Analog Bicycle Light Schematic

flux

The editable layer value is Bottom for standalone artwork on this stackup, so I’m applying that exact layer now.

flux

The artwork is now on the valid bottom-side layer. I’m visually checking the result and running DRC.

flux

The layout checks are clean; I’m explicitly setting the PCB silkscreen color to white so the new bottom artwork renders as intended in 3D.

flux

Updated only the PCB bottom-side artwork: added the bicycle/light graphic, divider lines, five feature descriptions with line icons, and centered “Flux” branding. Silkscreen color is set to white.
Remaining issues:
  • None reported by DRC.
  • Schematic, electrical connections, component placement, and routing were unchanged.
Review and export
Final manufacturing review
Verify BOM
Export fabrication files
Create assembly notes
J3
IC1
Manufacturer Part Number
TLC555CDR
C_COMP P2 - C_DARK_DEC P2
J_USB SHIELD - R_CC1 P2
GND
GND
J_USB SHIELD - R_CC1 P2
GND
GND
GND
J_USB SHIELD - J_USB SHIELD
J_USB SHIELD - R_CC1 P2
GND
J_USB SHIELD - R_CC1 P2
J_USB SHIELD - J_USB SHIELD
J_USB SHIELD - R_CC1 P2
J_USB SHIELD - R_CC1 P2
J_USB SHIELD - R_CC1 P2
C_TIMER_DEC P2 - C_LED_DEC P2
GND
J_USB SHIELD - R_CC1 P2
J_USB SHIELD - R_CC1 P2
J_USB SHIELD - R_CC1 P2
GND
J_USB SHIELD - R_CC1 P2
C_TIMER_DEC P2 - C_LED_DEC P2
C_TIMER_DEC P2 - C_LED_DEC P2
J_USB SHIELD - R_CC1 P2
GND
GND
C_COMP P2 - C_DARK_DEC P2
GND
J_USB SHIELD - R_CC1 P2
C_TIMER_DEC P2 - C_LED_DEC P2
R_LDR P1 - R_LDR_BIAS P2
R_MOTION_PU P2 - S_MOTION 1
D_BOOST K - C_LED_OUT P1
RV_DARK_3P WIPER - U_DARK 1IN-
J_USB VBUS_B - C_USB_IN P1
U_TIMER CONT - C_CTRL P1
U_CHG BAT - J_BAT 1
R_LED_EN_PU P2 - D_AND1 A
U_CHG BAT - J_BAT 1
U_LED SW - L_BOOST ~
U_CHG BAT - J_BAT 1
R_LED_EN_PU P2 - D_AND1 A
D_CHG A - R_CHG_LED P2
U_CHG BAT - J_BAT 1
R_MOTION_PU P2 - S_MOTION 1
R_LED_EN_PU P2 - D_AND1 A
U_DARK 1OUT - R_DARK_PU P2
U_DARK 1OUT - R_DARK_PU P2
J_USB VBUS_B - C_USB_IN P1
D_BOOST K - C_LED_OUT P1
U_CHG BAT - J_BAT 1
U_TIMER OUT - D_AND2 K
U_CHG BAT - J_BAT 1
U_CHG BAT - J_BAT 1
J_USB VBUS_B - C_USB_IN P1
U_TIMER THRES - R_TIME P2
J_USB VBUS_B - C_USB_IN P1
R_MOTION_PU P2 - S_MOTION 1
J_USB VBUS_B - C_USB_IN P1
U_CHG BAT - J_BAT 1
U_CHG BAT - J_BAT 1
U_CHG BAT - J_BAT 1
U_CHG BAT - J_BAT 1
U_CHG PROG - R_PROG P1
U_TIMER THRES - R_TIME P2
D_LED2 K - U_LED FB
J_USB CC2 - R_CC2 P1
J_USB CC1 - R_CC1 P1
D_CHG A - R_CHG_LED P2
R_LDR P1 - R_LDR_BIAS P2
U_DARK 1OUT - R_DARK_PU P2
U_CHG BAT - J_BAT 1
J_USB VBUS_B - C_USB_IN P1
C_COMP P1 - U_LED COMP
D_LED2 K - U_LED FB
U_LED SW - L_BOOST ~
U_CHG CHRG - D_CHG K
U_CHG BAT - J_BAT 1
D_LED2 K - U_LED FB
U_CHG BAT - J_BAT 1
U_CHG BAT - J_BAT 1
R_LED_EN_PU P2 - D_AND1 A
U_CHG BAT - J_BAT 1
RV_DARK_3P WIPER - U_DARK 1IN-
U_CHG BAT - J_BAT 1
C_COMP P1 - U_LED COMP
U_TIMER OUT - D_AND2 K
R_MOTION_PU P2 - S_MOTION 1
RV_DARK_3P WIPER - U_DARK 1IN-
D_BOOST K - C_LED_OUT P1
J_USB CC1 - R_CC1 P1
U_TIMER OUT - D_AND2 K
D_BOOST K - C_LED_OUT P1
U_TIMER THRES - R_TIME P2
J_USB CC2 - R_CC2 P1
U_CHG BAT - J_BAT 1
U_DARK 1OUT - R_DARK_PU P2
R_LDR P1 - R_LDR_BIAS P2
J_USB VBUS_B - C_USB_IN P1
U_CHG CHRG - D_CHG K
U_CHG BAT - J_BAT 1
U_TIMER CONT - C_CTRL P1
U_CHG PROG - R_PROG P1
U_LED SW - L_BOOST ~
C8
Capacitance
10nF
D2
C3
Capacitance
100nF
TP4
C10
Capacitance
10uF
TP1
C7
Capacitance
220nF
C1
Not Recommended for New Designs
Capacitance
4.7uF
TP3
C12
Capacitance
47uF
C5
Capacitance
100nF
D1
C6
Capacitance
100nF
TP5
C11
Capacitance
1uF
TP2
TP6
C9
Capacitance
10uF
C2
Not Recommended for New Designs
Capacitance
4.7uF
TP
C4
Capacitance
100nF
R2
Resistance
5.1kΩ
D3
R9
Resistance
2kΩ
R6
Resistance
100kΩ
D4
R10
Resistance
0.68Ω
J2
R5
Resistance
100kΩ
R3
Resistance
1kΩ
U3
R4
Resistance
100kΩ
R8
Resistance
8-20kΩ light, ~1MΩ dark
J1
U2
Not Recommended for New Designs
R7
Resistance
100kΩ
R1
Resistance
5.1kΩ
U1
R11
Resistance
1MΩ
L1
Inductance
10uH
RV1
Resistance
100kΩ
SW1

