Controlling a Hot Plate’s Temperature for the Lab

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When you need precise heating — like for the acetone polishing shown above — the control hardware is everything. Buying a commercial, programmable, controller unit can cost a pretty penny. Instead of purchasing one, try creating one from scratch like [BrittLiv] did.

[BrittLiv] is a Chemical and Biological Engineer who wanted something that performs well enough to be relied upon as a lab tool. Her design utilizes a plain, old hot plate and with some temperature feedback to run custom temperature ramps from programs stored on an SD card.

The system she developed was dealing directly with temperatures up to 338°F. The heating element is driven from mains, using an SSR for control but there is also a mechanical switch in there if you need to manually kill the element for some reason. An ATmega328 monitors the heating process via an MAX6675 thermocouple interface board. This control circuitry is powered from a transformer and bridge rectifier inside the case (but populated on a different circuit board).

She didn’t stop after getting the circuit working. The project includes a nice case and user interface that will have visitors to your lab oohing and aahing.

Mr. Tea is a hot plate and magnetic stirrer in the same enclosure

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Not being a coffee drinker [Hunter Scott] wanted a way to make tea while lurking in his workshop. Well it’s not exactly rocket science, as all you need is water at the right temperature and a vessel in which the tea can be steeped. But we do commend him on not only building a nice little hot plate enclosure, but rolling a magnetic stirrer into the other side of the box.

You heard us right, the stirrer is not combined with the plate, but resides on the underside of the same PSU enclosure. The plate itself is from a unit he bought at the store and cannibalized. The light switch dimmer lets him adjust the heat it puts out. When not hot, he can flip it over and use the stir plate. This consists of a hard drive magnet attached to a PC fan. For the stirrer itself he encased a neodymium magnet in some thermoplastic. The magnetic combination works well together with a demonstration which shows it stirring water through the base of a tea-cup.

Hackaday Links: November 15, 2012

Another way to break out dual pin headers

[Uwe] wrote in to share his technique for breaking out dual pin headers. He uses two single pin headers, a piece of protoboard, and a dual row pin socket to make an adapter. This is removable where the other method we saw this week was not.

Web-based slide show hack

Wanting to use an old Android tablet as a digital picture frame, [Gordon] coded up a simple way to use an HTML page to scan your picture directories to feed a rotating background image.

The simplest hot plate

For his chemistry experiments [Charlie] is using a plain old clothes iron for a hot plate. he simply clamps it upside down to the bench. It doesn’t have any stirring abilities, but we already have an old iron in the shop which we use for toner transfer so we’ll have to keep this in mind if we ever need to heat chemicals (might be a good way to warm etchant).

A charging VU meter

This Cambrionix series8 universal charger has columns of LEDs that are animated when a device is charging. [Steve Tyson] works for the company and has had some fun messing with the firmware. He’s showing off the display as a VU meter.

Game Boy knockoff teardown

This wide-form-factor Game Boy is a knockoff from way back when the original system hit the market. You won’t want to miss this lengthy post that takes a look at what’s inside. [Thanks Neil]

 

Thermosonic wedge bonding

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In the past, if we’ve been doing smd soldering, we’ve used pretty basic hot plates. This project takes that idea a bit further.  Since [kc6qhp] will be using parts that aren’t conducive to soldering, he has to use wire bonding. After locating a fairly cheap wire bonding machine and microscope, he built the heated stage to fit perfectly with his other tools.  You’ll notice that he has machined a lip around the heat plate for small custom C-clamps as well as made it adjustable height. Very nice work [kc6qhp].

PID SMD reflow hot plate

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[mightyohm] put together a nice piece of lab kit. It’s a PID controlled hot plate. The plate is capable of reaching 500F, hot enough to do SMD reflow soldering. The large chunk of metal has a hole drilled through the center to contain a cartridge heater. A thermocouple is used to monitor the temperature of the plate. Ceramic standoffs separate the plate from the rest of the device, but he still needs to come up with a way to stop the radiant heating. The control box houses the surplus PID controller along with the power switch and solid state relay (SSR).

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