Small SMD hotplate - Page 1
Forum section: electronics / projects

author: djsb
author_rank: Super Contributor
timestamp: July 10, 2011, 12:49:32 pm
content: I thought I would have a go at making this hotplatehttp://www.flyelectric.ukgateway.net/hot_plate.htmI will be using 4 off 15 ohm 50 watt resistors to heat the plate which is 50mm x 100mm x 6mm (instead of 50 x 50 x 6).Using PSPICE I have found that the voltage needs to be increased to 45 volts (instead of 30 volts in the link above) in order to create the same amount of power. To start with I am going to use a variac and an inline fuse for testing (as I don't have a power supply that supplies enough voltage and current). I'm going to log the temperature of the plate at a series of set point voltages.Just wondering if power resistors are a good enough solution compared to a cartridge heater (and PID unit) as described herehttp://mightyohm.com/blog/2009/01/diy-pid-controlled-soldering-hotplate/Can anyone point out anything I should be considering and offer any suggestions?Thanks.David

author: FreeThinker
author_rank: Frequent Contributor
timestamp: July 10, 2011, 02:42:00 pm
content: For that size of board would a iron not make more sense? It has a built in thermostat so you could control the temperature quite accurately? Or if it does not get hot enough you could use a dimmer and short out the thermostat. Unless you have a reason for low voltage?

author: Bored@Work
author_rank: Super Contributor
timestamp: July 10, 2011, 03:12:19 pm
content: I don't think it gets any simpler:http://www.sparkfun.com/tutorials/59#Hot%20Plate%20Reflowing

author: FreeThinker
author_rank: Frequent Contributor
timestamp: July 10, 2011, 03:32:18 pm
content: Quote from: BoredAtWork on July 10, 2011, 03:12:19 pmYes and you can rustle up a nice bacon sandwich at the same time.Lol Agreed the skillet would be my choice, an you get them in the uk?

author: Rufus
author_rank: Super Contributor
timestamp: July 10, 2011, 06:55:53 pm
content: Quote from: djsb on July 10, 2011, 12:49:32 pmMetal clad resistors have plastic internals and typical power dissipation de-rated to 0 at 200C.No good for anything but a 'warm' plate IMO.You can buy 1500W single plate electric cooking hobs for very cheap (look on Amazon), temperature control will be rubbish but you can add a thermocouple and controller like the mightyohm thing you linked.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: July 10, 2011, 10:54:44 pm
content: Quote from: Rufus on July 10, 2011, 06:55:53 pmI have seen the end termination of of one of these come off explosively when grossly overloaded. Fun thing is it leaves a trail of unwound resistance wire behind it like a taser. More fun if there is high voltage on it!

author: Unknown
author_rank: Unknown
timestamp: July 11, 2011, 12:02:15 am
content: You can always try coiling up some length of tungsten wire from a hair dryer and pot it with some ceramic compound.RS used to have some ceramic heating elements in the form of plates, but I can't find a damn thing on RS now.

author: bobski
author_rank: Contributor
timestamp: July 20, 2011, 03:46:13 pm
content: A process controller as used in the second link is definitely overkill. The heavy plate used in these designs acts as a big thermal mass which will greatly slow any changes in temperature. As such, there's no need for proportional control (or associated integral/derivative action) of the heating element - on/off control should do fine. If you can find a temperature controlled soldering iron in the power range you're looking for, that would be an ideal source of heating element and control electronics. A station/iron combo would be nice as it would only require disassembling the iron, while the power supply and control electronics could remain unmodified in the station housing.