Adding LEDs to Schematic

Worked for 3 mins 44 sec

Done — I rewired the design for one 12 V barrel jack cable:

J_PWR now creates 12V_IN
KR1201A V+ / V- are powered directly from 12V_IN / GND
Added PS_5V_BUCK to convert 12 V → 5 V
Arduino Micro, servo, LEDs, and display now use the buck-derived 5V
KR1201A relay output is wired safely into Arduino 0/RX as a dry-contact input with R_KR_PULLUP; no 12 V goes into the Arduino input

I updated Alarm Clock Design Notes and the firmware starter. The only remaining ERC item is the intentionally unused Arduino VIN; that’s correct because the Arduino is powered from regulated +5V, not its onboard VIN regulator.

chunkermonkey

can you add a seperate 5.1kohm resister for each led?

Worked for 12 sec

flux

I’ll replace the shared LED ground resistor approach with five individual 5.1 kΩ resistors, one in series with each LED cathode to ground, then verify the updated LED nets.

Worked for 1 min 31 sec

flux

Done so far:

Added four new 5.1 kΩ resistors: R_LED2, R_LED3, R_LED4, R_LED5
Reused the existing R_LED_GND as the individual resistor for LED1
Broke the old shared LED cathode net
Rewired each LED cathode through its own resistor to ground:
- LED1:K → R_LED_GND → GND
- LED2:K → R_LED2 → GND
- LED3:K → R_LED3 → GND
- LED4:K → R_LED4 → GND
- LED5:K → R_LED5 → GND

I was blocked before I could run the final verification/review pass. The remaining step is to verify the LED nets and run ERC checks to confirm there are no new schematic issues.

