Light Dimmer with Capsense Brightness Control

Abstract
Light Dimmer with Capsense Brightness Control
Author: Petro Koblyuk
Associated Project: Yes
Associated Part Family: CY8C21x34, CY8C24x94
GET FREE SAMPLES HERE (CY Sample Request Form for all Product Lines)
Software Version: PSoC Designer 4.4
Associated Application Notes: AN2302, AN2394, AN13943
Sometimes there is a need to regulate the incandescent lamp brightness to gain more comfortable and pleasant room lighting.
This Application Note describes the Light Dimmer for smooth incandescent lamp brightness control. User adjusts the lamp
brightness level by touching the CapSense slider. Dimmer includes the LED bar graph to display actual brightness as
additional feature.
Introduction
Triac Control
The modern lighting systems allow controlling brightness
smoothly to obtain more comfortable and pleasant room
lighting. Some popular devices use potentiometer with triac
phase control technique for lamp brightness regulation. The
proposed dimmer uses a touch-sensitive control to enable
the user to control brightness in the convenient, easy and
understandable way.
110-220V,
AC~
Triac
Lamp
Design demonstrates the PSoC ability doing more than only
Capsense: one chip is used for capacitance sensing, lamp
power phase control, AC frequency calibration for worldwide
use, multiplexed LED bar graph driving with night slight
backlight.
Table 1 shows the technical specification of the Light
Dimmer.
Table 1. Light Dimmer Specifications
Characteristic
AC Supply
Lamp Power
CapSense Slider Overlay Thickness 1
Quantity of Brightness Levels 17
Value
110 – 220 V, 47 – 63 Hz
Depending on triac,
200W for current design
1 mm – 6 mm
Notes
1. The silicon glass, ABS, plexiglass can be used for overlay. The slider
segments dimensions should be adjusted accordingly to the overlay
thickness.
Figure 2. The Timing Diagram of Lamp Power Phase
Control
AC 110-220V
AC
Zero Crossing
Triac Turning-
On Pulses
Lamp
Waveform
t
t
t
t
Power Phase Control
The Light Dimmer uses the principal of power phase control,
which is easy in implementation. The phase control
operation principle lies in controlling triac turning on phase
within AC supply period. Figure 1 shows the typical triac and
lamp interconnection circuit. The delay variation between
AC Zero Crossing signal and triac turning on time is used to
control the amount of power provided to lamp, see Figure 2.
Figure 1. Typical Interconnection Circuit of Triac and Lamp
Delay 1 Delay 2 Delay 3
Light Dimmer Block Diagram
The Light Dimmer consists of the following blocks: AC zero
crossing detector, PSoC’s CPU core for general control,
power supply, CapSense slider for load power control, LED
bar graph (see Figure 3).
Figure 3. Light Dimmer Block Diagram
January 10, 2008 Document No. 001-08990 Rev. *B (AN# is same as last 5 digits of doc #.) 1

Error! Reference source not found.
AC~
Lamp
Triac Control
AC Zero
Crossing
Zero Crossing
Power Supply
220V AC to 5V DC
Vcc
PSoC
triggering prevention when noised AC signal is close to zero,
the D 4 limits the reverse voltage applied to Q 2 base-emitter
junction, R 17 is zero-crossing detector pull-up. The zerocross
detection operation is shown on Figure 4
Figure 4. The Timing Diagram of “Zero Crossing” Signal
110-220V, AC ~
t
User
Interface
Capsense
Slider
LED Bar
Graph
Zero Crossing
t
Dimmer Hardware
Figure 5 shows the Light Dimmer schematic. The R 4…R 7
resistors are used for limiting of Q 2 base current, C 9 and
R 4…R 7 form the LPF for zero-crossing detector false
