Circuit Boards and Sensor/Initiator Circuitry > Light Level Rising > Light Sensitive IED



Product Code: ITA-110

Price: $225.00

Circuit Boards and Sensor/Initiator Circuitry Item Description:

In ITA-110, the sensor (photocell, photodiode, or photoresistor) which is exposed to light, sends an electronic impulse to the associated circuitry on the attached circuit board. The circuitry senses that the light level impacting the sensor is ABOVE a preset exposure threshold and the circuit triggers on. There is a miniature relay or other type of electronic “gate” which then functions and triggers the attached detonator. In the case of a relay, the contacts close, sending power from a second battery dedicated to the detonator, through the detonator legwires.
In this model, the detonator shell contains a light-emitting diode which glows through a hole near the end when power flows from the relay. There is also a pisco whistle wired in parallel to the detonator, and it will produce a high pitched sound when the relay contacts close.
Along of the edge of the left side of the circuit board are three sets of words which describe the various operating sectors of the board. These are:

  1. sensor level
  2. output timer
  3. output trigger

The sensor level sector is where the photocell is plugged into the terminal block, and it has a sensitivity control beside that block. The control is a small square plastic block with a slotted screwhead in the center. We have set this at the factory for sensor input threshold, so that it will or will not send an electronic signal to the rest of the circuit at a particular level or above or below it. There is also a light emitting diode (LED) associated with the sensor. When the sensitivity of the sensor is adjusted so that it will detect the current light level in the room (or outdoors) the LED will glow. If you hold your hand over the sensor, it will stop glowing.
The output timer processes the signal from the sensor, and determines an operating time in seconds. Once it sends a signal to the relay to close its open contacts, the timer will control for how long the relay contacts will remain closed.
The output trigger consists of another sensitivity adjustment (potentiometer or variable resistor which is a small square with a screw adjustment set at the factory), a capacitor and the electro-mechanical relay.
During the period that the output timer is active, the relay contacts will close and remain closed. The 9 volt battery marked on the diagram as 9V. #1 provides power through the relay contacts to the detonator LED and the Whistle. It also runs power through the LED on the circuit board, located beside the words “Output Trigger”. This LED will glow as long as the relay contacts remain closed. It will shut off when the contacts open. The circuit returns to standby after the time period is complete.
To operate this training aid, the two toggle switches should be set to SAFE and to OFF, respectively. A fresh 9 volt battery should be inserted into each U-shaped spring clip on the board, and the terminal clips should be correctly connected. The switch marked POWER is for circuit board power. It operates everything on the circuit board. The switch marked DETONATOR controls power from battery no.1 through the relay contacts to the detonator LED and the whistle It should be set to SAFE.
This is an arming switch that prevents power from prematurely going through the relay contacts while you are setting the device up to demonstrate it. In a bomb, it would also prevent the bomber from killing himself while setting up or transporting the bomb.
Cover the light sensor (photocell near the front of the board) with your hand, or turn the overhead lights down to a very low level if possible. Alternatively, turn the lights off and control room lighting either with the light switch or with blinds, shades or curtains.
Turn the power switch to the ON position. You should see the LEDs on the circuit board flicker or glow, indicating power is going through, but this partly depends on the light level.
Set the other toggle switch (SAFE-ARM) to ARM.
Take your hand off the light sensor, or turn on the lights, or open the window blinds as necessary, to introduce strong light to the sensor surface.
If the light level is sufficient, the sensor will immediately transfer its impulse to the circuitry, triggering the relay.
The whistle will sound and the detonator on the inert simulated explosive charge will indicate continuity through it when its internal LED glows.
After 10 – 15 seconds the circuit will reset to standby and will require that you cover the sensor with your hand, turn down the lights, or close the blinds or curtains to limit light to it. Again when the light level that is required returns to the surface of the sensor, the relay will trigger.

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