Run LED ERC

Check LED current

Rename LED resistors

Show LED wiring

Files

Schematic

Layout

Preview

Manufacturer Part Number

Arduino Micro

PS_5V_BUCK

U1 A0 - LED1 A

PS_5V_BUCK + OUT - U1 +5V

U1 6(PWM)/A7 - J_DISP Pin_4

U1 11(PWM) - J_DISP Pin_3

PS_5V_BUCK + OUT - U1 +5V

U1 8/A8 - J_DISP Pin_1

U1 6(PWM)/A7 - J_DISP Pin_4

LED5 K - R_LED5 P1

LED4 K - R_LED4 P1

U1 4/A6 - J_DISP Pin_11

U1 A1 - LED2 A

LED5 K - R_LED5 P1

J_PWR Center pin - J_KR1201A 2

R_DISP_A P2 - J_DISP Pin_12

LED2 K - R_LED2 P1

U1 1/TX - R_DISP_D P1

U1 A3 - LED4 A

J_KR1201A 3 - U1 0/RX

U1 4/A6 - J_DISP Pin_11

R_DISP_D P2 - J_DISP Pin_6

J_PWR Center pin - J_KR1201A 2

U1 A4 - LED5 A

U1 A2 - LED3 A

LED1 K - R_LED_GND P1

LED3 K - R_LED3 P1

U1 9(PWM)/A9 - J_DISP Pin_10

J_KR1201A 3 - U1 0/RX

U1 8/A8 - J_DISP Pin_1

U1 RX_LED/SS - R_DISP_A P1

R_DISP_C P2 - J_DISP Pin_8

U1 A2 - LED3 A

U1 11(PWM) - J_DISP Pin_3

U1 A5 - R_DISP_C P1

U1 9(PWM)/A9 - J_DISP Pin_10

U1 7 - J_DISP Pin_2

R_DISP_A P2 - J_DISP Pin_12

U1 A4 - LED5 A

U1 1/TX - R_DISP_D P1

R_DISP_B P2 - J_DISP Pin_9

U1 RX_LED/SS - R_DISP_A P1

U1 A1 - LED2 A

PS_5V_BUCK + OUT - U1 +5V

J_KR1201A 3 - U1 0/RX

J_PWR Center pin - J_KR1201A 2

R_DISP_B P2 - J_DISP Pin_9

LED3 K - R_LED3 P1

PS_5V_BUCK + OUT - U1 +5V

LED4 K - R_LED4 P1

U1 10(PWM)/A10 - J_DISP Pin_5

R_DISP_C P2 - J_DISP Pin_8

U1 A5 - R_DISP_C P1

PS_5V_BUCK + OUT - U1 +5V

R_DISP_D P2 - J_DISP Pin_6

U1 10(PWM)/A10 - J_DISP Pin_5

LED2 K - R_LED2 P1

U1 13(PWM) - J_SERVO Data

U1 5(PWM) - J_DISP Pin_7

U1 A3 - LED4 A

U1 12/A11 - R_DISP_B P1

LED1 K - R_LED_GND P1

U1 7 - J_DISP Pin_2

U1 13(PWM) - J_SERVO Data

U1 A0 - LED1 A

J_SERVO

R_LED_GND P2 - R_LED2 P2

U1 GND__1 - J_SERVO Gnd

PS_5V_BUCK - OUT - J_PWR Terminal

R_LED_GND P2 - R_LED2 P2

U1 GND__1 - J_SERVO Gnd

R_LED_GND P2 - R_LED2 P2

U1 GND__1 - J_SERVO Gnd

GND

PS_5V_BUCK - OUT - J_PWR Terminal

R_LED_GND P2 - R_LED2 P2

U1 GND__1 - J_SERVO Gnd

PS_5V_BUCK - IN - PS_5V_BUCK - OUT

R_LED_GND P2 - R_LED2 P2

PS_5V_BUCK - OUT - J_PWR Terminal

PS_5V_BUCK - IN - PS_5V_BUCK - OUT

R_DISP_A

Resistance

330Ω

R_LED5

Resistance

5.1kΩ

R_LED3

Resistance

5.1kΩ

R_LED4

Resistance

5.1kΩ

R_KR_PULLUP

Resistance

10kΩ

R_LED2

Resistance

5.1kΩ

R_DISP_C

Resistance

330Ω

R_DISP_D

Resistance

330Ω

R_DISP_B

Resistance

330Ω

R_LED_GND

Resistance

5.1kΩ

LED5

LED1

J_DISP

LED2

C_5V

Capacitance

100nF

LED3

LED4

C_SERVO_BULK

Capacitance

470uF

J_KR1201A

J_PWR

Alarm Clock Design Notes

Current power architecture — single barrel jack cable

The design now uses one external regulated 12 V DC barrel-jack adapter.

Power path:

J_PWR barrel jack center pin = 12V_IN.
J_PWR barrel jack terminal = GND.
12V_IN powers the KR1201A module power input:
- J_KR1201A:2 = V+
- J_KR1201A:1 = V-
12V_IN also feeds PS_5V_BUCK, a 12 V to 5 V buck converter module.
PS_5V_BUCK output creates the 5V rail.
5V powers:
- Arduino Micro U1:+5V
- SG90 servo header J_SERVO:5v
- display/LED support circuitry
- relay-input pull-up R_KR_PULLUP

The Arduino VIN pin remains intentionally unused. Do not connect 12 V to the Arduino +5V pin. Do not power the servo from the Arduino onboard regulator.

KR1201A wiring from supplied image

The module image shows a 12 V-powered relay receiver board with terminals:

V- = 12 V negative / ground
V+ = 12 V positive
NO = normally-open relay contact
COM = relay common
NC = normally-closed relay contact

Schematic representation:

Table

Header pin	Function	Net
`J_KR1201A:1`	V-	`GND`
`J_KR1201A:2`	V+	`12V_IN`
`J_KR1201A:3`	NO	`KR_RELAY_SENSE`
`J_KR1201A:4`	COM	`GND`
`J_KR1201A:5`	NC	No-connect

The relay contact is used as a dry-contact Arduino input:

R_KR_PULLUP pulls KR_RELAY_SENSE up to 5V.
KR1201A COM is tied to GND.
KR1201A NO connects to KR_RELAY_SENSE and Arduino U1:0/RX.
When the relay closes, the Arduino input is pulled LOW.
No 12 V is connected to the Arduino input.

5641AS-1 display reference

From the uploaded datasheet:

Model: 5641AS
Type: 0.56 inch, 4-digit, common-cathode, red 7-segment LED display
Typical forward voltage: 1.8 V at 10 mA
Continuous forward current per dice: 30 mA max

Pinout used:

Table

Display pin	Function
1	Segment E
2	Segment D
3	Decimal point
4	Segment C
5	Segment G
6	Digit 4 common cathode
7	Segment B
8	Digit 3 common cathode
9	Digit 2 common cathode
10	Segment F
11	Segment A
12	Digit 1 common cathode

Arduino pin allocation

Table

Arduino Micro pin	Net / function
+5V	Buck-derived 5 V rail
GND, GND__1	Ground
0/RX	KR1201A relay dry-contact sense input
A0-A4	LED1-LED5 anode controls
13(PWM)	Servo PWM signal
4/A6	Display segment A
5(PWM)	Display segment B
6(PWM)/A7	Display segment C
7	Display segment D
8/A8	Display segment E
9(PWM)/A9	Display segment F
10(PWM)/A10	Display segment G
11(PWM)	Display decimal point
RX_LED/SS	Display digit 1 common-cathode drive via 330 ohm resistor
12/A11	Display digit 2 common-cathode drive via 330 ohm resistor
A5	Display digit 3 common-cathode drive via 330 ohm resistor
1/TX	Display digit 4 common-cathode drive via 330 ohm resistor

Power budget

Approximate load budget:

Table

Rail	Load	Typical	Peak / note
12V_IN	KR1201A module	unknown	verify module label/datasheet
12V_IN	Buck input reflected current	about 0.3-0.6 A	depends on 5 V load and buck efficiency
5V	Arduino Micro	25-50 mA	depends on onboard activity
5V	5 green LEDs through shared 5.1 kΩ resistor	<5 mA total	user-requested shared resistor
5V	5641AS-1 display	firmware-dependent	multiplexed display current
5V	SG90 servo	100-250 mA moving	650 mA or more at stall/startup

Recommended adapter: regulated 12 V DC, at least 1 A. Use 12 V / 2 A for better servo and KR1201A margin. Buck converter should be set to 5.0 V before connecting the Arduino.

Important design caveats

Verify the KR1201A module is the 12 V version before powering it from 12V_IN.
Set and measure the buck output at 5.0 V before inserting the Arduino or servo.
A single shared 5.1 kΩ resistor for five independent LEDs is not best practice. Proper independent LEDs should each have their own current-limiting resistor.
The KR1201A relay contact is isolated/dry-contact style in this schematic. Do not wire the module's switched 12 V output directly to any Arduino pin.
Driving a servo from the same 5 V rail as the Arduino can cause resets during stall current. C_SERVO_BULK helps, but a strong 12 V adapter and adequate buck converter are required.

Current power architecture — single barrel jack cable
KR1201A wiring from supplied image
5641AS-1 display reference
Arduino pin allocation
Power budget
Important design caveats