Sciencemadness Discussion Board - Heating mantle blew up WTF!!!!!

Heating mantle blew up WTF!!!!!

draculic acid69 - 19-7-2019 at 04:15

Ok a year ago I bought a heating mantle/stirrer as soon as I bought it I plugged it in turned it up to max and let it burn off the coating, put a flak of water in it and boiled it for an hour let it cool down,played with the stirrer then put it back in the box.no problems.box then sits in back of cupboard until I pulled it out and setup everything to give it its first trial run today. Then as I go to put the cord from the power pack into the mantle and it makes contact with the pins BOOM!!! the fucking thing shoots out a massive spark followed by smoke.something inside either shorted or malfunctioned and after opening it up it looks like the transformer has shorted against the leads and the cover but why now and how? No metal was touching any other metal no wires were exposed or split . just black burn marks on part of the transformer. I don't get this.has anyone ever had one short out like this?

XeonTheMGPony - 19-7-2019 at 04:28

A ton of things will cause this, any thing from china, open it up and check all the electricals, that is oft the weak point of made in China is sloppy assembly, lose connections, poor ones.

Odds are, the brains will still be good, so replace Xformer, do the above and it aut to come back to life.

Heating it dry = very bad bty

Sulaiman - 19-7-2019 at 05:05

Quote: Originally posted by XeonTheMGPony

...any thing from china, open it up and check all the electricals, that is oft the weak point of made in China is sloppy assembly, lose connections, poor ones...

VERY good advice.

draculic acid69 - 19-7-2019 at 05:27

It was the 2nd time I've ever plugged it in. Nothing wrong with it when I put it back in the box.then I plug it in and its fucked.dont get it.

Ubya - 19-7-2019 at 07:59

Quote: Originally posted by draculic acid69

It was the 2nd time I've ever plugged it in. Nothing wrong with it when I put it back in the box.then I plug it in and its fucked.dont get it.

maybe the leads were 1mm from touching at the beginning and once stored for a long time they touched (insulation contracting/expanding?), you never know sith this things, it could work 100 times and blew up the 101

Herr Haber - 19-7-2019 at 10:00

Hehe, the one I got from China never worked.
I stored it planning on doing exactly what was suggested above but maybe it'll work when I plug it in !

draculic acid69 - 20-7-2019 at 18:03

It looks like an insulated wire touched between the cover and top of the xformer but how would that cause a short bcoz the cover wasn't touching? Also looks like the 2 secondary wires coming out of the xformer have burned and melted slightly.i dont know if it fried anything else. Who's the best ppl to get to fix this stuff? Do I need to find an electrical engineer? Is there a company that fixes this type of stuff?

Sulaiman - 20-7-2019 at 18:35

Repairs cost components (cheap) and labour time (not cheap)

If you are not in a hurry, and have a multimeter, I presently have the time to help remotely.
If you do not have a multimeter I can recommend the cheap Aneng AN8002 as I've used and tested it a lot.
(I've used it many many times with domestic 240 Vac but I've not used (do not trust) it on 415 Vac even though it is 'rated' for it - high power arc flash in your hand is not funny. Multimeter fuses for high energy systems are expensive but necessary)

draculic acid69 - 20-7-2019 at 21:08

While I trust my soldering and low risk DC electrical skills I don't trust my safety on doing AC work.i just don't understand it enough and one fuckup can lead to death.thanks for the offer sulaiman but I'll have to think about it.

Sulaiman - 20-7-2019 at 22:13

I understand your concerns, 240 Vac can be fatal,
but I'm a lucky optimist ... I've felt 240 Vac more than once - PAIN !
Electrocution by 240 Vac is quite unlikely, but if in doubt ... do not mess with 240 Vac.
Comparing with hobby chemistry, I'd put the risk at equivalent to chlorine gas generation.

wg48temp9 - 21-7-2019 at 02:16

Quote: Originally posted by draculic acid69

While I trust my soldering and low risk DC electrical skills I don't trust my safety on doing AC work.i just don't understand it enough and one fuckup can lead to death.thanks for the offer sulaiman but I'll have to think about it.

I good/minimum design rule is insure that a minimum of two failures/fuckups are required to kill or seriously injury you. For example the metal enclosure of 240Vac electrical equipment should be earthed and internal wiring should be insulated so it would require failure of the insulation and failure of the enclosure earth before the enclosure becomes live and potentially lethal.

An other example is when boiling a liter of drain cleaning fluid ensure that the boiler is sitting in a container that will capture all drain cleaner in the event that the boiler fails and releases the boiling drain cleaner. Of cause this is only applicable if the probability of a single failure is low as the probability of two simultaneous low probability failures occurring together is very low.

.

Herr Haber - 21-7-2019 at 05:04

Quote: Originally posted by wg48temp9

Of cause this is only applicable if the probability of a single failure is low as the probability of two simultaneous low probability failures occurring together is very low.

Unless you are just about to replace a failed HDD from a Raid array.
Feeling good an cozy and then... :mad:

second one fails !

I might take you up on your offer Sulaiman

XeonTheMGPony - 21-7-2019 at 06:00

Quote: Originally posted by draculic acid69

AC work is same as dc for all intents and purposes of this repair, Volts must match, the current rating of new Xformer can be larger but never lower

ensure all connections are clean tight and well insulated you will have no issues

Sounds like the failure point was an internally shorted transformer where it arced out the top.

