exploding traces.

[Pommie]

Because it would take 30A or so to blow it, the PCB track fused at a much lower current.

As this was an earth fault then surely the RCD would trip at the required 35mA?

Mike.

 

[Nigel Goodwin]

As this was an earth fault then surely the RCD would trip at the required 35mA?

Mike.

Depends if he even has an RCD?, but the track would probably blow faster than the RCD anyway? - no anti-surge properties in a piece of thin PCB track!

 

[HerbertMunch]

Chris,
Just rebuild the circuit, there is a good chance the transformer is not damaged as the PCB tracks acted as your fuse. However, you were lucky this time, had you handled the low voltage side of the board you could have been electrocuted. Hopefully, your first big bang scared the xxxx out of you as it did me and you will double check everything involving mains in the future. I had a very good friend who lost his life through a silly mistake like this.

Mike.

The transformer is broken.

it did indeed scare me, but I had taken adequate measures to ensure safety and stayed well away from the board, touching no metal contacts. I treated the low voltage side as if it were high voltage , and used insulated connectors.

next time though, i will indeed check and recheck all connections to mains electric.
i was foolish to assume the layout of the relay pins

My house is only 2 years old; would this not have the new type of breaker?

Thanks,
chris

 

[audioguru]

A very high current will trip a breaker quickly. But when the current is close to the rating of the breaker then it takes many seconds or minutes.

I have made a few (OOPS) slips and made huge arcs without blowing a breaker.
I blew the breakers with a shorted cord to identify which breaker powered which room and the breakers tripped immediately.

 

[HerbertMunch]

@HerbertMunch,
The scope lead clip is earthed, did you touch this earthed clip to any point on circuit which has LIVE potential?

hi thanks for your concern.

please see the pic that i have included.

thanks
chris

 

[Pommie]

My house is only 2 years old; would this not have the new type of breaker?

Your house should have an RCD fitted. These trip when there is a difference of 35mA between live and neutral caused by current flowing to earth. In this case your scope earthed the supply and so it should have tripped. Check your consumer box, you should have a (maybe two) breaker(s) with the test button on them.

I have a plug with a 4.7K resistor from live to earth that I use to trip the correct breaker when I'm going to work on a particular circuit. It is only a 1/8th watt resistor and there is no spark or bang, the breaker just does it's job.

Mike.

 

[HerbertMunch]

ok thanks mike ill look into it.

 

[kchriste]

You can also buy ones that just plug into the wall for your scope and AC projects:
**broken link removed**

 

[HerbertMunch]

ok thanks very much for taking the time to find one on an English site.

 

[Pommie]

Putting an RCD on the scope would not help in this case. It would have to be powering the project.

Mike.

 

[HerbertMunch]

ill keep that in mind thanks.

 

[Nigel Goodwin]

Your house should have an RCD fitted. These trip when there is a difference of 35mA between live and neutral caused by current flowing to earth. In this case your scope earthed the supply and so it should have tripped. Check your consumer box, you should have a (maybe two) breaker(s) with the test button on them.

Yes, a two year old house WILL have an RCD, like I said before the PCB track will have fused faster than the RCD could activate.

The RCD will have a 'test button', pressing that will cause it to trip.

 

[3v0]

RCD's are called GFI's (ground fault interrupt) over here. Outlets with them built in are less expensive then ones fitted to breakers. We also have GFI equipped power strips.

A RCD/GFI Incorporated into an outlet connected to a power strip or 2 could power most workbenches. That would be a Good Idea.

I think that your relay is wired wrong. It looks OK in the schematic, but on the PCB layout it appears that you've mixed up the coil connections with the NO and NC contacts!

A PCB layout program with schematic capture can prevent this type of error. It can save many hours of hand verifying the PCB with the schematic.

 

[HerbertMunch]

A PCB layout program with schematic capture can prevent this type of error. It can save many hours of hand verifying the PCB with the schematic.

You would think so wouldnt you! im using eagle, but i created the device footprint from scratch!

I totally agree with you though. It does save alot of time.

 

[3v0]

You would think so wouldnt you! im using eagle, but i created the device footprint from scratch!

I totally agree with you though. It does save alot of time.

Ouch! ...

 

[Hero999]

Using an isolation transformer to power projects from is also a good idea as it eliminates the posibility of getting a shock from only touching one conductor.