Let's Make Robots!


What to do with a whole lot of resistors still on tape? Value doesn't match color code.


Years ago I got a box full of resistors and other components, all new. A lot of them are grey colored resistors, 6 band with a tolerance of 1%. The problem is that they aren't what they should be. 390 ohm resistors for example give a reading between 400 and 430 ohm. I double checked with two different multimeters and then checked the color code which says it should be 390 ohm. (color code: orange, white, black, black, brown, red.) Even if brown accidentaly is gold then the resistor still should read max. 410 ohm.

Once a CD Drive, now a scanner
I created this scanner after working with it, either directly or indirectly (I mean I had to learn how to use Stepper motors, program in the Processing software, … Read more

QRD1114 Resistor Values

Hi all,

I'm using a QRD1114 sensor for a line-follower. Datasheet: http://www.fairchildsemi.com/ds/QR/QRD1114.pdf

Im hooking it up with this schematic:

However, I'm unsure how the value for the 10K resistor was calculated? It's acting as a potential divider, right?

For the LED im guessing that the value of 220 was taken from doing:

R=(Input Voltage - Max Forward Voltage)/(Optimum forward current)

Using SMD resistors on a prototyping board


I'm thinking of using SMD (surface mounting resistors) instead of the normal ones (throught hole) on a prototyping board in order to save space.

It`s a good idea?

Or it will be easier using normal resistors?

After my old trusty analog multimeter's 0Ω adjust pot stopped working I had no reliable way to measure my resistors. Read more
  Here I will try to help begginers with the most attractive electronic device the LED. :D First of all the definition of a LED: An LED or Light Emitting Diode, … Read more

Breadboard Jumper Wires Conspiring with Resistance?

Yup, that's:
no black
not so brown
still no black
brown, finally

Servo and picaxe: need resistor ?

hello, i'm trying to use a servo with my picaxe. I tried it on Arduino before, and it worked just connecting the pins at the right position, without resistors.

now i just connected the same way on the picaxe, and it doesn't move.. I then remembered that in the "start here" project, a resistor was used.. So the question is: is it necessary? why do i need a resistor? and how do i wire it ?

Another thing that is probably messing up.. i have the darlington chip there.. shoud i remove it?


thanks :) 

Resistor for Servo!

hi guys!!

i have just joined the forums, how cool!

anyways.. i wanted to ask you guys a question about resistors. I already gone through all the "start here" page and when it talks about the servo it also says i need to apply a 330 ohm resistor to my board (since i don't have the "yellow thing").

but when i went to the shop the other day i found that they were selling various resistor according to W values. for example i found the 330 ohm resistor with 0.25W , 0.5W and so on.... but i don't actually know which one to use.