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Posts posted by Enac
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Google "float switch". I found some inexpensive ones, and plans for a homemade one.
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Is there some reason you can't use a switching regulator? A 10 amp linear regulator is bulky, expensive, and hot!
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Do a Google search on "kill-a-watt". You can buy one for around U.S. $20 - $30.
Of course, if you really want to build one, you could learn a lot. -
I use Linear Technology's LTSPICE/SWITCHERCAD III. It's totally free, but is not easy to use unless you have a good understanding of Spice.
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How about a digital pot driven by a variable-frequency oscillator (555)? Maxim, or other mfrs, may have other parts that will work as well or better. Google (digital pot".
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Hi Mudhall,
Welcome to our forum. ;D
Common-mode signals to an opamp are signals that are the same at both inputs. The range of common mode signals for most opamps is within a few volts from each supply voltage. A few opamps like the LM324 and LM358 have inputs with a common mode voltage range that includes the negative supply, which sometimes is the circuit's ground. A feww opamps have an input common mode range that includes the positive supply voltage. New Cmos opamps have an input common mode voltage range that includes all its voltages and are called input rail-to-rail.
An opamp is supposed to have differential inputs and therefore amplify only the difference between its inputs, but the inputs are not perfect and amplify common mode signals a little, and more at higher frequencies. The amount of rejection is called input common mode rejection.
Great explanation, AG! -
Hi
As i suggested, roughly!
And what do you say pebe?
Anyone else?
//Staigen
I see that now. I'm sure glad I pre-apologized for missing it! :) -
Forgive me if one of you guys already suggested this solution.
All you need is two equal-valued resistors and a rail-to-rail I/O op amp. One resistor (Rs) goes from +5V to the inverting input. The other (Rf) goes from the inverting input to the output. The 2.5V-5V input signal goes on the noninverting input.
The transfer function is Vout = Vin*(1*Rf/Rs) - 5V*(Rf/Rs). -
The 1uF cap needs to be nonpolarized.
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Actually, my data sheet lists 3.5 mA as minimum typical load current for the LM317. ;)
<snip>MP
MP, the National datasheet says the typical minimum current is 3.5ma, but the maximum minimum current (sounds like an oxymoron) is 10ma. Whose datasheet are you using?
Constant current source for a low Ohm load
in Electronic Projects Design/Ideas
Posted
If your resistor is really a constant 20 ohms, then you only need a variable voltage source with a range of zero to 2.4V, which is what Indulis's circuit does (although it may oscillate).
A current source provides constant current independent of the load. Does your load vary? If so, I can provide you with the schematic for a variable constant current source.