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electronichobbyist.tribe.net/thr...5731
I have never been an electronics guy. The math made my eyes go off in different directions.
electronichobbyist.tribe.net/thr...5731
I have never been an electronics guy. The math made my eyes go off in different directions.
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Re: Electronics question
Fri, September 25, 2009 - 1:40 AMTry this:
led.linear1.org/led.wiz
> Resistors are supposed to be cheap
The one you have selected is a big one (5W), I don't think you need one this powerful.
In general, for common parts, Radio Shack is way cheaper than DigiKey.
> I should have thought the Resistor would need to be on the + terminal of the LED and not the - terminal.
It should be the same
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Re: Electronics question
Fri, September 25, 2009 - 11:34 AM*************It should be the same ***************
Same as what? The negative terminal or the positive?
Or does it matter? -
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Re: Electronics question
Fri, September 25, 2009 - 11:27 PMIt doesn't matter....
You can put the resistor on the + or on the - terminal -
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Re: Electronics question
Sat, September 26, 2009 - 6:11 AMI forgoe the peak voltage too. It's the square root of 2 times the base voltage.
I think I'll use the transformers and a bridge rectifier.
I think a capacitor will smooth out the current but I don't know which kind.
I understand start and run capacitors just fine and I know that bigger is always better so the down stream cascade doesn't make 'em burst but this is different isn't it?
I need a different capacitor but the words I know: reservoir capacitor don't get a response when I plug it into any electronics supply house search protocols.
I figure a 6 LED string Of about 2 VDC draw (each LED) powered by a 24 Volt Transformer will need a 1.2 kΩ 1/2 W resistor which would would give a bit less than 20 mA . A little Cap on that circuit would make smooth the flow out.
I still don't full understand the power consumption issue. I figure I'll build a board and add Serial strings of LEDs (6 in Parallel) until the power draw. starts to make 'em dimmer.
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Re: Electronics question
Sat, September 26, 2009 - 1:04 PM> I think a capacitor will smooth out the current but I don't know which kind.
Electrolytic: en.wikipedia.org/wiki/Elec...capacitor.
The bigger the better. Use a voltage higher that the rectified AC.
Electrolytic capacitors have polarity, if you reverse them they can (often will) explode.Nothing dangerous though.
> A little Cap on that circuit would make smooth the flow out.
Yes, but rectified/filtered DC will have a slightly higher voltage than the transformer output (don't remember the constant...)
> I still don't full understand the power consumption issue.
Unless you are building something really big, any small transformer will have plenty of juice. I wouldn't worry about it.
For the capacitor, I would desolder one form some old electronics. Elecrolytic can get expensive.
This is a nice doc on the subject:
www.st.com/stonline/boo...docs/1707.pdf
If you really want to get fancy, you can decide to add a voltage regulator (see Fig 16-18) the 78XX and 79XX (XX is your output voltage) are very simple to use.
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Re: Electronics question
Mon, September 28, 2009 - 7:05 PMOh cool Mili Grazi.
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