question on relay circuit......

[shaku]

Hi,

I am looking for relay (relay circuit) which can operate on wide voltage range. I need to design relay circuit which can switch between two voltage ranges.
I have one voltage range between 20-40 V and other is 100-280 V.
I need to switch relay between this two range. For example, if my input voltage is 35, it trips to path "A". And on the other side, if my input is 250, it trips to path "B".

How can I design this kind of circuit? I am still learning electronics as I am a student of 2nd-year university.
This is a part of my project.

Thank you,
sjs

 

[HMS1021]

Without a top level schematic it is impossible to give you an answer.
Are the voltages AC or DC?
Are you switching 10ma or 10kA or something in between?
Is there a need to isolate the two voltages to different outputs?
Can both input voltages be present at the same time?
What if the voltage is outside of the range, say 75V, does it select either input?

A successful design must start with clear requirements.....

 

[tpetar]

You can measure both voltages and on specific voltage level circuit switch relay. Relay coil can be on lower voltage (5V, 12V, 24V). Also control circuit can work on lower voltage 3,3V-5V.

Additional to this load controls and switching can be done using triacs, but triacs offers dissadvantages and advantages compared to standard relay device.


Best regards,
Peter

 

[shaku]

Without a top level schematic it is impossible to give you an answer.
Are the voltages AC or DC?
Are you switching 10ma or 10kA or something in between?
Is there a need to isolate the two voltages to different outputs?
Can both input voltages be present at the same time?
What if the voltage is outside of the range, say 75V, does it select either input?

A successful design must start with clear requirements.....

Hi HMS,
I totally agreed with you.
I am not sure about all specifications but I can give you few of them. 20-40V is DC and 100-280V is AC. Yes isolation is required for two outputs. Any one voltage be present at a time. If voltage is outside then output should goes to zero.
I apologize for my incomplete post.

Thank you,
sjs

 

[Venkadesh_M]

in ac mode your input is 100 to 280 v. are you will step down and rectify the output for some purpose.. (example in televison this both inputs will be there. the DC voltage can be directly fed into rectified output of AC no schematic and nothing more required any one supply will available at a time.)...

 

[shaku]

in ac mode your input is 100 to 280 v. are you will step down and rectify the output for some purpose.. (example in televison this both inputs will be there. the DC voltage can be directly fed into rectified output of AC no schematic and nothing more required any one supply will available at a time.)...

Hi Venkadeshm,
I could not understand your post. Could you please explain in different way?
Thank you,
sjs

 

[Venkadesh_M]

you are having this two power supplies for what purpose.?

 

[shaku]

I need to only build this circuit. That is my task.

 

[shaku]

help please

 

[Venkadesh_M]

then this is what you wanted to do... after this just you need that cntrl circuit......

 

[shaku]

Hi Venkadeshm,
I thought the same way but problem is "control circuit". What logic should I create to decide AC vs DC? Any idea? I am thinking really hard on it but nothing came up yet.

 

[HMS1021]

The logic circuit could be a window comparator driving a MOSFET used the switch the current thru the relay's coil.
A window comparator is made with 2 comparators, op amps can be used, and resistors. As an example for the 20 - 40V a resistor would come from the 20-40V to a 10v Zener to ground. In parallel with the Zener are 3 resistors making a divider. The divider R values can make any voltages from 0 to 10V, I choose 2v and 4v. These two points are the reference for the comparators. Now I use 3 more resistors to make another divider from the 20-40v input to ground. I chose the divider resistors so that at 20v input the divider tap is 2v at 20v and at 40v the tap is at 4v. These are connected as inputs to the window comparator. The output of the window comparator is high only when the input voltage is between 20-40v. The comparator output is connected to the gate of a N CH MOSFET, the source is ground, when the gate is high the MOSFET is on (low Rds) and current flows through the relay coil connected between its drain and the 20-40v input.
When the input is between 20-40v the relay is closed and the input is switched to the output. It is powered from the input without a separate power supply.

The 100-280vac can use most of the same circuit except the ac must be rectified and the R values are larger.

So, you need to review window comparators, MOSFET switches, and calculate the resistor dividers.

 

[Venkadesh_M]

Hi Venkadeshm,
I thought the same way but problem is "control circuit". What logic should I create to decide AC vs DC? Any idea? I am thinking really hard on it but nothing came up yet.

Its not that much complicate.. its very easy... Let me give you some ideas...........



