Homemade Electrical Equipment

[ban-all-sheds]

How not to do it:

 

[JohnW2]

I think the only way to demonstrate to an isurer or anyone else that the equipment is safe will be to test to an appropriate BS EN; 60950 and 61010 would be a start, although there are some specialist standards for home automation equipment.

Is not the problem there that, even if a DIYer were equipped and competent to undertake such tests, the insurer (or whoever) would probably not take a DIYer's test results very seriously. As I've suggested, I really doubt that, in relation to domestic premises, they would even try to 'understand' whether or not the equipment was safe - they would simply 'react' (or, maybe, 'not react') to someone volunteering that such 'DIY equipment' existed in the property.

In terms of common sense, if the control equipment is all ELV and the interface between it and the 'mains' electrical installation is through commercial, Standard-compliant relays/contactors/whatever of appropriate specification, and if there is sensible physical separation between ELV and LV wiring, then I really don't think that such systems are any less safe than any other equipment connected to the electrical installation via switching devices. There are, of course, some inherent dangers of any system which can switch electrical appliances on in an unoccupied house (e.g. think heaters) - but those risks are just as great with commercial time-switches as with more sophisticated systems.

Kind Regards, John

 

[i_am_fubar]

I normally try and use 10mm spacing between LV and ELV tracks.

The opto isolation is to protect the micro-controller / processor from inductive spikes and other nasties as well as providing an increased current handling capability of the controller pin (100's mA rather than 10's mA). The contactor or relay would then be driven from the output of the opto.

Controller -(ELV 3.3/5v)-> Opto - (ELV 12/24v)-> Relay/Contactor -LV(110/240v)-> Appliance / device

Fubar.

 

[i_am_fubar]

Nice pic. At least they've used heatshrink on the wires. Beats some of the electrical tape (or worse, masking tape) bodges I've seen.

Does it really cost that much to build it into an enclosure and actually route the wires sensibly

Fubar.

 

[JohnW2]

I normally try and use 10mm spacing between LV and ELV tracks. ... The opto isolation is to protect the micro-controller / processor from inductive spikes and other nasties as well as providing an increased current handling capability of the controller pin (100's mA rather than 10's mA). The contactor or relay would then be driven from the output of the opto.
Controller -(ELV 3.3/5v)-> Opto - (ELV 12/24v)-> Relay/Contactor -LV(110/240v)-> Appliance / device.

That all sounds eminently reasonable (and safe) to me (probably would still be, in terms of electrical safety, even without the opto-isolation).

Personally, I would usually avoid having LV and ELV tracks on the same board, but if one is going to do it, then 10mm sounds like reasonable spacing.

Kind Regards, John

 

[JohnW2]

Nice pic. At least they've used heatshrink on the wires. Beats some of the electrical tape (or worse, masking tape) bodges I've seen. Does it really cost that much to build it into an enclosure and actually route the wires sensibly

IIRC, apart from all the bits of bare copper all over the place and other 'interesting' features, one of BAS's main concerns about this is that CAT5e insulation is probably not rated for proximity to LV.

Kind Regards, John

 

[ban-all-sheds]

Sheds, want all the way. With luck, I can use the installs as a test platform for furthering development to a commercial product.

An essential skill these days:

http://developer.android.com/training/basics/firstapp/index.html

 

[i_am_fubar]

I've got the android dev pack. But no time to play with it All this damn DIY.

Fubar.

 

[SimonH2]

Does it really cost that much to build it into an enclosure and actually route the wires sensibly

It's in an enclosure, that photo is from a DIY energy monitor project - those are the CTs added to the branch circuits in a US distribution board (CU).
http://www.delorie.com/electronics/powermeter/

 

[ban-all-sheds]

He doesn't exactly take pride in his work, though.

 

[SimonH2]

The electrician who installed the dist board, or DJ Delorie ?

BTW - Did you fail to notice his instruction not to hotlink to images on his site ?

 

[ban-all-sheds]

The electrician who installed the dist board, or DJ Delorie ?

The latter.

BTW - Did you fail to notice his instruction not to hotlink to images on his site ?

Yes.

But as there is no such instruction here: http://www.delorie.com/electronics/powermeter/ or with the images then that's hardly surprising.

 

[ericmark]

I think a question arises as to what is home made? Buy a box designed for electrical equipment likely with DIN rail pre-installed and clip in ready made relays, timers, current transformers, 5 - 20 ma converters and a PLC and wire together and program is hardly home made. All parts are tested by the manufacturer of that part and voltages and currents decided on by the manufacturer.

However a bread board nails resistors made from springs is a completely different thing. Even once one has tested and etched ones own board with resistors, IC chips and relays with a PIC controlling all now this is completely different. I have tried programming PIC's and I take my hat off to those that do this as not easy and as a result far more likely to contain errors.

 

[i_am_fubar]

A core issue that many PIC programmers fail to consider is fail-safes.

A well written program is only as stable as the silicone it's programmed on. As such, it is imperative to include fuses, MCBs, external watchdog controllers... etc

My favorite fail safe system is a high current relay held open by a watcher circuit. If the watcher circuit detects an error OR fails itself, the relay closes, shorting the supply. That then blows a fast blow fuse and removes power to the circuit in one go.

Fubar.

 

[ericmark]

He doesn't exactly take pride in his work, though.

I always hot link. Mainly so the owner can remove if they wish. Should I find an image on a web site which the site did not have permission to use if they get told to remove it then it's auto removed from mine.

The problem with hot link is band width giving permission to copy is however a real problem I made a website for a friend and was given a load of pictures to include then found many were copy write belonging to members of local camera club and he only had permission for personal use not web use. So were removed however in mean time some were copied.

Personally I feel if you don't want a picture copied and used without your consent you need to have some ID on the picture. I think law also takes same view. As to what is accepted I don't know but I put GW7MGW as a watermark in the corner since that call sign is in the book no one can say they didn't know how to contact me.