Reed relay required for electric gate project

[joe90]

For any electronics experts out there, I have just installed electric gates and want to provide lights (led strips) to the gate pillars as we have no street lights here. The travel stops for the motor is by magnet-Reed relays and I wanted to add a Reed relay on the “open” magnet so the lights come on when the gates are in the open position. I am struggling to find a reed relay (operated by an external magnet) that switched 240 volt at above 0.5 amps ( 75 watt ish led driver.) any suggestions please.

[Alan Ambrose]

You want to add another contact to an existing reed relay? Hmmm, reed contacts are not sold separately so much. The conventional way would be to see what voltage is being used to drive the existing relay and then put another relay with that drive voltage in parallel. Are the motors driven with 240V also, in which case, can you not parallel the led transformer across the motor cables (it'll probably take little current compared to the motors)? Another possibility is to exchange the relay for one that has several sets of contacts, then use one contact for the motor and one for the led transformer. We might need more info to be more specific.

[joe90]

9 minutes ago, Alan Ambrose said:

You want to add another contact to an existing reed relay? Hmmm, reed contacts are not sold separately so much. The conventional way would be to see what voltage is being used to drive the existing relay and then put another relay with that drive voltage in parallel. Are the motors driven with 240V also, in which case, can you not parallel the led transformer across the motor cables (it'll probably take little current compared to the motors)? Another possibility is to exchange the relay for one that has several sets of contacts, then use one contact for the motor and one for the led transformer. We might need more info to be more specific.

Not quite, the existing Reed relay is actuated by a magnet on the gate, (one each end fir open and close “stop” the motor. I want to put an additional Reed next to the existing one ( the stop open one) to control the 240 volt led driver for the led lamps. This will illuminate the lights when the gates are open, if I attach to the motor they will only be on when the gate is moving. I need just the “reed” bit but one that copes with 240 volt AC and about 0.5 amps. I can buy reeds from Amazon etc but fir low voltage/current only. I am reluctant to load the existing electronics In case I blow anything and can’t replace/repair it. 

Edited November 10, 2023 by joe90

[joe90]

Ah, think I have found one.  https://uk.rs-online.com/web/p/magnetic-proximity-switches/6138195  Worth a punt !!!

[Conor]

Or fit an PIR sensor to the lights.

[joe90]

2 minutes ago, Conor said:

Or fit an PIR sensor to the lights.

I could do but better if the lights are only on when the gates are open and ready to reverse  out, (forgot to mention I have to reverse out)  driving in at night I have my headlights on. 👍 I have order that r/s one 🤞

[ProDave]

You are slightly confusing the discussion by talking about a "reed relay"  Those do exist but they are not what you want.  you want a "reed switch" that is just a switch that closes when it gets near a magnet.

 

You might find the contact rating a bit low for your needs so you might need to use the reed switch to switch an conventional relay to turn the lights on.

 

My personal preference in that situation would be to reverse in.  Reversing out you are putting the rear end of your car in danger before you can see if anything is coming.  That is actually safer at night because you hope they would have lights on so you should see someone coming.  If you were building that house now they would insist you had turning space so you could enter and then leave in forward gear.

[TonyT]

Does the gate opener not have a light connection?

 

seen that in the past.

[joe90]

50 minutes ago, TonyT said:

Does the gate opener not have a light connection?

 

seen that in the past.

No mention of it in the (Chinese translation) instructions, my last gate had a light terminal but only working whilst the gates were opening/closing.

[joe90]

2 hours ago, ProDave said:

My personal preference in that situation would be to reverse in.  Reversing out you are putting the rear end of your car in danger before you can see if anything is coming.

It’s a very narrow lane, very little traffic and only a few neighbours, but yes I agree reversing  in was my original idea but visitors tend to drive in anyway 🤷‍♂️. 

Edited November 10, 2023 by joe90

[joe90]

2 hours ago, ProDave said:

You are slightly confusing the discussion by talking about a "reed relay"  Those do exist but they are not what you want.  you want a "reed switch" that is just a switch that closes when it gets near a magnet.

Yes I discovered this a little while ago. The one I posted about above copes with the small load I want at 240v AC so should work 🤞

[joe90]

Feck, what am I doing wrong, Reed switch above arrived, rated at max ac voltage 400v, max current 1 amp so I thought it would cope, no, switched on with magnet but won’t let go, also then found it only switches  10va 🤷‍♂️the led driver is below, so draws less than 1 amp. I was buying these from RS. I cannot find another Reed switch that quotes the va switching just the max voltage and current like the one I bought 🤷‍♂️

[Alan Ambrose]

>>> I cannot find another Reed switch that quotes the va switching

 

For simple devices an approximation max VA ~= max W ~+ max Current x max Voltage and gets you in the right ballpark. I would generally allow a headroom factor of, say, x2. In fact, more modern things have VA > W as they have weirder power factors i.e. the voltage and current are a bit out of phase. LED drivers, PC PSUs, Wall Warts etc have 'dodgy' power factors <1. Simple resistive heating will have a power factor ~=1.

