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Using earth (ground) as 0V return wire

Started by Unknown February 1, 2016
I have a Remote Control unit I made years ago for toggling various lights, hi-fi, TV, etc. I have a few spare buttons so I'm using one as a 'Shed Signal' so that SWMBO can summon me indoors occasionally. The simple oscillator circuit, feeding a miniature speaker, has its own DC power supply in the shed (workshop) and its 0V line is earthed. So is the 0V line of the RC unit in the lounge. Therefore I assumed I could simply run just the signal wire to the shed, without an accompanying 0V line, as that's provided by mains earth.

But at the shed end I'm seeing a voltage of about - 1.0 V when I'd expect 0V. Is that a consequence of my wire-saving approach, and if so, why?

Terry, East Grinstead, UK

On Mon, 1 Feb 2016 14:38:36 -0800 (PST), terrypingm@gmail.com wrote:

>I have a Remote Control unit I made years ago for toggling various lights, hi-fi, TV, etc. I have a few spare buttons so I'm using one as a 'Shed Signal' so that SWMBO can summon me indoors occasionally. The simple oscillator circuit, feeding a miniature speaker, has its own DC power supply in the shed (workshop) and its 0V line is earthed. So is the 0V line of the RC unit in the lounge. Therefore I assumed I could simply run just the signal wire to the shed, without an accompanying 0V line, as that's provided by mains earth. > >But at the shed end I'm seeing a voltage of about - 1.0 V when I'd expect 0V. Is that a consequence of my wire-saving approach, and if so, why? > >Terry, East Grinstead, UK
I bought this... <http://www.amazon.com/gp/product/B0132VRBVO?ref_=pe_823600_114105210> after SWMBO fell and fractured two vertebrae. Excellent range and loud enough to wake the dead ;-) ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: skypeanalog | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
On Monday, 1 February 2016 22:38:41 UTC, terry...@gmail.com  wrote:

> I have a Remote Control unit I made years ago for toggling various lights, hi-fi, TV, etc. I have a few spare buttons so I'm using one as a 'Shed Signal' so that SWMBO can summon me indoors occasionally. The simple oscillator circuit, feeding a miniature speaker, has its own DC power supply in the shed (workshop) and its 0V line is earthed. So is the 0V line of the RC unit in the lounge. Therefore I assumed I could simply run just the signal wire to the shed, without an accompanying 0V line, as that's provided by mains earth.
yes, if you don't mind your device seeing full mains during a fault event
> But at the shed end I'm seeing a voltage of about - 1.0 V when I'd expect 0V. Is that a consequence of my wire-saving approach, and if so, why?
It would take quite a bit of current, mains or dc, to produce that V drop. You've not given much detail on that. NT
On Mon, 1 Feb 2016 14:38:36 -0800 (PST), terrypingm@gmail.com wrote:

>I have a Remote Control unit I made years ago for toggling various lights, hi-fi, TV, etc. I have a few spare buttons so I'm using one as a 'Shed Signal' so that SWMBO can summon me indoors occasionally. The simple oscillator circuit, feeding a miniature speaker, has its own DC power supply in the shed (workshop) and its 0V line is earthed. So is the 0V line of the RC unit in the lounge. Therefore I assumed I could simply run just the signal wire to the shed, without an accompanying 0V line, as that's provided by mains earth. > >But at the shed end I'm seeing a voltage of about - 1.0 V when I'd expect 0V. Is that a consequence of my wire-saving approach, and if so, why? > >Terry, East Grinstead, UK
Possibly separate grounding rods, and some underground chemistry? That sounds like free energy to me. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
On Monday, February 1, 2016 at 2:38:41 PM UTC-8, terry...@gmail.com wrote:
> I have a Remote Control unit I made years ago for toggling various lights, hi-fi, TV, etc. I have a few spare buttons so I'm using one as a 'Shed Signal' so that SWMBO can summon me indoors occasionally. The simple oscillator circuit, feeding a miniature speaker, has its own DC power supply in the shed (workshop) and its 0V line is earthed. So is the 0V line of the RC unit in the lounge. Therefore I assumed I could simply run just the signal wire to the shed, without an accompanying 0V line, as that's provided by mains earth. > > But at the shed end I'm seeing a voltage of about - 1.0 V when I'd expect 0V. Is that a consequence of my wire-saving approach, and if so, why?
Probably you're seeing electrochemistry, and multiple alloys of grounding posts in the electric grid connections in your neighborhood. If it were critical, you could receive the oscillator signal through a capacitor with a tone decoder (NE567) and disable the speaker when the frequency was wrong. Or, you could use a cordless phone's 'locate handset' feature instead of outdoor runs of wire.
On 2/1/2016 2:38 PM, terrypingm@gmail.com wrote:
> I have a Remote Control unit I made years ago for toggling various lights, hi-fi, TV, etc. I have a few spare buttons so I'm using one as a 'Shed Signal' so that SWMBO can summon me indoors occasionally. The simple oscillator circuit, feeding a miniature speaker, has its own DC power supply in the shed (workshop) and its 0V line is earthed. So is the 0V line of the RC unit in the lounge. Therefore I assumed I could simply run just the signal wire to the shed, without an accompanying 0V line, as that's provided by mains earth. > > But at the shed end I'm seeing a voltage of about - 1.0 V when I'd expect 0V. Is that a consequence of my wire-saving approach, and if so, why? > > Terry, East Grinstead, UK >
give it up. Too much hassle for too little gain. Run two wires. Or run an air line with a whistle on the end. You don't say how far, but there are numerous cheap wireless devices that could be used. toy walkie talkie?
Thanks all. I'll probably end up simply running another wire, although it's a hassle. But curiosity is the main driver. There's thick copper mains earth wire between the lounge and my heavily equipped shed workshop. I suspect I'm missing some obvious point and will investigate more methodically and report back.

