Automatic line voltage switch?

If the user sets the AC voltage wrongly, the breaker will trip immediately due to the very large magnetising current that will flow in its primary.

.... Phil

If you're in the USA, you could just put a two-pole ganged breaker across the 230V "mains."

I don't know if there's such a thing as a 230V GFI, but what is the original question anyway? To protect people from electrocution? The answer to that is firm, reliable Earth ground bonding.

(is there such a thing as a, say, 5A, 230V, two-gang breaker?)

Hope This Helps! Rich

How about a 240 volt relay at the input? If it is energized the stepup transformer isn't used. Of course, the switch to power the motor would have to be after the relay.

mary

Thanks Phil, that's clever. I'd do that in a heartbeat. The dream is of plugging the thing into any outlet world-wide and having it work without ever having to flip a switch, yet I have no budget or schedule to do any of this. I prefer the switch, personally, or COTS.

-- Cheers, James Arthur

Something like that may be the end result, I just have to be very sure it's failsafe so I never, ever apply 440VAC to the pump and fry it, ever. A commercial gizmo I could simply specify would save me sweating that, plus mechanical design, etc.

As usual the constraints are more the circumstances--money, time, and the imposed goal of having no switches--than technical.

Thanks,

James Arthur

On a sunny day (Wed, 15 Dec 2010 11:15:39 -0800 (PST)) it happened snipped-for-privacy@yahoo.com wrote in :

I would probably uses a PIC and maybe 2 relays. I would first measure when power was applied what range it was in, either 120 +/- some tolerance or 230 +/- some tolerance, and then have the PIC switch I one of the circuits say a second later. PIC powered with some small transformer maybe over full voltage range (8 - 20 V). And then you can add RS232, touch switches, timers, flashing light if out of range, LCD display with phone number for pizza, the works, for almost free.

V).

almost free.

Could potentially be done with one relay. Let it default to 230V and when the circuit detects that only 120V is coming in, switch the relay. That doesn't need a PIC.

I have an application coming up as well but no space for that relay. The client wants to stay with the old form factor box and it's already very full :-(

Sure, they exist, they're generically called "Voltage relays" or "Voltage monitors". Commonplace in industrial situations and easily available off-the-shelf.

If you need thousands, consider a custom solution, otherwise the COTS stuff is fine, well proven, and they generally carry all the appropriate safety approvals you'll want or need for world-wide use.

On a sunny day (Wed, 15 Dec 2010 11:32:30 -0800) it happened Joerg wrote in :

I think the implied computer remote control feature that a PIC provides may be an additional sales argument in some cases. Because with 2 relays you can also do 'off' 'on' control.

BTW I tried 'rubbing' the Samsung LCD monitor, no luck. The manual is full of guarantee, except for burn-in. Maybe I will write a un-burn program myself, one that flips every bit for 24 hours from 0 to 100%.

Relays win in many cases from some semiconductor, I even used relays driven by a PIC to modify my old washing machine. Works great, very small box. Even use a PIC as dual thermostat, a modified version of this:

an additional sales argument

That's what amazes me about the old Trinitron tube here at my computer. From the late 90's, runs 10h each day, no burn-in whatsoever. I wouldn't have though burn-in could be so bad on an LCD.

Actually, my old Inspiron 2500 that ran for a whopping 35,000 hours has no burn-in on its old LCD either. Even the backlight is still fine. But the touchpad and keyboard are rather worn, and its RAM is too small for SPICE sessions. I sure got my money's worth out of that computer.

Yes, I have to stay low-tech on this one. Semiconductors die too often because this gear is exposed to tropical weather. If I could find a small low-cost 12V/1A switcher module that goes from 100-260VAC I'd be home. But unfortunately they pretty much all statrt derating at 50-60C.

V).

almost free.

Are there places in the world where 120VAC and 230VAC plugs are the same? ...Jim Thompson

almost free.

Yes, in Cameron Park. In our garage, to be exact :-)

Of course, I do not have 230V on 120V NEMA outlets. But I do have 120V on a few German Schuko outlets so I can use the angle grinder, jig saw, electric drill and other things I brought from over there. To my surprise the Metabo drill still has lots of gusto in low gear, it's just a lot slower which is no problem. Much quieter as well.

The only easy way to power a motor from either 120VAC or 240VAC is to rectify to DC, and use a DC motor with a switching (buck) regulator to limit the power. Adding a 300W transformer, just to keep the "AC motor" requirement, is costly. Also heavy.

The DC motor also gives speed control, and independence of that speed from the local power frequency.

Not the wall sockets, but the usual power brick for laptops has one of the equipment-cord plugs that takes an IEC 320 connection, and THAT plug/socket combo is used for both ranges.

You don't even need a buck regulator. A selection between full wave or half wave rectification is enough. IIRC autoranging PSUs use a triac and some circuitry to switch between ranges.

Yep. That's the way the switchers worked in the GenRad Portable Tester... my design ~1980. ...Jim Thompson

Where guy came, rocked the power switch, and the switcher's guts came flying out?

:-)

I acknowledge all your points, but the pump exists, and I must please it. The decision isn't and wasn't mine to make.

Thanks, James

I found a few "Voltage monitoring relay(s)" that could provide the switching function. I'd still prefer a complete black box, 110-230VAC in, 220-260VAC out, 300VA.

The voltage monitoring relays I found had pot-settable thresholds. I don't like that--anything that can be set can be mis-set. OTOH, I think it can be arranged so that wrong thresholds aren't damaging.

Thanks for the tips.

James Arthur