hi to all, although i've not posted for a while, i've been at the forum almost every day ! A question about 3 phase. I want to build an emergency light system for my woodwork shop ( it's on a farm where the 3 phase goes down quite often ) powered from 4 - 6 car batteries that will be charged from a wind turbine ( yet to be built). The question is , how can i detect when the mains power goes down without actually making a live connection ? My first thought was to wrap several turns of copper wire to form a coil, round the main incoming cable to try and get an induced (small) voltage that could be rectified and used to interface with an 'axe ? any comments or suggestions would be appreciated.
3 phase interface
- Thread starter wildbill
- Start date
Hippy, Thanks for the rapid response, i've not played with the input side of an 'axe, only outpu stuff, i suppose i could use a small mains power pack that would be permenantly on the supply ( i may have a sony 3v minidisk one ) and run two led's from that to control the ldr. Early days, but your suggestion is probably the simplest.
Thanks , wildbill.
Thanks , wildbill.
As you want an isolated connection between the mains and the PICAXE system rather than entirely unconnected physically, you have a number of options. The simplest is possibly a mains powered relay, which can then be treated as as simple switch for the PICAXE. More complex options would include proper opto-isolators.
personally I'd power the PICAXE circuit from the mains via a PSU, with backup coming from your batteries, and use the low voltage supply to also indicate if mains is working or not, using a diode and current limiting resistor. Similar to your PSU idea, and as safe as a normal mains PSU powered project and avoids the need for LED's or anything else.
personally I'd power the PICAXE circuit from the mains via a PSU, with backup coming from your batteries, and use the low voltage supply to also indicate if mains is working or not, using a diode and current limiting resistor. Similar to your PSU idea, and as safe as a normal mains PSU powered project and avoids the need for LED's or anything else.
Wild Bill - can't quite see your real need here. Hence suggest you expand on - location? Budget? Steady mains load? Auto switch over? Reliability ? Is it just the 3ph. (lighting?!) that's unreliable? Are you nearby when it goes dead?
I've had a lot of past mileage using cheap automotive inductive spark plug lead pickup clip units to "read" mains AC in the cable they straddle. These typically give a few mV AC - load proportional as well- that can easily be read via a simple moving coil meter. Naturally this responds to reactive VA rather than true W power.
There are numerous tricks of the trade to indicate loss/presence of mains power of course, with perhaps a neon wired across a mains outlet as the most traditional & reliable visible one, with a held off piezo for audio alerts.
Extra: ~ 200W 24V 3ph. Asian wind genes are now turning up at prices cheaper (~US$300) than you could build one. See Jaycar's =><A href='http://www.jaycar.com.au/productView.asp?ID=MG4510&CATID=&keywords=wind+gene&SPECIAL=&form=KEYWORD&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=' Target=_Blank>External Web Link</a> I wouldn't recommend if in a hurricane belt, but they're amazing in steady trade wind locations.
I've had a lot of past mileage using cheap automotive inductive spark plug lead pickup clip units to "read" mains AC in the cable they straddle. These typically give a few mV AC - load proportional as well- that can easily be read via a simple moving coil meter. Naturally this responds to reactive VA rather than true W power.
There are numerous tricks of the trade to indicate loss/presence of mains power of course, with perhaps a neon wired across a mains outlet as the most traditional & reliable visible one, with a held off piezo for audio alerts.
Extra: ~ 200W 24V 3ph. Asian wind genes are now turning up at prices cheaper (~US$300) than you could build one. See Jaycar's =><A href='http://www.jaycar.com.au/productView.asp?ID=MG4510&CATID=&keywords=wind+gene&SPECIAL=&form=KEYWORD&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=' Target=_Blank>External Web Link</a> I wouldn't recommend if in a hurricane belt, but they're amazing in steady trade wind locations.
I guess one of the issues that wildbill may also want to consider is that sometimes when 3 phase power fails, it may only be one of the three phases which is out.
Hence a monitoring system should ideally be monitoring all 3 phases -although obviously this wouldn't be a requirement if it’s just a single phase being used in the woodworking workshop which he is interested in providing a backup for.
Hence a monitoring system should ideally be monitoring all 3 phases -although obviously this wouldn't be a requirement if it’s just a single phase being used in the woodworking workshop which he is interested in providing a backup for.
Summertown
Member
Hi I have the same prob. Simplest way to detect if any of the phases go down is use 3 x opto couplers into a simple delay of 100 milliseconds using a 74C14, this in turn kicks the picaxe off.
Gonzo
Gonzo
Good thinking Summertown. And three LED’s on the low voltage side could be used to give a handy instantaneous readout of which phase(s) that are actually missing.
Edit:
Uh Oh, wildbill did specifically state: “<i>detect… without actually making a live connection”. </i> Maybe an alternative method might be preferable. Hope Dippy hasn’t noticed my mistake here!
Edited by - whizzer on 06/06/2006 15:32:56
Edit:
Uh Oh, wildbill did specifically state: “<i>detect… without actually making a live connection”. </i> Maybe an alternative method might be preferable. Hope Dippy hasn’t noticed my mistake here!
Edited by - whizzer on 06/06/2006 15:32:56