# HEM27EC Dither Box ## Description Battery-powered minimal ST-4 dither timer for iOptron HEM27EC: two AAA cells, ATtiny1616 controller, opto-isolated RA+/RA-/DEC+/DEC- contact closures, physical interval/intensity selectors, DITHER NOW button, and low-power status LED. The previous ESP32-S3 USB-host design is preserved only as a conditional V2 archive. ## Project Details - **Owner:** pereguerra - **Created:** 7/21/2026 - **Last Updated:** 7/21/2026 - **Visibility:** Public - **Implementation Details:** V1 baseline is a two-AAA ATtiny1616 ST-4 dither timer with opto-isolated contact closures; archived V2 USB-host design retained in project files. - **Human Interface:** Buttons - **Power Requirements:** Battery - **Domain:** Astronomy - **Connectivity:** ST-4 - **Software:** ESP-IDF ## Key Components ### BT1 — [Battery Holder SMD 2 Cells AAA](https://www.flux.ai/jharwinbarrozo/battery-holder-smd-2-cells-aaa~q7.md) - Role: Energy Storage - Manufacturer Name: MYOUNG - Manufacturer Part Number: BH-AAA-B5AA001 - Part Type: Connector - Role Details: Two AAA cells in series; no charger, no boost; expected VCC about 1.8V to 3.2V after reverse-protection MOSFET - Datasheet URL: https://datasheet.lcsc.com/lcsc/2012311835_MYOUNG-BH-AAA-B5AA001_C964881.pdf **Pins:** - 1neg - 1pos - 2neg - 2pos ### D1 — [150060RS73220](https://www.flux.ai/vasy_skral/150060rs73220~kj9.md) - Datasheet URL: https://www.we-online.com/components/products/datasheet/150060RS73220.pdf - License: https://creativecommons.org/licenses/by/4.0/ - Manufacturer Name: Würth Elektronik - Role Details: Low-duty-cycle red status LED for heartbeat, dither-active, and low-battery/fault patterns - Role: Status Indication - Manufacturer Part Number: 150060RS73220 - Part Type: LED **Pins:** - A [pin 2] - K [pin 1] ### J1 — [5555165-1](https://www.flux.ai/adrian95/5555165-1~umv.md) - Role: Connector - Manufacturer Part Number: 5555165-1 - Part Type: Connector - Datasheet URL: https://www.verical.com/datasheet/te-connectivity-telephone-and-telecomm-5555165-1-128425.pdf - License: https://creativecommons.org/licenses/by/4.0/ - Manufacturer Name: TE Connectivity AMP Connectors - Role Details: 6P6C/RJ12 ST-4 connector; official HEM27 Figure 3 pinout: 1 NC, 2 common, 3 RA+, 4 DEC+, 5 DEC-, 6 RA- **Pins:** - 1 [pin 1] - 2 [pin 2] - 3 [pin 3] - 4 [pin 4] - 5 [pin 5] - 6 [pin 6] ### J2 — [Pin Header 01x03 2.54mm Vertical](https://www.flux.ai/adrian95/pin-header-01x03-254mm-vertical~cp4.md) - Role Details: 3-pin UPDI programming header: Pin 1 VCC, Pin 2 GND, Pin 3 UPDI - License: https://creativecommons.org/licenses/by/4.0/ - Role: Debug - Part Type: Connector **Pins:** - Pin_1 [pin 1] - Pin_2 [pin 2] - Pin_3 [pin 3] ### Q1 — [DMG2305UX-7](https://www.flux.ai/jwace81/dmg2305ux-7~06.md) - Role: Reverse Polarity Protection - Manufacturer Name: Diodes Incorporated - Role Details: P-channel MOSFET ideal-diode style battery reverse-polarity protection with minimal drop at low V1 current - Datasheet URL: https://www.diodes.com/assets/Datasheets/DMG2305UX.pdf - Manufacturer Part Number: DMG2305UX-7 **Pins:** - ~ [pin 3] - ~ [pin 1] - ~ [pin 2] ### S1 — [1TS028B-1600-0450-CT](https://www.flux.ai/lcsc/1ts028b-1600-0450-ct~chn6.md) - Datasheet URL: https://storage.googleapis.com/graviton-electric-symbols/document_assets/lcsc/2001131709_HYP--Hongyuan-Precision-1TS028B-1600-0450-CT_C482008.pdf - Role Details: DITHER NOW active-low momentary button; immediate dither and interval timer restart - Manufacturer Part Number: 1TS028B-1600-0450-CT - Product Info Url: https://lcsc.com/product-detail/New-Arrivals_HYP-Hongyuan-Precision-1TS028B-1600-0600-CT_C482008.html - Manufacturer Name: HYP(鸿源精密) - Part Type: Tactile Switches - LCSC Part Number: C482008 - Package or Case Code: SW-SMD_4P-L2.8-W1.9-P1.20-LS3.0_1TS028B - Role: Switching - JLCPCB Part Class: Extended Part **Pins:** - 1 [pin 1] - 2 [pin 2] - 3 [pin 3] - 4 [pin 4] ### SW1 — [DS04-254-2-01BK-SMT](https://www.flux.ai/jecstronic/ds04-254-2-01bk-smt~t2.md) - Datasheet URL: https://www.cuidevices.com/product/resource/ds04-254-smt.pdf - Role Details: Simple SPST ON/OFF power switch, DS04-254-2-01BK-SMT; one unambiguous ON and OFF state - Role: Switching - Manufacturer Part Number: DS04-254-2-01BK-SMT - License: https://creativecommons.org/licenses/by/4.0/ - Part Type: Switch - Manufacturer Name: CUI Devices **Pins:** - ~ [pin 1B] - ~ [pin 1A] ### SW2 — [OS103011MA7QP1](https://www.flux.ai/adrian95/os103011ma7qp1~4fe.md) - Role: Switching - Manufacturer Name: C&K - License: https://creativecommons.org/licenses/by/4.0/ - Part Type: Switch - Manufacturer Part Number: OS103011MA7QP1 - Role Details: DITHER INTENSITY selector: SOFT / NORMAL / STRONG via active-low MCU inputs and internal pull-ups - Datasheet URL: https://www.ckswitches.com/media/1428/os.pdf **Pins:** - COM [pin 2] - MH1 [pin MH1] - MH2 [pin MH2] - NC_1 [pin 3] - NC_2 [pin 4] - NO [pin 1] ### SW3 — [OS103011MA7QP1](https://www.flux.ai/adrian95/os103011ma7qp1~4fe.md) - Role: Switching - Datasheet URL: https://www.ckswitches.com/media/1428/os.pdf - Part Type: Switch - Manufacturer Part Number: OS103011MA7QP1 - License: https://creativecommons.org/licenses/by/4.0/ - Role Details: INTERVAL selector: 60s / 120s / 300s via active-low MCU inputs and internal pull-ups - Manufacturer Name: C&K **Pins:** - COM [pin 2] - MH1 [pin MH1] - MH2 [pin MH2] - NC_1 [pin 3] - NC_2 [pin 4] - NO [pin 1] ### U1 — [ATTINY1616-SFR](https://www.flux.ai/lcsc/attiny1616-sfr~d0yd.md) - Manufacturer Name: MICROCHIP(美国微芯) - Role Details: ATtiny1616 low-power timer/controller; direct two-AAA operation, watchdog, RTC/PIT wake, internal VCC/battery measurement, UPDI programming - Part Type: MICROCHIP - Role: MCU - JLCPCB Part Class: Extended Part - LCSC Part Number: C145558 - Datasheet URL: https://storage.googleapis.com/graviton-electric-symbols/document_assets/lcsc/2304140030_Microchip-Tech-ATTINY1616-SFR_C145558.pdf - Product Info Url: https://lcsc.com/product-detail/MICROCHIP_MICROCHIP_ATTINY1616-SFR_ATTINY1616-SFR_C145558.html - Manufacturer Part Number: ATTINY1616-SFR - Package or Case Code: SOIC-20_L13.0-W7.6-P1.27-LS10.3-BL **Pins:** - GND [pin 20] - PA0/~{RESET}/UPDI [pin 16] - PA1 [pin 17] - PA2 [pin 18] - PA3/EXTCLK [pin 19] - PA4 [pin 2] - PA5 [pin 3] - PA6 [pin 4] - PA7 [pin 5] - PB0 [pin 11] - PB1 [pin 10] - PB4 [pin 7] - PB5 [pin 6] - PC0 [pin 12] - PC1 [pin 13] - PC2 [pin 14] - PC3 [pin 15] - TOSC1/PB2 [pin 9] - TOSC1/PB3 [pin 8] - VDD [pin 1] ### U2 — [TLP171A(TP,F](https://www.flux.ai/lcsc/tlp171atpcf~u57v.md) - Manufacturer Part Number: TLP171A(TP,F) - Package or Case Code: SOP-4_L3.9-W4.4-P2.54-LS7.0-BR - Role Details: RA+ TLP171A normally-open PhotoMOS relay; pin 1 LED anode, pin 2 LED cathode, pins 3/4 bidirectional isolated output - Datasheet URL: https://toshiba.semicon-storage.com/info/TLP171A_datasheet_en_20250819.pdf?did=13862&prodName=TLP171A - JLCPCB Part Class: Extended Part - Part Type: Solid State Relays - MOS Output (PhotoMOS) - Role: Isolation - Manufacturer Name: TOSHIBA(东芝) - LCSC Part Number: C2153054 **Pins:** - 1 [pin 1] - 2 [pin 2] - 3 [pin 4] - 4 [pin 4] ### U3 — [TLP171A(TP,F](https://www.flux.ai/lcsc/tlp171atpcf~u57v.md) - Manufacturer Part Number: TLP171A(TP,F) - Package or Case Code: SOP-4_L3.9-W4.4-P2.54-LS7.0-BR - Role Details: RA- TLP171A normally-open PhotoMOS relay; pin 1 LED anode, pin 2 LED cathode, pins 3/4 bidirectional isolated output - Role: Isolation - JLCPCB Part Class: Extended Part - Datasheet URL: https://toshiba.semicon-storage.com/info/TLP171A_datasheet_en_20250819.pdf?did=13862&prodName=TLP171A - LCSC Part Number: C2153054 - Part Type: Solid State Relays - MOS Output (PhotoMOS) - Manufacturer Name: TOSHIBA(东芝) **Pins:** - 1 [pin 1] - 2 [pin 2] - 3 [pin 4] - 4 [pin 4] ### U4 — [TLP171A(TP,F](https://www.flux.ai/lcsc/tlp171atpcf~u57v.md) - Manufacturer Part Number: TLP171A(TP,F) - Package or Case Code: SOP-4_L3.9-W4.4-P2.54-LS7.0-BR - Datasheet URL: https://toshiba.semicon-storage.com/info/TLP171A_datasheet_en_20250819.pdf?did=13862&prodName=TLP171A - Role: Isolation - JLCPCB Part Class: Extended Part - Role Details: DEC+ TLP171A normally-open PhotoMOS relay; pin 1 LED anode, pin 2 LED cathode, pins 3/4 bidirectional isolated output - Part Type: Solid State Relays - MOS Output (PhotoMOS) - Manufacturer Name: TOSHIBA(东芝) - LCSC Part Number: C2153054 **Pins:** - 1 [pin 1] - 2 [pin 2] - 3 [pin 4] - 4 [pin 4] ### U5 — [TLP171A(TP,F](https://www.flux.ai/lcsc/tlp171atpcf~u57v.md) - LCSC Part Number: C2153054 - Datasheet URL: https://toshiba.semicon-storage.com/info/TLP171A_datasheet_en_20250819.pdf?did=13862&prodName=TLP171A - Manufacturer Name: TOSHIBA(东芝) - Part Type: Solid State Relays - MOS Output (PhotoMOS) - Role: Isolation - JLCPCB Part Class: Extended Part - Role Details: DEC- TLP171A normally-open PhotoMOS relay; pin 1 LED anode, pin 2 LED cathode, pins 3/4 bidirectional isolated output - Package or Case Code: SOP-4_L3.9-W4.4-P2.54-LS7.0-BR - Manufacturer Part Number: TLP171A(TP,F) **Pins:** - 1 [pin 1] - 2 [pin 2] - 3 [pin 4] - 4 [pin 4] *The full schematic, PCB layout, bill of materials, and interactive design are available at [https://www.flux.ai/pereguerra/hem27ec-dither-box~gh](https://www.flux.ai/pereguerra/hem27ec-dither-box~gh).* --- *Generated from [https://www.flux.ai/pereguerra/hem27ec-dither-box~gh](https://www.flux.ai/pereguerra/hem27ec-dither-box~gh)*