I have a bunch of red LEDs, I don't have their data sheet and I am trying to figure out a safe resistor to use to lower the current across them safely.
My current setup is as follows:
simulate this circuit – Schematic created using CircuitLab
I figured a 100 Ohm resistor and 68 ohm resistor in series because, assuming a forward voltage of the led of 3 volts, and a desired current of 20mA (which I assume is ok?) I get:
R=V/I
R=3.3/0.02
R=165 Ohms.
So, I pop that into the circuit lab as shown below, click run, then click DC simulation, but then it just throws an error saying : "unable to get solution"
How do I use this tool to allow me to inspect various values at various points in the circuit? Have I got this wrong somehow?!
Best Answer
simulate this circuit – Schematic created using CircuitLab
Figure 1. Add a GND to the schematic so the simulator has a zero volt reference.
Figure 2. Add nodes at the points you want to monitor. Rename them to suit your purposes. Run the DC solver.
Figure 3. Click each named node to add it to the DC solver tab.
Figure 4. Click on a wire to monitor the current.