12v AC to 12V DC

[Aviz]

I have one of these:

http://www.screwfix.com/p/deedlock-dorcas-8-12v-ac...

which is connected to the light in my garage door opener. When the garage door is opened using the fob, the lock disengages. The Light on the garage door is 12v AC, and this all works fine.

The annoying thing is : because it is AC, the lock makes an irritating buzzing noise, and The light stays on for 1 minute after operation (hence the buzzing continues).

The lock can use DC, which means it is silent (tested using a battery charger).

What i'm looking for is a simple 12v AC to DC convertor. The current is tiny. I'm not really any good at electronics, so i'm hoping there might be a cheap "out of the box" solution to this ?

Anyone any ideas?

Cheers

Andy

[anonymous-user]

Why do you need DC? A light will work off AC or DC.

[marshalla]

Before thinking about rectifiers for 12V AC to 12V DC - where are you getting the 12V AC from ? If it's a step-down transformer, why not just swap that for a proper 12V DC power supply rather than trying to build your own from separate components ?

[marshalla]

Dave_ST220 said:

Why do you need DC? A light will work off AC or DC.

Because the lock buzzes if it uses AC. For a whole minute!

[Aviz]

The light is fine. I am powering the electric lock from the feed to the light. The feed is AC to the light, which in turn feeds the lock with AC. This causes the annoying buzzing that the lock makes. What i want to do , is convert the AC to DC before it reaches the lock. The lock will then silently operate.

Thanks

Andy

[anonymous-user]

What is this "light"? If simply a bulb then it won't matter if it is DC or AC.

[Aviz]

marshalla said:

Because the lock buzzes if it uses AC. For a whole minute!

This! It's very loud, and irritating. Especially as i can still hear it in the Lounge of the house. Those who know the sound electric locks make will understand!

[Aviz]

Dave_ST220 said:

What is this "light"? If simply a bulb then it won't matter if it is DC or AC.

The light is a 12v 20w bulb, and yes i know it will work on AC or DC. There is no problem with the light. I need the DC for the lock.

The trigger for the lock to open is the 12v AC that feeds the light.

[Mr Pointy]

Where are you getting the 12v AC for the light from? Would it not be simpler to use a 12v DC PSU to feed both the light & the lock?

[anonymous-user]

marshalla said:

Before thinking about rectifiers for 12V AC to 12V DC - where are you getting the 12V AC from ? If it's a step-down transformer, why not just swap that for a proper 12V DC power supply rather than trying to build your own from separate components ?

This would be alot easier than making a rectifier.

[anonymous-user]

btw, are you sure it is silent on DC? Those things usually buzz when activated anyway?

[Aviz]

Mr Pointy said:

Where are you getting the 12v AC for the light from? Would it not be simpler to use a 12v DC PSU to feed both the light & the lock?

The light is actually part of the garage door opener unit. The lock needs to "unlock" and have 12v supplied to it, when i press my fob, hence this is the simple way to do it.

[Aviz]

Dave_ST220 said:

btw, are you sure it is silent on DC? Those things usually buzz when activated anyway?

Definitely. Tested with battery charger.

[road_rager]

I think you need more than 12v ac to be able to get a decent 12dc ( if my memory from doing electronics is correct)

[Aviz]

road_rager said:

I think you need more than 12v ac to be able to get a decent 12dc ( if my memory from doing electronics is correct)

I think you are right. 10% more (ish)

The lock says it is fine with 8v though

http://www.screwfix.com/p/deedlock-dorcas-8-12v-ac...

[jhfozzy]

Bridge rectifiers from £0.44.

http://www.maplin.co.uk/bridge-rectifiers-19088

[Aviz]

jhfozzy said:

Bridge rectifiers from £0.44.

http://www.maplin.co.uk/bridge-rectifiers-19088

Excellent. There's a maplins right near work, but which one's do i need ?

It's all gobbldygook to me

[jhfozzy]

There is no current rating on the screwfix lock, but they're all about 0.5A - 1A so the 2A KBPC1005 [AQ98G @ £0.69] should be sufficient.

All of the rectifiers on that page have a maximum voltage above the 12v that you need.

[Aviz]

jhfozzy said:

There is no current rating on the screwfix lock, but they're all about 0.5A - 1A so the 2A KBPC1005 [AQ98G @ £0.69] should be sufficient.

All of the rectifiers on that page have a maximum voltage above the 12v that you need.

Thankyou!!

I'll get one and give it a try.

Andy

[marshalla]

jhfozzy said:

There is no current rating on the screwfix lock, but they're all about 0.5A - 1A so the 2A KBPC1005 [AQ98G @ £0.69] should be sufficient.

All of the rectifiers on that page have a maximum voltage above the 12v that you need.

Unless they have built-in smoothing capacitors, those rectifiers will produce choppy DC. I rather think that will still cause buzzing, but I hope I'm wrong.