# Beginner's dilemma

O

#### OldBuzzard

Jan 1, 1970
0
Hi,
I just took-up electronics as a hobby. Purchased a breadboard and a fe
jumper wires(?). And am waiting to light-up my first LED. I have
resistor of 657 Ohms( or K Ohms;blue, green, brown and gold bands). M
question is, can I strip the ends of a mobile phone charger and connect i
to my breadboard as a power supply ? It does say on the charger that th
output is about 5V / 500mA.

Any help will be appreciated.

Thanks,

BSingh.

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J

#### John Fields

Jan 1, 1970
0
Hi,
I just took-up electronics as a hobby. Purchased a breadboard and a few
jumper wires(?). And am waiting to light-up my first LED. I have a
resistor of 657 Ohms( or K Ohms;blue, green, brown and gold bands). My
question is, can I strip the ends of a mobile phone charger and connect it
to my breadboard as a power supply ? It does say on the charger that the
output is about 5V / 500mA.

---
The resistance of the resistor is 650 ohms, and the tolerance on
that value is +/- 5%.

The first color band indicates that the first significant figure of
the value of resistance is blue (6), the second is green (5), and
the third indicates that the decimal multiplier ( the number of
zeroes after the second significant figure) is brown (1). The
fourth band, gold, indicates that the tolerance is +/- 5%. Ergo,
650 ohms, +/-5%.

It's difficult to say whether your charger will make a good power
supply since it's designed to charge your cellphone batteries and
may supply more than 5V if it's not loaded properly. It also may
produce what's called "ripple" which may not be acceptable for a
breadboard supply. What kind of test equipment do you have
available?

A

#### Anders Nesheim Vinje

Jan 1, 1970
0
That will work. However i would recomend a powersupply with higer voltage if
you are interested other things. I guess its ok for simple circuits and
digital stuff. Working with audio circuits would often require a more
powerful PSU.

Just rember that leds dont like to much current. 20 -30 mA is often the max
value. It will work fine with the resistor you have. 5 V / 650Ohms = 7.6mA.
You could even wire 65 leds in this fashion and the PSU would still do.
Maybe you could wire a similar resitor in paralell to make it brighter. Then
the current would be 15.2mA. Now you only could wire 32 leds.

Just remember that leds are polarised devices. If you can feel the flat edge
on one of the sides of the diode. That pin will got to the negative (ground)
side of the PSU. Hope you have a multimeter.

Have fun.

Anders N. Vinje

P

#### Peter Bennett

Jan 1, 1970
0
650 ohms isn't a standard value, according to my references - the OP
should check the colour code again. The nearest standard values to
650 are 620 (blue red brown) or 680 (blue grey brown)

J

#### John Fields

Jan 1, 1970
0
650 ohms isn't a standard value, according to my references - the OP
should check the colour code again. The nearest standard values to
650 are 620 (blue red brown) or 680 (blue grey brown)

J

#### Jim Gregory

Jan 1, 1970
0
If you are not yet equipped, buy a small cheap handheld multimeter, analogue
or digital, and makes sure it
has a diode test and a beeper continuity range. They are very cheap
RESISTOR values (unwired, out of circuit) are easy to prove by reading the
display! No such commonplace thing as a 650 Ohm.
Some efficient LEDs are happy running at down to one mA.
Caution! You said your power supply is a charger so it might give a much
higher voltage (maybe +33%) than it quoted if just driving an LED. But 560r
is a safe dropper at 7-8V DC.

C

#### Chris

Jan 1, 1970
0
Peter said:
650 ohms isn't a standard value, according to my references - the OP
should check the colour code again. The nearest standard values to
650 are 620 (blue red brown) or 680 (blue grey brown)

Or possibly 750 ohms, also a standard value. It might be as easy to
mistake violet for blue as it would be to mistake red or especially
grey for green.

Chris

J

#### JeffM

Jan 1, 1970
0
I have a resistor of 657 Ohms
650 ohms isn't a standard value
The nearest standard values to 650
are 620 (blue red brown) or 680 (blue grey brown)
Peter Bennett

The same thing struck me so I checked my chart
http://home.san.rr.com/nessengr/techdata/stdresval.html

657 is a standard value--for 0.5% or better
Of course, it would take more bands.
Not sure where the OP got that number.

I wondering if Chris Foley didn't call it right
when he alluded to color perception problems.