Colour blind guy needs help with resistors

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fizzos

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Hi guys, my first post here as just starting to look into electronics, but have hit the first obstacle. I'm not too good with colours, commonly called colour blindness, and need to select a specific resistor from the starter pack I have, but just cant tell which one is the 270ohm which I understand should be red-violet-brown-gold, or something in the range 270 to 330 if the 270 isn't there.

Would be great if someone could identify it for me from the numbers I've written on each group.

Hopefully the photo is good enough res, but I can upload a better one if need be.

Thanks

 

None are close to 270 Ohms. But you can use 3 #13's in series. (82R I think grey red black silver)

I had been in electronics for 35 years and after a health nurse tested me for colour blindness using pastel coloured numbers, I failed the test.

Good thing it,was only a requirement for assemblers as I was the Engineer Mgr at this Contract Mfg at the time. :lol:

DMM's cost only $5 to $10. Label all your bags after testing them.

And get a high intensity light and magnifying eye piece x10 for inspection. that helps me.

BTW, if this is to limit current on an LED from 5V, dont forget to factor the diode voltage drop.
 

Mattylad, dont have a multimeter to hand, but can get one so looks like I should measure them and bag, thanks.

SunnySkyGuy, thanks for the 3x#13, will give it a go. Also thanks for the info about the light and glass, good to know theres several ways to do it with colour probs.
Interested that you say about the current limit on an LED, as thats what I'm doing. What I'm doing is to test the GPIO from a RaspberryPi with the LED and to later get it going with a motor through a L293D chip. Not sure what I need to do about the voltage drop though?
 

Boats have a red light on one side(left) and a green one on the other (right). So at night you can tell the direction of a boat by the position of the lights. So colour blind sailors have a great problem with this, so they wear a pair of spectacles with a red and a green lens. So shutting one eye makes that colour stay and the other disappear. So you could make some handheld filters (labelled) to view the components, if the colour is the same as the lens it stays, if its different it will go black.
Frank
 

fizzos said:
Interested that you say about the current limit on an LED, ... Not sure what I need to do about the voltage drop though?
Click to expand...


  • I'm psychic
  • a quick study of LED specs vs colour reveals ...
  • Vf@20mA increases with lower wavelength [nmD],
  • D stands for Dominant eye corrected vs P for peak , uncorrected
  • where white uses a blue substrate
  • IR being the lowest Vf=1.2,
  • deep Red=1.7,
  • HB Red,Yellow=2-2.2V,
  • Blue,Green=3-3.2V
  • 25% tolerances exist
  • LED ESR is 10 Ohms per 100mW
  • ESR can be neglected until selected Rs approaches these value, where you apply Ohm's Law for current limit.
 

Its all up and working now. The LED with resistors proved that the GPIO ports work ok and I can now use it for the project as intended, which luckily doesnt involve colours. Thanks for the help.

SunnkSkyGuy, if I understand what you are saying, and I may not, is that the amount of power an LED needs is determined by its colour?
 

Hi fizzos. If you take photographs of your resistor sets (up close using a good camera) and load them into an image editor you may be able to get the RGB value of each colour (obviously, you will need to set up appropriate lighting in the picture), hope this helps.
 

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