Is there anything special about the 4.7 value?

[riccardo manfrin]

I see it recurring in every circuit around (especially the 4K7 Ohm resistances).
Is there some reason behind that (I've read around that it is considered a safe series resistance for leds.. but I've seen it used not just for that)..

RM

 

[Tim Wescott]

On Sat, 26 Oct 2013 08:30:09 -0700, riccardo manfrin wrote:

I see it recurring in every circuit around (especially the 4K7 Ohm
resistances).
Is there some reason behind that (I've read around that it is considered
a safe series resistance for leds.. but I've seen it used not just for
that)..

RM

See http://en.wikipedia.org/wiki/Preferred_number#E_series. 47 shows up
in the 20%, 10%, and 5% standard resistor value series, so it's commonly
used whenever any old thing will do.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

 

[Daniel Pitts]

On 10/26/13 10:14 AM, Tim Wescott wrote:

On Sat, 26 Oct 2013 08:30:09 -0700, riccardo manfrin wrote:

I see it recurring in every circuit around (especially the 4K7 Ohm
resistances).
Is there some reason behind that (I've read around that it is considered
a safe series resistance for leds.. but I've seen it used not just for
that)..

RM

See http://en.wikipedia.org/wiki/Preferred_number#E_series. 47 shows up
in the 20%, 10%, and 5% standard resistor value series, so it's commonly
used whenever any old thing will do.

Awesome bit of information there. I've often wondered this myself. I
had noticed 33, 47, and 56 frequently. Now I know.

 

[riccardo manfrin]

See http://en.wikipedia.org/wiki/Preferred_number#E_series. 47 shows up

in the 20%, 10%, and 5% standard resistor value series, so it's commonly

used whenever any old thing will do.

I knew there were some black magic in those numbers..
R

 

[John Larkin]

On Sun, 27 Oct 2013 09:52:56 -0700 (PDT), riccardo manfrin
<riccardomanfrin@gmail.com> wrote:

See http://en.wikipedia.org/wiki/Preferred_number#E_series. 47 shows up

in the 20%, 10%, and 5% standard resistor value series, so it's commonly

used whenever any old thing will do.


I knew there were some black magic in those numbers..
R

The color codes look nice, too.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

 

[George Herold]

On Sunday, October 27, 2013 2:17:46 AM UTC-4, Daniel Pitts wrote:

On 10/26/13 10:14 AM, Tim Wescott wrote:

On Sat, 26 Oct 2013 08:30:09 -0700, riccardo manfrin wrote:



I see it recurring in every circuit around (especially the 4K7 Ohm

resistances).

Is there some reason behind that (I've read around that it is considered

a safe series resistance for leds.. but I've seen it used not just for

that)..



RM


See http://en.wikipedia.org/wiki/Preferred_number#E_series. 47 shows u
in the 20%, 10%, and 5% standard resistor value series, so it's commonly
used whenever any old thing will do.

Awesome bit of information there. I've often wondered this myself. I
had noticed 33, 47, and 56 frequently. Now I know.

I've always thought of this as equal divisions on a log scale. So if there are 6 divisions, and if the first point is is one, the inverse log of zero
log ^-1(0) =1 (is that how you write an inverse log???) then the next is log^-1(1/6) = 1.467... and then log^-1(2/6) = 2.15... etc.

Now where the 6/12/24 divisions of the log scale came from I have no idea?
Was this picked to match 20% and 10% tolerances?

George H.

 

[Daniel Pitts]

On 10/28/13 6:52 AM, George Herold wrote:

On Sunday, October 27, 2013 2:17:46 AM UTC-4, Daniel Pitts wrote:
On 10/26/13 10:14 AM, Tim Wescott wrote:

On Sat, 26 Oct 2013 08:30:09 -0700, riccardo manfrin wrote:



I see it recurring in every circuit around (especially the 4K7 Ohm

resistances).

Is there some reason behind that (I've read around that it is considered

a safe series resistance for leds.. but I've seen it used not just for

that)..



RM


See http://en.wikipedia.org/wiki/Preferred_number#E_series. 47 shows u
in the 20%, 10%, and 5% standard resistor value series, so it's commonly
used whenever any old thing will do.

Awesome bit of information there. I've often wondered this myself. I
had noticed 33, 47, and 56 frequently. Now I know.

I've always thought of this as equal divisions on a log scale. So if there are 6 divisions, and if the first point is is one, the inverse log of zero
log ^-1(0) =1 (is that how you write an inverse log???) then the next is log^-1(1/6) = 1.467... and then log^-1(2/6) = 2.15... etc.

Now where the 6/12/24 divisions of the log scale came from I have no idea?
Was this picked to match 20% and 10% tolerances?

According to the Wikipedia article, you're pretty much exactly right on
that last bit.

Take "E6" for example:
10 15 22 33 47 68

10*1.20 = 12.0 15*0.80 = 12.0
15*1.20 = 18.0 22*0.80 = 17.6
22*1.20 = 26.4 33*0.80 = 26.4
33*1.20 = 39.6 47*0.80 = 37.6
47*1.20 = 56.4 68*0.80 = 54.4
68*1.20 = 81.6 100*0.80 = 80.0

 

[amdx]

On 10/27/2013 8:02 PM, John Larkin wrote:

On Sun, 27 Oct 2013 09:52:56 -0700 (PDT), riccardo manfrin
riccardomanfrin@gmail.com> wrote:

See http://en.wikipedia.org/wiki/Preferred_number#E_series. 47 shows up

in the 20%, 10%, and 5% standard resistor value series, so it's commonly

used whenever any old thing will do.


I knew there were some black magic in those numbers..
R

> The color codes look nice, too.

Maybe you've been in San Fransisco a little to long?
Mikek

 

[Jasen Betts]

On 2013-10-28, George Herold <gherold@teachspin.com> wrote:

in the 20%, 10%, and 5% standard resistor value series, so it's commonly
used whenever any old thing will do.

Awesome bit of information there. I've often wondered this myself. I
had noticed 33, 47, and 56 frequently. Now I know.

I've always thought of this as equal divisions on a log scale. So
if there are 6 divisions, and if the first point is is one, the
inverse log of zero

log ^-1(0) =1 (is that how you write an inverse log???)

Inverse of y=log(x) is x=pow(10,y).

10^0

> then the next is log^-1(1/6) = 1.467... and then log^-1(2/6) = 2.15... etc.

10^(1/6)

Now where the 6/12/24 divisions of the log scale came from I have no idea?
Was this picked to match 20% and 10% tolerances?

Yes

--
⚂⚃ 100% natural

--- news://freenews.netfront.net/ - complaints: news@netfront.net ---

 

[amdx]

On 10/28/2013 9:01 PM, John Larkin wrote:

On Mon, 28 Oct 2013 12:29:58 -0500, amdx <nojunk@knology.net> wrote:

On 10/27/2013 8:02 PM, John Larkin wrote:
On Sun, 27 Oct 2013 09:52:56 -0700 (PDT), riccardo manfrin
riccardomanfrin@gmail.com> wrote:

See http://en.wikipedia.org/wiki/Preferred_number#E_series. 47 shows up

in the 20%, 10%, and 5% standard resistor value series, so it's commonly

used whenever any old thing will do.


I knew there were some black magic in those numbers..
R



The color codes look nice, too.

Maybe you've been in San Fransisco a little to long?
Mikek

If you're happy with 100 ohms...


ah right, ah right, the color code is pretty!

Mikek