go_away

Author Topic: Can not find 340 Ohm 0.4 Watt resistor? Any alternative please??  (Read 3326 times)

0 Members and 1 Guest are viewing this topic.

Offline BeckyTopic starter

  • Jr. Member
  • **
  • Posts: 38
  • Helpful? 0
  • "Bollocks to the rules" (George Orwell)
Can not find 340 Ohm 0.4 Watt resistor? Any alternative please??
« on: February 22, 2009, 10:24:06 AM »
 ???
Hello I am new to electronics (sorry if my question is very simple) but am building my first robot with the help of this site (saw it for the first time yesterday and have started ordering my parts today).

Basically I can not find a 340 Ohm 0.4 Watt resistor.  I have found other users making do with 330 Ohm so I think that would do... ...?

...however how important is the watts?  Can not find many 0.4 Watt but loads of 1/4 - 0.25 Watt.  What effect would this have?  (Sorry again - my electronics is very beginner).

Thanks!

Becky  ;)

Offline airman00

  • Contest Winner
  • Supreme Robot
  • ****
  • Posts: 3,653
  • Helpful? 21
  • narobo.com
Re: Can not find 340 Ohm 0.4 Watt resistor? Any alternative please??
« Reply #1 on: February 22, 2009, 10:35:51 AM »
just use a 330ohm resistor , shouldn't be too big of a deal
Check out the Roboduino, Arduino-compatible board!


Link: http://curiousinventor.com/kits/roboduino

www.Narobo.com

Offline BeckyTopic starter

  • Jr. Member
  • **
  • Posts: 38
  • Helpful? 0
  • "Bollocks to the rules" (George Orwell)
Re: Can not find 340 Ohm 0.4 Watt resistor? Any alternative please??
« Reply #2 on: February 22, 2009, 10:51:56 AM »
 :)  Ok that simple?  So just to double check... the ohms come in different Watts but it doesn't matter?

Kind regards

Becky

Offline airman00

  • Contest Winner
  • Supreme Robot
  • ****
  • Posts: 3,653
  • Helpful? 21
  • narobo.com
Re: Can not find 340 Ohm 0.4 Watt resistor? Any alternative please??
« Reply #3 on: February 22, 2009, 11:16:20 AM »
1/4 watt would be fine too
Check out the Roboduino, Arduino-compatible board!


Link: http://curiousinventor.com/kits/roboduino

www.Narobo.com

Offline pomprocker

  • Supreme Robot
  • *****
  • Posts: 1,430
  • Helpful? 16
  • Sorry miss, I was giving myself an oil-job.
Re: Can not find 340 Ohm 0.4 Watt resistor? Any alternative please??
« Reply #4 on: February 22, 2009, 01:06:44 PM »
I'd rather you learn why you are to use a resistor of that resistance rather than just tell you which resistor to get.

Visit the LED wizard page and enter values to see different resistor values. Most LEDs you're going to be using will have a forward voltage drop of 2v, and a forward current of 20ma. And for the source current it depends on how many batteries you will be using. 1xAA = 1.5v, 2xAA= 3v, 3xAA = 4.5v, 4xAA = 6v, etc.  So by entering 6, 2, 20..You will see it will recommend a 1/4watt 5% 220ohm resistor (even gives you the color codes!). Now where does 330 and 340 come from? That is just people being over protective of their Light emitting diodes!! It is current that drives the LED, and resistors limit current. So if you give it less current it will be dimmer but will last longer. Visibly though, you won't be able to see the difference if you use 220, 330, 340, etc. You may however see a difference if you use no resistor (which will blow the LED in a few seconds), or a 1K resistor which will be pretty dim.

If you ever build a circuit with LEDs powered by 2xAA (3v) as 3.3v tolerant components are common in electronics, you will be using LED resistors in the area of 47, 51, or 56 ohms.


http://led.linear1.org/1led.wiz
« Last Edit: February 22, 2009, 01:08:21 PM by pomprocker »

Offline BeckyTopic starter

  • Jr. Member
  • **
  • Posts: 38
  • Helpful? 0
  • "Bollocks to the rules" (George Orwell)
Re: Can not find 340 Ohm 0.4 Watt resistor? Any alternative please??
« Reply #5 on: February 22, 2009, 01:39:41 PM »
Thank you for the helpful information I have book marked that page and will use it.

Great answer :-)

Becky

Offline Soeren

  • Supreme Robot
  • *****
  • Posts: 4,672
  • Helpful? 227
  • Mind Reading: 0.0
Re: Can not find 340 Ohm 0.4 Watt resistor? Any alternative please??
« Reply #6 on: February 22, 2009, 02:04:34 PM »
Hi,

Basically I can not find a 340 Ohm 0.4 Watt resistor.  I have found other users making do with 330 Ohm so I think that would do... ...?

