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Twilight Controllers

          AS2000DR            AS20002              TC-5                     AS2K1


AUTOSWITCHER is a twilight controller. Any twilight controller has a photosensitive device which senses the change in ambient light level (ALL) in Lux. At sunset, when ALL is low, it gives a command to switch on the lights and after sunrise to switch off.

AUTOSWITCHER, though basically a twilight controller has many more interesting and useful features to make it unique in several ways.

It has time delay facility to switch on and off the load. When ALL is low, it does not switch on the lights instantly but takes 3 to 7 minutes to do so. The same delay is provided for switching off, too. This helps in avoiding erratic working of switching at the time off temporary darkness in cloudy weather, lightening or flashes of lights etc..
It is observed that at some places/streets, traffic is negligible after midnight ( or, for advertisements, neon displays are not required after midnight). For such requirements, we have type 200x series in which provision is made to automatically switch off one phase or two phases after a desired time (normally 3 to 7 hours typically). This will save precious electricity everyday. In some versions, MCBs of rated capacity are provided for each phase independently.
All models come with independent photo sensor assembly in a weather-proof, dust protected ABS moulding which is to be installed outside to sense ALL. It is electrically isolated from the mains with absolutely no shock hazards.


ADVANTAGES ( For detailed analysis of exact savings,   please click here)


Once the ALL setting is done( normally it is factory-set for 6 to 10 Lux), it will regularly switch on and off the lights exactly as desired ,not a few Lux more or less. Hence, once installed, no recalibration is needed for its entire life.

It is not worried about the time of day for its operation but exclusively the ALL, twilight level. Nor does it have any moving part. Hence, practically, it is maintenance free in operation.

It does not need any battery to count the delay time. Lapsed time is counted and stored in electrostatic devices which are non-volatile in nature for a few hours. Even if supply fails, off-delay counting will start from where it has stopped and not from zero.


On and Off times are to be set for control. Due to seasonal changes, sunrise and sunset times are changed. Setting is to be carried out regularly to track these changes.

Electromechanical clock is required which is a continuously moving part. Being so, it may run slow or fast resulting in erratic switching. Maintenance is required.

In electronic times, off delay facility is provided with the help of built-in battery. Without the battery, timer is reset to zero every time mains fails. Maintenance of battery is another problem.







This is the compact control module to replace electromechanical time-switch or microporocessor controlled one.  It has function switch, TWILIGHT SET control and 3 LEDs to indicate the operation. It has built-in time delay of 5 min for switching on and off the load.  Its output is potential-free contact of 5A/250VAC (2A/415VAC). Hence, contactor with coil voltage of 230VAC or 415VAC can be driven by this module.


Mains Input                                                : 230VAC/50 Hz

Output                                                       : Potential free contacts, 5A/230VAC or 2A/415VAC

Switching Device                                        : Mini Relay

Control Action                                            : Dusk to Dawn

Switching Delay                                         : 5 Min (Typ) for both on and off action

Dimensions                                               : 95x95x50 (mm)

Weight                                                      : 300 gms

CONTROLS (Operator Accessible):

FUNCTION switch                                      : 3-way mini slide switch with f positions marked AUTO (for automatic operation), OFF (manual off) and ON (manual ON).

TWILIGHT set control                                  : Adjustable with screw driver to precisely set the twilight level at which to switch on and off the load. It is factory set for 16 Lux level which is best suited for street lights control.


MAINS: Red LED to indicate mains is connected to the unit. When FUNCTION switch is in OFF position, this will be off.

TWILIGHT: Green LED to indicate that the desired darkness has set in. Count down of 5 Min will start and load will be on after this delay. Similarly, in the morning this LED will be off when desired light level is reached and load will be off after the delay.

LOAD: Red LED to indicate connected load is on.



It is the best and fool-proof design in higher current range, best suited for the control of street lights in big cities.  It has two independently controlled power relays, "Normal" capable of switching two phases simultaneously and "Aux" capable of switching third phase.  Two phases will be on throughout the night and third phase will be automatically shut off after desired time, if needed. An independent MCB of rated capacity is provided inside the box for each phase. Thus only the affected phase will be shut off in the event of overload or short circuit in a particular phase keeping supply to other phase undisturbed. It works on single phase for its operation. This unit is useful when a certain phase is to be switched off after say, midnight, keeping only two phases on thereby saving the electricity.


