Reading Dave's tweet "HELP: I'm looking for a quality ... 600mm or 1200mm LED panel ceiling lights ... 5000K-5500K and high CRI ... lots of crap out there",
https://twitter.com/eevblog/status/1230984296065716224 , I thought I would post a work-hobby project of mine.
I has been undergoing various spurts of attention for the past 20 months.
In the various offices (cubicles) I have worked in, I have been very dissatisfied with the environmental controls. Too hot, too cold, too bright, too dark, etc. A big goldilocks problem.
Over the past few years, I have reached out to various HVAC and lighting companies about the solution. My research has shown that solution are divided into 2 broad categories 1) the one off solution aka, home automation, 2) the 10,000 SQFT+ office solution. In the first set of solutions, they offer no price breaks, energy efficiency, or freedom to tinker/avoid dial home apps. In the second set of solutions, price is "not an objective", SCADA controls are proprietary and individual comfort is not a concern. Lighting follows in the same pattern.
Here are some of the project' requirements/goals:
- low unit cost @ QTY1 retail; linear price increase with SQFT
- One unit per seat
- Each seat can set HVAC temperature
- Each seat can set lighting (on/off)
- operation costs <= existing HVAC & Lighting (combined or seperate) annually
- Total installation and operation pricing ~< existing HVAC & Lighting (combined or seperate) solutions over first 2 years
- 208 - 240 mains
- addressable via IPv4/IPv6
- Each seat can set lighting temperature
- Each seat can set lighting RGB
- Two lights per seat
- Very low standby power consumption (commercial electric billing)
- Very low waste power consumption in use (commercial electric billing)
- Support IEEE 802.3
- Support IEEE 802.11
- Support IEEE 802.15
- Support Occupancy sensor and relays
- Support LEED (U.S. Green Building Council) goals. Efficiency in more than just electricity...
- Support time of day lighting
Current project status:
- Dampers: Supply chain established. Prototypes tested. The HVAC damper control unit cost is 10$ @ 100 units. The damper controller is a servo with zero standby power usage and 12VDC motor voltage. Parts are currently machined, leaving an area for further cost reductions.
- CPU: Supply chain established. Prototypes tested. The CPU board is "based" on the Raspberry PI 4. It is a 12VDC supply, I/O breakout, including I2C and SPI, 802.3, 802.11, and 802.15. 25$ @ 1 unit, difficulty in negotiating price reductions for larger QTY.
- Lights' frames: Supply chain in negotiations, Prototypes tested. are 24"x24" or 600mmx600mm drop ceiling style. Aluminium frame, pcb bonded with thermal epoxy (2 parallel sides), polycarbonate diffuser, plastic / mylar white reflector, sheet steel backing - screwed to aluminium frame. Prototype unit cost 12$ @ QTY 2.
- Lights' LEDs: Temporary supply chain: digikey - QTY 100. currently selecting LED bar layout (PCB physical dimensions design vs power/heat vs light output usefulness). Two competing designs [RGB] [W3k] [W5k] vs [RGB] [W3k] [W5k] [W3k] [W5k] ; max 120 LEDs / PCB, 2 PCBs / light - prototype cost between 10$ and 90$ per light fixture based on LED models selected
- Power supply: status = paper napkin sketches; Goals 1) modular (socketed) digitally controllable CC supply rails - allowing for different LED panel max voltage, max current; 2) high efficiency 12V rail supporting CPU (no brownout on accessory draw) and accessories; 3) I2C or similar control
- Chassis: supply: status = paper napkin sketches; Goals 1) fit in standard 2 gang grounded metal box; 2) have a high mains side isolated from a stackable 2 gang low voltage side.
Block diagram:

Thoughts?