A couple pictures will help. as it could be an RF choke too, with out seeing it to much guess work for my liking.

[Edited on 21-7-2019 by XeonTheMGPony]

Sulaiman - 21-7-2019 at 07:24

Quote: Originally posted by Herr Haber

Unless you are just about to replace a failed HDD from a Raid array.
Feeling good an cozy and then... :mad:

second one fails !

I might take you up on your offer Sulaiman

Long ago I ignored a mainframe memory IC failure
not a problem, as the chance of a second memory IC in the same word failing before the next scheduled maintenance were negligible...I assumed.

At the moment I'm free so, you have a multimeter ?
(I should remember or search but I'm lazy)

Dr.Bob - 21-7-2019 at 14:07

"as soon as I bought it I plugged it in turned it up to max and let it burn off the coating"

This is the problem, you burned it to a crisp. They are not made to heat dry and to a maximum unless being cooled by a load. They are designed to be controlled and heated slowly while a flask full of material is in them. Doing what you did is the worst thing possible for a heating mantle. They are not like self cleaning ovens, they are made of fabric that will melt and char if heated too much. I get them from people all of the time like that. I have been using the same heating mantles for 10-30 years and they don't ever fail, so I am pretty sure that I am doing it right, plus I was actually taught the proper use of them. Don't ever heat them above about 50% of their rated power until you have tried lower power and it did not overheat, you should only need to heat above 50% when using water or other high boiling solvents. For most organics, they rarely are above 30-50%.

What you did was like testing a new car by holding the gas pedal down with a brick until the engine blows. For many things, you don;t need to go to 11...

[Edited on 21-7-2019 by Dr.Bob]

XeonTheMGPony - 22-7-2019 at 04:29

Quote: Originally posted by Dr.Bob

"as soon as I bought it I plugged it in turned it up to max and let it burn off the coating"

This is the problem, you burned it to a crisp. They are not made to heat dry and to a maximum unless being cooled by a load. They are designed to be controlled and heated slowly while a flask full of material is in them. Doing what you did is the worst thing possible for a heating mantle. They are not like self cleaning ovens, they are made of fabric that will melt and char if heated too much. I get them from people all of the time like that. I have been using the same heating mantles for 10-30 years and they don't ever fail, so I am pretty sure that I am doing it right, plus I was actually taught the proper use of them. Don't ever heat them above about 50% of their rated power until you have tried lower power and it did not overheat, you should only need to heat above 50% when using water or other high boiling solvents. For most organics, they rarely are above 30-50%.

What you did was like testing a new car by holding the gas pedal down with a brick until the engine blows. For many things, you don;t need to go to 11...

[Edited on 21-7-2019 by Dr.Bob]

This^

I break mine in by putting a flask of water in them, start off low power and hold the water at 50 for 30m to an hour, then to boiling for 30m, during this I check for ground leakage and any weird hot spots.

Then I use it. My mantle has don several sulfuric acid distillations and a crap load of much cooler distillations and still going strong.

draculic acid69 - 22-7-2019 at 05:27

The instructions say to burn off the coating with nothing in it first.then I boiled a flask of water in it this was actually done a few days apart.nothing wrong at this point.
Just took the board off mantle and its cooked.the copper tracks have come off the board.it looks like the power has surged thru from the plug thru the board and then out into the xformer where it arced and smoked.
The black at the base of red wires is where it must have arced out and melted.
The spot on the cover is where the spark hit the metal plate. that was right over the top of the transformer. On the board where you can see the shiny copper tracks is where they have come off the board.they are the tracks between the red xformer wires and the mains input.

[Edited on 22-7-2019 by draculic acid69]

[Edited on 22-7-2019 by draculic acid69]

draculic acid69 - 22-7-2019 at 06:04

Now that the board is fukt I can either replace the transformer with a new one and resolder a new board bcoz I'm sure I can't buy one or I can just plug a Variac directly into the nichrome element.or I can use my other mantle only problem there is no stirrer and it's all in Chinese.

[Edited on 22-7-2019 by draculic acid69]

highpower48 - 22-7-2019 at 08:44

Best just to get a Variac and be done with it. This will also a allow you to buy cheap mantel heating liners and make your own. And a Variac will give you a lot more control of the temperature. ..

markx - 22-7-2019 at 09:33

How much "furniture" is on the other side of the control board? It does not look too complicated....perhaps there is still hope for repairing it.
It sure seems that there was a serious short somewhere in the circuitry and most probably it was caused by a semiconductor device failing.
Is the stirrer motor asyncrhonous type (AC driven) or a dc motor? I trust most of the control board deals with the rpm control of the AC motor....usually it is built that way.

To regulate the heating mantle a simple thyristor driven "dimmer" circuit can be used instead of a variac. They are dirt cheap, small, and can commute a serious amount of power without oveheating.
Like this one e.g.:
https://www.ebay.com/itm/Electronic-2000W-Imported-Thyristor...

I use one to regulate the temperature of my soldering iron...works beautifully.

The stirrer motor control, if it happens to be AC is a bit trickier. But if you are lucky and it is a DC motor then a variety of PWM speed control modules are available. These can be used to regulate the stirrer speed.

E.g.:
https://www.ebay.com/itm/PWM-DC-Motor-Speed-Control-Regulato...

In case of AC motor you basically need a VFD type solution....actually I saw a really small single phase module that could be used for the purpose, but I can not find a reference right now.