Mains for operation: 230V/50Hz

Load:  3 Phase

Switching Devices: Power Relays, 2 Nos., 30A 

Control Action: At dusk, both relays are on. "Aux" relay will be off after the set time delay adjustable between 3 hours and full night. One phase will be off after this set time while two other phases connected to "Normal" will be on throughout the night.

Control Delay: 5 Min for both on and off action.


1. FUNCTION: This is a 3-way switch marked 'AUTO', Manual 'ON' and Manual 'OFF'

2. OFF DELAY SET: A potentiometer to adjust the off-delay of "Aux" phase any where between 3 hours to full night.

3. SET TWILIGHT: Accessible on the side panel. Lux level at which the unit should operate is adjusted. Default level 10 Lux.


Four LEDs to indicate MAINS ON, TWILIGHT, NML LD and AUX LD.

Three neon indicators to show the status of 3 phases.

AS2K1 (twilight controller with a difference)


1.Twilight controller, AUTOSWITCHER AS2K1 is a single unit used to control two independent circuits, one for dusk to dawn operation and the other for dusk to midnight hours adjustable as desired. 

2.The unit works in wide mains fluctuations from 160V to 400V, AC, single phase. 

3. Extra Safety Feature is provided built-in to safeguard the entire unit as well as connected load form dangerously high voltages upto 400VAC on normal mains line of 230V.  The unit withstands this dangerous voltage for indefinite time while it immediately disconnects the connected load.  Load is reconnected when supply resumes in the normal range. Load can be set to disconnect at any voltage level from 250 to 300 VAC.  By default, it is kept at 270V

4.The unit comes complete with the sensor supplied with 5 meter length of wire to make connection to the main unit. Sensor is electrically isolated from the mains  supply; hence, there is absolutely no chance of shock hazards.
5.Two outputs are called NML OUTPUT and AUX OUTPUT meaning respectively
dusk-to-dawn output and midnight hours output. 

6. Both the outputs are  available in potential-free contacts in pairs; 2 pairs of NO contacts are  available for both the outputs by means of two independent relays with the  current capacity of 5A / 230VAC.

7. Individual fuses for outputs as well as for main unit.
8.Delay time of 5 min (typical) is provided for both ON and OFF actions of the
relays to avoid false triggering during momentary lightening or sudden flash of lights, 
9.Counting of the time for midnight operation is done by electronic storage devices and they are designed to have memory even without mains power.
10.No batteries are required for the storage of elapsed time data. During night, if mains supply fails for some time, it will not reset to zero but stores the time elapsed. When mains supply resumes, it will start from the moment it had reached when supply failed. This is the beauty of this unique circuitry that it totally eliminates the use of battery for retention of memory.

11. Twilight zone can be set between 0 to 40 Lux.







AUTOSWITCHER AS2001A, works on the principle of detecting the  ambient light level (ALL) by means of light sensor and giving the command to control  the potential free contacts to operate accordingly. The twilight zone at which this should happen is adjustable and accessible to the operator to set anywhere between 0 and 40 Lux by means of a simple preset. Once set as per desired level, there  is no necessity of adjusting it in its life time as the seasonal changes in Sunset  and Sunrise are automatically taken care of by the sensor. This is the biggest advantage  of the product over any real-time switch where, with the changes in these timings, it needs recalibration during different seasons. It is not the time of the day that is sensed by AUTOSWITCHER but it is actual ALL that is sensed. Secondly, no batteries are needed as the storage of the time elapsed is done by electronic circuitry only.

The unit uses a single light-sensor housed in weather-proof moulding with the long-horn
design such that no direct light is possible to fall on it.

The unit has two independent outputs, NML and AUX, for dusk to dawn and midnight hours operations. Two pairs of potential free contacts for both the outputs are provided as an added security; in the event a pair of contact breaks down for any reason, stand-by pair is available for use.

The unit has following controls accessible by the operator.