...however how important is the watts?  Can not find many 0.4 Watt but loads of 1/4 - 0.25 Watt.  What effect would this have?  (Sorry again - my electronics is very beginner).
You probably wouldn't find a 0.4W resistor easily, but you can allways use a higher wattage than mentioned.
To get 340 Ohm, you could take two 680 Ohm (0.25W) resistors, which is a standard E-12 value, and wire them in parallel to get 340 Ohm (0.5W).
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline pomprocker

  • Supreme Robot
  • *****
  • Posts: 1,430
  • Helpful? 16
  • Sorry miss, I was giving myself an oil-job.
Re: Can not find 340 Ohm 0.4 Watt resistor? Any alternative please??
« Reply #7 on: February 22, 2009, 08:56:36 PM »
Thank you for the helpful information I have book marked that page and will use it.

Great answer :-)

Becky


Glad I could be helpful  [click for yes] http://www.societyofrobots.com/robotforum/index.php?action=modifykarma;sa=applaud;uid=1765;topic=7092.0;m=53680;sesc=3f92b8411f19d5738a3e6f9782a75265

Offline SmAsH

  • Supreme Robot
  • *****
  • Posts: 3,959
  • Helpful? 75
  • SoR's Locale Electronics Nut.
Re: Can not find 340 Ohm 0.4 Watt resistor? Any alternative please??
« Reply #8 on: February 22, 2009, 11:26:20 PM »
this is for the $50 robot? are you sure its .4 watt and not 1/4 (.25) watt?
and using them for leds adding or subtracting a few ohms doesnt really matter to much.
just for future reference (incase you dont have access to the wizard page.
R=v1-v2/A where v1 is vin and v2 is the amount of voltage needed and A is current in amps.
(eg 5v-2v/.02=150ohms) hope this helped :)
Howdy

Offline Admin

  • Administrator
  • Supreme Robot
  • *****
  • Posts: 11,632
  • Helpful? 169
    • Society of Robots
Re: Can not find 340 Ohm 0.4 Watt resistor? Any alternative please??
« Reply #9 on: March 01, 2009, 07:24:26 AM »
Unless you are dealing with AC current, resistor and capacitor values don't need to be exact. Even a resistor value 50% from the specified value will often work.

As for wattage rating . . .

power (wattage) = voltage * current

Just do the math, and make sure your resistor wattage is higher than you calculated. Otherwise, the magic smoke will come out (circuits only work when the magic smoke stays inside the components). ;D

Offline SmAsH

  • Supreme Robot
  • *****
  • Posts: 3,959
  • Helpful? 75
  • SoR's Locale Electronics Nut.
Re: Can not find 340 Ohm 0.4 Watt resistor? Any alternative please??
« Reply #10 on: March 01, 2009, 12:39:35 PM »
admin are you saying the current in the buses or that the led consumes? im confuzzled...
Howdy

Offline Admin

  • Administrator
  • Supreme Robot
  • *****
  • Posts: 11,632
  • Helpful? 169
    • Society of Robots
Re: Can not find 340 Ohm 0.4 Watt resistor? Any alternative please??
« Reply #11 on: March 01, 2009, 10:30:33 PM »
admin are you saying the current in the buses or that the led consumes? im confuzzled...
I was referring to Becky's question:

Quote
...however how important is the watts?  Can not find many 0.4 Watt but loads of 1/4 - 0.25 Watt.  What effect would this have?

Offline SmAsH

  • Supreme Robot
  • *****
  • Posts: 3,959
  • Helpful? 75
  • SoR's Locale Electronics Nut.
Re: Can not find 340 Ohm 0.4 Watt resistor? Any alternative please??
« Reply #12 on: March 01, 2009, 11:30:18 PM »
admin are you saying the current in the buses or that the led consumes? im confuzzled...
I was referring to Becky's question:
wait so if your led is 3V@20ma the power would be .06W?
Howdy

Offline Admin

  • Administrator
  • Supreme Robot
  • *****
  • Posts: 11,632
  • Helpful? 169
    • Society of Robots
Re: Can not find 340 Ohm 0.4 Watt resistor? Any alternative please??
« Reply #13 on: March 01, 2009, 11:50:17 PM »
wait so if your led is 3V@20ma the power would be .06W?
Total power consumed, yes, but not necessarily the power dissipated by the LED alone.

Offline SmAsH

  • Supreme Robot
  • *****
  • Posts: 3,959
  • Helpful? 75
  • SoR's Locale Electronics Nut.
Re: Can not find 340 Ohm 0.4 Watt resistor? Any alternative please??
« Reply #14 on: March 02, 2009, 01:03:46 AM »
wait so if your led is 3V@20ma the power would be .06W?
Total power consumed, yes, but not necessarily the power dissipated by the LED alone.
hmm yes good point but for that situation i most likely wouldnt need a wattage higher than 1/4
Howdy

 


Get Your Ad Here

data_list