XeonTheMGPony - 22-7-2019 at 15:51

the three pin unit that the track leads to I suspect is a triac or scr, it may have shorted. lets get a pic on the top side, other wise a bit of ruffled tracts are of no concern, just get some conformal coating and recoat, and if broken just solder wires in their place

now days you can get cheap dimmer style motor speed controles.

[Edited on 22-7-2019 by XeonTheMGPony]

draculic acid69 - 22-7-2019 at 22:44

The motor is d.c. controlled. I talked to an electrical engineer and he said there should be a fuse attached somewhere.there isn't one.no rf choke on there anywhere but is it even needed on a heating mantle?.they really make this shit cheap.
Are these thyristor things really a suitable thing to control a mantle? What's the difference between a Variac and a thyristor?

Sulaiman - 22-7-2019 at 22:52

Quote: Originally posted by draculic acid69

The motor is d.c. controlled. I talked to an electrical engineer and he said there should be a fuse attached somewhere.there isn't one.no rf choke on there anywhere but is it even needed on a heating mantle?.they really make this shit cheap.
Are these thyristor things really a suitable thing to control a mantle? What's the difference between a Variac and a thyristor?

Fuses and chokes cost the manufacturer money

I doubt that a thyristor is used, possibly a pair but almost always a triac is used.

The main difference between a variac and a phase angle controller (dimmer) is cost.

A variac will eventually need a new carbon brush, and a dimmer will need a new potentiometer.
A variac will not need rfi supression, unlike a dimmer.
(dimmers work just fine without rfi supression, nearby radios or sensitive electronic equipment may pick up noise if the dimmer is not rfi supressed)

[Edited on 23-7-2019 by Sulaiman]

draculic acid69 - 22-7-2019 at 23:20

The board doesn't look too complicated and apart from the lifted tracks the components or "furniture"as you refer to it dont look burned out or damaged
there's an electrolytic capacitor and it isn't popped or leaking and that's usually the first sign there's something wrong with them.they don't have burn marks anywhere.so maybe I can desolder and make a new board.its doable.might be quicker to learn Chinese and put a stirrer in my other one.

markx - 22-7-2019 at 23:42

Quote: Originally posted by draculic acid69

The thyristor/triac circuits are absolutely spot on for controlling passive loads like a heating element or incandecent light bulb....or a soldering iron in my case. Just do not trust the wattage rating on these things to the maximum. Get at least a double size beefier unit (e.g if your mantle is rated at 1kW then get at least a 2kW control module). They work by switching off part of the AC wave....how much is cut off depends on the position of the control knob. Effectively this regulates the amount of energy that is fed into the heating element. A simple analogy would be to include a diode in series with an AC heater circuit. The diode conducts only in one direction, cutting off the halfwave and thus also 50% of the energy:
http://www.pcbheaven.com/wikipages/Dimmer_Theory/

A variac is simply a tunable transformer that can vary the output voltage by turning the knob....thus, the lower the output voltage, the lower the generated energy in the heating element. They tend to be bombproof, but are bulky....a triac/thyristor circuit is tiny and light. It can be hidden in the original case of the equipment with ease and it shall accomplish the same effect. I do not think one can fit a variac into the original casing.

If your stirrer motor is DC type then you are in great luck....there is an endless selection of DC PWM type speed control boards available. Again they are cheap, small and really functional.

So even if you are not able to repair the original board then you can take replacement modules for a couple of dollars and with a little bit of soldering and common sense get your equipment back in full operational condition

Also it would be a good idea to include fuses if they are missing in original schematic. Chinese tend to be really cheap and I've seen circuits that lack absolutely any safety measures....a shortcoming that can cost dearly. So take care of that aspect also once you already are in there

draculic acid69 - 23-7-2019 at 01:38

Sulaiman the thyristor isn't in the mantle it's just suggested as a replacement to the board that's currently there.

Markx: so you are pretty sure that the 2000w thyristor would almost certainly SAFELY handle going between the mains and the nichrome element without anything going wrong as long as I don't turn it up to max and "glass it" ie: melt the fiber mat or should I get a 1000w one to be on the safe side?

And just a question to anyone who knows about this: how big of a fuse and what type should I wire in? I was told a 5A would be ample for my 400w 240v mantle.i just don't know if theres like a special thermal type used for this sort of thing that's different to a normal inline one you use on your car.

XeonTheMGPony - 23-7-2019 at 04:53

Quote: Originally posted by draculic acid69

Sulaiman the thyristor isn't in the mantle it's just suggested as a replacement to the board that's currently there.

Markx: so you are pretty sure that the 2000w thyristor would almost certainly SAFELY handle going between the mains and the nichrome element without anything going wrong as long as I don't turn it up to max and "glass it" ie: melt the fiber mat or should I get a 1000w one to be on the safe side?

And just a question to anyone who knows about this: how big of a fuse and what type should I wire in? I was told a 5A would be ample for my 400w 240v mantle.i just don't know if theres like a special thermal type used for this sort of thing that's different to a normal inline one you use on your car.

Standard calculation for a fuse is 135% max of the load for resistive load I'd go for 125%.

Soooo: Mantle watts divided by mains voltage = A*1.25 = Fuse ampacity

Dimmer should be 2 times Mantles max watts for long lasting unit that will run cool.

Is it a brushed DC motor or is it an ECM 3phase style motor.

