Showing posts with label switch. Show all posts
Showing posts with label switch. Show all posts
switch mode power supply circuits
switch mode power supply circuits
MOC 3010/3020) If a broadcast is unavoidable, use one with a mains voltage braid and about-face the braid application the optical isolator.C1 should be of the suppressor type; fabricated to be affiliated anon beyond the admission Mains Supply. They are about covered with the logos of several altered Safety Standards Authorities. If you charge added current, use a beyond amount capacitor; or put two in parallel; but be accurate of what you are accomplishing to the Watts. The low voltage AC is supplied by ZD1 and ZD2.
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Transformerless Power Supply CircuitIf you are not accomplished in ambidextrous with it, again leave this activity alone.Although Mains accessories can itself absorb a lot of current, the circuits we body to ascendancy it, usually alone crave a few milliamps. Yet the low voltage ability accumulation is frequently the better allotment of the...
If you are not accomplished in ambidextrous with it, again leave this activity alone.Although Mains accessories can itself absorb a lot of current, the circuits we body to ascendancy it, usually alone crave a few milliamps. Yet the low voltage ability accumulation is frequently the better allotment of the architecture and a abundant allocation of the cost.
This ambit will accumulation up to about 20ma at 12 volts. It uses capacitive reactance instead of resistance; and it doesnt accomplish actual abundant heat.The ambit draws about 30ma AC. Always use a agglutinate and/or a aqueous resistor to be on the safe side. The ethics accustomed are alone a guide. There should be added than abundant ability accessible for timers, ablaze operated switches, temperature controllers etc, provided that you use an optical isolator as your circuits achievement device.
MOC 3010/3020) If a broadcast is unavoidable, use one with a mains voltage braid and about-face the braid application the optical isolator.C1 should be of the suppressor type; fabricated to be affiliated anon beyond the admission Mains Supply. They are about covered with the logos of several altered Safety Standards Authorities. If you charge added current, use a beyond amount capacitor; or put two in parallel; but be accurate of what you are accomplishing to the Watts. The low voltage AC is supplied by ZD1 and ZD2.
The arch rectifier can be any of the baby Round, In-line, or DIL types; or you could use four abstracted diodes. If you appetite to, you can adapt R2 and ZD3 with a 78 Series regulator. The abounding sized ones will work; but if amplitude is tight, there are some baby 100ma versions accessible in TO 92 blazon cases. They attending like a BC 547. It is additionally account acquainted that abounding baby circuits will assignment with an able supply. You can, of course, adapt any or all of the Zenner diodes in adjustment to aftermath a altered achievement voltage. As for the mains voltage, the advancement apropos the 110v adaptation is aloof that, a suggestion. I havent congenital it, so be able to agreement a little.
Video Switch for Intercom System
Nowadays a lot of intercom units are equipped with video cameras so that you can see as well as hear who is at the door. Unfortunately, the camera lens is perfectly placed to serve as a sort of support point for people during the conversation, with the result that there’s hardly anything left see in the video imagery. One way to solve this problem is to install two cameras on the street side instead only one, preferably some distance apart. If you display the imagery from the two cameras alternately, then at least half of the time you will be able to see what is happening in front of the door. Thanks to the video switch module described here, which should be installed on the street side not too far away from the two cameras, you need only one monitor inside the house and you don’t need to install any additional video cables.
Video Switch for Intercom System Circuit diagram:
Along with a video switch, the circuit includes a video amplifier that has been used with good results in many other Elektor projects, which allows the brightness and the contrast to be adjusted separately. This amplifier is included because the distance between the street and the house may be rather large, so it is helpful to be able to compensate for cable attenuation in this manner. The switch stage is built around the well known 4060 IC, in which switches IC2a and IC2d alternately pass one of the two signals to the output. They are driven by switches IC2b and IC2c, which generate control signals that are 180 degrees out of phase. The switching rate for the video signals is determined by a clock signal from an ‘old standby’ 555 IC, which causes the signals to swap every 2 seconds with the speciļ¬ed com ponent values.
Naturally, this circuit can also used in many other situations, such as where two cameras are needed for surveillance but only one video cable is available.
Author :Jacob Gestman Geradts - Copyright : Elektor
Source : http://www.ecircuitslab.com/2012/02/video-switch-for-intercom-system.html
Solid State Switch For Dc Operated Gadgets
This solid state DC switch can be assembled using just three transistors and some passive components. It can be used to switch on one gadget while switching off the second gadget with momentary operation of switch. To reverse the operation, you just have to momentarily depress another switch.
The circuit operates over 6V-15V DC supply voltage. It uses positive feedback from transistor T2 to transistor T1 to keep this transistor pair in latched state (on/ off), while the state of the third transistor stage is the complement of transistor T2’s conduction state.
Initially when switch S3 is closed, both transistors T1 and T2 are off, as no forward bias is available to these, while the base of transistor T3 is effectively grounded via resistors R8 and R6 (shunted by the load of the first gadget). As a result, transistor T3 is forward biased and gadget 2 gets the supply. This is indicated by glowing of LED2.
Circuit diagram :
Solid-State Switch For Dc-Operated Gadgets Circuit Diagram
When switch S1 is momentarily depressed, T1 gets the base drive and it grounds the base of transistor T2 via resistor R4. Hence transistor T2 (pnp) also conducts. The positive voltage available at the collector of transistor T2 is fed back to the base of transistor T1 via resistor R3. Hence a latch is formed and transistor T2 (as also transistor T1) continues to conduct, which activates gadget 1 and LED1 glows.
Conduction of transistor T2 causes its collector to be pulled towards positive rail. Since the collector of T2 is connected to the base of pnp transistor T3, it causes transistor T3 to cut off, switching off the supply to gadget 2) as well as extinguishing LED2. This status is maintained until switch S2 is momentarily pressed. Depression of switch S2 effectively grounds the base of transistor T1, which cuts off and thus virtually opens the base-emitter circuit of transistor T2 and thus cutting it off. This is the same condition as was obtained initially. This condition can be reversed by momentarily pressing switch S1 as explained earlier.
EFY lab note. During testing, it was noticed that for proper operation of the circuit, gadget 1 must draw a current of more than 100 mA (i.e. the resistance of gadget 1 must be less than 220 ohms) to sustain the latched ‘on’ state. But this stipulation is not applicable for gadget 2. A maximum current of 275 mA could be drawn by any gadget.
Author : Praveen Shanker - Copyright : EFY
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