- #1
Automatic electrical switch to between two paths
- Thread starter radaballer
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- Automatic Electrical Switch
In summary, the conversation discusses the need for a switch that can alternate the flow of electrical current between two wires at a specific rate. It is suggested that a relay or two MOSFET or transistor switches could fulfill this function. However, more information is needed, such as the type of loads being switched, the control circuit, the frequency and duty cycle of the switch, and whether an OFF position is needed. It is also mentioned that a square wave oscillator and non-overlapping waveforms may be necessary for smooth switching. The use of PMOS power MOSFETs is suggested, as well as low side switching for easier interface with logic.
- #2
davenn
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you could use a relay connected to a square wave oscillator would probably be the easiest
could be done with transistor switching as well using the same square wave oscillator
could be done with transistor switching as well using the same square wave oscillator
- #3
meBigGuy
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The function you need is a single pole double throw switch. As dave said, that could be a relay, or it could be two MOSFET or transistor switches.
But, you need to provide more info if you want help:
What sorts of loads are you switching (voltage and current).
What sort of control circuit are you using to produce the "decided rate" .
What is the frequency range and duty cycle of the decided rate?
How accurate does the duty cycle need to be?
Does there also need to be an OFF position?
Does there need to be a guaranteed off time when switching (time between loads being powered)?
Can there be overlap when switching load? Or is guaranteed non overlap required?
Does the circuit really need to operate upside down :)
We will probably think of a few more things that need to be decided as we continue.
But, you need to provide more info if you want help:
What sorts of loads are you switching (voltage and current).
What sort of control circuit are you using to produce the "decided rate" .
What is the frequency range and duty cycle of the decided rate?
How accurate does the duty cycle need to be?
Does there also need to be an OFF position?
Does there need to be a guaranteed off time when switching (time between loads being powered)?
Can there be overlap when switching load? Or is guaranteed non overlap required?
Does the circuit really need to operate upside down :)
We will probably think of a few more things that need to be decided as we continue.
- #4
sophiecentaur
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Yes. A bit of (quantitative) context would help. In engineering, it's the numbers that count,
- #5
anorlunda
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The word demultiplexer also comes to mind.
- #6
sophiecentaur
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Perhaps . . . . from kW to mW.anorlunda said:
- #7
radaballer
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meBigGuy said:
What I know:
The power source is a 12 v car battery, so the amplitude is unknown until I can test it , it needs to oscillate every .006 seconds (167 hz)so the switch needs accuracy to the thousandth of a second , duty cycle .5, duty cycle Should be as accurate as possible, there should be no time between the current changing directions, guaranteed non overlap is required, thanks for the help
- #8
berkeman
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radaballer said:
That's too fast for a mechanical relay, so you need to use pass transistors. Can you say more about the application? What is the load current? Are the two load currents equal? What is the nature of the load -- is it inductive?
- #9
radaballer
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The load current is 1.25 amps on both sides, the load is purely resistiveberkeman said:
- #10
berkeman
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So you need to use 2 power transistors (probably power Darlingtons based on the current), with the base drive circuits based off of a square wave oscillator at your frequency. You will want to tune the drive circuits to make the current switchover smooth, with little glitching of the total current out of the battery. Are you comfortable taking it from here?
- #11
meBigGuy
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I'd recommend PMOS power mosfets. Lower voltage drop, but driving power MOSFET gate capacitance can be tricky. The non overlap part can be tricky in either case (BJT or PMOSFET)
Look at circuits on google (2 phase clock generator) to create non-overlapping waveforms.
On the other hand, It would be a lot easier to use low side switching. then you can interface logic directly to NMOS or NPN transistors (Connect both loads to +12 and ground one or the other to turn it on).
http://reibot.org/2011/09/06/a-beginners-guide-to-the-mosfet/ show PMOS and NMOS switches.
Look at circuits on google (2 phase clock generator) to create non-overlapping waveforms.
On the other hand, It would be a lot easier to use low side switching. then you can interface logic directly to NMOS or NPN transistors (Connect both loads to +12 and ground one or the other to turn it on).
http://reibot.org/2011/09/06/a-beginners-guide-to-the-mosfet/ show PMOS and NMOS switches.
- #12
radaballer
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yes thank youberkeman said:So you need to use 2 power transistors (probably power Darlingtons based on the current), with the base drive circuits based off of a square wave oscillator at your frequency. You will want to tune the drive circuits to make the current switchover smooth, with little glitching of the total current out of the battery. Are you comfortable taking it from here?
FAQ: Automatic electrical switch to between two paths
What is an automatic electrical switch?
An automatic electrical switch is a device that is used to control the flow of electricity between two paths. It can be manually or automatically operated, and is commonly used in electrical circuits to turn on or off power to a specific circuit or device.
How does an automatic electrical switch work?
An automatic electrical switch typically consists of a switch mechanism that is connected to an actuator, which is responsible for triggering the switch to open or close. The actuator can be controlled by a variety of methods, such as timers, sensors, or manual inputs. When triggered, the switch will change the flow of electricity from one path to another.
What are the benefits of using an automatic electrical switch?
One of the main benefits of using an automatic electrical switch is convenience. It eliminates the need for manually flipping switches and can be programmed to turn on or off at specific times or in response to certain conditions. This can save time and energy for the user. Additionally, it can help prevent electrical accidents by automatically cutting off power in case of a malfunction or overload.
What are the different types of automatic electrical switches?
There are several types of automatic electrical switches, including time switches, motion sensors, occupancy sensors, and light sensors. Time switches are programmed to turn on or off at specific times, while motion and occupancy sensors detect movements and turn on lights or devices accordingly. Light sensors detect changes in light levels and can trigger switches to turn on or off based on the amount of light present.
Are there any safety considerations when using an automatic electrical switch?
Yes, it is important to follow safety precautions when installing and using an automatic electrical switch. Make sure to turn off the power supply before installing or making any changes to the switch. Also, ensure that the switch is properly rated for the amount of electricity it will be controlling. It is also important to regularly check and maintain the switch to ensure it is functioning properly and prevent any potential hazards.