alive&kickin - 25-9-2015 at 19:20
I've seen on the boards lately of hotplates/stirrer hotplates that have a bimetallic switch that has gone bad. A lot of these seem to be the vwr 375
hotplate stirrer. It's been discussed of changing the existing switch with a thermostat or a light dimmer. The original bimetallic switch is called
an infinity switch. I changed out 2 of these and they work great. The only modification to the hotplate is drilling two holes for the screw
mounting. Here is the link to the one I used.
https://www.etundra.com/restaurant-parts/electrical-parts/sw...
Hope this helps someone in need.
Feel free to move this if it's in the wrong place.
Sulaiman - 25-9-2015 at 22:47
or you could buy this set http://www.ebay.co.uk/itm/311389111031?_trksid=p2060353.m274...
and have temperature controland indication.
A little more work to integrate but you do get a self-tuning PID controller.
alive&kickin - 27-9-2015 at 15:47
Sulaiman, you're right, a little bit more work and now you've got external equipment and a temp probe to deal with. This bimetallic switch just gets
the hotplate-stirrer to it's original condition. I can say that for the vwr375, it's a great little hotplate. I can set it from 50 to 170 C (and
anything in between) and it holds that temp rock solid. Switches on and off with no more than a 1/2 degree drift. I need to get some oil with a
higher smoke point. I've only been able to test this up to 170 (setting #5 on the hotplate dial). Extra virgin olive oil don't like to go no hotter.
I've got to find me some avocado oil. Thanks for the link though, I'm sure some will like my find and others will prefer your find. Hopefully we'll
make everyone happy.
Sulaiman - 27-9-2015 at 23:38
the temperature controller that I pointed to is somewhere on a boat from China,
when it arrives I'll post a few photo's and results of the conversion.
My hotplate is working, it is just that I want to be able to distil volatile flammable solvents etc.
without worrying about sparks from the bi-metalic switch.
I will actually be trying constant temperature control using the above
and constant power control (using a Variac)
as I do not know which will be best for distillations.
I can definitely see the advantage of a power controller small enough to fit in place of the bi-metalic switch,
I'm going to look for similar, but cheaper .....
[Edited on 28-9-2015 by Sulaiman]