Friday Teardown: Novitas Super Switch 2 (Motion Activated [PIR] Occupancy Lighting Switch)

These wall and ceiling mounted occupancy sensors have been installed all over California, and many installations remain in use.

Pictured Above: A Novitas Inc product box showing logo and slogan.

Today on friday teardown we take a look at a Novitas Incorprated Super Switch 2.

About Novitas

Novitas Incorporated was a business located in Torrance, California that produced occupancy sensors, switch packs and other lighting devices aimed at both residential and business applications. Occupancy sensors in particular allowed businesses to meet stringent California Title 24 Energy Efficiency Standards. These wall and ceiling mounted occupancy sensors have been installed all over California, and many installations remain in use.

Occupancy sensors such as this one detected movement in a room and automatically turned the lights off if a room was left unoccupied. Novitas produced occupancy sensors that used Passive Infra-Red (such as this one) and others thats used ultrasonic sensors.

Novitas Inc was acquired by Cooper Industries in November 2005 to bolster Cooper Industries' commercial occupancy sensor line up. Cooper Industries was itself later acquired by Eaton in November 2012.

Where I Got The Switch

My father worked for Novitas for over 17 years, and was laid off when the company was sold. Since the company was being relocated to Cooper Industries' headquarters in another state, employees were allowed to take various things home as Novitas Torrance headquarters was being shuttered. My father brought home some furniture from his workspace, an oscilloscope that was being tossed out, and box of 5-6 Novitas Super Switch 2.

As he worked in the Testing/RMA department (to the best of my knowledge), I'm not sure what the state of these switches are. Whether these are defective units, or spares left behind in the closing of the Torrance Headquarters, I'm not sure. My father passed away in 2010 (love you, dad), so unfortunately I cannot get some definite answers.

These switches sat outside in our shed for 8 years, before eventually being moved to my personal belongings in my room where they sat for another 6 years.

Novitas Super Switch 2

I didn't have the manual for this particular switch model, but Eaton thankfully has a PDF copy on their website. Thank you Eaton for supporting legacy products!

The Novitas Super Switch 2 is designed to detect motion in a 300 sq ft room (10x15ft size office). A coverage diagram shows the switch has a field of view of around 180 degrees horizontal. The manual states you should avoid placing the switch in a location that gives the switch a view outside the room (like a hallway). Otherwise inadvertent activation of the switch may occur. If this can't be avoided, the packaging includes some stickers to reduce the field of view of the motion sensor.

Above: Coverage diagram from Super Switch 2's manual.

It can work with many load types and voltages. At 120 Volts, it can handle a 800 Watt incandescent or fluorescent load. At 277 volts, it only works with fluorescent loads, but increased 1200 watts. In both cases there are no minimum load requirements (meaning you can use this switch with a 5 watt load if you so pleased).

The switch has configurable options, using 8 dip switches under the switch's main button plate:

Above: Removing the button press plate reveals DIP switches that control switch functionality. A sticker notes that switching DIP switch 8 to on allows the switch to function in the event of failure.

Above: Button press plate. A sticker details how to operate DIP switches.

Opening The Switch

Four philips head screws hold the front of the switch in place. Removing them frees the metal mounting plate used to mount the switch to a junction box and the plastic front of the switch. This immediately reveals the PCB:

Above: once the four screws holding the front on are removed, the PCB is free to be removed from the switch housing.

I have marked the major features of the board above:

PIC16F627 Microcontroller. This is a Microchip manufactured PIC microcontroller. Has an operational voltage of 3-5.5 volts, program memory size of 1.75 kilobytes, and CPU speed of 5 Million Instructions Per Second (MIPS). This microcontroller runs the show, taking the motion sensor output and using that information to control the lights on a timer.

Throughhole Pushbutton Switch. A common pushbutton switch style found in many electronic devices. In this application, it is the button the user presses to manually turn on/off the switch.

8 Position DIP Switch. Allows the user to configure the available options of the switch, including time delay shutoff, manual mode, energy saving mode and switch failure override.

Red LED. Lights up when motion is detected.

Heimann LHI 968 PIR Sensor. According to its datasheet, the LHI 968 positions itself as a high-end pyroelectric detector for intrusion alarm systems. Pyroelectric refers to electrical devices that detect changes in temperature. This is useful for PIR (Passive Infra-Red) Sensors that use IR light given off by body heat for detection. So this is the main sensor that does the occupancy detection and turns the lights on and off accordingly.

MCP607 Opamp. Another Microchip manufactured chip. Takes the signal from the LHI 968 and amplifies it to levels usable by the PIC microcontroller.

Pulling the entire board out, we find that the board is actually double stacked PCB. A row of 5 pin headers run between the top and bottom boards, connecting them together.

Above: The switch consists of two boards, stacked together. (Labeled in blue) A row of 5 pin headers sends power and relay control signals between the boards.

On the second board, we find the main power components:

Wire Termination. Mains and Load wires are terminated at the top of the bottom PCB. Wires are fed through the PCB and out of the switch housing. As this switch needs to be powered at all times, this switch is not compatible with older building wiring where only the "HOT" wire is available in the switch junction box. Neutral wire is required.

Omron G6CU Miniature Relay. This switches the main lighting load on and off. The coil side (turns the relay on and off) is driven off 3 Volts DC. The load side is capable of 10 amps at 100-250 Volts AC or 10 amps at 30 Volts DC. Another thing to note is that above this relay is an unpopulated space for a second relay. Certain versions of the Super Switch 2 came with the ability to switch two lighting loads, necessitating two relays, one for each load.

Full Bridge Silicon Rectifier. Manufactured by Rectron Semiconductor. This converts the AC coming in from the wall to DC for use by the electronics on the top board.

Voltage Step Down?

A question I still haven't figured out is how the switch steps down the ~120 Volts AC to the 3.3v/5v required by the microcontroller components and sensor. Several small ICs and a dozen or so transistors are found on both boards. Unfortunately with the exception of one transistor (which is used by the microcontroller to drive the relay) none have any markings that turned up successful searches.

My best guess is a capacitive dropper circuit drops the voltage from ~120/270 Volts AC to around the working DC voltage required by the microcontroller/sensor, around 6-12 volts. From there a Linear Regular (unmarked ICs) or multiple Linear Regulators convert the capacitive dropper output to 3.3v/5v.

Supporting this theory is the fact that there are no Inductors (meaning no switching power supply) and no Transformer (meaning no stepping 120VAC to 5VAC then using a full bridge rectifier/capacitors to get 5VDC). Capacitive dropper circuits are cheap and more importantly, extremely compact. In a switch already jam packed with electronics, the more complex your power circuit, the more space you need, the more money spent trying to get everything to fit.

Closing Thoughts

I've always been fascinated by this switch and this company. Many times when my father came home from working at Novitas, he would bring components like LEDs, or he would bring home some random electronic circuit he built for me to play and learn from. This part of my childhood help fostered my curiosity and my love of electronics. In a way, I feel this switch was waiting for me to get old enough to tear it apart and study it. A culmination of a childhood of learning in a way.

In a follow up post, I hope to power this thing up for the first time in 14 years, and see if it still works. Additionally, I have an idea to convert this switch to run off DC power and run DC loads. Finally, I want to figure out how the switch failure overrride works. Whether the failure override requires the microcontroller to still be functioning or whether it is able to bypass the microcontroller completely.

Until next time.

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