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Schematic Correction Summary
Applied corrections from the attached review file.
Updated block structure
  • USB-C input uses +5V_USB as the 5 V charging input.
  • Charger and battery connector feed BAT_SYS, the protected/external 1S Li-ion/Li-Po system rail, approximately 3.0 V to 4.2 V.
  • Darkness detector generates DARK_OK.
  • Motion sensor and TLC555 timer generate MOTION_ON.
  • DARK_OK and MOTION_ON feed Schottky diode OR logic into LED_ENABLE.
  • LED_ENABLE drives TPS61165 CTRL directly.
  • TPS61165 drives the 2-white-LED series string from LED_OUT.
Corrections applied
  • Removed external MOSFET LED cathode switching path: Q_LED, R_GATE, and R_GATE_PD were removed.
  • Added R_LED_EN_PD, a 100 kΩ pulldown from LED_ENABLE to GND.
  • Replaced the 2-pin RV_DARK placeholder with RV_DARK_3P, a real 3-pin 100 kΩ trimmer potentiometer.
  • Wired RV_DARK_3P as BAT_SYS-to-GND divider with wiper on DARK_REF.
  • Renamed timer output net from LED_CONTROL to MOTION_ON.
  • Renamed comparator reference net from DARK_THRESH to DARK_REF.
  • Kept LDR_SENSE into LM393 IN+ and DARK_REF into LM393 IN-, with DARK_OK pulled up to BAT_SYS.
Notes
  • No MCU and no firmware.
  • Fully analog automatic bicycle light.
  • Motion OR darkness turns on the light.
  • Use an external protected 1S Li-ion or Li-Po battery through J_BAT.
  • High-power LEDs need thermal management.
  • LED_OUT is the boosted LED-string voltage only, approximately 6 V to 9 V depending on LED string; it is not a general power rail.

  • Updated block structure

  • Corrections applied

  • Notes

Automatic Bike Light

Automatic Bike Light thumbnail
Fully analog automatic bicycle front light with USB-C charging, 1S Li-ion/Li-Po battery input, darkness detection, motion-triggered timer control, and a TPS61165 boost LED driver. The circuit automatically enables the front LEDs when it is dark or motion is detected, without any microcontroller or firmware.

Properties

Properties describe core aspects of the project.

Pricing & Availability

Distributor

Qty 1

Arrow

$3.36–$6.24

Digi-Key

$2.85

HQonline

$0.77–$0.97

LCSC

$3.86–$4.18

Mouser

$13.25–$24.65

TME

$7.52

Verical

$19.64–$91.41

Controls