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Author: Subject: Does anyone know how to use one of these?
monolithic
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[*] posted on 30-10-2019 at 03:26


Quote: Originally posted by draculic acid69  
Ill try the boiling water when I've got an empty flask. What's the knob with rst written on it for?
I'm thinking it means rheostat.but what's it there for if you can set the temperature with the number wheel thing?

[Edited on 30-10-2019 by draculic acid69]


Quote:
V. Operation instruction

Place the equipment on level worktable, equip test-tube stand, and insert plug of sensor into sensor socket.
Put the container with liquid inside into the heating jacket, and dip the sensor into heating liquid.
Switch on the power accords with the machine, then the equipment screen will show the current temperature of heating liquid.
Press dial switch to set the temperature as heating needs.
Make sure the power line and the power socket are connected to heating jacket well; the.
When the displayed temperature reaches the setting point, the red indicator light will be lighten, then it gets into constant temperature state.
Adjust the RST knob to the left side, where is the smaller value position; wait until the temperature does not rise anymore, for example, when the displayed temperature is lower than the setting temperature, then turn it to right side gradually.


http://webcache.googleusercontent.com/search?q=cache:http://...

I have no idea what it does. Probably a classic case of shitty Chinese reverse engineering where they rip something off without understanding what the fuck they're even doing.
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[*] posted on 30-10-2019 at 05:21


The RST is some sort of fine calibration setting maybe?
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draculic acid69
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[*] posted on 31-10-2019 at 19:22


So no one knows what the rst knob actually does?once the display temp is lower than the setting temperature you adjust the knob to the right bcoz it does what?
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[*] posted on 31-10-2019 at 20:08


Maybe it will allow you to calibrate the display temperature to match the setting temperature?
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draculic acid69
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[*] posted on 2-11-2019 at 00:26


Tried boiling a flask full of water.mantle still gets to 300~ish degrees'c even when dial is set to 100.it appears that the temperature probe isn't more than 2 degrees off when it comes to boiling water.dont have a higher boiling liquid available ATM. Did figure out my glass thermometer is a lil bit off.reads 108 in boiling water but the mantles 2-300'c spikes make it useless for anything other than boiling water.theres not one rxn I can do that wouldn't be ruined by this kind of overheating.the knob doesn't seem to make a difference which ever way it's turned.this thing as it is is no better than those 2000w hotplates from kmart.i might just rip the guts out and put a Pwm thyristor circuit in there like my other one which is working fine.
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[*] posted on 2-11-2019 at 05:24


Quote: Originally posted by draculic acid69  
Tried boiling a flask full of water.mantle still gets to 300~ish degrees'c even when dial is set to 100.it appears that the temperature probe isn't more than 2 degrees off when it comes to boiling water.dont have a higher boiling liquid available ATM. Did figure out my glass thermometer is a lil bit off.reads 108 in boiling water but the mantles 2-300'c spikes make it useless for anything other than boiling water.theres not one rxn I can do that wouldn't be ruined by this kind of overheating.the knob doesn't seem to make a difference which ever way it's turned.this thing as it is is no better than those 2000w hotplates from kmart.i might just rip the guts out and put a Pwm thyristor circuit in there like my other one which is working fine.


Temperature controlled hot plates and mantles don't regulate the voltage to the heating element. It's expected that the mantle is going to hit 300 C or whatever its maximum output is. Put the probe in a flask of water, completely ignore the temperature of the heating element, and set the temperature of the mantle to something below boiling, like 70 C. Does it eventually stabilize at 70 C? Then it is working as it should. If the probe is off by 8 C then I don't think there's much you can do as there doesn't seem a way to adjust the calibration. You can buy PID controllers pretty cheap ($50 or less on Amazon or eBay) that offer a ton of configuration: support for different types of thermocouples/thermistors, support for K/F/C units of temperature, calibration adjustment, etc. It wouldn't be much work to wire one up to an SSR or mechanical relay, to control a hot plate.

