Taz - 8-4-2005 at 12:34
I recently went to a garage sale and found one of these
http://www.labequip.com/catalog.php?stkno=18210
for $10.00 looks brand new though it doesn't have a power cord also it has variac
only writen on it does this mean I am going to have to buy a variac transformer to operate this it does have a dial for temp control.Does
anyone know where to get a power cord or any thing else about it . Thanks
mick - 8-4-2005 at 13:45
I would guess that it depends on the age. The old heating mantles were a bit sparky because of the electrics and could over heat when they burnt out.
The ones around today seem better than the stirrer / hotplate with an oil bath.
mick
runlabrun - 8-4-2005 at 17:52
you went to a garage sale and got a heating mantle??!?!?!?!
DAMN YOU!
-rlr
Taz - 9-4-2005 at 19:15
It was more like an estate sale but I figure same thing
I have been looking into ot though I need a variac power supply I slowly increase voltage to increase the heat as for as a cord goes I guess I could
make my own its a pretty nice mantle scince it will hold a variety of flask sizes
[Edited on 10-4-2005 by Taz]
neutrino - 9-4-2005 at 20:38
A simple light dimmer spliced into the power cord should work just as well. It works for me, anyway.
Heating mantle
MadHatter - 10-4-2005 at 08:20
I'm still looking around for a decent power supply for my 2 heating mantles. They came
with a set of lab glass that I bought on eBay.
neutrino - 10-4-2005 at 11:42
Again, I advise a dimmer switch. Just make sure that they're rated at or above the mantles.
Quince - 28-4-2005 at 02:07
You can make a variable AC supply quite easily. Get an optoisolated, AC capable solid state relay (or make one from low Ron MOSFETs), and drive it
with a PWM. If you add an LC filter to the output, you can drive anything that needs whatever AC voltage up to the outlet's 120V. This is a
fraction of the cost, and tiny fraction of the weight, of a variac; efficiency is usually on the same order or better.
unionised - 30-4-2005 at 05:06
"You can make a variable AC supply quite easily. Get an optoisolated, AC capable solid state relay (or make one from low Ron MOSFETs), and drive
it with a PWM. If you add an LC filter to the output, "
Or buy a dimmer.
Quince - 30-4-2005 at 14:45
Yeah, but a dimmer doesn't put out a nice sine waveform. A lot of equipment, especially if it has a transformer, won't work with dimmer
output.
12AX7 - 30-4-2005 at 17:05
A dimmer into a transformer into a resistive load is fine.
Tim
Quince - 30-4-2005 at 17:25
Other than lights and heaters, what is a resistive load?
BTW Tim, for filtering the output of a PWM sampled AC mains, how do I calculate the inductor? Of course I can use the simulator and guess/try values,
but obviously that's the dumb way to do it. I know that higher switching frequency needs smaller inductor, but there's a limit to how fast
the SS relay can switch. Also, what frequencies are more/less likely to cause interference with other things on the circuit/nearby? Finally, I
assume a slow-blow fuse should be used?
[Edited on 1-5-2005 by Quince]
unionised - 1-5-2005 at 06:45
"Other than heaters" is off topic.
Any purely reactive load isn't doing anything (no transfer of energy) so, to a greater or lesser extent, all loads are resistive.
I'm not sure I agree with your definition of easilly.
The cut-down description of the technique runs to a couple of lines and has already sparked questions.
Designing solid-state transformers is really quite involved, particularly when you want them to behave themselves with very inductive loads.
Archimede - 11-6-2005 at 16:33
If it was me, I would inspect the inside of the mantle to see if it's just made of the heating element without any other electronic part.
An heating element is just a resistor and it shouldnt be sensitive to the wave form of the electricity . Just make sure the machine is rated to work
with 115V or so. If this is the case a dimmer switch should be just fine and before you turn it on make sure the dimmer is set very low and increase
gradually to experiment the results.
Also, looking at the link it seems that there may be 2 different heating elements and/or some additional resistor to half the power output (150/300W).
[Edited on 12-6-2005 by Archimede]