Electronics-Lab.com Community

# 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).

The 1uF cap needs to be nonpolarized.
11. ## LM317 Variable power supply

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?
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