Another beginner question - OpAmp and schematic diagram

Hi Guys,

I wanted to learn about opamps and came across this schematic... http://www.eeweb.com/blog/extreme_circuits/a-very-simple-led-tester

I have a number of questions about this:

In his description he talks about R2, I didn't see this or am I going nuts?

I understand the capacitor symbol but whats the single bar just below it? Also appears on the other side of the circuit.

I think the answer to both of these will probably help me to understand exactly how this all works.

Thanks,

Shags

I think they wrote too quickly, and "R2" is actually R1 on the schematics, while "R1" is P1 on the schematics. The thick black line under the capacitor is GND (0v)

thanks heaps alnath.

Its a dumb circuit since with a 12V supply all you need to push a given current through an LED is a series resistor, 330 ohms for 30mA, 1k for 10mA, etc. LED forward voltages are in the 1.4 to 3V range, leaving roughly 10V across the series resistor.

It does show a voltage-programmed current source using an opamp though, which is instructive...

There's much easier ways to create an LED tester lol....

use a 1k resistor, if it lights up it works lol

Actually most LEDs have a reverse-breakdown voltage in the region of 5V, so you wouldn't use 12V in a tester in the first place.