I'd just fix the board personally for simplicity, add a panel mount fuse.

draculic acid69 - 1-8-2019 at 03:37

Ok I've got a 2000w thyristor on the way I'm thinking I should just rip the guts(wiring) out of the mantle and use a 12vmotor controller for the stirrer.im still wondering if I should try and get a 1000w one just to be on the safer side

XeonTheMGPony - 1-8-2019 at 04:02

Do you know what type of motor is in it now? That's where I'd start!

draculic acid69 - 1-8-2019 at 05:57

It's a d.c. motor, not an issue it's handled.its the nichrome element I'm worried about.the mantle is rated at 400w and the thyristor is 2000w and it's not a precise instrument.i really think going down to a 1000w is the sane move.i just can't trust using that little dial to not overheat stuff.even if I only turn it to 1/3rd of the way on that's the max limit for the mantle and in that third I've got to have a whole dials worth of settings and that mm between low and medium is not fine enough for what I need I realize now.

wg48temp9 - 1-8-2019 at 06:59

Quote: Originally posted by draculic acid69

It's a d.c. motor, not an issue it's handled.its the nichrome element I'm worried about.the mantle is rated at 400w and the thyristor is 2000w and it's not a precise instrument.i really think going down to a 1000w is the sane move.i just can't trust using that little dial to not overheat stuff.even if I only turn it to 1/3rd of the way on that's the max limit for the mantle and in that third I've got to have a whole dials worth of settings and that mm between low and medium is not fine enough for what I need I realize now.

I assume by thyristor your referring to a phase angle controller using a thyristor. If that is the case the control knob adjusts the power from almost 100% (400W) to about 10%-0% (40W-0W)of the power rating of the mantel.

The 2,000W is the maximum wattage of the load that can be connected to the controller and not have it over heat or have a short operating life.
The stated maximum wattage is frequently optimistic hence the suggested the safety margin.

The controllers also have a minium load rating but that is probably much smaller than 400W

draculic acid69 - 1-8-2019 at 08:01

By thyristor I mean like the link earlier in the post.2000w Pwm thyristor motor control thing.apparently good for controlling hotplates.much cheaper than variacs

draculic acid69 - 1-8-2019 at 08:06

Even with a safety margin 2000w seems possibly damaging to the mantle.1000w seems like a safer bet.

Sulaiman - 1-8-2019 at 09:41

Quote: Originally posted by draculic acid69

Even with a safety margin 2000w seems possibly damaging to the mantle.1000w seems like a safer bet.

The controllers do not increase the line voltage so the mantle cannot draw more current / consume more power than if connected directly to the a.c. source.

The wattage rating of the controller is an indication of the maximum load that it can handle.
(usually it is the a.c. voltage multiplied by the triac maximum current)

e.g. I use a '4000W' 220V controller for my 380W heating mantle,
another member uses a '10000W' controller.
The supplied heatsinks are, in my opinion, too small for continuous operation at full rated load, which is why most people recommend using an over-rated controller.
I did not add a fuse as UK plugs have an inbuilt fuse.

draculic acid69 - 2-8-2019 at 20:22

Quote: Originally posted by Sulaiman

Quote: Originally posted by draculic acid69

Even with a safety margin 2000w seems possibly damaging to the mantle.1000w seems like a safer bet.

Sulaiman - 2-8-2019 at 21:24

380W is my diy 500ml heating mantle.
The dimmers have very fine control - as fine as I've ever needed.

draculic acid69 - 3-8-2019 at 08:08

What kind of dimmer is it?

Sulaiman - 3-8-2019 at 10:07

search eBay for "4000W" or "10000W"

draculic acid69 - 3-8-2019 at 17:48

Like this?

s-l225.jpg - 16kB

Sulaiman - 3-8-2019 at 18:05

Yes

draculic acid69 - 4-8-2019 at 01:06

A decision has been made: screw trying to replace and repair transformers.pwm thyristor circuit control board on the way from China at $3 it's not much of a loss if it's not precise enough. an old 12v500ma power pack will power a motor control board all of which will be mounted (they are small enough I believe) in the mantle if I can detach the pots and wire them so they can be mounted in the same holes as the old ones.
Mantle guts on the left and blank canvas on the right.

[Edited on 4-8-2019 by draculic acid69]

XeonTheMGPony - 4-8-2019 at 04:28

that is a tiny motor

draculic acid69 - 4-8-2019 at 05:44

Why would it be any bigger?

JoeyJoystick - 4-8-2019 at 06:24

Quote: Originally posted by Herr Haber

Quote: Originally posted by wg48temp9

Of cause this is only applicable if the probability of a single failure is low as the probability of two simultaneous low probability failures occurring together is very low.

Unless you are just about to replace a failed HDD from a Raid array.
Feeling good an cozy and then... :mad:

second one fails !

I might take you up on your offer Sulaiman

I am new here and normally spend my time reading. However, I have to reply to this.

I was on the way from the Hotel in Hanoi to the airport in, yes Hanoi as well. I got into a car accident. Not a biggy, I wait and get a new taxi. And guess what, I got in an other car accident. By now I know I have missed my flight, so I just sit back and wait in the taxi. And while I am sitting there, the 2 drivers arguing outside on the side of the road, right in front of me an other accident on the middle of the intersection. What are the odds....

Joey

draculic acid69 - 4-8-2019 at 17:58

Yeah that's one in a million.hows the food there? I'm imagining lots of lemongrass and coconut cream.