 

You can kind of see that the reed switch is a bit small-ish physically which suggests it's a bit wimpy electrically. I see the RS menus don't let you search in max W/VA, so I can see how you got here .

 

I guess you need 72W min / 150 VA min (0.65A x 230V). The highest one on Farnell seems to be 

 

https://uk.farnell.com/comus-assemtech/pra-sa-002/proximity-reed-switch-al-120w/dp/3762694?st=proximity switch

 

- at 120W/VA - which is probably a bit low. Reed switches in general are usually smallish current but faster than a relay.

 

Digikey / Mouser / Rapid etc?

 

Maybe you need a different solution?

[joe90]

24 minutes ago, Alan Ambrose said:

Maybe you need a different solution?

Using a Reed switch is perfect because the gate stop is already actuated by a magnet/Reed so another Reed using the same magnet is simple.

[joe90]

Farnell, great, found this https://uk.farnell.com/comus-assemtech/psc150-30/reed-proximity-switch/dp/732000 but it says….

• C/change over contact form/style
• 150VAC Maximum switching voltage
• 1A Maximum switching current
• 20VA Maximum switching capacity (resistive)
• 8mm Minimum switching distance
• 100mR Maximum Contact resistance

??? What’s the 20VAswitching capacity (resistive)

[Alan Ambrose]

>>> What’s the 20VAswitching capacity (resistive)

 

Well 20 VA resistive means 20W (or 20 VA 'with a power factor of 1') and you're looking for > 150 VA and  > 72W. It's also 150 V AC max and you want to switch 230V AC.

Edited November 13, 2023 by Alan Ambrose

[ProDave]

Your reed switch is rated at 1 amp.

 

Your light driver is rated at 0.65 amp.  So in theory you might be okay.  BUT that will be a switch mode power supply so the input circuit us usually a bridge rectifier then a smoothing capacitor.  So on first power up there will be a high starting current to charge the capacitor quickly.  It is likely that high starting current has welded the contacts of the reed switch.

 

Seriously, i would look at a little mechanical switch of the type used for limit switches on machinery that will be activated when the gate gets to end of travel.

 

Or hack the existing circuit to find a way of triggering a relay from the existing switch.

 

Do you have a picture of the insides of the controller?

[joe90]

43 minutes ago, ProDave said:

BUT that will be a switch mode power supply so the input circuit us usually a bridge rectifier then a smoothing capacitor.  So on first power up there will be a high starting current to charge the capacitor quickly.  It is likely that high starting current has welded the contacts of the reed switch.

That makes sense and yes the Reed is permanently closed now. Because the magnet/Reed devise is already there an additional Reed is the simplest solution, I have found this one and it says “This unit has a maximum switching current of 5A to handle light to medium-duty loads.”. on EBay https://www.ebay.co.uk/itm/293178384140 🤷‍♂️

Edited November 13, 2023 by joe90

[SteamyTea]

Can you do it with one of these, or similar.

Just pop the live wire that the gate motor is on  through the unit.

https://www.ebay.co.uk/itm/404322983939

 

[Onoff]

Or just use a limit switch?

[Adrian Walker]

Just use the output of the reed relay as a trigger to drive a “normal” relay or a solid state relay. Relays are mechanical and will/do fail. Powered gate suppliers like them because they can charge you to come out and fix them when they fail. 

[joe90]

28 minutes ago, SteamyTea said:

Just pop the live wire that the gate motor is on  through the unit.

But I want the lights on when the gate is open, not when it’s moving (the lights are for seeing both gate pillars in the dark)

[joe90]

20 minutes ago, Onoff said:

Or just use a limit switch?

The current limit switch is a Reed so I want to use the same proximity magnet with an additional Reed.

[joe90]

17 minutes ago, Adrian Walker said:

Just use the output of the reed relay as a trigger to drive a “normal” relay or a solid state relay. Relays are mechanical and will/do fail. Powered gate suppliers like them because they can charge you to come out and fix them when they fail. 

True, I think it’s just simpler to find a Reed that will cope with the current to start the led driver, if not this is what I will do, I have ordered that one on EBay, only a fiver, worth the punt.

Edited November 13, 2023 by joe90

[Onoff]

Got a picture of the control board connection diagram?