Component value summary

COMPONENT AND DESIGN VALUE SUMMARY

-Thomas Shaw

Component Values

Source and measurement

Ref	Value	Type	Function
R6, R7	1 Ω each (0.5 Ω total)	Resistor	Current shunt
R4	270 kΩ	Resistor	Voltage divider (top)
R8	15 kΩ	Resistor	Voltage divider (bottom)

Rectifier

Ref	Value	Type	Function
CR1	1N4007	Rectifier diode	Half-wave rectifier
R2, R3, R18	TBD (4.7–6.8 Ω range)	Resistor	Inrush current limiting
C2	100 µF, 35 V	Electrolytic	Reservoir (farthest from buck)
C32	220 µF, 35 V	Electrolytic	Reservoir
C3	100 nF	X7R	HF bypass

7 V buck converter

Ref	Value	Type	Function
U1	LM2596S-ADJ	Buck regulator	7 V rail, 150 kHz
C4	220 µF, 35 V	Electrolytic	Buck input capacitor
D2	M7	Rectifier diode (SMD 1N4007)	Reverse-polarity protection
R1	4.7 kΩ	Resistor	Feedback (top)
R5	1 kΩ	Resistor	Feedback (bottom)
C1	2.2 nF	Ceramic	Feedforward compensation
L1	47 µH	Power inductor	Buck inductor
CR2	SS34	Schottky diode	Catch diode
C5	220 µF, ≥ 16 V	Electrolytic	Buck output
C6	100 nF	X7R	HF bypass

Linear regulators

Ref	Value	Type	Function
V1	LM1117-5.0	LDO regulator	5 V power rail
V2	LM1117-3.3	LDO regulator	3.3 V reference rail
C19, C34	47 µF, ≥ 16 V	Electrolytic	LDO inputs
C20	47 µF, ≥ 10 V	Electrolytic	5 V LDO output
C35	47 µF, ≥ 6.3 V	Electrolytic	3.3 V LDO output

Offset (Vref) generation

Ref	Value	Type	Function
R25, R26	10 kΩ each	Resistor	1.65 V divider
C15	100 nF	X7R	3.3 V rail bypass
C17	100 nF	Ceramic	Divider filter (318 Hz)
U8B	TLC082	Op-amp	Vref voltage follower
C33	Not fitted	—	Removed (caused oscillation)

Current signal conditioning

Ref	Value	Type	Function
U4B	TLC082	Op-amp	Difference amplifier
R9, R10	10 kΩ	Resistor	Input resistors
R11, R12	33 kΩ	Resistor	Feedback / Vref resistors (gain 3.3)
C9, C10	300 pF	C0G	Active filter (16.08 kHz)
R13	1 kΩ	Resistor	Output RC filter
C11	10 nF	C0G	Output RC filter (15.92 kHz)
D10, D11	3.3 V Zener	Zener diode	Input clamps (±4 V)

Voltage signal conditioning

Ref	Value	Type	Function
U5B	TLC082	Op-amp	Difference amplifier
R20	82 kΩ	Resistor	Inverting input
R22	68 kΩ	Resistor	Non-inverting input (+14.21 kΩ divider R_th)
R19, R23	100 kΩ	Resistor	Feedback / Vref resistors (gain 1.2195)
C14, C16	100 pF	C0G	Active filter (15.92 kHz)
R21	1 kΩ	Resistor	Output RC filter
C30	10 nF	C0G	Output RC filter (15.92 kHz)
D7, D9	3.3 V Zener	Zener diode	Input clamps (±4 V)

Peak current detection (not used for measurement)

Ref	Value	Type	Function
U4A	TLC082	Op-amp	Precision peak detector
D5	SS34	Schottky diode	Peak detector diode
C18	4.7 µF	Ceramic	Peak hold
R27	22 kΩ	Resistor	Discharge (τ = 103 ms)

Zero crossing detection

Ref	Value	Type	Function
U5A	TLC082	Op-amp	Vvm buffer
C13	Not fitted	—	Avoids capacitive load on follower
R16	10 kΩ	Resistor	Schmitt input
R17	390 kΩ	Resistor	Schmitt feedback (106 mV hysteresis)
U8A	TLC082	Op-amp	Schmitt trigger

MCU and support circuitry

Ref	Value	Type	Function
U2	ATmega328PB-AU	Microcontroller	Digital processing
Y1	16 MHz (ABLS-16.000MHZ-B4-T)	Crystal	Clock (÷8 → 2 MHz)
C21, C22	22 pF	C0G	Crystal load capacitors
R28	10 kΩ	Resistor	Reset pull-up
C31	100 nF	X7R	Reset delay (1 ms)
R14, R15	Not fitted	—	I²C pull-ups (on screen PCB)
R24	470 Ω	Resistor	LED current limit
D4	LTST-C191KGKT	Green LED, 0603	7 V power indicator (~10 mA)
U7	TXS0108EPWR	Level shifter	5 V ↔ 3.3 V (ESP32)

Decoupling

Ref	Value	Type	Location
C23	100 nF	X7R	MCU V_CC
C24	100 nF	X7R	MCU AV_CC
C25	100 nF	X7R	MCU AREF
C26	100 nF	X7R	U8 (TLC082)
C29	100 nF	X7R	U5 (TLC082)
C38	100 nF	X7R	U4 (TLC082)
C7	100 nF	X7R	Level shifter 5 V
C8	100 nF	X7R	Level shifter 3.3 V
C27	100 nF	X7R	I²C screen header
C28	100 nF	X7R	7-segment header
C37, ESP32 header cap	100 nF	X7R	ESP32 header
ESP32 bulk	Optional	Electrolytic	Spare footprint

Key Design Values

Power

Parameter	Value
Source	12.6–15.4 Vrms, 500 Hz
Rectified peak	17.8–21.8 V
Bulk capacitance	540 µF
Buck output	7.01 V
Power rail	5 V (LM1117-5.0)
Reference rail	3.3 V (LM1117-3.3)
Vref	1.65 V (ratiometric)
Typical / peak load	72 mA / 366 mA

Signal conditioning

Parameter	Current channel	Voltage channel
Sensing	0.5 Ω shunt	270k / 15k divider (k = 0.05263)
Amplifier gain	3.3 V/V	1.2195 V/V
Overall gain	1.65 V/A	0.0641 V/V
Active filter fc	16.08 kHz	15.92 kHz
Output RC fc	15.92 kHz	15.92 kHz
Combined −3 dB	~10.25 kHz	~10.25 kHz
Phase at 500 Hz	−3.58°	−3.60°
Worst-case output range	0.29–3.01 V	0.26–3.04 V
ADC window	0.25–3.05 V	0.25–3.05 V

Detection

Parameter	Value
Zero-crossing hysteresis	106 mV
Rising / falling threshold	1.688 V / 1.582 V
Peak current method	√2 × I_rms (firmware)
MCU clock	16 MHz ÷ 8 = 2 MHz