1. SET-TWILIGHT: On-board control accessible from the outside to adjust the desired
Lux level for twilight zone, right from 0 to 40 Lux. Once, set as per your needs, it should
never be disturbed during its entire life time.

2. ON-OFF-AUTO: Three way switch to have the load manually ON or OFF and AUTOmatically
operated. Manual ON and OFF positions are provided for routine maintenance of  connected load.

3.OFF-DELAY SET: Not to be confused with on/off delay of 5 min provided built-in by the circuitry. This is the time to be set for midnight hours of operation on AUX output. This can be set from a few minutes to overnight. If the control is kept at fully anticlockwise position, it will switch off the load in a few minutes after dusk. If it is kept fully clockwise,  the lights connected to AUX terminals will be on throughout the night as in the case of NML output. The range of this time is, by default, kept between 3 hours and 10 hours.

The unit has the following indications.

1. MAINS ON: By LED to indicate the unit is connected to mains and supply is available.

2. TWILIGHT: By LED to indicate that set lux level of twilight zone has reached. This indication is useful to adjust the desired twilight level by means of SET-TWILIGHT control. When this LED turns on it also indicates that both the relays (NML and AUX) will be on within 5 min. 
In the morning, when this LED turns off, it indicates that the NML contacts will be off after 5 min (AUX contacts must have been off in the midnight itself as per OFF-DELAY-SET)

3. NML LD: This LED indicates the state of load connected to NML output.

4. AUX LD: This LED indicates the state of load connected to AUX output. At dusk, both the LEDs, NML LD and AUX LD will be on simultaneously. AUX LD will be off at midnight hours as per setting done by operator.


Normally a battery is required to have the memory of elapsed time. In our circuit, this  has been done electronically by sample and hold circuitry. This circuit hold the data even if mains supply fails for hours in the night. During daytime, the data is positively cleared to have fresh timing cycles to start at dusk. The circuit needs  the data only for a night as it is going to be refreshed every day. The designed sample--and-hold  circuitry has the capacity to hold the data for well over 20 hours and hence no need of battery.


Do you want your existing lighting fixture to operate automatically without any external control gear? This is the most economical way to do it.  Just insert this all-weather proof metallic controller inside any lighting fixture and it will have automatic on/off control at dusk and dawn! With just three wires!

Fully Automatic.
Ecological It Saves Electricity.
Absolutely Maintenance Free.
No Batteries Required.
No Moving Parts.
Extremely Economical Pays for itself in less than 1 year.
Entire Assembly can be directly mounted in open air.
Fully weather proof.
Automatically tracks local Sunset and
Sunrise times as per the seasonal changes.
Complete Unconditional Warranty
Can be fitted in the housing of any lighting fixture for automatic control.
Salient Features:
Rugged, water-proof, weather-resistant, metallic housing (Copper body, chrome plated) for directly mounting in open air.
Operates on 230V/50 Hz and controls any mains operated load upto 500W
Only three wires for connection. Black (Neutral), Red (Live In) and Grey (Live Out)
Sensor is integrated to the metallic housing and made weather-resistant.


General Information:

The TC-5 is an exceptional twilight control device. It comes complete with a smart photosensitive unit that acutely senses the changes in the Ambient Light Level (ALL). At sunset the TC-5 photosensitive unit automatically detects the low ALL and sends a command to activate your desired lighting. The same holds true at sunrise when the TC-5 detects the rise in ALL and commands the appropriate lighting to be switched off.

The TC-5 does not stop there!

The TC-5 comes with a uniquely developed time delay facility for switching the load on and off. In this respect the TC-5 is capable of thinking for itself, while it passes the savings on to you. For example, when the ALL becomes suddenly low, the TC-5 does not instantly activate the lights, but instead waits for 3-7 minutes before issuing the command.

This unique time delay feature also works when there are sporadic increases in ALL..

This cost-saving attribute prohibits the lights from being turned on unnecessarily in instances of temporary darkness, such as cloudy or stormy weather, or being turned off by lightning of haphazard flashes of flight.




TEL:+91-9823116655      E-mail : info@sadhana.co.in


Sadhana Energy Devices, 2016