StillSmart

So i have ordered the parts to build myself a power controller. Couple of weeks before they get here.

I thought a long time about metering the power out. Thanks to chatting on with my clever mate I realised that, somewhat counter intuitively, there is no need to measure output at all. The best results come from measuring the input to the device. An input ammeter is all you need for linear indication of power out. The good news here is that if you already have an ammeter on the output then moving it to the input should make it more useful.

I must say here that although i did an apprenticeship and went to college as my first proper job many years ago that only allows me to understand my much cleverer mate. He is the sun of electrical knowledge and I am merely the moon reflecting his light.

The first thing I bought was the 100a 0-240v phase angle controller. Overkill? Yes. Why? Well i do have 100a power so it might be handy for something one day.
Item number:
190836678049

Also I am a big believer that if any device or structure is over engineered then it will have an easy long life. In this case it was not a question of "what would Jesus do?" rather "what would Brunel do?" Also it was only about £10.50 which is not too dear.

Instead of a simple ammeter i splashed out the extra £3 and spent £8.50 on an LCD wattmeter. Basically a panel mounted version of the device easy uses. It will connect to the input of the PAC and give me a direct reading of watts used. If i want it to it will tell me how much a run has cost me in heating. I was tempted to shell out another £2 and put a voltmeter on the output just for bling and in case it came in handy for some other use. Resisted so far.

Item number:
191219170003
Found a UK seller that does 500k 1/2w pots for a quid plus quid postage. He can do me a knob for another quid on the same postage.

So total spend around £22. I have boxes, heat-sinks, sockets, cable etc in my tat pile so no spend there but may be a factor for you if you make one.

For that I get a 100A power controller with a direct reading of power. Bearing in mind the device consumes a little as heat etc so the reading is slightly off by that amount.

Ant,

What about a fan? or do you think that the rating of the SSR is enough to handle it?

100a controller - what size cable are you using?

Can't wait to see what you recycle for this one.

Brian

Hi Ant, just a thought, what will knowing a particular number gain you? You might as well just mark up the dial 1 through 10 and know that when its on 6 the output is what run hearts on, or 2 is where you pull off heads (knowledge gained through experimentation)

My controller is a PWM controller so when I have it on my 1800w still at number 6 the amps being drawn are much less when I have it on number 6 on my 3kw still.

Repeatable results are what we are after - knowing what a particular power consumption is less important. If you are keen to do it as a project, don't let me put you off, just saying no need to over think the issue.

I agree Captain, but to get to that point I found it so much easier having a power rating.

When I was given good advice by a guy in Scotland such as "when you are compressing the Heads keep the power at 850 watts" I knew what that meant and how to make that setting, if that person had told me "I keep the dial at number six" or "just left of the pencil mark" it would not have been much of a help.

I vote for power ratings.

Brian: I hope the size of the controller and the heatsink will mean I don't need a fan. I have quite a few lying around but they do tend to cause dust build up in the long term which then means occasional maintenance or potential overheat and failure. . So if passive works then good.

Cabling is a very valid point as is plugs and sockets. I do have 16mm2 cable lying around which is good for 100a in short runs but bulky. I also have pyro which can do the same job more compactly. As it is mostly for longevity and I doubt I will ever actually use the 100a i will probably compromise and use 32a blue euro sockets and plugs, if I have enough in my box of bits, and wire accordingly. I am a fan of that flex cable with the clear outer sheath and steel braiding just underneath. Got some of that around too. I can't see me actually using more than 30A even in the future when I get a 100lt boiler going. This gives me a 70% buffer to give the device a cool easy life. Why expect my machines to work harder than I like to myself? We all wear out faster if we work harder.

Good point YHB, you could do a rough calibration though. Charge the pot still with water, so the contents don't change over the course of the distillation.

Run full power (you'll know the wattage of your element), measure the output in ml per min. Adjust the controller to get 75% 50% and 25% of this output.

You can then mark these on the face plate and know roughly what the power is.


Or buy a 20 quid power monitor from maplin

Capt: yes i agree with you too.

However as Brian has pointed out if you wish to exchange information then a standardised system of measurements helps.

I also believe ithat the non linear nature of adjusting a PAC makes it hard to know how much to turn the knob to get the amount of adjustment you think you need. Yes you will get used to it and you could do what Brian and others have done and mark up an accurate non linear scale. But it is easier to just read the power directly and the fact Brian et al took the time and trouble to make a non linear scale indicates it is desirable.

It may be different for you because you use burst fire.

And of course I just like having data to see and think about. I believe it will make learning easier. For me it is £8 well spent on the same gadget you could spend £20 on as a stand alone, limited to 13a, device. Of course you could get a stand alone for less than Maplins through eBay but still, I considered that and decided to go this way instead and sacrifice being able to use it in other devices for the sake of the cash saving and the extra current capacity.

Capt: fwiw This is the one kind of measuring device that should work pretty well for burst fire.

fwiw when powering 2 x 1.5kw elements controlled by a PID and 40a ssr the heatsinks at the 2nd vane down when close to target were about 60C


so i tend to mount them externally, cutting a small tab out of copper tube to secure between the screwhead and ssr of the heatsink fitting, and screwing that to the box side/poking into a screw hollow...

That is helpful. Thank you Fil.

Depends what box I end up using but external heat sink fins sounds like a plan.

May seem stupid but I don't sort through my tat and make firm plans until i have the core bits to start with. I only have a vague idea of the scale of the bits. Despite drawings with numbers in the ads. Dumb I know but I like to think with my fingers and eyes.

My power controller has only a passive heatsink and runs a 3kw element, it only ever get a little warm during a stripping run, I don't have a power meter but I'm guessing it's at about 2.5kw for a strip, I also only use a 13amp plug (3kw =12.5amps), the plug can get warm though and last time I did a big strip of 38litres, I damaged the wall socket, can't switch the socket off anymore, the switch contacts must have welded together!!!

I do like your idea of putting a power monitor on the input, have you a link to the item you got off eBay?

Sorry just spotted the item number on your original post, thanks

Ah, that's encouraging to know. Thank you.

You might consider the blue 16A plugs and sockets. They are not really dear. Less than a tenner a pair. As in life the females cost more.

That is all I actually need right now but if I have them I will use the 32a to future-proof a bit. I like making things but not enough to enjoy rebuilding and upgrading if I can just build it right once.

Still waiting for my bits. Just an update on the measuring power situation. My moon recently reflected the light from another star and has made me rethink what is happenning at the input and output. Long story short, while a lot hinges on the specific meter you use, reading input and output will actually be very close to each other and amps on the input is still a non linear relationship. It boils down to 240v being an averaged illusion of the constantly rising and falling voltage of the sine wave. I could post a link to "the forum where people are rude" but prefer not to. You can find it if you want to read the long version. My name there is anthoney.

For anyone with the money to burn this is the dogs precious bits in accurate metering.

http://www.newark.com/murata-power-solu ... dp/39T1184