Off topic electronics/electrics question ... sorry!

[Dickjotec]

When using sketchup, have you had planes that split into unbounded triangles or shoot unbounded triangles off into space?

Yes and other strange effects that I had not expected but for free software I am very impressed with it.
I will keep your printer offer in mind but realistically I already have too many projects on the go!

[julesandtash]

Jules ... how does that unit switch?  It looks for all the world like a straight forward power supply I have for the LEDs in the kitchen.

It doesn't, it just supplies 13.8V at the output as long as the mains is on. No mains, no output.
In the caravan it is just in parallel with the battery and, as such, maintains it at float voltage. Loads connected to the battery just draw power from the power supply (unless they exceed it's capacity I guess but nothing seems to do that).
When there is no mains power, the loads just take their power from the battery.

I know it is probably not the best for the battery but it works. Most caravans have a similar system (just the commercial ones are a lot more expensive).

[Julian]

Jules ... how does that unit switch?  It looks for all the world like a straight forward power supply I have for the LEDs in the kitchen.

It doesn't, it just supplies 13.8V at the output as long as the mains is on. No mains, no output.
In the caravan it is just in parallel with the battery and, as such, maintains it at float voltage. Loads connected to the battery just draw power from the power supply (unless they exceed it's capacity I guess but nothing seems to do that).
When there is no mains power, the loads just take their power from the battery.

I know it is probably not the best for the battery but it works. Most caravans have a similar system (just the commercial ones are a lot more expensive).

So what you're describing is what I described in the first post? Or am I being my usual thick self?

[Julian]

When using sketchup, have you had planes that split into unbounded triangles or shoot unbounded triangles off into space?

Yes and other strange effects that I had not expected but for free software I am very impressed with it.
I will keep your printer offer in mind but realistically I already have too many projects on the go!

Glad I'm not the only one.  There seems to be very little info on the problem available on the net.  That glitch has cost me hours, but appart from that Sketchup seems to do pretty much every thing I want at the moment, biggest limitation is my inability to use it!

[Julian]

For those interested here's the finished item ...



Those are M3 bolts and the servo is only 12mm thick.

[julesandtash]

No your are not being thick, that is basically what you described in your first post.
I was more pointing out that it is a tried and tested system that should work, even if it isn't the kindest to your batteries in the long run

The only addition is a possible voltage regulator between the batteries and the printer if it is particularly keen on regulated 12V. If it has it's own voltage regulators on board then unlikely to be an issue.

[therecklessengineer]

If it helps, that's exactly the system used on many ships for backup power, including the one I'm on at the moment.

[Julian]

James, Jules, thanks.  I'll have a check on how fussy the electronics are ... I have a feeling something in there is quite sensitive.

Where should the regulator go if I need one?  On the input to the printer after the transformed suppply and battery have been commend or on the battery supply before it's connected to the transformed supply?  I'm guessing the latter.

Only issue will then be how to smuggle two dirty batteries upstairs without the domestic authorities noticing.

[therecklessengineer]

Batteries are actually very good at keeping a voltage nice and smooth without spikes.

I'm sure that the electronics will drop the voltage to 5v or even 3.3v for everything sensitive. The heater and nozzle might be unregulated 12V, however, I doubt these will put up much fuss at 13.8V.

If you want a regulator, it'll need to go after the supply and batteries and before the printer. However, there might not be enough overhead voltage in the event of power failure to run the regulator. It'll need to drop normally around 1.5V to work properly.

The alternative is to use the batteries as a +24V supply and then use a 24/12 DC/DC converter. But for that price, you might as well buy a UPS. Here's one for £35. http://www.ebay.co.uk/itm/UPS-Uninterruptible-Power-Supply-650VA-/390792861873?pt=UK_Computing_Uninterruptible_Power_Supplies&hash=item5afd11d8b1

If the batteries are bad, just use yours! It looks to be a 24V model.

[Julian]

Thanks.  The Arduino board is OK with up to 20v and as far as I can gather the RAMPS can handle the same voltage, so I may give it a go.

James, a while back you sneaked in a comment about building a printer yourself ... how's it going?

[photoman290]

i agree with reckless. the easiest way is to just get a ups and use that. i have a 350 watt one kicking about if you cant find one. it is 36 volt,  like most of them so you would have to sort out some batteries for it. it is a sine wave one so kinder on the electronics than a msw one would be. sometimes that doesn't matter sometimes it does. i would find out how much current it draws for a first off as that will dictate how big a ups you need.

[therecklessengineer]

Badly.

Small life redirection resulting in no funds available for fun.

[Julian]

Badly.

Small life redirection resulting in no funds available for fun.

Oh, sorry to hear that. Doesn't sound good ...hope it gets sorted soon.

[therecklessengineer]

It's good actually. An entirely conscious decision on my part rather than being thrust into anything unprepared. Let's just say I'm going to be a student (yet!) again for a year - so I'm going to need funds for supernoodles.

Thanks for your concern though!

Tony...watch out. I'm coming your way.

[Tony]

Cool.  I'm a Soton alumnus - got my MEng there.