Exposed over door contact

[Hulmerous]

Hi guys,could do with some advice on a matter I came across today on a job. It's to do with a over door contact that is installed from a bell chime unit with built in transformer. The door contact is the two metal strip kind so when the door opens the metal strips connect and sound them chime. My question is those metal strips are exposed to touch. The chime transformer output is 12 volt 1amp. Is that safe? I was always told that anything over 10ma is dangerous. Can someone guide me on this please?

 

[telectrix]

and i thought fred dibnah was dead.

 

[cobrauk]

I think you will find that all chime transformers are all DC no AC

 

[snowhead]

I think you will find that all chime transformers are all DC no AC

There is ambiguity in that statement.

If it said all chime power supplies are D.C, it wouldn't be ambiguous but it would be wrong.

 

[SPARTYKUS]

Tazz



have you picked up screwfix syndrome.... Are you sure its "safe extra low voltage"

(I am being picky and feel free to tell me to naff off!)

sparty

 

[SPARTYKUS]

A level physics. 1985. Top teacher (ex RAF engineer). Demo'd this beautifully.

he rigged up a...well a rig at the front with thousands of windings versus well, two or three about a centimetre thick (or a centimeter if you're American) with huge clamps either end. Got a monster nail out (all to prove the amps point), asked what we thought would happen etc, then clamped the nail betwixt the ...clamps and powered up. By the way ( can't put btw it just feels wrong!!!!!) this was way before H&SE gone mad but he had a huge perspex shield for the class of grunty 17 year olds and he was wearing a mask

massive bang, nail literally exploded ( as Im sure you expected). Them were the days "ay it" still remember watching the chemistry teacher whimper and panic because he'd realised he had the phosphorus stick out too long and spent too long trying to scalpel a slice off, it lit up and he threw it down the sink in the fume cupboard! Water and phosphorus?!? Never did find out what happened to the drainage system

 

[Geordie Spark]

A level physics. 1985. Top teacher (ex RAF engineer). Demo'd this beautifully.

he rigged up a...well a rig at the front with thousands of windings versus well, two or three about a centimetre thick (or a centimeter if you're American) with huge clamps either end. Got a monster nail out (all to prove the amps point), asked what we thought would happen etc, then clamped the nail betwixt the ...clamps and powered up. By the way ( can't put btw it just feels wrong!!!!!) this was way before H&SE gone mad but he had a huge perspex shield for the class of grunty 17 year olds and he was wearing a mask

massive bang, nail literally exploded ( as Im sure you expected). Them were the days "ay it" still remember watching the chemistry teacher whimper and panic because he'd realised he had the phosphorus stick out too long and spent too long trying to scalpel a slice off, it lit up and he threw it down the sink in the fume cupboard! Water and phosphorus?!? Never did find out what happened to the drainage system

I left school in the early 60's aged 15.

I've forgotten the names of most of my teachers - and much of what they tried to teach, but will NEVER forget our science teacher Mr Jacobson who was just brilliant - every demonstration / experiment ended in spectacular chaos, but only AFTER he has succeeded in getting the point across. A very talented man and a wonderful teacher.

(and yes, one of his mishaps was with phosphorous too)

 

[tazz]

A level physics. 1985. Top teacher (ex RAF engineer). Demo'd this beautifully.

he rigged up a...well a rig at the front with thousands of windings versus well, two or three about a centimetre thick (or a centimeter if you're American) with huge clamps either end. Got a monster nail out (all to prove the amps point), asked what we thought would happen etc, then clamped the nail betwixt the ...clamps and powered up. By the way ( can't put btw it just feels wrong!!!!!) this was way before H&SE gone mad but he had a huge perspex shield for the class of grunty 17 year olds and he was wearing a mask

massive bang, nail literally exploded ( as Im sure you expected). Them were the days "ay it" still remember watching the chemistry teacher whimper and panic because he'd realised he had the phosphorus stick out too long and spent too long trying to scalpel a slice off, it lit up and he threw it down the sink in the fume cupboard! Water and phosphorus?!? Never did find out what happened to the drainage system

Used to love that experiment.....vertually zero ohms...so very high current ...V/IR again....You can buy the nails in srewfix tho...!!

 

[Knobhead]

I think you will find that all chime transformers are all DC no AC

I think you will find you are WRONG!

 

[cobrauk]

@Tony As most chimes/door bells in the UK run off battery's having a mains transformer is an extra to save having battery's that would explain why my statement was correct yes ?

 

[telectrix]

most door chimes will run on a.c. or d.c. the output of a transformer is a.c. and can only be converted to d.c. by rectification, using diodes and other wizardry.

 

[tazz]

The old convetional coil type chime will work on AC or DC, modern electronic chimes have votage regs at 3v or 5v, and can take ac or dc over 5-14v. Manufactures make products fit for purpose, knowing their customers may want dc batteries or ac transformers, unless otherwise stated on the box..

 

[Geordie Spark]

most door chimes will run on a.c. or d.c. the output of a transformer is a.c. and can only be converted to d.c. by rectification, using diodes and other wizardry.

AC/DC ...... a canny band and their chanter is from my home toon !!!

 

[telectrix]

aye, they're all gobby sods up there.

 

[Silly Sausage]

AC/DC ...... a canny band and their chanter is from my home toon !!!

They used to be a good band before him.

 

[Geordie Spark]

They used to be a good band before him.

He was in a good band before he joined them too.