Networked dimmer, 3000 watts?

[dennis]

Anyone know where to get an affordable 3kw dimmer that can be controlled over ethernet or wireless or USB or similar?

Its for a resistive load and control in about 10 steps would be fine.

Ta.

[Dave Liquorice]

Plenty about that talk DMX, the hard part might finding a single dimmer rather than a pack of 12 or more...

They are about but may not fall into your definition of "affordable" and you'd need something to generate the DMX control.

Presumably as you mention USB you don't need that much range as USB will only reach 30 m maximum and thats with the maximum number of active 5 m extensions.

[dennis]

I had come across that sort of thing but, as you say, they come in lots of channels and I really only want one.

I have looked at some power controllers that take a DC control voltage and vary the AC power output. They are about £50-£60 before you add in the heat sinks, etc.

I was thinking of controlling it with a RPi. The DC ports would work the above power controller but then I want some sensors and they would have to be remote instead.

Its part of my plan to "stabilise" the grid by storing all the solar energy using the immersion heaters.

You can buy a "Parson switch" for a few hundred pounds and may even get it fitted for a few more. Its basically a 1 kw immersion heater that turns on when the solar PV is generating 1.5 kw.

AISI why not measure the current being exported and use the power controller to dump it into the existing immersion.

Hence trying to find an easy to fit power controller and a couple of current sensors to hang on a RPi or an arudino (sp is wrong I expect).

I wonder if there is an X10 power controller?

[harry]

I don't think you would have a big enough water store to do that. What's the point? When the energy is available, you don't need it. By the time you do, there is none. There are only short "shoulder periods" when this would be useful. So an almost complete waste of time.

You can buy purpose made gizmos BTW to do this.

Or do as I did. Get an electric car and have free petrol.

Or if you are feeling flush, this is the way to go.

Personally I'll wait for the price to come down a bit.

[dennis]

8< stuff about HW storage..

Its stored harry, that's what happens if you don't fit a combi.

I know but they don't do it very well. Those that read the post will have noticed that I talked about one of them.

What's the point in that? It would take me more than 100,000 miles to recoup the extra cost. More if I drive economically.

Your car won't even manage 100,000 miles on a set of batteries. Its about 1000 charge cycles and you are only going to get about 500 if you are lucky.

I also tend to drive the car during the day so its quite hard to charge it from solar panels at home. Maybe you think I should have a spare battery pack to charge?

Personally I would suggest you fit a bigger HW tank and wash more when its sunny.

You can also use a bike rather than a car as you obviously don't actually drive yours as its plugged in all day.

[Dave Liquorice]

Well you need one anyway if you are actually going to use the car. Just been to the Dentist, 60 mile round trip, that's the best part of the range and I'll have missed out on the "free" charge in todays nice bright sunshine as well. Need to go out again later only five miles but it's a 400' climb back up to home...

The thermal solar system in the meantime have got the whole 300l store 2 C hotter than it was before I cooled it by 7 C by having a bath just after 1100 this morning...

[dennis]

Is it cloudy where you are? I expect my solar thermal has raised my 200l tank by a lot more than that today. Yesterday it managed to raise the top of the solar coil to 54C and the bottom to 42C, I don't have a sensor at the top of the tank (yet). It was at about 30C before the sun came out.

[Dave Liquorice]

No sunny all day, but I have 1/2 as much again to of water heat up, ie a 300 l store.

The upper sensor (in a pocket) got to about 73 C with the bottom one (not in a pocket) to 56 C. The bottom started at about 33 C this morning.

I have four 1 wire sensors on the store but only the upper is in a pocket, but about 15" down from the top. The others are just stuffed down holes in the insulation and don't make very good thermal contact with the cylinder. I've round tuit of some brass tube to put them in packed with thermal grease and a flat end and blobe of grease to get better thermal contact. It's that or finding some fine insulated and heat resistant wire so they can share pockets with the control sensors.

[Dave Liquorice]

The Thomann pages has several singles but they all seemed to be limited to 10 A...

About the cost of the single, stage lighting, dimmers.

I was thinking of Pi but controlling the triac more directly via an opto isolator under control of something else over ethernet. But with a current transformer on the out going mains(*) connected to the Pi I can't see why it can't do the lot.

(*) If more than X current is flowing out switch on the heater to reduce it but can you sense the direction of current transformer? I sort of feel you should be able to but not sure.

[dennis]

I agree the Pi should be able to do without the power control module but from a safety point of view I think the module would be a lot safer and probably complies with regulations.

You fit two current transformers, one for the PV and one for the total. Simple maths tells you what power to use. The only problem is you don't know if the answer if positive or negative but that wouldn't be a problem, it would only take a few seconds to work out the total current had gone up when the heater was switched on and correct the "error".

The way I think it should operate is to constantly monitor the total current and try to reduce it to zero using the heater. This would be the most economic for the owner and better for the grid as all the short term transients would go away.

You would need to feed it through the normal stat for the heater so you can't overheat the cylinder.

Of course it would have to be an open source project, we don't want someone making money.

[harry]

Tch Kirchoffs first law.

You have a three conductor node. (Sum of currents is zero)

You need to monitor the power generated by the PV array (Already metered.) Monitor current to house appliances. (Not usually metered) The difference gives the full story

Current is bi-directional on the mains connection. Only imported power is monitored.

[dennis]

If you are trying to tell me something I haven't already stated you will have to be more explicit.

[harry]

What I am saying is that of the PV power generated, without additional metering, you don't know how much you have used on site and how much is exported.

You might get some clue by the reduction of your electricity bill compared with pre-solar panel days. Assuming nothing else has changed. But the weather has changed so it will only be approximate.

[dennis]

What do you think the current sensors do?

[harry]

Most current sensors are just that. They can't sense direction. Buy yourself a cheap electronic KWh meter and connect in reverse direction to your existing mains meter.

[dennis]

Tyr reading what I said. Its not a difficult thing to do.

And this gives real time information that is actually useful in watt way?