Thanks for the link. That is pretty good pre-packaged solution.

For motors, use 20% of rated... so 15A x .2 = 3Amp max.

Niceeeee!!!

If it's a DC motor, you can use an SCR (Silicon Controlled Rectifier).
If it's an AC motor, you can use a TRIAC. 

You can also use mechanical relays, or solid state relays, or Mosfets.

Since it's line voltage, might also help to have some physical isolation between your low voltage electronics and the high voltage section (for added safety). You can use "optical" equipped mosfets, etc...  basically, your low voltage electronics turns on a small LED (inside the mosfet), and the light emitted is detected, which then switches/turns on the high voltage side of the Mosfet (everything happening internally).

If your load is using up 100 milliAmps (mA), then it will only draw 100 mA even if your power supply (in this case, a battery) is capable of supplying a lot more.

So what if you designed a product that uses an AVR micro with a 16mhz clock, when does it cross from being a hobbyist product to a consumer product.  (I see lots of projects on Kickstarter, for example).

When do you need FCC certification?

I understand if you're a big conglomerate corporation, I guess FCC/CE/UL cert costs is just peanuts ... but if you're a small business (or one-man business), they could certainly cost more double/triple than your whole R&D and production costs combined.

So I guess one can bite the bullet and either go for the FCC cert (and spend what? 10K-$20K?)
or just ignore it and release their product?
But what's the penalty?
Is there a penalty? If you're product isn't causing nuisance, interference with other equipment/TV/radio/etc...

Now... to be a good citizen, I guess one can be pro-active in adding EMI/RF protection to their "whatever" product. Just to make sure it doesn't cause interference to others.

Anybody here use EMI/RF protection on their power and/or data lines?
I checked Mouser and they're pretty cheap... costing only cents (SMD).

Use a 0.1uf if you're worried about it.

The diode is for flyback protection.

The mosfet is voltage driven, while a transistor is a current driven device. For this purpose, a "LOGIC LEVEL" mosfet is really more appropriate (to be driven by the arduino's output).

Why don't you connect the load (i.e. your motor) on the "collector" side, so the emitter is connected directly to ground. 

And for that matter, might as well use a "logic level" Mosfet. You can connect the "gate" of the mosfet (via small 100R) directly to Arduino output pin (or other cmos output pin). 

Then you can connect the Mosfet's (Drain/Source) to your 12Volts (or whatever) voltage source to power your load, and the Gate is turned on/off by your logic circuit (with it's own 5V supply voltage).

Me too!!!  I'm sorry, help!!!

Last summer, I bought an adjustable wrench. I want to build an engine, or a small transmission. But I don't have any clue about cars.

i'm told what i want to accomplish is not an easy thing.. how can it not be - they are just freaking bolts!!!

"Magneto Tesla" sounds more cool and "bad ass"... kids in the playground wouldn't dare bully him.

Plus besides, Tesla worked with magnets, not atoms

Maybe you need to be like Robert de Niro... "talking italian"   

Never mind. It will work, but the On resistance of the OptoMos is "too much" (10 ohm) for my specific application. I'll be using 16 of these, and that's 160ohm minimum at least, which will cause a big cumulative error in this analog circuit ... back to using Reed Relays, only 0.16 ohm On resistance.

I don't have any experience with OptoMOS, and the datasheet isn't clear...
maybe somebody can answer my question?

Is this possible with OptoMOS?  i.e. one of the "load" terminals of the OptoMOS is not connected to GND, but wired like this.

I'm trying to see if an OptoMOS will be a suitable substitute here, instead of an SPST mechanical Relay.

Hmmm I thought connecting traces diagonally to a pad is "bad design practice"... but Eagle's auto-router seems to be doing it.

This is just a small simple board... do it manually.

Well, a toaster can consume 150watts of energy so I guess the glow from it's heating coils is 150 watts of light output also.

You know what I mean? 

Something is not right...

LEDs light output are measured in lumens...

Kinda odd the scientists used "watts" to measure the light output. What gives?