I don't follow the warning about mains voltage? That must be equally true about a variety of my other circuits, including test equipment, in which the 0V line is connected to mains earth. If 240V touches an earth wire at point X then I assume it triggers the circuit breaker and quickly cuts all power to all circuits and appliances at X, Y and Z throughout the house.

Re the comments about 'stakes' etc. Are those relevant here? I confess I've never really understood the whole topic of Earthing, but surely the pertinent point is the one I just made, about there being a physical network of heavy wire linking all the mains sockets on my property?

Terry, East Grinstead, UK
On 2/1/2016 10:58 PM, terrypingm@gmail.com wrote:
> Thanks all. I'll probably end up simply running another wire, although it's a hassle. But curiosity is the main driver. There's thick copper mains earth wire between the lounge and my heavily equipped shed workshop. I suspect I'm missing some obvious point and will investigate more methodically and report back. > > I don't follow the warning about mains voltage? That must be equally true about a variety of my other circuits, including test equipment, in which the 0V line is connected to mains earth. If 240V touches an earth wire at point X then I assume it triggers the circuit breaker and quickly cuts all power to all circuits and appliances at X, Y and Z throughout the house. > > Re the comments about 'stakes' etc. Are those relevant here? I confess I've never really understood the whole topic of Earthing, but surely the pertinent point is the one I just made, about there being a physical network of heavy wire linking all the mains sockets on my property? > > Terry, East Grinstead, UK >
If you've got power lines, use something like X10 or a power line network connection.
On Tuesday, 2 February 2016 06:58:20 UTC, terry...@gmail.com  wrote:
> Thanks all. I'll probably end up simply running another wire, although it's a hassle. But curiosity is the main driver. There's thick copper mains earth wire between the lounge and my heavily equipped shed workshop. I suspect I'm missing some obvious point and will investigate more methodically and report back. > > I don't follow the warning about mains voltage? That must be equally true about a variety of my other circuits, including test equipment, in which the 0V line is connected to mains earth. If 240V touches an earth wire at point X then I assume it triggers the circuit breaker and quickly cuts all power to all circuits and appliances at X, Y and Z throughout the house. > > Re the comments about 'stakes' etc. Are those relevant here? I confess I've never really understood the whole topic of Earthing, but surely the pertinent point is the one I just made, about there being a physical network of heavy wire linking all the mains sockets on my property? > > Terry, East Grinstead, UK
When a live to earth fault occurs, a current of 10s/100s/1000s of A flows. The resulting voltage on the earth wiring depends on details, but is frequently near 240v/120v, ie your earth becomes live until the fuse/breaker acts. Connecting low v equipment to this means 2 things: 1. all touchable LV bits are briefly live 2. in some circumstances you also get 240/120v across your low voltage electronics US experience with neutral grounded cookers does seem to show the risk to be very small, as long as the appliance does not electrically connect to people eg via headphones, bathwater, etc. If it does of course it's liable to be fatal. NT
On Mon, 1 Feb 2016 14:38:36 -0800 (PST), terrypingm@gmail.com wrote:

>I have a Remote Control unit I made years ago for toggling various lights, hi-fi, TV, etc. I have a few spare buttons so I'm using one as a 'Shed Signal' so that SWMBO can summon me indoors occasionally. The simple oscillator circuit, feeding a miniature speaker, has its own DC power supply in the shed (workshop) and its 0V line is earthed. So is the 0V line of the RC unit in the lounge. Therefore I assumed I could simply run just the signal wire to the shed, without an accompanying 0V line, as that's provided by mains earth. > >But at the shed end I'm seeing a voltage of about - 1.0 V when I'd expect 0V. Is that a consequence of my wire-saving approach, and if so, why? > >Terry, East Grinstead, UK
What kind of meter did you use ? At least some analog multimeters in DC position shows something when feeding it with completely symmetrical AC. So if you have PEN (separate PE protective ground and N neutral) there will of course be some voltage drop across the PEN due to the AC load, that might well show up as a negative voltages on some multimeters. In a PEN (TN-C) environment https://en.wikipedia.org/wiki/Earthing_system do not use PE as signal reference. Use separate signal ground or better a balanced connection or in this case some wireless means.