If you're looking for something to control the temperature output at the heating element, you need something like a soft heating mantle (Glas-Col or a knockoff) plugged into an AC transformer (Variac or a knockoff), set atop a magnetic stirrer or magnetic hot plate/stirrer with the heating circuit turned off.

[Edited on 11-2-2019 by monolithic]
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[*] posted on 2-11-2019 at 06:10


Yeah, it looks like maybe the best thing to do with these Won Hung Lo hotplates might be to just use the mechanical guts of them, rip out/bypass the control circuitry and replace it with a working configuration of your own.

IME, the vast majority of heaters use a kind of PWM to regulate the heat. By that, I mean that they use full power 'pulses' of current of varying lengths to the heating element to keep it within the desired temperature range.

IDK if it'd improve things a lot if a controller was used which allowed the current to the heating element to be continuously variable instead. I guess it would remove the hysteresis that the 'full power PWM' heaters exhibit, where a 100C set temperature would result in the element would vary in temperature from like 96-103C or whatever.
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[*] posted on 2-11-2019 at 07:11


Quote: Originally posted by monolithic  
Quote: Originally posted by draculic acid69  
Tried boiling a flask full of water.mantle still gets to 300~ish degrees'c even when dial is set to 100.it appears that the temperature probe isn't more than 2 degrees off when it comes to boiling water.dont have a higher boiling liquid available ATM. Did figure out my glass thermometer is a lil bit off.reads 108 in boiling water but the mantles 2-300'c spikes make it useless for anything other than boiling water.theres not one rxn I can do that wouldn't be ruined by this kind of overheating.the knob doesn't seem to make a difference which ever way it's turned.this thing as it is is no better than those 2000w hotplates from kmart.i might just rip the guts out and put a Pwm thyristor circuit in there like my other one which is working fine.


Temperature controlled hot plates and mantles don't regulate the voltage to the heating element. It's expected that the mantle is going to hit 300 C or whatever its maximum output is. Put the probe in a flask of water, completely ignore the temperature of the heating element, and set the temperature of the mantle to something below boiling, like 70 C. Does it eventually stabilize at 70 C? Then it is working as it should. If the probe is off by 8 C then I don't think there's much you can do as there doesn't seem a way to adjust the calibration. You can buy PID controllers pretty cheap ($50 or less on Amazon or eBay) that offer a ton of configuration: support for different types of thermocouples/thermistors, support for K/F/C units of temperature, calibration adjustment, etc. It wouldn't be much work to wire one up to an SSR or mechanical relay, to control a hot plate.

If you're looking for something to control the temperature output at the heating element, you need something like a soft heating mantle (Glas-Col or a knockoff) plugged into an AC transformer (Variac or a knockoff), set atop a magnetic stirrer or magnetic hot plate/stirrer with the heating circuit turned off.

[Edited on 11-2-2019 by monolithic]


Imagine your doing a 100ml size grignard and you set the temperature control to 60'c
and then within a minute it's boiling and then it's out of control spewing out of the flask bcoz this 'operating as it should' mantle heated up to over 250'c within a minute
(gets hot quick) other than boiling water that kind of temperature difference has the potential to ruin rxn's.

[Edited on 2-11-2019 by draculic acid69]
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[*] posted on 2-11-2019 at 09:05


Quote: Originally posted by draculic acid69  
Imagine your doing a 100ml size grignard and you set the temperature control to 60'c
and then within a minute it's boiling and then it's out of control spewing out of the flask bcoz this 'operating as it should' mantle heated up to over 250'c within a minute
(gets hot quick) other than boiling water that kind of temperature difference has the potential to ruin rxn's.

[Edited on 2-11-2019 by draculic acid69]


You should use a soft mantle, AC transformer, and a magnetic stirrer for situations like that. Even a hot water bath on a magnetic stirrer/hot plate would work well for something that has to run at 60 C, speaking from experience. Also, I doubt even your current setup would heat the reaction mixture to 250 C within a minute. The heating element would hit 250 C within a minute but it takes time to transfer that heat through the glass and to the reaction mixture.
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[*] posted on 2-11-2019 at 10:43


Okay, I probably missed something in this thread, but did you try adjusting with the RST knob as directed?

