Showing posts with label low. Show all posts
Showing posts with label low. Show all posts
Friday, May 3, 2013
Low Voltage High Current Time Delay Circuit diagram
In this circuit a LM339 quad voltage comparator is used to generate a time delay and control a high current output at low voltage. Approximatey 5 amps of current can be obtained using a couple fresh alkaline D batteries. Three of the comparators are wired in parallel to drive a medium power PNP transistor (2N2905 or similar) which in turn drives a high current NPN transistor (TIP35 or similar
The 4th comparator is used to generate a time delay after the normally closed switch is opened. Two resistors (36K and 62K) are used as a voltage divider which applies about two-thirds of the battery voltage to the (+) comparator input, or about 2 volts. The delay time after the switch is opened will be around one time constant using a 50uF capacitor and 100K variable resistor, or about (50u * 100K) = 5 seconds. The time can be reduced by adjusting the resistor to a lower value or using a smaller capacitor. Longer times can be obtained with a larger resistor or capacitor. To operate the circuit on higher voltages, the 10 ohm resistor should be increased proportionally, (4.5 volts = 15 ohms).
Sunday, April 21, 2013
stream powers low cost Macro Lens
For all photography and video enthusiasts, a macro lens is quite simply a basic necessity. A macro lens is incredibly helpful to produce detailed pictures of tiny objects or options. despite the fact that nearly each photographer or video recorder wants one among these, theyre quite expensive and hence not everybody will afford it.
Nevertheless, theres the simplest way to create yourself a macro lens. Everything may be achieved by using any lens, 2 plastic bottles, super glue, and duct tape. A photography or video device to that the lens has got to be connected is additionally needed.
1st of all, the neck of a bottle is cut employing a hot knife. Another piece of plastic thats the same as the form of the bottle’s neck is cut out from a special bottle. This plastic section is placed at the lowest. This forms the bottom on that the lens can ought to be placed.
The lens are held near the bottle neck using super glue. once holes are created at applicable positions at each ends of the device, its currently able to be connected to any camera. It may be connected permanently using super glue, or quickly with some duct tape.
The lens device are placed directly over the quality lens, permitting the camera to require a definite photograph of tiny options using the first programming.
Monday, April 8, 2013
High And Low Voltage Cut Off Circuit
This is a design for protection voltage. This circuit is called as high and low voltage cut off. The circuit is using time delay for cut off the voltage. This is a low cost and reliable circuit for protecting such equipments from damages. This is the figure of the circuit.
Whenever the power line is switched on it gets connected to the appliance only after a delay of a fixed time. If there is hi/low fluctuations beyond sets limits the appliance get disconnected. The system tries to connect the power back after the specific time delay, the delay being counted from the time of disconnection. If the power down time (time for which the voltage is beyond limits) is less than the delay time, the power resumes after the delay: If it is equal or more, then the power resumes directly. This circuit is using op-amp 741 and 555 IC for control the operation.
The complete circuit is consisting of various stages. They are: - Dual rail power supply, Reference voltage source, Voltage comparators for hi/low cut offs, Time delay stage and Relay driver stage. Under normal operating conditions i.e. when the input voltage is between maximum and minimum limit the output from the both the comparators are low. The transistor Q1 is OFF and the relay is in de-energized (pole connected to N/C pin) state and the output is obtained. When the input voltage is below or above the limits set by the pre-sets R8 or R9, the output of the Op-Amps goes either low or high and diodes D1 or D2 would be forward biased depending on the situation. Transistor Q1 switches ON and the flow of current from collector to emitter energizes the relay and the output is cutoff.
Whenever the power line is switched on it gets connected to the appliance only after a delay of a fixed time. If there is hi/low fluctuations beyond sets limits the appliance get disconnected. The system tries to connect the power back after the specific time delay, the delay being counted from the time of disconnection. If the power down time (time for which the voltage is beyond limits) is less than the delay time, the power resumes after the delay: If it is equal or more, then the power resumes directly. This circuit is using op-amp 741 and 555 IC for control the operation.
The complete circuit is consisting of various stages. They are: - Dual rail power supply, Reference voltage source, Voltage comparators for hi/low cut offs, Time delay stage and Relay driver stage. Under normal operating conditions i.e. when the input voltage is between maximum and minimum limit the output from the both the comparators are low. The transistor Q1 is OFF and the relay is in de-energized (pole connected to N/C pin) state and the output is obtained. When the input voltage is below or above the limits set by the pre-sets R8 or R9, the output of the Op-Amps goes either low or high and diodes D1 or D2 would be forward biased depending on the situation. Transistor Q1 switches ON and the flow of current from collector to emitter energizes the relay and the output is cutoff.
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