POWER BOARD
Figure 5. Light Dimmer Schematic
Power Supply
J2
1
2
AC main con
F1
FUSE
D2
1N4007
C3
4.7uF 400V
+
5
4
D
U1
B
F
3
P
B
S 2
S 1
S
LNK304
8 C1
0.1uF
S 7
R1 12k 1%
R2
2k 1%
+ C2
10uF 35V
L1
1mH 280mA
D3
UF4005
D1
1N4007
R3
3.3k
+ C4
100uF
+11.5V
+5V
U2 LP2950/TO92
3
1
IN OUT
D
N
G
C5
2
1uF
C6
1uF
VCC
C7
0.1uF
J1
Lamp con
Q1
MAC15
1
2 R5 107k 0.5W
C8
0.47uF
Triac Control
R10
10E
TriacControl
AC Zero Crossing Detector
R4 107k 0.5W
R6 107k 0.5W
R7 107k 0.5W
C9
470pF
VCC
R17 4.7k
D4
LL4148
ZeroCrossing
Q2
BC847
CAPSENSE BOARD
CapSense Slider
SEGMENT1
SEGMENT2
SEGMENT3
SEGMENT4
SEGMENT5
SEGMENT6
SEGMENT7
SEGMENT8
SEGMENT9
LED Bargraph
0 X 1
X 2
X
D
D
D
E
E
E
L
L
L
R11
R12
255E
255E
D20 LED D11 LED
D5 LED D8 LED
R24
R15
R18
R19
R20
R21
R22
R23
R16
R13
255E
D15 LED
D12 LED
X 3
D
E
L
1k
1k
1k
1k
1k
1k
1k
1k
1k
R14
255E
D19 LED
D16 LED
sl0
sl1
sl2
sl3
sl4
sl5
sl6
sl7
sl8
LED Y0
LED Y1
PSoC's CPU Core
LED Y3
LED Y2
LED Y1
LED Y0
ZeroCrossing
TriacControl
R26
C10
0.1uF
VCC
2 1 0 9 8 7 6 5
3 3 3 2 2 2 2 2
V ss V dd
1
P 0[3] P 0[5] P 0[7] P 0[6] P 0[4] P 0[2]
2
P0[1]
3
P2[7]
4
P2[5]
U3
5
P2[3]
CY8C21434
6
P2[1]
7
P3[3]
8
P3[1]
P1[7]
2k
P 1[5] P 1[3] P 1[1] V ss P 1[0] P 1[2] P 1[4] P 1[6]
9 0 1 2 3 4 5 6
1
1 1 1 1 1
24
P0[0]
23
P2[6]
22
P2[4]
21
P2[2]
20
P2[0]
19
P3[2]
18
P3[0]
XRES 17
sl8
sl7
LED X3
sl6
sl5
sl4
LED X2
LED X1
sl3
sl2
sl1
LED X0
sl0
D6 LED
D9 LED
D13 LED
D17 LED
D7 LED
D10 LED
D14 LED
D18 LED
LED Y2
LED Y3
C13
0.1uF
C L
S
D A
S
January 10, 2008 Document No. 001-08990 Rev. *B (AN# is same as last 5 digits of doc #.) 2

Error! Reference source not found.
Power Supply
A dimmer power supply is implemented using the
transformer-free switching DC-DC regulator, type LNK304
from Power Integrations [1]. The F 1 self-recovered fuse
serves two functions: it protects from possible over
currents and its resistance (about 8 Ohms) limits the C 3
inrush current at power-on. The values of R 1-R 2 divider
define the U 1 regulator output voltage, it is about 11.5 V.
The U 1 output voltage can vary with input voltage change
and load current variations. Usage of CapSense requires
stable PSoC power supply [2]. That is why the additional
U 2 linear regulator has been used to form the clear 5 V
supply.
Triac Control
Triac is driven by short pulses for power consumption
optimization. These pulses are generated by PSoC and
are differentiated by C 8R 10 network. Triac is turned on by
series from 3 pulses, see Figure 6. At full brightness triac
turning on time is some delayed from zero-crossing event
to guarantee reaching the minimum triac turning on
voltage. This scheme provides stable operation if AC
mains signal is noised.
Figure 6. The Timing Diagram of Triac Control
duration and 170us interval between them. After 3 pulses
generation PWM disables itself and is re-enabled by
following zero-crossing interrupt.
LED Bar Graph Control
Dimmer uses multiplexed LED control to drive 16 LED
using only 8 PSoC’s pins. LEDs control occurs on four
phases. On each phase only one appropriate LEDs row is
turned-on. The row switching time base is formed by CSD
sensor scanning time taking into account that scanning
time is constant. The LED control state machine switches
each row after each slider segment scanning for getting
high refresh rate (about 250Hz) and it prevents the visible
bar graph flickering. In each LED scanning cycle all LED
are turned on for 3 us by using the software delay routine
for providing low-intensity night backlight for all LED.
