Can I join two switched circuits into one circuit?


I really strongly do not go this route with 120 v 30 amp circuit the code is pretty spefic on this one

espcally true with HID's { belive me I done this all the time with large commercal / Industrail complexs }

you will end up using more wires and circuits for genral lighting circuit at 120 v than what you can do on 240 volt circuits.

I will give you a example how I dealt with this and been sucessfull with alot of my customers

If this building do have service doors on both end all you need just one circuit that wired for 3 way's that circuit you can used with flourscent luminaire something like over workbench or in few spots where you can able turn them on pretty fast instead of waiting quite few minutes for the HIDs to warm up { you know how long to get them back on when someone say opps hit wrong switch }

For the HID's just a standard double pole toggle switch will do the task or otherwise you can use the breaker as switch due most breaker...

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Circuit switching is a method of implementing a telecommunications network in which two network nodes establish a dedicated communications channel (circuit) through the network before the nodes may communicate. The circuit guarantees the full bandwidth of the channel and remains connected for the duration of the communication session. The circuit functions as if the nodes were physically connected as with an electrical circuit.

The defining example of a circuit-switched network is the early analog telephone network. When a call is made from one telephone to another, switches within the telephone exchanges create a continuous wire circuit between the two telephones, for as long as the call lasts.

Circuit switching contrasts with packet switching, which divides the data to be transmitted into packets transmitted through the network independently. In packet switching, instead of being dedicated to one communication session at a time, network links are shared by packets...

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I am new to logic design and circuity. I saw two diagrams from a learning resource that are circuits will supposed operate an LED light as shown below:

Diagram A:

Diagram B:

Based upon these two diagrams I am trying to understand the logic level for each must be to turn on the LED light, and which switch must be closed to turn on the light.

From my understanding, a HIGH logic level corresponds to a binary 1 meaning on, and a LOW logic level corresponds to a binary 0 meaning off. I thought that diagram A's logic level to turn on the light would be 1 since I thought the circuit is in 0 position currently; that the diagram A's S1 switch must be turned on to turn on the light; that the diagram B's logic level to turn on the light would be 0 since I thought the circuit is in 1 position currently; that the diagram B's S1 switch must be turned on to turn on the light.

After much research, I am still not understanding the logic levels these two diagrams...

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Combinational Logic Circuit vs. Sequential Logic Circuit

Logic Circuits can be divided into two types:

Combinational Logic Circuit Sequential Logic Circuit

In this article we will discuss Combinational Logic Circuit vs. Sequential Logic Circuit.

Combinational Logic Circuits

Combinational Logic circuit contains logic gates where its output is determined by the combination of the current inputs, regardless of the output or the prior combination of inputs. Basically, combinational circuit can be depicted by diagram-1 below:

In a combinational logic circuit, the value of the outputs depends only on the current values of the inputs. The circuit has no memory or feedback loops, and the output does not depend on the history of the inputs.

Examples of Combinational circuits are adder, Subtractor, encoder, decoder, parallel adder, multiplexer and de-multiplexer.

Combinational Logic Circuits are made up from basic logic gates such...

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Yes, forgot to mention about voltage drop - but that's quite obvious.
One solution for that may be to place a "big" cap in parallel with your circuit.

Yet there will always be some different between the voltage sources, so there will always be a little change in voltage when switching between them.

A transistor may also provide a little "jump" in the voltage when switching, only it happens faster though. I guess it's better having a cap over the circuit any way, and using another cap between the transistors emitter/base in order to get it conducting gradualy and smooth.
Problem you might face here is that it will also turn off smooth, and then you will have a short lived situation where both the power supply and the battery is conected in parallel - just what you want to avoid.
You might think out a relatively simple solution for that, a diode/cap/resistor coupling to get it slow on, but fast off.

You could also put a drossel in series between the...

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If you’ve ever thought, “I wish I had another switch for this bunch of lights,” then you’re not alone. You can actually achieve that functionality by converting a single-switched circuit to a 3-way switched circuit without too much work. 3-way switches allow you to control a circuit from two different locations, and they’re commonly used for lighting to conveniently turn the lights on and off from two different places.

How 3-Way Switches Work

3-way switches are named for the fact that each switch has three hot terminals- two traveler terminals and one common terminal. The traveler terminals are used to interconnect two 3-way switches on the same circuit, and the common terminal supplies (or dumps) power. Rather than off and on, the switch toggles power between the two traveler terminals.