I'm not sure what it does either. But it seems to be something they definitely want you to do.

Maybe it calibrates the thermocouple.

Maybe it limits the current flow to the heating element.

Maybe its worth a try.

EDIT: Thanks for the information, G-coupled. (Below)

[Edited on 2-11-2019 by SWIM]





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[*] posted on 2-11-2019 at 10:54


They tried the RST knob, but it didn't appear to change anything.

I'd have a lookyloo inside and see where the RST knob is attached, and see if that might help figure out what it's supposed to do.
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[*] posted on 2-11-2019 at 21:30


Tried the knob didn't do much.its wired directly to the board.
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[*] posted on 2-11-2019 at 23:04


Yes, but attached to *what* - where do the traces go to from where it's attached? :cool:

Any chance of a photograph of all the gubbins inside?

[Edited on 3-11-2019 by G-Coupled]
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[*] posted on 3-11-2019 at 00:07


Quote: Originally posted by draculic acid69  
Quote: Originally posted by monolithic  
Quote: Originally posted by draculic acid69  
Tried boiling a flask full of water.mantle still gets to 300~ish degrees'c even when dial is set to 100.it appears that the temperature probe isn't more than 2 degrees off when it comes to boiling water.dont have a higher boiling liquid available ATM. Did figure out my glass thermometer is a lil bit off.reads 108 in boiling water but the mantles 2-300'c spikes make it useless for anything other than boiling water.theres not one rxn I can do that wouldn't be ruined by this kind of overheating.the knob doesn't seem to make a difference which ever way it's turned.this thing as it is is no better than those 2000w hotplates from kmart.i might just rip the guts out and put a Pwm thyristor circuit in there like my other one which is working fine.


Temperature controlled hot plates and mantles don't regulate the voltage to the heating element. It's expected that the mantle is going to hit 300 C or whatever its maximum output is. Put the probe in a flask of water, completely ignore the temperature of the heating element, and set the temperature of the mantle to something below boiling, like 70 C. Does it eventually stabilize at 70 C? Then it is working as it should. If the probe is off by 8 C then I don't think there's much you can do as there doesn't seem a way to adjust the calibration. You can buy PID controllers pretty cheap ($50 or less on Amazon or eBay) that offer a ton of configuration: support for different types of thermocouples/thermistors, support for K/F/C units of temperature, calibration adjustment, etc. It wouldn't be much work to wire one up to an SSR or mechanical relay, to control a hot plate.

If you're looking for something to control the temperature output at the heating element, you need something like a soft heating mantle (Glas-Col or a knockoff) plugged into an AC transformer (Variac or a knockoff), set atop a magnetic stirrer or magnetic hot plate/stirrer with the heating circuit turned off.

[Edited on 11-2-2019 by monolithic]


Imagine your doing a 100ml size grignard and you set the temperature control to 60'c
and then within a minute it's boiling and then it's out of control spewing out of the flask bcoz this 'operating as it should' mantle heated up to over 250'c within a minute
(gets hot quick) other than boiling water that kind of temperature difference has the potential to ruin rxn's.

[Edited on 2-11-2019 by draculic acid69]


monolithic is right, you can't expect everything to work the way you think it should in your brain. A heating mantle designed the way you think it should work would be useless, imagine wanting to boil some water and your mantle only heats to 100C. Your water is never going to boil.

Your "hypothetical" situation is like saying, this masonry drill doesn't work well when I try to use it for dentistry, it just destroyed my patient's entire mouth. They should have finer speed control on it. It's not the problem with the equipment, but with the way you're using it.
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[*] posted on 3-11-2019 at 00:18


To be fair, until recently all kitchen microwaves worked like that until recently, using full power but with less duty cycles when the heat setting is turned down, but a couple of years ago Panasonic brought out a new type of microwave which used actual true variable power to heat things.