This is full scheme you wanted to do but both supplies should not come at a time.........

 

[shaku]

Thanks a lot HMS1021!!
I will defiantly read about that and try to come up with circuit. If possible, could you draw roughly circuit diagram??
really appreciated your inputs.


- - - Updated - - -

Thanks Venkadeshm. I will study your suggested circuit.
I will get back with you soon!!

 

[HMS1021]

View attachment 93436

Its not that much complicate.. its very easy... Let me give you some ideas...........

View attachment 93436

This is full scheme you wanted to do but both supplies should not come at a time.........

Hello Venkadeshm,

I have 3 questions:
1. Why have the relays? The output is on when there is an input almost the same as a wire except there is a minimum.
2. Will the 20-40v circuit's relay turn on at 20v and turn off at >40v? What about the 100-280?
3. What prevents both circuits from being on at the same time?

 

[tpetar]

On both diagrams there is no control circuit.


Best regards,
Peter

 

[Venkadesh_M]

Hello Venkadeshm,

I have 3 questions:
1. Why have the relays? The output is on when there is an input almost the same as a wire except there is a minimum.
2. Will the 20-40v circuit's relay turn on at 20v and turn off at >40v? What about the 100-280?
3. What prevents both circuits from being on at the same time?

sorry for mis understanding i left the high voltage cuttoff things

Use this before both relays and put a extra relay directly parallel to DC and run the AC through normaly connected for protection(I took that both voltages will never appear on same time)........

- - - Updated - - -

Connect the Vcc and input and give the rectified voltage to that point...

 

[shaku]

Hi venkadeshm,
I looked at your diagram and have a question on it.
My aim was for single input (AC or DC) but in your diagram there are two inputs. Separate AC and DC. (I think this is what HMS1021 indicated in his first question.)

In your last post, you have mentioned that " i left the high voltage cuttoff things Use this before both relays and put a extra relay directly parallel to DC and run the AC through normaly connected for protection(I took that both voltages will never appear on same time)........"

Did you attache anything? I am not able to open it. Can you re-post it?

Thank you,

- - - Updated - - -

You can measure both voltages and on specific voltage level circuit switch relay. Relay coil can be on lower voltage (5V, 12V, 24V). Also control circuit can work on lower voltage 3,3V-5V.

Additional to this load controls and switching can be done using triacs, but triacs offers dissadvantages and advantages compared to standard relay device.


Best regards,
Peter

Can you explain in detail? or give rough circuit diagram?thank you

 

[HMS1021]

A good link for Solid State Relays (SSR) is found here. https://en.wikipedia.org/wiki/Solid-state_relay
It is only a couple of pages and worth a read. Especially the section on Advantages and Disadvantages.

Whether a SSR or a standard contact relay is used the solution is nearly the same. You need to sense the input voltage and depending on the voltage either drive the correct relay coil or pass current through the opto device in the SSR. There are many ways to sense the voltage such as ADC's, or window comparators.

If you use a ADC you will need some "smarts" after the ADC to decode its digital output
To reduce part count I would probably use a cheap ADC and a CPLD, window comparator is also a good solution

From the last post we now know there is a single input that can range from 20-40VDC to 100-280VAC. One last question: does the control circuit need to be power by this input or is there a another power supply for the control circuit?

I'm assuming the following:
1.) there are two wires coming in: Ground and [20-40VDC to 100-280VAC]
2.) there are three wires on the output: Ground, 20-40VDC, and 100-280VAC
3.) the input and output ground are common (i.e. connected together)
4.) there are no additional connections or power supplies

Are these assumptions correct?

 

[Venkadesh_M]

Hi venkadeshm,
I looked at your diagram and have a question on it.
My aim was for single input (AC or DC) but in your diagram there are two inputs. Separate AC and DC. (I think this is what HMS1021 indicated in his first question.)

In your last post, you have mentioned that " i left the high voltage cuttoff things Use this before both relays and put a extra relay directly parallel to DC and run the AC through normaly connected for protection(I took that both voltages will never appear on same time)........"

Did you attache anything? I am not able to open it. Can you re-post it?

Thank you,

- - - Updated - - -



Can you explain in detail? or give rough circuit diagram?thank you

Hi Shaku,
Now you are saying there is only two input and output lines look at #10 I already asked for it, give clear explanation ..
I think you in need of a black box which automatically detects the input and gives the output right??