Lamp Light Intensity Linear Control
The incandescent lamp power is not linearly proportional
to the triac turning on delay (see Figure 7) due sinusoidal
AC mains current waveform nature.
Figure 7. Lamp Power vs. Triac Turning on Delay
Lamp
Power, %
110-220V, AC ~
t
100
Zero Crossing
t
50
Threshold
110-220V, AC ~
Zero Crossing
Triac Control
340µs
170µs
3 pulses
Note: In Figure 6 the “Triac Control” signal at minimal
delay i.e. at the maximum brightness level is shown.
Dimmer Firmware
t
t
t
0
T/8
T/4
3T/8
T/2
Note: In Figure 7 the “T“ is equal to AC mains period.
The human eye has logarithmic visible brightness vs. lamp
brightness; also lamp visible brightness is non-linear
function from applied voltage RMS value via variation
lamp resistance due lamp coil temperature change.
To provide linear visual lamp brightness change, a nonlinear
lookup table (baConst array in C code) has been
used. This table has 17 entries and Figure 8 shows a
lookup table graph. Customers can adapt this table per
need.
t
Triac Control
The controllable delay between zero-crossing signal and
triac turning on is used for lamp brightness control. The
delay is generated by PWM8 user module for low-jitter
operation. The both edges of zero-crossing signal are
used for interrupt triggering. The interrupt handler restarts
the PWM with appropriate period value, depends on
required delay. Initially PWM generates a first pulse with
delay, set by expected brightness level. Once delay
interval expiration, the PWM registers are reloaded for
generation series triac turning on pulses with 340us pulse
January 10, 2008 Document No. 001-08990 Rev. *B (AN# is same as last 5 digits of doc #.) 3

Error! Reference source not found.
T delay
T/2
3T/8
connectors, located at the opposite board sides. The PCB
Gerber files are provided in the supporting archive
together with PSoC project can be used for PCB routing
reference. Figure 9 shows different Light Dimmer photos.
Figure 9. Light Dimmer Photos
a) Front View
T/4
T/8
0
0
1
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
N slid
b) Back View
Figure 8. Triac Turning on Delay vs. Slider Position
AC Mains Frequency Calibration
There are several frequency AC standards in the world;
some countries use 50Hz frequency, other 60Hz. For
dimmer operation ability worldwide without any manual
adjustments, the additional calibration procedure is
implemented. This procedure measures the actual AC
mains frequency and calculates a scale coefficient to
transform the lookup table array in the actual triac turning
on delay values. The calibration procedure is initiated
once after dimmer power up.
Calibration takes in three stages. At first stage the duration
of AC half period is measured using a CSD UM counter
block. The 32 measurements are taken, averaged value is
calculated. For this purpose a CSD is manually
reconfigured by re-routing counter enable signal from
comparator bus to zero-cross detector output.
At the second stage the scale coefficient is calculated as
relation of measured period (T C) to expected period (T C50)
for 50Hz AC:
K
T
T
C
= Equation 1
C 50
At third stage the triac turning on delay table (baConst) are
scaled by coefficient K.
Dimmer Mechanical Construction
The dimmer is composed from two boards. The LED array
and Capsense slider are placed on the first board, only
SMT components are placed on this board. The reverse
mount LEDs were placed in the slider segments.
The power supply, zero-crossing detector, triac and screw
power/lamp connectors were placed on second board. All
through hole components were located on this board as
well. The boards were connected together using 2
Safety Warnings
c) Side View
The Light Dimmer does not have galvanic isolation from
AC Mains Line. Plastic overlay should have thickness
more than 2mm for user electrical shock preventing.
Please newer touch PCB or dimmer components when
supply voltage is applied. For device debugging and
testing, please use the isolation transformer or galvanically
isolated scope probes.
