Voltage activated relay

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

Reply to
Gabriel Vanderdonck
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I don't understand.

Why can't you use a 230VAC DPDT relay like this:
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Reply to
John Fields

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.

| | - | y | | | NC NO | | | | +-----o o----------+------+ | \ | | +---->

| o | | | | |COM | | | | | | | | | | | | | | | | | | | | | | triac | | | | (35V) ---- | | | +---DIAC-----/\\/ | | | | ---- | | | === | | | | |0.1U | | +--------------------+-----+-------------+--------+

Reply to
Fred Bloggs

You want something like these:

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A relay with 'Adjustable Pick-Up & Drop Out Voltage Sensor'

Cheers.

Ken

Reply to
Ken Taylor

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.

Reply to
Ross Herbert

supply

up

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relay

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?

What sort of V accuracy do you need? If its ok to switch on at

200-240v, a series resistor is the simplest option. Relay latch v is quite repeatable, just tweak the R. Relays run like this will switch slower, so you also get a little time delay which helps.

Next simplest option: if supply frequency is out of spec during the 1.5 secs, and it likely will be, use C or L instead of R to get more discrimination and thus more accurate latching v.

Best option is a diode & RC on the relay. The RC ramps up the coil v over a second or 2, giving time delay. I cant think of a need to get into fancier solutions like triacs, diacs, neons, et al.

But this does raise the q of why your invertor ramps up slowly: is it perhaps trying to avoid some switch on surges? If so, connecting load at 240v might possibly cause it problems. If it does, it might become necessary to do some tweakage to get round this.

NT

Reply to
bigcat

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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

Reply to
Gabriel Vanderdonck

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 !

Best regards,

Gabriel

Reply to
Gabriel Vanderdonck

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Then it seems you've set yourseld an imposible task, according to your
request for:
Reply to
John Fields

Can't you put a "threshold" circuit in between that would trigger a high (1) when your input voltage is above a given value ?

Reply to
OBones

voltage

your

Sounds like much more info on the app would be appropriate. The OPs idea of a solution might not be the best solution after all.

NT

Reply to
bigcat

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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:
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Cheers.

Ken

Reply to
Ken Taylor

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