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# Enac

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1. ## Constant current source for a low Ohm load

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.
2. ## Pool water level stabelizer

Google "float switch". I found some inexpensive ones, and plans for a homemade one.
3. ## 60VDC 10A Power supply design.

Is there some reason you can't use a switching regulator? A 10 amp linear regulator is bulky, expensive, and hot!
4. ## Electricity Meter

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.
5. ## hm

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.
6. ## Timed resistor

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".
7. ## common-mode??

Great explanation, AG!
8. ## Voltage level shifting

I see that now. I'm sure glad I pre-apologized for missing it! :)
9. ## Voltage level shifting

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).