Possible Modifications
Some customers are willing optimizing the dimmer price
for cost sensitive applications. The most expensive part is
switching DC-DC converter. To reduce BOM amount, the
power supply can be redesigned by using the simplest
capacitive current source, see
January 10, 2008 Document No. 001-08990 Rev. *B (AN# is same as last 5 digits of doc #.) 4

Error! Reference source not found.
Figure 10.
Figure 10. Simplified Power Supply
C1
0.47uF 400V
R1
47 Ohm 0.5W
J1
1
2
3
4
- +
D1
BRIDGE
1
VCC
6.8V
up to 20 mA
AC
D2
6.8V
+ C2
470uF 25V
2
In this case the total current consumption should be
reduced to 25mA by supplying smaller currents to LED
array and reduction the LED amount. The C 1 capacitor
value should be selected accordingly for AC voltage (110
or 220V), the provided value was intended for 220V
supply.
Note: for successful passing of EMC tests a AC Mains
filter can be required if radiated noise due triac turning on
is too large.
Alternative Dimmer Applications
Originally, dimmer has been designed for incandescent
lamps control. Without any modifications device can be
used for control speed of universal motors in various
applications, as electric drill, pumps, air-conditioners,
kitchen machines, etc. That is good chance to replace the
potentiometers with capsense control.
Appendix
1) LNK304 datasheet,
http://www.powerint.com/linktnproduct.htm
2) CSD UM datasheet
January 10, 2008 Document No. 001-08990 Rev. *B (AN# is same as last 5 digits of doc #.) 5

Error! Reference source not found.
About the Author (optional)
Name:
Title:
Petro Koblyuk
Application engineer
Background: Petro graduated from National
University “Lviv Polytechnica”
(Ukraine) in specialty ‘computer
systems’ in 2001. Working in the
Ukraine Solution Center since 2005.
Contact:
Petro.Koblyuk@cypressua.com
Document subject-specific trademark information, if any.
Example - PSoC is a registered trademark of Cypress Semiconductor Corp. "Programmable System-on-Chip," PSoC Designer, and PSoC
Express are trademarks of Cypress Semiconductor Corp. All other trademarks or registered trademarks referenced herein are the property of
their respective owners.
The blue bar and the information below it are placed at the bottom portion of the page.
Cypress Semiconductor
198 Champion Court
San Jose, CA 95134-1709
Phone: 408-943-2600
Fax: 408-943-4730
http://www.cypress.com/
© Cypress Semiconductor Corporation, 2007. The information contained herein is subject to change without notice. Cypress Semiconductor
Corporation assumes no responsibility for the use of any circuitry other than circuitry embodied in a Cypress product. Nor does it convey or imply any
license under patent or other rights. Cypress products are not warranted nor intended to be used for medical, life support, life saving, critical control or
safety applications, unless pursuant to an express written agreement with Cypress. Furthermore, Cypress does not authorize its products for use as
critical components in life-support systems where a malfunction or failure may reasonably be expected to result in significant injury to the user. The
inclusion of Cypress products in life-support systems application implies that the manufacturer assumes all risk of such use and in doing so indemnifies
Cypress against all charges.
This Source Code (software and/or firmware) is owned by Cypress Semiconductor Corporation (Cypress) and is protected by and subject to worldwide
patent protection (United States and foreign), United States copyright laws and international treaty provisions. Cypress hereby grants to licensee a
personal, non-exclusive, non-transferable license to copy, use, modify, create derivative works of, and compile the Cypress Source Code and derivative
works for the sole purpose of creating custom software and or firmware in support of licensee product to be used only in conjunction with a Cypress
integrated circuit as specified in the applicable agreement. Any reproduction, modification, translation, compilation, or representation of this Source
Code except as specified above is prohibited without the express written permission of Cypress.
Disclaimer: CYPRESS MAKES NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, WITH REGARD TO THIS MATERIAL, INCLUDING, BUT
NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. Cypress reserves the
right to make changes without further notice to the materials described herein. Cypress does not assume any liability arising out of the application or
use of any product or circuit described herein. Cypress does not authorize its products for use as critical components in life-support systems where a
malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of Cypress’ product in a life-support systems
application implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress against all charges.
Use may be limited by and subject to the applicable Cypress software license agreement.
January 10, 2008 Document No. 001-08990 Rev. *B (AN# is same as last 5 digits of doc #.) 6