Dazza

Hi Ante, Alun Thanks for your help, its greatly appreciated :). I shouldn't have too many problems getting this project to work now 8). Ante, I was thinking there was two opamps in the one package, but of course there isn't ::), so I will have to use another opamp to drive the LED to influence the LDR. I have been busy setting up the rest of the equipment I will need for the foundry, it's coming along nicely with the exception of obtaining a product called (Bentone) >:( which is an ingredient used in high-quality moulding sand. I have done a test casting using (green sand) which is a very basic moulding sand, and I'm not happy with the results :(, so I need to use a better quality moulding sand which is called K-Bond or O-Bond, which contains the Bentone. I have come up with a few product ideas, that I can apply electronics and aluminium casting to, to produce a product I can market locally :D. I now have to get my foundry set up, and produce a marketable product as quick as possible :o, to produce some extra income, as we have recently found out that there will soon be a new member to the family :D 8) 8). Here are some smiley faces to show how excited and happy I am. [move]8) :D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D :D[/move] [move];D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D[/move]

Hi Ante, (Alun ;D) Ante, here are the results of comparing the thermocouple voltage output to the thermometer. There is quite a difference between the temperature of the Molten aluminium and from where I measured the temperature of the furnace. I think I should be able to use the 200mV range of my 3.5 digital panel Meter, to represent the temperature. Ok 18.8mV = 560 so 188mV as it would be seen with out the decimal point on my digital panel Meter, times it by 3 A gained of 3 = 564mV, so what value resistors should I use for R2 and R1. Also I should be able to use the second amplifier of the TL 061 as an inverted amplifier to drive the LED? Amateur I M does it show ::) ;D. 18.8mV = 560C air temperature inside furnace. 25.2mV = 780C temperature of Molten aluminium. 200C = 07.3mV 190C = 07.0mV 180C = 06.6mV 170C = 06.1mV 160C = 05.6mV 150C = 05.1mV 140C = 04.7mV 130C = 04.2mV 120C = 03.7mV 110C = 03.3mV 100C = 02.8mV 90C = 02.4mV 80C = 01.9mV 70C = 01.6mV Thanks Alun, I understand much better now how it works. You still want me to go with your idea, of the on-off switching, very persistent aren't you ;D ;D. I helped my neighbour lay a few slabs of concrete, I told him that he needs to soak the ground before pouring the concrete, as the ground is very dry and it will draw the water from the concrete very quickly and it will crack, he just wouldn't have it, and sure enough it cracked ::), man I was very persistent as I can be ;D, and he was starting to get very annoyed with me >:(, he has moved house now not because of me, we are still good mates, last week I went for a visit and he had laid a slab of concrete leading from the front of his house, yet again he still didn't soak the ground first and it was full of cracks, he believed that it would be sufficient to occasionally hose down the concrete, sometimes there is just no changing someone's mind ;D. I'm sticking with the way I am going with the temperature control, but you have convinced me that your way will work fine ;), once I have got everything set up for my foundry, I want to build a small furnace that is capable of casting a large heat sink or a good size project box, and offer it as a project in the project section 8), that is if mixos wants it there. So when the time comes I would greatly appreciate your help in setting up the temperature control, your way ;D ;D.

Members request for assistance was microcontroller related. [iurl]http://www.electronics-lab.com/forum/index.php?board=10;action=display;threadid=2747[/iurl]

Yes Ante :), amplify the voltage to the correct level, to display the temperature on to my 3.5 LCD panel Meter, then I can work on the inverting amplifier to drive the LED, then look at what else can be done ones that is working correctly :D. I can borrow a thermometer from my neighbour that he uses for his homebrew, its maximum temperature read out isn't very high, but it should be enough to get a fairly accurate idea of what my thermocouple voltage output represents. I will post the results tonight :D.

Hi Ante, Alum, Ante, sure I like the idea, but it's the putting it all together I'm not too sure about, by the time I'm finished that is if I can work out where to start or how to start, I should be able to pick up satellite TV with it, the way things are going ;D. Alum, Sorry my electronic knowledge is very limited :-\, I don't understand the circuit you have provided or how to use it, I understand it is for creating a slow rise and fall response to the elements ???.

I have a little more to add, the temperature did eventually rise to the point where it would have been suitable for casting 18.7mV. I also measured the temperature of the molten aluminium 25.2mV, unfortunately I didn't think to measure the resistance of the thermocouple ::), that probably would have been handy.

Hi Ante, Alun, Ok, I have the thermocouple and some more pic too ;D. On the 200mV range, my DMM reads 18.0mV. It doesn't seem to want to go higher than that, the aluminium is Molten but not hot enough for casting, and I don't think I can give any more power to the elements :(, hmm maybe I need another element, or the refractory isn't keeping the heat in good enough, well this doesn't matter for now, I think I should concentrate on getting this temperature control sorted out first :).

Hi vinash, The ICL7107 doesn't need to be programmed ;D. Yes, you just need to buy the chip, and have fun putting this project together 8).

Hi, Matt/flat black, was preferred over gloss black in regards to painting a radiator, because Matt black has more surface area. When it comes to the colour of the paint you choose, I doubt it would make any difference in regards to the heat being disbursed from within an object, what can make a difference is the type of paint you use and its formula. Paint your radiator any colour in a matt/flat and it will disbursed heat just the same, although if you add sunlight, black will be less efficient.

It looks like someone has been creating chaos, or is planning to ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D. That's quite a collection you got there Ante :o :o.

Hi Ante, Alun :), The op amps that you suggested Ante, are not easy for me to get, that is not available from Jaycar or Dick Smith >:( but luck is on my side this time, I have two recycled (TL061) that should be ok :D. Yes the calculating thing, haven't got the hang of that yet :o, and there is still that problem of having nothing on top, to pull out ;D ;D. My thermocouple hasn't arrived from Jaycar yet :( , so I'm not sure what the voltage output will be, I know it's in the very low millivolt range. I do have a thermocouple that I think is from a convection oven or something like that, I connected it to my DMM set to the 200m range and applied heat, it rose to 00.6mV and went no further, although I don't really know if this thermocouple is working properly ???. Alun, Yes it is true that thermal shock will damage this kind of element Nichrome 80 :), when they are first fired the aluminium within the wire burns off, creating a protective layer around the wire preventing oxygen from entering and rapidly deteriorating the wire, I have read about this on the net, and unfortunately I have already discovered it to be true, after I had fired my elements, I found that there was a small portion of the element protruding out from the furnace wall, I made a small kink in the wire to fix the problem and sure enough after a while it burnt out, not only where I made the kink, it burnt out in several places where I touched it. Alun, I really wish I could go with the way you are suggesting, I really do it would make things so much simpler 8), but from what I have read it strongly suggests, to avoid switching the power on and off to these elements and it is also a good idea to leave the top on the furnace to allow the temperature to decrease slowly, to avoid thermal shock and the same would apply for heating the furnace up. Ok I think I need to plan my angle of attack for this project, this is what I am thinking, start with getting the thermocoupler to register the temperature on my 3.5 LCD panel meter. Then I can use the output of the op amp to the LCD, to drive an LED via another op amp, I think I need to try to get it this far, then work on what needs to be done after that, does this sound like the way to go.

Alum, thank you so much for your help and advice :), what you are suggesting, would basically mean a complete do over , I think that the big problem that I will find with the switching on and off, is that it may be very stressful on the type of elements I am using Nichrome 80 wire. This is one of the reasons why I wanted to avoid using a on off type of control. With Ante's idea, all I have to do to the original circuit is replace R4 100K with an LDR which will be varied by a LED, the LED has to be varied accordingly to the temperature I want to maintain, I also want the temperature displayed on an 3.5 LCD panel Meter, I could really use some help on getting started on this circuit, any suggestions of a suitable opamp that is commonly available, and some resistor values to get me going please :-\.

ArcAngel2479, check this out(http://www.autospeed.com/cgi-bin/browse.cgi?category=4334&sc_add=100770004&) the programmable ignition timing module, may make the purchase worthwhile :).

This is all I have been able to find so far :-\.

Ante, I'm going with the LDR and LED ;), I just need to find a thermocouple Preamp circuit, that uses commonly available components to work from, I'm just not to good at starting from scratch :-\.

Hi Alun, I don't know much but Yes I did know they were the wrong symbols ;), ExpressSCH unfortunately didn't have them available, so I went with near enough, I could have made a custom component but I guess I was being lazy ;D. It is very likely I will make mistakes along these lines in the future, I do hope you will keep an eye on my future projects :), thanks for your reply Alun. Alun, what do you think of Ante's idea :D, do you think using a optoisolator would be better, I do have available to me a(4N25) optoisolator, I would like to try to keep things as simple as possible.

