A standard red LED from Radio Shack (regular pack of 10) will be attached to the switch along with a 10K OHM resistor. The light should eluminate when the power is turned on and vice versa. The power supply I am turning on (the robots power supply) is 14.4V DC (2X 7.2V 1400MaH in series). Im assuming the LED will have to have a regulator on it becuase the 14.4v will be too great? I assume this can be acheived with a scotchy diode rated to regulate 5V. Correct me where needed, Im just getting into the whole âdo-it-yourselfâ electronics and only have experience with simple LED projects.
For LEDs one usually calculates the required resistance using the formula E=IR. Find the ma rating of the LED and then use the formula to get the ball park resistance needed when used with 14.4v.
A standard LED is ok, current, not voltage is the problem. You donât need a voltage regulator.
You need to know what current is permitted by the LED (20ma works for me, your mileage may vary). You need to select the resistor to suit.
R = (Vs - Vl) / I
R = resistor value
Vs = Supply voltage (14.4)
Vl = LED voltage (I go with 2v for red and green, 4v for white or blue)
I = LED current permitted (20ma is usually safe)
Also, you donât want to hook it up in series with the load, that will burn it out right smart. Put it in parallel.
meh, anything bigger than 620 ohms 1/4 watt should be fine, wired in series with the LED between your switched +14.4V and ground (or -14.4V or 14.4 return whatever you call the negative side of the battery in your system.) too much resistance and the LED will not be very bright, no harm done.
DO NOT wire it backwards even for an instant or it will likely go bye-bye at 14.4V.
Two common polarity indicator rules of thumb are âflat side denotes cathode (-)â and âlong lead anode (+).â If neither of those apply or they conflict with each other (it IS possible but usually only on special order parts) then use a digital volt meter in diode mode. when measured with the correct polarity the LED will usually glow faintly⊠not enough current to turn it on brightly but enough to make a slight glow. I do this with 0603 SMT parts all the time because I canât see the damned parts well enough to figure out the polarity.
funny link for the LED⊠like how the package has a radio shack part number and some other brand on the package.
The switch diagram doesnât look very functional for what you appear to want to do. Save some $$$ and grt a pack of LEDs and resistors at Radio Shack instead of your mail order link. Below is a good LED info page.
This is how you should wire it up if you want to use the one switch for powering everything.
And as EddieB said, a 620 ohm resistor would be good too. It would give you more light than the 1k. But they will both work if itâs a standard resistor.
ahhh, that makes sense. I realised from the start my schematic was not right after hearing opinions from others. This looks very good, thanks for the replyâs
)
DO NOT wire it backwards even for an instant or it will likely go bye-bye at 14.4V. 