JoeyJoystick - 7-8-2019 at 01:40

Quote: Originally posted by draculic acid69

Yeah that's one in a million.hows the food there? I'm imagining lots of lemongrass and coconut cream.

I live in Thailand and one of the best things in Thailand is the food I think. Tends to be quite spicy. Also, Thais eat much more meat and since I am not crazy about veggies I am a happy bunny. And this is why I did not like the food in Vietnam. Too many vegetables and no spices which makes the food pretty much tasteless. Having said that, in central Vietnam, the food is definitely more spicy than in both the north and the south, but still a lot of veggies and little meat. I did find some great seafood restaurants though! And at prices that are hard to believe. I remember on 1 occasion I took 3 customers to the beach to eat seafood. We ate crab, prawns, fish soup, Crayfish and clamps + a box of warm Heineken. Cooled to drinking temperature in 5 minutes by submerging the bottle in ice and throwing a whole bag of salt over it. (Works like a charm!) I clearly remember this because I broke a nut cracker on the crab legs... All this for about 100USD. (yes only one hundred!) Location was Chu Lai Airport, well the beach next to it anyway. This must have been late 2009 or early 2010. During the 4 years I was there I pretty much travelled between north, south and central Vietnam on a weekly basis.

Anyways, it's all a matter of taste I guess. I hear many people tell me that they love the food in Vietnam. I'm just not one of them. Better to go there yourself and find out for yourself.

Not sure if these kind of postings are appreciated on this forum though. In that case my apologies and I won't do it again.

Joey

draculic acid69 - 2-9-2019 at 02:02

Ok everything has arrived.thyristor on the left was purchased first but I realized it's flat panel wouldn't fit flush against the curved surface of the mantle and I wanted it all internally mounted in the middle is a motor control governor with the pot on a long enough cord that I can put the pots where the old ones were.on the right is the 2nd thyristor circuit purchased 2wks after the first one from a different company than the first one yet they all turned up on the same day in the same bag.

So the thyristor and motor control will be mounted inside somehow then a fuse will be installed everything soldered and then we'll see how it goes.

[Edited on 2-9-2019 by draculic acid69]

[Edited on 2-9-2019 by draculic acid69]

draculic acid69 - 3-9-2019 at 08:01

Does anyone know if this would be a brushless motor or not? It's not magnetic on the outside like some other DC motors I've had.im guessing that it would be brushless so as not to cause sparks.the motor control governor I bought doesn't work for brushless motors I think.a lot of motor control governors don't work with brushless motors.pretty sure the one I got is defective I plugged it in without the potentiometer cord plugged in and the on led came on but when the pot cord is plugged in it goes out like something has shorted out.even without the potentiometer cord plugged in it still wouldn't work.

[Edited on 3-9-2019 by draculic acid69]

wg48temp9 - 3-9-2019 at 11:13

From what I remember your motor was driven by a low voltage probably not more than 24V. If that is the case you can check the motor by connecting it to a 6V battery. With a brushed motor its shaft turn continuously while a brush-less motor (no built in drive electronics) may turn a fraction of a turn and then you should be able to feel some resistance if you try to turn the shaft by hand.

The end of your motor looks similar to a brush-less motor I dismantled.
It was a brush-less motor but with built in driver electronics. Such motors will turn continuously on a battery but only when connected with the correct polarity. Note you may damage the electronics of such a motor by powering it from the wrong polarity and it may not work correctly with your controller.

You could also check the motor by using it as a generator and spin the shaft by hand or a with an electric drill but that is more involved.

I hope you purchased a low voltage motor controller and not mains powered one.

markx - 4-9-2019 at 00:16

It definitely looks like a brushless motor. You could try to peek into the venthole at the backside of the motor. If there is a circuit board visible underneath then it usually signals that the drive electronics are built into the unit.
If they are functional, the motor should turn by connecting it to a DC source, but mind the polarity as already mentioned.

I would not deem the motor controller defective yet....they tend to be rather foolproof. At least I have not encountered a faulty one yet. You could check the controllers functionality with another brushed dc motor.

draculic acid69 - 4-9-2019 at 00:40

I don't have access to the shaft at all so can't go down that road.it has the polarity written on it which usually signifies that correct polarity is important which for most DC motors isn't important.the green circuit board bit it's contacts are connected to signifies that it has somesort of internal circuitry that a normal DC motor doesn't have.so polarity important, internal circuitry what type of motor am I looking at here?
What kind of driver will I need?

As for the driver I already have I'd say it's fucked.when first powered with 12v300mA
Its led came on but when the motor was connected it didn't do anything so it was unplugged and rewired and when the pot cord was plugged in after it was powered on and the led was on it just went out like the pot cord was causing a short .the led won't come on at all now.

draculic acid69 - 4-9-2019 at 00:59

The motor works fine when the 12v charger is directly connected to it.im just wondering if I can just directly put the pot between the charger and motor? There's also the old mantle board I can pick a resistor and voltage regulator off if I need to make my own driver.

draculic acid69 - 4-9-2019 at 02:38

Wired in the thyristor and turned it on for a minute and it heated up so all good there.next step is drilling holes for the fuse and an on/off switch which sucks bcoz I don't have a drill with me.just need to get the stirring working and then it's all good.

wg48temp9 - 4-9-2019 at 03:04

Quote: Originally posted by draculic acid69

The motor works fine when the 12v charger is directly connected to it.im just wondering if I can just directly put the pot between the charger and motor? There's also the old mantle board I can pick a resistor and voltage regulator off if I need to make my own driver.

Yes you can put a variable resistor in series with power supply to the motor if that's what you mean. When you say "the pot" if you mean the potentiometer that was connected to a motor control board then its probably not a suitable resistance (ohms) or power rating.

Its best to drive the motor from a variable regulated supply as its rpm will be less effected by it load and provided a more reliable start up at low rpm. But if you have a suitable pot that is a simple uncomplicated solution. if you do have start up problems you can turn the pot up to its lowest resistance to get the motor going then reduce the speed.

draculic acid69 - 4-9-2019 at 08:51

Ok so using the potentiometer in between the charger and motor is a no-go as a 500k pot is easily fried by 12v 300mA.you can really smell the clorinated plastic in the fumes.the motor started reluctantly and was very finicky about being slowed down and would stop altogether when the pot was turned down too fast it was a fine line between struggling to start and completely stopping.so with this information is anyone onto what type of motor I'm dealing with here?

draculic acid69 - 23-9-2019 at 22:13

Got the stirring happening so that's no longer an issue but the thyristor circuit is problematic as even when it's turned down to zero it can boil a flask 1/3rd full of water
and the mantle fabric is sitting at 185'c and hovers around that.someone mentioned that with the thyristor circuit you lose control over the lower end of things which basically means it's useless for nything that boils under 150'c.trying to maintain a 80'c reflux just won't happen. Don't even want to think what happens when turned up to halfway.im going to try a dimmer circuit next.

draculic acid69 - 23-9-2019 at 22:19

Quote: Originally posted by draculic acid69

Ok so using the potentiometer in between the charger and motor is a no-go as a 500k pot is easily fried by 12v 300mA.you can really smell the clorinated plastic in the fumes.the motor started reluctantly and was very finicky about being slowed down and would stop altogether when the pot was turned down too fast it was a fine line between struggling to start and completely stopping.so with this information is anyone onto what type of motor I'm dealing with here?

I realized that the pot I used the original one from the the mantle for the heating was probably too much resistance for the motor and I should have just used the pot from the stirrer as I think it's only 100k instead of 500k.

wg48temp9 - 24-9-2019 at 03:29

Quote: Originally posted by draculic acid69

You need to swot up on basic circuit theory try one of these sites: https://www.google.com/search?q=electrical+resistance+for+be...

In short and approximately. If the motor at full power uses 12V @0.3A it has a resistance of 4 ohms. If you want to reduce that to say 10% then you must decrease the voltage/current to 10% then means adding a variable resistance in series with the motor of 36 ohms max. 100k ohms is way too large.

Power dissipation with a maximum resistance of 40 ohm would be 0.9((12x12)/40) 3.2W that too much for many variable resistors.
But the maximum power is with a resistance of only 4 ohm the power would then be 9W but dissipated in only 3/36 of the variable resistors track. So you need something like the following

Attachment: reo200ws-l225.webp (7kB)
This file has been downloaded 365 times
see ebay: https://www.ebay.com/itm/200W-50-OHM-Wirewound-Potentiometer...

0UAAOSwxada-xyO

PS: sorry the last link confused the forum

[Edited on 9/24/2019 by wg48temp9]

markx - 24-9-2019 at 03:32

Quote: Originally posted by draculic acid69

Got the stirring happening so that's no longer an issue but the thyristor circuit is problematic as even when it's turned down to zero it can boil a flask 1/3rd full of water
and the mantle fabric is sitting at 185'c and hovers around that.someone mentioned that with the thyristor circuit you lose control over the lower end of things which basically means it's useless for nything that boils under 150'c.trying to maintain a 80'c reflux just won't happen. Don't even want to think what happens when turned up to halfway.im going to try a dimmer circuit next.

Are you sure the mantle is rated to operate at line voltage AC? Perhaps it was operated at a lower voltage from the main transformer in the original setup? That transformer looked a bit bulky just for powering the stirring motor as I remember.
If the mantle is rated to operate at a lower voltage then you will get the kind of overheating effects by trying to tune down with a thyristor/dimmer circuit. Even in the low end of power setting it manages to draw enough current for getting to high temperatures.
Try measuring the resistance of the heating mantle. It will be lower in the cool condition as the heating elements resistance is a function of temperature, but it should give you at least a ballpark figure wether you can operate it at line voltages:
P=U²/R

P- dissipated power
U- voltage drop across the resistance (line voltage if directly connected)
R- resistance of the mantle

If according to the above formula your dissipated power is much higher than the rated power of the mantle (it should be marked on the apparatus), then it is likely that it is meant to be operated at lower voltages.
Reasonably such heating mantles should operate near 400-500W at full power.

Keras - 24-9-2019 at 06:57

What the heck is all that about? I mean:

1. A motor has a resistance and a counter-EMF. If your source voltage doesn't exceed the motor's counter-EMF, nothing happens (you don't have enough power to set up a suitable magnetic field). You can't say that a motor which consumes 300 mA @ 12 V has a resistance of 4 Ω because that disregards its counter-EMF.

2. A thyristor doesn't work with DC. Once you've switched it on with the gate, you can't turn it off. A thyristor only "chops" AC, and turns off when the voltages crosses 0, and cannot be turned on when it is reversed polarised. So you get at most 50% duty cycle. AC choppers use triacs, which are basically two thyristors in head-to-tail mode.

draculic acid69 - 24-9-2019 at 17:04

Don't need to worry about the motor and stirring.got that half of the equation sorted out.the reason I tried sticking the pot between the 12v charger and the motor is I remember using an ATX power supply from an old computer and a plastic computer fan with a pot in between them and even though there's way more current in the ATX box it didn't fry the pot and worked fine for dimming the fanspeed. And yes I'm fairly sure the mantle runs off AC line voltage and is controlled somehow with the original board which is fairly similar to the thyristor circuit I've been trying to use.i can't completely trace the flow but it seems like the transformer just lowered the voltage for going to the motor but I can tell it's only for the motor and that the mantle runs on AC.
I've got a dimmer circuit on the way and hopefully that works.if not then FUCK!!!!. other ppl seem to support the dimmer switch idea as it's what they use and a new mantle is cheaper than a variac so that's a worst case scenario.

draculic acid69 - 24-9-2019 at 21:52

Are you sure the mantle is rated to operate at line voltage AC? Perhaps it was operated at a lower voltage from the main transformer in the original setup? That transformer looked a bit bulky just for powering the stirring motor as I remember.
If the mantle is rated to operate at a lower voltage then you will get the kind of overheating effects by trying to tune down with a thyristor/dimmer circuit. Even in the low end of power setting it manages to draw enough current for getting to high temperatures.
Try measuring the resistance of the heating mantle. It will be lower in the cool condition as the heating elements resistance is a function of temperature, but it should give you at least a ballpark figure wether you can operate it at line voltages:
P=U²/R

P- dissipated power
U- voltage drop across the resistance (line voltage if directly connected)
R- resistance of the mantle

If according to the above formula your dissipated power is much higher than the rated power of the mantle (it should be marked on the apparatus), then it is likely that it is meant to be operated at lower voltages.
Reasonably such heating mantles should operate near 400-500W at full power.
[/rquo

When I first opened it up I also thought it ran off DC as well bcoz I didn't know you
could put AC thru a nichrome element but you can and it has to run off AC as no amount of 12v will make 400w without a 20amp transformer and there big and heavy and the one in there was only 12v 350ma.

markx - 24-9-2019 at 22:57

If you measure the resistance of the mantle, the guesswork becomes reduced. You know that the dissipated power in the mantle at full blast should be 400W (in case it is directly connected to 220V AC plug).
So accordingly your mantle resistance should be in the approximate range of 120ohm to arrive at such a power using 220V AC:

R=U²/P = 220²/400 = 121ohm

If you work off 110V AC mains then correct the values for this voltage. For 110V AC mains your mantle resistance should be near 30ohm to get 400W power output.

If your measured resistance is significantly lower than the values that lead to 400W output, then you know that it was used in a different configuration in the original setup. And it will be very difficult to lower the power output with a dimmer/thyristor circuit.

Was the original apparatus intended to run off a particular line voltage or was there a selector switch to choose between 220V and 110V option?

draculic acid69 - 24-9-2019 at 23:19

Nope.no switch to select 110v it's 240v AC rated. I'm thinking about putting my other thyristor back to back with the one I got in there as in the output of on turned on to like 10-20% who's output goes through the second thyristor circuit input so as to get a finer control of the temp.

Keras - 25-9-2019 at 02:17

Could you please post a closer picture of the PCB hosting the thyristor?
Thanks!

Sulaiman - 25-9-2019 at 03:52

The dimmer controllers that I have bought, as well as the main potentiometer also have a small preset potentiometer to set the minimum power,
maybe yours ha a similar preset potentiometer ?

draculic acid69 - 25-9-2019 at 04:41

Picture below is the type of thyristor I'm talking about.it does have what I assume is a variable resistor of somesort.ill try adjusting it tomorrow and see if that makes enough of a difference

download (1).jpeg - 16kB

[Edited on 25-9-2019 by draculic acid69]

Keras - 25-9-2019 at 06:17

Ok, I see. Well yeah, try tinkering with that trimpot. Let us know what you get out of it

[Edited on 25-9-2019 by Keras]

draculic acid69 - 25-9-2019 at 06:28

It's a variable resistor isn't it?

markx - 25-9-2019 at 22:57

Quote: Originally posted by draculic acid69

Picture below is the type of thyristor I'm talking about.it does have what I assume is a variable resistor of somesort.ill try adjusting it tomorrow and see if that makes enough of a difference

[Edited on 25-9-2019 by draculic acid69]

I'm using a module like that to control the temperature of my soldering iron from barely warm to scorching hot....works like a charm through the whole scale. It's only a 25W soldering iron, so it should be able to handle a 400W mantle with ease. My module does not have the additional blue pot on it so your's probably is a newer iteration of the circuit. Makes sense that it is put there to shift the scale of voltage regulation. Perhaps it was turned to such a position that one can not reduce the power to get a reasonable temperature in the mantle. Try adjusting it. These types of pots are not sensitive to small adjustments. It takes more than ten turns of the screw to scroll through the scale from one end to another. So do not be surprised if turning the adjuster by half a turn does not seem to make a great difference. Also they do not come to a dead stop when the end of scale is reached. Instead they start to jump over the threads on the inside of the pot with a very quiet click. It's a safety measure, so one does not break the thing by turning all the way to end of scale. So if you hear the quiet clicking then you know that it will not go any further in that direction. Some specimens do not make an audible click, so it can be difficult to judge if one has reached the end or not. In that case you can just turn it for 10-15 revolutions in one direction and claim with confidence that it is now in one of the extremes.

draculic acid69 - 26-9-2019 at 00:14

7turns counter clockwise seems to be keeping the temp in the120'c range for 15mins but now it's starting to creep up to about 130.i was hoping it would find a temp and sit there but apparently not.
Creeping up to 140 now.dammit

[Edited on 26-9-2019 by draculic acid69]

Keras - 26-9-2019 at 00:22

I'm not sure what's going on. If you have no digital multimeter, it's pretty much a crapshoot game.

