Doing my head in so im just gonna ask!

[Tsv Stiller]

I have been reading through all the threads related to building a element controller for my 2400w Mac element. I have a plastic box for it to go in and a sparky to wire it up.

I can find a heap of different options based on what other have done etc which is great but;

Can someone just tell me the basic "must have" components to build a temp controller for a 24oow element. Please.

Just the bare bones components that once wired up correctly will work at a cost effective price.

Thanks a heap!

[JayD]

there's a diagram in this forum just build what you need to do the job, so you want one with a knob to adjust the wattage...more to it than this but dont confuse yourself...pick your path (diagram) then follow it...

[Tsv Stiller]

well i assume punchy's original diagram is the most basic schematic that will work so according to that i only need

a PSR25
a switch rated for load?
a volt thing?
and cables and plastic enclosure

is this correct and is it this switch that adjust the actual temp?

What are the actual components called that i need to purchase? I scroll through and some say some things are needed some are not necessary some you can no longer get etc
thanks

[Andy]

might be worth talking to the guy that's going to put it together for you. if you get components that he doesn't know how to use, it wont help either of you.

[Yummyrum]

The PSR25 does the controlling of temps .It gets quite hot while working

You Must bolt it to a heatsink to help get the heat out of it otherwise it will overheat and fail .

You Need a Heatsink .You also need to buy a small tube of heatsink compound (Paste to smear between the PRS25 and the heatsink)

You also need the 500k Ohm Potentiometer Too that is connected to the PSR25 .That's the thing with the Knob on it that you adjust .

You also need a Plastic knob .It is the only thing between you and possible electrocution should the Potentiometer fail ,especially if you are going to use a plastic case .

And another thing ,All electrical controllers like this should be Built in a Earthed Metal case .....NOT a plastic one . There are several reasons for this .Please accept it is to be done .I know several people have built in plastic cases and I cringe every time I see one .

You should follow everything Exactly that is in Punches Controller .It is OK to leave out the Voltmeter if you wish .

Finally the Fan .Personally I think it should be included especially if you are going to insist on using a plastic case .but if you are going to use a metal case and only a 2400W element and never a 3600W then you will OK IMO .

And I hope that your sparky mate reads this .

[Dominator]

As opposed to the PSR, you can use on of these. Speed Controller
That is what I used. Then you just need a power point to mount on your box, some 2.5mm three core flex and a 10A three pin plug.
As for using a plastic case, for safety's sake it is best to use a metal case and earth it. I have used a plastic case, however I was very careful to earth the heatsink as well as the shaft and the case of my pot. I have not yet posted the details of my controller as I have not had a chance to test it to a point that I am happy with. I have done a 5 hr spirit run with it though and it worked a treat.

[Tsv Stiller]

thanks yummyrum exactly what i was after!

I think its the army background, call me simple but "like this do that" works for me.

Cheers

[Jonno]

I don't get why everyone says that it should be a metal case. Am I missing something? As long as you earth the controller I see no problem

[Dominator]

I don't get why everyone says that it should be a metal case. Am I missing something? As long as you earth the controller I see no problem

I guess with amateurs building these it was easer to say earth the case then to explain what, how and why.

[Yummyrum]

I don't get why everyone says that it should be a metal case. Am I missing something? As long as you earth the controller I see no problem

I guess with amateurs building these it was easer to say earth the case then to explain what, how and why.

OK I just sent this as a PM to another member asking me the same question .

I'm a TV tech not an electrician .

My main concern is that all switches ,potentiometers shafts and brass grub screws that hold the knobs on all have the potential to be live if they brake down internally .By having the case metal and Earthed then any exposed metal will be at earth potential .

Many constructors buy the cheapest components they can and you only need to pull them apart to see that there is often only a mm or less between metal conductors that are at 240V Ac and exposed metal actuators that if were in an unearthed plastic case could become lethal conductors in the unlikely event of a breakdown internally .

When I did my apprenticeship way back in 1983 in NZ we were told that things should be built in All earthed metal cases or double insulated plastic cases where all switch actuator mechanisms were to be of plastic or other non conductive material that protruded the case .IE anything that could be touched


Cheers Yummy

Also add that If we are bolting a a heatsink to a case I personally think it should be Metal Case .Things do get Hot .Things do melt . Metal dissipates heat much better than plastic .

If nothing ever failed then I would not have done an apprenticeship solely for the purpose of repairing brakedowns 8-}

Maybe I'm a pedantic wanker in this area but its all about building something as safely as we can :handgestures-thumbupleft:

[Dominator]

The thing is yummy, if the offending part is earthed then there is no problem, hence why we say 'earth you pot', that way if there is a fault in the pot and the knob becomes live, one of two things are going to happen: 1. It trips the RCD, 2. If the RCD fails for some reason or the house does not have one both of which are unlikely but possible (note to everyone: if your house does not have an RCD or 'Safety Switch' please get an electrician to put one in, it could save you or your loved ones life!) then the fault will follow the path of the earth wire and not flow through your body. If the pot is not earthed then the outlook is not so good.

I guess the thing with metal cases is it will earth the shaft of the pot. I soldered a earth wire onto the tab on the casing of the pot when I made my controller but I found when I tested it the shaft was not earthed so I ran a separate earth to the shaft. I guess if someone did the same and earthed the case of the pot and assumed it was ok then they could get hurt, whereas if it was in a metal case they would be protected.

I would also recommend earthing your heatsink, if your transistor fails it could liven your sink.

And yummy, the difference between now and when you did your ticket is RCD are now mandatory and by far majority of houses now have them.

[Jonno]

And with a metal box if your earth was to break down and a similar thing were to happen with shorting the whole box would be live instead of just a screw etc.

Both have there own advantages and disadvantages

[deejay]

Hi, just ask mac to send you the stuff you need
then you will be able to work it out from there i did

cheers :handgestures-thumbupleft:

[Yummyrum]

Dom .I agree completely with what you are saying that's why I stress the importance of this method . And RCDs just make it all the more reason to go this way.
Jonno .
I agree ,you also have a valid point ,an earth could fail .Again why RCD's are important .But we have lots of safety mechanisms built in to reduce this like yellow.green striped wires so the 10% of colour blind men don't fuck it up and longer insulation on pins of 3 pin plugs so earth contacts longer, and all earth leads being made longer so they are the last to break ETC ETC

The MEN system has been round for a lot more years than me though and Earthing Equipment for safety's sake was one of the main drives behind it . :handgestures-thumbupleft: