w, and I need to turn them off completely. I'd like to code this (seems it would be fairly easy) but the difficulty is determining the hardware to effectively run this circuit (or one of the circuits) from my Uno.

Essentially, what I'm looking around for is a circuit setup that will allow me to control my 12v light/lights (in tandem, two) much like the effect you would get of stomping on your brakes at night by utilizing a momentary normally off switch with instructions coded through arduino. Any advice or tips? I looked around a great deal and couldn't find anything much on this specific topic.

Thanks for your help!
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