Sulaiman - 26-9-2019 at 01:47

Quote: Originally posted by draculic acid69

Picture below is the type of thyristor I'm talking about.it does have what I assume is a variable resistor of somesort.ill try adjusting it tomorrow and see if that makes enough of a difference

That is exactly the model of controller that I use
(I have three of them, one for my diy 380W mantle, one for a 500W hotplate and one for a 1500W hotplate)

The controller sets a phase angle,
(a time delay before the triac is turned on after zero-crossing of the input voltage)
which for a constant voltage, frequency and load,
equates to a constant POWER (W)

So the temperature will climb as 'stuff' around the heating element heats up,
after a while thermal equilibrium will be attained.
BUT
if the environment changes, e.g. breeze/draught/wind/ambient temperature etc.
then the temperature will change.
In my experience, temperature is most affected by wind.

The power semiconductor is a triac, not a thyristor,
a triac is equivalent to a bi-directional thyristor. (two thyristors in inverse parallel)

For heating I set the preset potentiometer (the little blue one)
so that there is almost no power output when the main potentiometer is set to minimum,
this allows control in all circumstances.
You can temporarily replace the load with a filament lamp to adjust the preset potentiometer if you do not have a suitable meter.

If you put the controller in an enclosure (for convenience and/or safety)
then ensure that there is some ventilation to prevent the triac from overheating.
__________________________________________________________

@draculic acid69 : it is a preset potentiometer wired as a variable resistor.

[Edited on 26-9-2019 by Sulaiman]

draculic acid69 - 26-9-2019 at 02:03

I've turned it counter clockwise about 15 turns and got to the point where it clicks it seems to get the mantle to 110'c and then slowly creepup to 120'c and it's sat around there for 15mins and now it's slowly getting to 125 and it'll probably hit 130..this circuit seems to not be able to sit at a minimum temp.ill let it sit there now for an hour or two and see what happens then report back but there's been a definite improvement since I started adjustment. Once I get a constant temp with no rising I'll adjust the pot and see how it goes from there.seems to be sitting around 125 for now

markx - 26-9-2019 at 02:05

Quote: Originally posted by draculic acid69

7turns counter clockwise seems to be keeping the temp in the120'c range for 15mins but now it's starting to creep up to about 130.i was hoping it would find a temp and sit there but apparently not.
Creeping up to 140 now.dammit

[Edited on 26-9-2019 by draculic acid69]

It is not a temperature control setup, just a variable power source. You can not expect it to hold a certain temperature point according to the position of the knob. There is no feedback in the system, so if anything changes (line voltage fluctuations, heating element resistance change due to temperature, amount and composition of liquid in the flask, shielding, heating up of the surroundings, etc.) then there will be a change in the system temperature. The same will happen if one uses a variac to control the power. In essence it will eventually hold a certain temperature point once the inflow of energy matches the losses, but it will not be possible to determine at what exact temperature this will happen on a certain setting of the control knob.
To be honest it is very difficult to force such a system into holding an exact temperature setpoint even using PID controllers that are able to monitor and even predict certain changes so they can act prevetively.
What we have here is a rather high powered (400W) small scale system that has very different rates of heating vs. cooling. It shoots up very fast due to the powerful mantle and creeps down way slower due to convection or radiation losses. Boiling of liquids in the flask will act as an accelerant for cooling rate though and stabilize the system.
Also with PID control such systems tend to have profound fluctuations around setpoints because the heat spikes from mantle tend to overshoot the setpoint. A "garden variety" PID assumes cooling and heating rates to be the same and tries to work on a linear trendline. If cooling and heating rates are not matching then we shall have two trendlines with differing slopes.....understandably it is difficult to tune in a set of parameters that match both at the same time

draculic acid69 - 26-9-2019 at 03:43

Ok so I got it to sit at 125'c when turned down to zero and it has much finer control than expected and when turned 1/8th of the way up it rose to 140 a quarter of the way up it got to 155, a bit higher it went to 180~ and as I turned it up a bit more it reached over 200 and as my thermometer doesn't go any higher so I turned it off half way probably sits around the 250 mark so it's getting better than it was before.only thing is at zero it still sits at over a hundred 'c so it can't be set to zero power at all.

draculic acid69 - 26-9-2019 at 04:56

I've just hooked up the second thyristor circuit I have from a different company and even turned down to zero with no adjustments its slowly reached 90 and is still going up but it's happening slower than the other one.ill see how fine the temperature control
is with this one.

[Edited on 26-9-2019 by draculic acid69]

draculic acid69 - 26-9-2019 at 05:16

This second circuit seems to hover around 90'c when turned down to zero which is half as hot as the first one.
Seems to be a fair amount of variation in these things as even after adjusting the preset resistor thing I couldn't get it to sit at this low of a temperature.

[Edited on 26-9-2019 by draculic acid69]