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16  Community / Bar Sport / Re: Myth - ALL LED'S require Resistors or.... on: July 29, 2013, 06:30:00 pm
I was testing some leds with a variable voltage supply I had 12 leds in series I turned the supply up till they all came on.
Looked great I turned off the supply. I then came back to see how much I could go I turn on the supply and a big bang I now have a scar from
one of the leds. I must hit the pot on the supply..

I gave up on the voltage idea for leds and went with current controlled supply.  
17  Using Arduino / General Electronics / Re: [SOLVED] 16 Channel 12 volt relayboard and Arduino UNO on: May 09, 2013, 08:38:18 pm
Lol no one looked at the PDF if you cut the ground from the uno the relays are still hooked to the supply ground and if you turn on one closing the power loop. But the OP should rethink this and read the data sheet the relays are setup to use 20 mA to turn on, and Like I said you don't need a resistor from the uno to turn these on with five volts but your using a resistor and 12 volts that sets it to about 21mA.

That's why it works now but it's not a good idea you forget the 4.7 good by port pin.

So if you left off the resistor and just use 5 volts it should work too and no worries off blowing a port pin.
18  Using Arduino / General Electronics / Re: 16 Channel 12 volt relayboard and Arduino UNO on: May 08, 2013, 09:05:53 pm
The way it shows in the pdf you hook the pin from the uC to ground the led of the Optocoupler
it has a built in resistor to limit it to 20 mA.

You didn't add one did you? 
19  Using Arduino / General Electronics / Re: 16 Channel 12 volt relayboard and Arduino UNO on: May 08, 2013, 07:47:38 pm
Well if you did what you show in the pic you probably killed your uno you are sinking 12 volts..  
http://elecfreaks.com/store/download/16_Relay.pdf
20  Using Arduino / General Electronics / Re: 74HC595 used for shift input not output! on: May 01, 2013, 04:53:52 pm
He is pulling the latch to ground. It's in the datasheet outputs active when E pin is low so you tie it low and just use the data and the clock
 
21  Using Arduino / General Electronics / Re: 74HC595 used for shift input not output! on: April 30, 2013, 09:54:47 pm
Its easy he is reading a keypad where you set just one columns high and scan the rows for a press.
Or set one row high and scan the columns which ever way you want to do it.
But he is not reading it as a input.
22  Using Arduino / General Electronics / Re: 1.8v to 5v logic level converter on: April 15, 2013, 07:54:27 pm
Try one of these http://www.ftdichip.com/Products/Cables/USBTTLSerial.htm
This one TTL-232RG-VREG1V8-WE
23  Using Arduino / Project Guidance / Re: two pwm channels, for 5-12v and 0-100mA output on: April 13, 2013, 05:08:50 pm
Quote
Am I on the right track with the lm334z/nopb?
Nope that's  Voltage Reference
24  Using Arduino / General Electronics / Re: DIY recharging a battery on: March 29, 2013, 11:34:49 pm
I don't think that's for charging batteries.
Quote
At any node (junction) in an electrical circuit, the sum of currents flowing into that node is equal to the sum of currents flowing out of that node, or:
 

That word sum means you added some thing to get a total in this case we are charging 4 cels we only have a set current of 360 and each will charge to that just like a cap 
25  Using Arduino / General Electronics / Re: DIY recharging a battery on: March 29, 2013, 09:32:46 pm
The op has his charger set to output 360 ma 18/50 = .360 amps divided by  cels 4 is 90ma a cel.
It will take 3.3 hours to charge and he better keep a eye on it there not anything to stop it from over charging.

Once the pack hits 5.6 volts you'll need to stop changing the pack. Thats if it is Ni-MH

 
26  Using Arduino / General Electronics / Re: P=V*I applied on DC resistor circuits. on: March 06, 2013, 09:42:26 am
Quote
Yeah but 12 Ohms is little more than a dead short....

Yep and could look like a glowing heater if you used the right wire, or put it in a bulb and make some light.

27  Using Arduino / Project Guidance / Re: need help understanding code on: March 04, 2013, 01:00:52 am
You don't have to down load it to look at it But the OP is really lazy not to post it.
And what help does he need with the code looks fine and it worked in his video.

So the problem is how you make this work on his uno where to hook what and the like.


https://code.google.com/p/aguaviva-libs/source/browse/arduino/sketches/laserpojector/laserpojector.pde

28  Using Arduino / General Electronics / Re: 109.3035 ohm resistor on: March 03, 2013, 10:47:42 pm
Yep it looks like a match i just don't see a $100 for a resistor to set that.But who no's Thanks for the math PapaG
I would use hot and cold. And thanks for posting this It sure been fun racking my brain. But maybe we should ask the suppler. LOL just to see whats what.
29  Using Arduino / General Electronics / Re: 109.3035 ohm resistor on: March 03, 2013, 09:40:22 pm
I been racking my brain about this and I no I seen these things used in some thing just don't no what it was
But I don't think it's to set for 75 F cause it didn't add up on any chart I seen.

30  Using Arduino / General Electronics / Re: 109.3035 ohm resistor on: March 03, 2013, 08:05:21 pm
Where did you find that a PT100 is 109.3035   It's 109.73 at 25C could you show how you did the math for Fahrenheit
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