Voltage activated relay

  • Thread starter Gabriel Vanderdonck
  • Start date
G

Gabriel Vanderdonck

Guest
Hi Everyone !

This is my very first message in a Google group (well, not only in a
"Google" group). I am a newbie, so, please, be gentle with me.

Here is my problem.

I want to be able to switch between a main and a backup 230Vac supply
with a relay.

My main supply comes from an inverter (110Vdc / 230Vac) that ramps up
the voltage when switched on (from 0 to 230 in about 1,5 seconds). The
result thereof is that I do not have a clean switch between backup and
main supply when the main supply returns and sometimes devices powered

To correct that, I would like to add a small piece of electronics to
switch the relay voltage on when it reaches a certain level. My relay
switches on at about 150~160Vac.

I does not have to withstand a huge quantity of power as :
- it's only a relay. It should not need much more than 1 W.
- this switching only occurs once a year or so.
- I intend to use a contact of the relay as self-holding contact : as
soon as the relay switches on, the electronics is shorted by the
contact of the relay.

I was thinking of something based on a triac. Can somebody help me ?

I hope I have been clear. English is not my mother language. "Mes
excuses".

Best regards,

Gabriel
 
"Gabriel Vanderdonck" <gabriel.vanderdonck@steel-sa.com> wrote in message
news:6efb48ee.0503220111.7ef4dc67@posting.google.com...
Hi Everyone !

This is my very first message in a Google group (well, not only in a
"Google" group). I am a newbie, so, please, be gentle with me.

Here is my problem.

I want to be able to switch between a main and a backup 230Vac supply
with a relay.

My main supply comes from an inverter (110Vdc / 230Vac) that ramps up
the voltage when switched on (from 0 to 230 in about 1,5 seconds). The
result thereof is that I do not have a clean switch between backup and
main supply when the main supply returns and sometimes devices powered

To correct that, I would like to add a small piece of electronics to
switch the relay voltage on when it reaches a certain level. My relay
switches on at about 150~160Vac.

I does not have to withstand a huge quantity of power as :
- it's only a relay. It should not need much more than 1 W.
- this switching only occurs once a year or so.
- I intend to use a contact of the relay as self-holding contact : as
soon as the relay switches on, the electronics is shorted by the
contact of the relay.

I was thinking of something based on a triac. Can somebody help me ?

I hope I have been clear. English is not my mother language. "Mes
excuses".

Best regards,

Gabriel
Click to expand...
You want something like these:
http://catalog.rselectronics.com/cardonet/transactive?action=EXPAND&internal_id=22874
A relay with 'Adjustable Pick-Up & Drop Out Voltage Sensor'

Cheers.

Ken
 
Gabriel Vanderdonck wrote:
Hi Everyone !

This is my very first message in a Google group (well, not only in a
"Google" group). I am a newbie, so, please, be gentle with me.

Here is my problem.

I want to be able to switch between a main and a backup 230Vac supply
with a relay.

My main supply comes from an inverter (110Vdc / 230Vac) that ramps up
the voltage when switched on (from 0 to 230 in about 1,5 seconds). The
result thereof is that I do not have a clean switch between backup and
main supply when the main supply returns and sometimes devices powered

To correct that, I would like to add a small piece of electronics to
switch the relay voltage on when it reaches a certain level. My relay
switches on at about 150~160Vac.

I does not have to withstand a huge quantity of power as :
- it's only a relay. It should not need much more than 1 W.
- this switching only occurs once a year or so.
- I intend to use a contact of the relay as self-holding contact : as
soon as the relay switches on, the electronics is shorted by the
contact of the relay.

I was thinking of something based on a triac. Can somebody help me ?

I hope I have been clear. English is not my mother language. "Mes
excuses".

Best regards,

Gabriel
Click to expand...
Something simple would be a 230VAC miniature bulb and photocell (CdS) in
combination with DIAC/TRIAC. The bulb is only used for the few seconds
it takes for the backup supply to come on and no more, so it will last
forever. Put the whole thing in a sealed enclosure- and add pot in
series with PCell or shunt with C so that light level at >=200VAC or
more triggers TRIAC and no less.

View in a fixed-width font such as Courier.





-----------------+---------------------------+--------------+
| | NC NO |
Click to expand...
| +------+ | o o---+
VAC --- | | | \
----+ | L | light _ | | o
| 230vac| A | -/\/\--> |/| | r | |COM
Click to expand...
| | M | photo|\| | e K|| |
| | P | cell |/| | l K|| |
| --- 1M |\| | a K|| +---->
| | - | y |
| | NC NO | | |
| +-----o o----------+------+
| \ | | +---->
| o | | |
| |COM | | |
| | | | |
| | | | |
| | | | |
| | | | triac |
| | | (35V) ---- |
| | +---DIAC-----/\\/ |
| | | ---- |
| | === | |
| | |0.1U | |
+--------------------+-----+-------------+--------+
 
On 22 Mar 2005 01:11:57 -0800, gabriel.vanderdonck@steel-sa.com
(Gabriel Vanderdonck) wrote:

Hi Everyone !

This is my very first message in a Google group (well, not only in a
"Google" group). I am a newbie, so, please, be gentle with me.

Here is my problem.

I want to be able to switch between a main and a backup 230Vac supply
with a relay.

