What is it?

Main control DIYUPS3 PCB for a 3-channel DC UPS system. It provides simultaneous control for three DC outputs (e.g. Mini PC, router, switch). The system manages each DC output (ON/OFF) based on user-defined battery voltage thresholds (vH/vL); voltageHIGH/LOW and time delays (tB/tS); timeBOOT/SHDWN to ensure a proper boot and shutdown sequence. Monitoring and configuration are handled via a Serial port (USB) or through a Node-RED dashboard.

Note: Additional DC-DC modules (available via eBay/AliExpress) are required for full functionality! See below.

Why did you make it?

For Home Automation, Home Lab, and similar setups, my goal is to keep the entire internet infrastructure running on battery in case of a power outage. I used commercial UPS systems, but aside from their large physical size, I was always bothered by the pile of different AC/DC adapters plugged in. Also, I wanted independent control of each individual output—both based on battery charge state and the ability to maintain power for proper boot/shutdown sequences.

Shutdown & Boot Sequence Example

Power Loss Scenario (Battery Discharge):

When AC power fails, devices shut down in priority order to maximize network uptime:

• First: NAS shuts down immediately (prevents data corruption); battery voltage < vL3
• Second: PC (Proxmox/Home Assistant) shuts down when battery voltage drops further; battery voltage < vL2
• Last: Network infrastructure (router/AP/switch) stays online as long as possible; battery voltage < vL1

This ensures critical connectivity remains available longest while protecting storage devices.

Power Restoration Sequence (Battery Charge):

When AC power returns, devices boot in reverse priority order to maintain battery reserve capacity:

• Battery charges to first voltage threshold → Network infrastructure turns ON (router/AP/switch); battery voltage > vH1
• Battery charges to second voltage threshold → PC turns ON (Proxmox/Home Assistant); battery voltage > vH2
• Battery fully charged → NAS turns ON; battery voltage > vH3

This approach guarantees the battery system always maintains reserve capacity to execute proper shutdown procedures if power fails again during the boot sequence.

What makes it special?

• User-defined ON/OFF voltage thresholds for each DC output (device)
• User-defined boot and shutdown delay timers for each DC output (DC is locked in ON state during this time)
• Monitoring and control via serial port(USB)
• Graphical dashboard via Node-RED
• Command execution based on system state via Node-RED
• Battery charging via independent pre-assembled module
• Pre-made DC-DC buck-boost converter modules; eBay, AliExpress
• Standard notebook AC/DC power supply as DC input (19-20V)
• Standard UPS lead-acid battery (12V, 7-9Ah)
• Fanless operation (silent, passive cooling)
• Compact dimensions matching Dell Optiplex Micro footprint (182mm wide)
• 3D-printed PCB and other holders (step files)
• All other small parts accessible from eBay/AliExpress (screws, threaded inserts, connectors, etc.)

What you get

• DIYUPS3 Main PCB (fully assembled and tested)
• Auto Mini Blade fuses (input, battery, and output protection; 5pcs)
• Optional: Pre-assembled battery charger module (SDLA12TA) with user-selectable charging current

Documentation, Pictures, and Others

See Documentation link for details, commands, modifications, 3D step files, Node-RED flow, ...