[Edited on 3-11-2019 by G-Coupled]
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[*] posted on 3-11-2019 at 01:25


From reading the instructions the control knob varies the maximum heating power. Assuming it not faulty (stuck on full power) you should be able to verify that by checking the max temperature of the mantle say at 0% 50% and 100% rotation of the knob while the temperature thumb switches are set at max temperature or better yet check the power consumed with an in-lead power meter in place of measuring the mantle temperature.





i am wg48 but not on my usual pc hence the temp handle.

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[*] posted on 3-11-2019 at 21:52


Quote: Originally posted by Deathunter88  
Quote: Originally posted by draculic acid69  
Quote: Originally posted by monolithic  
Quote: Originally posted by draculic acid69  
Tried boiling a flask full of water.mantle still gets to 300~ish degrees'c even when dial is set to 100.it appears that the temperature probe isn't more than 2 degrees off when it comes to boiling water.dont have a higher boiling liquid available ATM. Did figure out my glass thermometer is a lil bit off.reads 108 in boiling water but the mantles 2-300'c spikes make it useless for anything other than boiling water.theres not one rxn I can do that wouldn't be ruined by this kind of overheating.the knob doesn't seem to make a difference which ever way it's turned.this thing as it is is no better than those 2000w hotplates from kmart.i might just rip the guts out and put a Pwm thyristor circuit in there like my other one which is working fine.


Temperature controlled hot plates and mantles don't regulate the voltage to the heating element. It's expected that the mantle is going to hit 300 C or whatever its maximum output is. Put the probe in a flask of water, completely ignore the temperature of the heating element, and set the temperature of the mantle to something below boiling, like 70 C. Does it eventually stabilize at 70 C? Then it is working as it should. If the probe is off by 8 C then I don't think there's much you can do as there doesn't seem a way to adjust the calibration. You can buy PID controllers pretty cheap ($50 or less on Amazon or eBay) that offer a ton of configuration: support for different types of thermocouples/thermistors, support for K/F/C units of temperature, calibration adjustment, etc. It wouldn't be much work to wire one up to an SSR or mechanical relay, to control a hot plate.

If you're looking for something to control the temperature output at the heating element, you need something like a soft heating mantle (Glas-Col or a knockoff) plugged into an AC transformer (Variac or a knockoff), set atop a magnetic stirrer or magnetic hot plate/stirrer with the heating circuit turned off.

[Edited on 11-2-2019 by monolithic]


Imagine your doing a 100ml size grignard and you set the temperature control to 60'c
and then within a minute it's boiling and then it's out of control spewing out of the flask bcoz this 'operating as it should' mantle heated up to over 250'c within a minute
(gets hot quick) other than boiling water that kind of temperature difference has the potential to ruin rxn's.

[Edited on 2-11-2019 by draculic acid69]


monolithic is right, you can't expect everything to work the way you think it should in your brain. A heating mantle designed the way you think it should work would be useless, imagine wanting to boil some water and your mantle only heats to 100C. Your water is never going to boil.

Your "hypothetical" situation is like saying, this masonry drill doesn't work well when I try to use it for dentistry, it just destroyed my patient's entire mouth. They should have finer speed control on it. It's not the problem with the equipment, but with the way you're using it.



Not even close.i know how a usual mantle works it's just this one with a probe and setting the temperature using the dials is a lot different than what I'm used to.its just something with this much of a temperature spike above the set temperature makes it no more useful than a $30
hotplate from Kmart. how often do you need to boil water in a flask that can't be done in a pot? I didn't buy it to boil water and I just can't trust it to maintain set rxn temperature with the spiking up to 250'c+ all of a sudden even when it's sitting in the right temp range the way it did several times.my thermometer only goes up to 250 so for all I know it could have hit 400'c and when your distillation or reflux is all clamped in its not like I can just lower the mantle out of the way till it cools down and with the temperature spikes all the rxn's I'm doing would be ruined by that.as for trying to trace where the temp probe goes on the board I can't really follow it.the 8 pins on the transformer confuse me.theres shit loads of resistors though.25 of them.
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