My main supply comes from an inverter (110Vdc / 230Vac) that ramps up
the voltage when switched on (from 0 to 230 in about 1,5 seconds). The
result thereof is that I do not have a clean switch between backup and
main supply when the main supply returns and sometimes devices powered

To correct that, I would like to add a small piece of electronics to
switch the relay voltage on when it reaches a certain level. My relay
switches on at about 150~160Vac.

I does not have to withstand a huge quantity of power as :
- it's only a relay. It should not need much more than 1 W.
- this switching only occurs once a year or so.
- I intend to use a contact of the relay as self-holding contact : as
soon as the relay switches on, the electronics is shorted by the
contact of the relay.
Click to expand...
---
I don't understand.

Why can't you use a 230VAC DPDT relay like this:


BACKUP 230>----------------+
|
MAIN 230>----+---->\ <---+
| NO \ NC
| O--------------->230 OUT
|
[COIL]
|
|
|
BACKUP 230>--|-------------+
| |
MAIN 230>----+---->\ <---+
NO \ NC
O--------------->230 OUT


--
John Fields
 
On Tue, 22 Mar 2005 12:27:03 -0600, John Fields
<jfields@austininstruments.com> wrote:

On 22 Mar 2005 01:11:57 -0800, gabriel.vanderdonck@steel-sa.com
(Gabriel Vanderdonck) wrote:

Hi Everyone !

This is my very first message in a Google group (well, not only in a
"Google" group). I am a newbie, so, please, be gentle with me.

Here is my problem.

I want to be able to switch between a main and a backup 230Vac supply
with a relay.

My main supply comes from an inverter (110Vdc / 230Vac) that ramps up
the voltage when switched on (from 0 to 230 in about 1,5 seconds). The
result thereof is that I do not have a clean switch between backup and
main supply when the main supply returns and sometimes devices powered

To correct that, I would like to add a small piece of electronics to
switch the relay voltage on when it reaches a certain level. My relay
switches on at about 150~160Vac.

I does not have to withstand a huge quantity of power as :
- it's only a relay. It should not need much more than 1 W.
- this switching only occurs once a year or so.
- I intend to use a contact of the relay as self-holding contact : as
soon as the relay switches on, the electronics is shorted by the
contact of the relay.

---
I don't understand.

Why can't you use a 230VAC DPDT relay like this:


BACKUP 230>----------------+
|
MAIN 230>----+---->\ <---+
| NO \ NC
| O--------------->230 OUT
|
[COIL]
|
|
|
BACKUP 230>--|-------------+
| |
MAIN 230>----+---->\ <---+
NO \ NC
O--------------->230 OUT
Click to expand...

Should not the relay have a 'delayed ON' function to cover the
'soft-start' period of the main inverter? These devices are normally
obtainable off the shelf at electrical suppliers.
 
Can't you put a "threshold" circuit in between that would trigger a high
(1) when your input voltage is above a given value ?
 
On 4 Apr 2005 01:56:17 -0700, gabriel.vanderdonck@steel-sa.com
(Gabriel Vanderdonck) wrote:

John Fields <jfields@austininstruments.com> wrote in message news:<e8o041t7iou4hp13j78gloipgqio1utq9h@4ax.com>...
I don't understand.

Why can't you use a 230VAC DPDT relay like this:


BACKUP 230>----------------+
|
MAIN 230>----+---->\ <---+
| NO \ NC
| O--------------->230 OUT
|
[COIL]
|
|
|
BACKUP 230>--|-------------+
| |
MAIN 230>----+---->\ <---+
NO \ NC
O--------------->230 OUT

We currently use that circuit but, because the voltage at the output
of my inverter ramps up slowly (1 or 2 second ramp time), the
switching takes a few hundreths msec to occurs and the output voltage
goes down to zero during 20 msec.

That's it !
Click to expand...
---
Then it seems you've set yourseld an imposible task, according to your
request for:

---
"I want to be able to switch between a main and a backup 230Vac supply
with a relay."
---

Since, no matter what you do, there will always be a time when the
relay is switching from one supply to the other and will be connected
to neither. The problem will be further aggravated if your backup
supply fails abruptly, because the load will suddenly see zero VAC and
then would slowly see the inverter's output ramp up to 230VAC, even if
the relay transfer was instantaneous.

Also, your configuration seems to be unusual in that you say your main
supply is 230V coming from the inverter, while your backup 230VAC is
coming from somewhere else. Usually it's just the reverse, where the
"normal" AC is supplied by 230VAC mains and the backup supply is the
inverter. Are you sure that's not your case as well?

--
John Fields
Professional Circuit Designer
 
"Gabriel Vanderdonck" <gabriel.vanderdonck@steel-sa.com> wrote in message
news:6efb48ee.0504040043.118ade61@posting.google.com...
"Ken Taylor" <ken@home.nz> wrote in message
news:<hAR%d.11842$1S4.1224431@news.xtra.co.nz>...

You want something like these:

http://catalog.rselectronics.com/cardonet/transactive?action=EXPAND&internal_id=22874
A relay with 'Adjustable Pick-Up & Drop Out Voltage Sensor'

Cheers.

Ken

RS asks me for a user name and password. I googled on 'adjustable pick
up ...'. The only thing that came up was a 130 V~ version of what I
need in 230 V~.

Thanks anyway.

Best regards,

Gabriel
Click to expand...
You need to be a bit choosier about your search terms. By limiting it to '
+"adjustable pick up" +"voltage sensor" (yes, I use AltaVista), I got a
whole swag of results including this:
http://www.macromatic.com/products/vmp_series.html

Cheers.

Ken
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top