Hi Ante, Yes Ante I do get the idea, and it is a good one, and I think it will work. Your idea means that I won't have to worry about mains power, while trying to get it to work. I have no idea what range is used on the DMM, the thermocouple that I'll be using, is meant to be used with a DMM that is designed for measuring temperature. I guess the most important thing to know, would be how much current a K type thermocouple can handle. I'll also be wanting to use a LCD panel Meter to display the temperature, as well as drive the LED. The accuracy of the LCD temperature display and the temperature regulation, doesn't have to be all that accurate, near enough will be plenty good enough, for this application :).

Hi Ante, Alun Melting point for aluminium is around 660C. I don't know what the temperature should be for pouring into the mould ???, when I was working in the foundry we knew it was at the right temperature, by its texture and colour and it was very rare that we ever got it wrong, hopefully I still have that ability 8). This is the most common method for a backyarder to use as a mould, green sand (http://www.backyardmetalcasting.com/book_sc.html) and this is the method that I'll be using to begin with, there are many other methods as well for example, the loss foam method and dry sand. The time it takes to melt the aluminium, is about 2 to 3 hours, each melt after that takes about 30 to 45 minutes roughly, High-powered heaters, will help to a certain point, that is to reduce the time it takes to raise the furnace temperature up to its maximum temperature, which is governed by the maximum temperature the elements can handle which is 1200C, for the elements that I'm using, Nichrome 80. So now it looks like I'm going to have to maintain a constant temperature in the furnace, if I want to avoid the temperature rising above that of which the elements can handle and to help them last as long as possible. I was really hoping that I wouldn't have to do this, man nothing is simple is it. Ok, I can get a K type Thermocouple that is rated to over 1200C, for 13.00$ that is meant to be used with a DMM, that I think should do the job. Next I will need a Thermocouple Preamp, I have been searching the net for a circuit, that uses commonly available components, I haven't had any luck yet. I already have a LCD digital panel meter, that I could use to monitor the temperature, once I get that sorted out I don't know what to do, that is how to connect it to my existing temperature control circuit? Maybe I could connect a relay between the DIAC and the gate of the TRIAC, to switch the power on and off to the elements, this might be the simplest way for me to do it, but I would much prefer to be able to have the output from the temperature sensor, to very the power to the elements to maintain a preset temperature, I will also have to be able to set a maximum, as I do now or the elements will burnout straightaway. Any help please, I don't really know what I'm doing, this project is beginning to become more complicated than I expected

Hi Ante, Nothing went wrong, it was just that I had to go out and I didn't want to leave the furnace running unattended, always safety first ;). I have fired her up again this morning, the furnace temperature control works great, with a large heat sink it doesn't get hot enough to need to use a cooling fan. Here's a couple of better quality pics 8).

Well it looks like it works 8), and I am ahead of schedule :). In the first pic you can see my you beaut trolley ;D ;D, with the furnace mounted on it, I was planning on salvaging the wheels from this old lawnmower to use for making a trolley, then I thought why do that when all I have to do is sit the furnace on it and she's all done. The other pic shows her in action, the aluminium was not properly melted down, it would of taken about another 15 minutes to melt down to the point where it would have been right to go, unfortunately I had to cut this test run short :(. Sorry for the bad pic quality, there wasn't enough light :-\.

Hi audioguru :), Yes, that's probably what the problem is, my ISP.

All is well mixos, and has been for quite some time now 8). Your efforts are very much appreciated, Thanks mixos ;).

I have been receiving topic notifications now, I got 17 come through at once. I don't know why I wasn't receiving than, or why I started to receive them again. I guess these things just happen. [move] ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D ;D[/move]

Hi Ante, It's just about finished 8), if all goes well I'll post a pic of the first melt, which should be Saturday :D.

Ok, so far so good, every think is coming along nicely better than I expected :), I have applied heat to the furnace for several hours to drive out moisture, a few more hours and she should be right to crank up the heat, once I make the new heat controller unit, and install the second element 8). Ante, It is said to use this refractory mixture fairly dry, like cookie dough. It is also said that this concoction is sticky as I don't know what and it certainly is, what a nightmare to work with :o. Yes Ante, I was thinking the same thing ;), but then I realised if I made it to wet there would be too much shrinkage, I did wet it more than I knew I should, and still this gunk did not want to play nice >:(. Now that I have first-hand experience and know how nasty this stuff is, I'm pretty sure I have worked out a way to tame the beast, and make it do what I want :), Oh yes did I mention this stuff is very nasty to work with ;D ;D ;D ;D. I don't understand what's going on when I measure the voltage out from the heat controller unit, it measures around 330VAC ??? Here is a couple more pics :)