Pro-Tip: The common terminal is always a different color than the other two hot terminals.

Converting a Single-Switch Circuit to a 3-Way Switched Circuit


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Please select from the list below or the links on the right.

How to use
Electrical Switches

The most common switching circuits are:

Use a switch to turn On and Off one light bulb

Use two switches to turn On and Off one light bulb

Use three or more switches to turn On and Off one light bulb

Use one switch to alternate Off On two light bulbs

The following diagrams show how switches are used for the above four switching circuits.

Using SPDT or 3-way switches

of a light bulb circuit that can be controlled via two switches.

Using DPDT Switches

Control One Light Bulb With Three Switches

If you are want to control one light bulb with 3 or more switches, you will need two SPDT switches and some DPDT switches in between.

In the DPDT above when the connection are straight (Z-X and Y-W) or crossed (Z-W and Y-X). In some DPDT switches you will need to make...

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22 August 2011 09:49 PM


Posts: 110
Joined: 21 December 2008

In domestic installations there are often two different circuits in a two gang lightswitch. Not ideal, but very common. Not against the regs ?

What about, a larger installation with two circuits, from two different distribution boards, into the same switch. I feel very uncomfortable about this. Is this against the regs?

22 August 2011 09:56 PM


Posts: 22456
Joined: 23 March 2004

Nope - In some systems you could even have different supply sources - essential and non essential lighting in healthcare for example.

If you can't figure out if it's live then you shouldn't be fiddling about with it is a fairly broad but sensible approach.

Personally, I'm not a big fan of the idea but it's not "against" the...

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It isn't unusual to wire two or more light and switch combinations from the same power source -- in fact, it's common practice. Typically, the source is a circuit breaker in the main electrical panel that has a rating large enough to handle the lights. It's possible to mount the switches in the same or in different electrical boxes, but the latter case involves the extra task of running a circuit cable between the boxes. You maintain the continuity of the hot wire in the circuit cable by forming pigtails at the points where it connects to the switches.

Install appropriate electrical boxes for the lights and switches. You can mount the switches side-by-side in a double-gang electrical box or in different locations, each in a single-gang box. For each fixture and switch you have the choice of nailing a rough-in box to a stud or rafter or mounting a remodeling box on the drywall.

Run 12-gauge electrical cable between each switch and the light it controls. Pull one end of...

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Confusion abounds over the use of tandem circuit breakers in panelboards, even among electricians and electrical inspectors. Today I'll set the record straight as to when tandem circuit breakers can be used. This is an adaptation of an article I wrote for the ASHI Reporter, which was published in February of 2011.

First, a quick definition. A tandem circuit breaker is a double circuit breaker that takes up the space of a single circuit breaker on a panelboard. You'll also hear them called duplex, slimline, twin, half-height, half-inch, double and wafer breakers, depending on local customs. While a two-pole circuit breaker gets connected to two different poles at a panelboard and has a common trip or a handle tie for simultaneous disconnecting of two poles, a tandem breaker does not.

The photo below shows a 60 amp two-pole circuit breaker at the top, then a 15 amp tandem circuit breaker (highlighted), then a 20 amp tandem circuit breaker (highlighted), then a 20 amp...

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TRhere is no problem running two circuits to the same junction box provided there is enough space in the box and you do not combine neutrals from one circuit with neutrals from the other circuit there.

If the light did not come on when you hooked up the black and white wires in the small group (one cable?) are you sure it is a different circuit as opposed to a cable going down to the switch and nowhere else?

When you figure out that one cable goes down to the switch only then you connect the black wire of that cable to the light fixture black, the other wire of that cable to the live power wire (red or black), and the white of the fixture to the neutral (white) that accompanies the live power wire.
Four inch round (octagonal) metal boxes 2 inches deep are usually too small for handling...

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When there are two or more electrical devices present in a circuit with an energy source, there are a couple of basic means by which to connect them. They can be connected in series or connected in parallel. Suppose that there are three light bulbs connected together in the same circuit. If connected in series, then they are connected in such a way that an individual charge would pass through each one of the light bulbs in consecutive fashion. When in series, charge passes through every light bulb. If connected in parallel, a single charge passing through the external circuit would only pass through one of the light bulbs. The light bulbs are placed within a separate branch line, and a charge traversing the external circuit will pass through only one of the branches during its path back to the low potential terminal. The means by which the resistors are connected will have a major effect upon the overall resistance of the circuit, the total current in the circuit, and the current...

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