Arduino Nixie Clock v6 Operating Instructions Manual page 22

LEDs and front panel
Parts List:
R20 1k (*)
R21 1k (*)
R22 1k (*)
Q3 2N7000
Q4 2N7000
Q5 2N7000
R11 10k
LDR LDR
S1 SWITCH
LED RGB LED RGB
These are the final parts of the clock apart from the tubes, and are intended as the elements which the
user sees and touches.
This is the last step of the main board build.
Notes:
The FETs should be orientated with the flat side as shown on the board. Some FETs come with the
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leds in a row rather than in a triange. If this is the case, bend the middle lead slightly so that it fits
the holes in the board (see hint).
If you want to run more than one back light LED from the board, see the note below.
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(*) You can run more than one back light LED for each R,G or B channel. If you want to do this, replace this
resistor with a simple PCB link, and put a 1k resistor in series with each LED cathode instead. You can run
between 4 and 6 LEDs off the driver depending on the type and the supply (you can choose the regulated
5V or the unregulated VIN). The total current for each channel should not exceed 200mA.
To calculate the current drawn, you can measure the forward drop V
use the following formula to calculate the current:
I = V - V
LED CC FWD
For example, with a V
I = 5 – 2.2 / 1k = 2.8mA
LED
In this case, you can safely run 6 LEDs off the channel.
When all the components are installed, you are finished with the board.
The switch connects to ground when closed. It uses the internal pull-up resistor provided by the Atmega on
the input pin to pull the input to VCC when the switch is not closed.
The switch is de-bounced in software, so practically any switch you want to use is suitable. A simple switch
is provided in the kit, but you might want to substitute this switch with one that suits you case.
/ 1k
of 2.2V, the current is:
FWD
across the LED when it is on, and
FWD