I found a website whilst searching online which documented some experiments done with printed circuit boards with a serpentine pattern etched onto them, To use them as a heater.

Uses for a heater like this could be:
• To submerge in a liquid & heat it.
• Coffee Cup warmer
• Possible heat bed for a 3D Printer ?

It is resistance heating in its simplest form, Its essentially the same as putting a high current through a resistor, The resistor would heat up. This is doing the same but on a larger scale, on a Printed Circuit Board.

*I do apoligise for the bad pictures*

Step 1: Design of the Board

Firstly I looked on the internet to see if there were any available Vector format images of a serpentine pattern, But I was unable to find one. I quickly designed one in Eagle
(A design program to design printed circuit boards & schematics)
It’s a simple pattern with a trace in a serpentine pattern, which would provide resistance. Once a current is applied to this, it will heat up.
I have included the Eagle files below, for those of you who don’t have eagle on your computer I have supplied a picture in .PNG format.

Heater test 1.brd
Download

Step 2: Creating the Board

I then printed out this pattern onto a piece of glossy photo paper and used the common ‘Toner Transfer Method’ to transfer my design onto a piece of copper clad board.

There are a few simple steps in this method :

1.Print out your design on a LASER Printer, An inkjet will not work, Glossy paper is the best to use (or use a page out of a magazine)

2. Place your Board design on your copper clad board & iron it on the hottest temperature for about five minutes, just to be sure all the toner has been transferred.

3. Place your board in cool water for a few minutes, Then rub the paper off. You should be left with the design on the copper clad board.

4. Using your etchant of choice, Etch the board. I use ferric chloride & the method as described in 'TechShop Jim's' Instructable https://www.instructables.com/id/Sponge-Ferric-Chloride-Method-Etch-Circuit-Bo/ I use this method as its quicker & uses less etchant.

5. Once your board is etched remove the left over toner, There are a few methods to do this. I use a mixture of steel wool (To get the toner off to a rough standard) then clean the board up with acetone to ensure there are no bits of toner on the board.

Step 3: Drilling & Soldering Your Board.

Once your board has been etched & cleaned, You can drill and solder it.

This design is extremely simple and only requires two holes to be drilled.

I used a 1.0mm drill bit which i bought from Maplin Electronics in a set of 10 for £2.50.

To drill the hole i used a standard cordless screwdriver, But you can use a dremel or the tool of your choice. It's extremely easy to snap these small drill bits so use with caution.

Once my holes were drilled i used my multimeter to check for continuity, To ensure there were no breaks in the board. I measure its resistance, with my Fluke multimeter & it measured 8Ohms, When heated to full temperature it measured at 13 Ohms.

Step 4: Finding an Appropriate Power Source.

To get the most out of this heater, You need a power source with a high current. I have tested 3 so far:

An ATX Power Supply, It heated up quickly & got to a good temperature. Easily available, And cheap.

A 'Wall-Wart' - Rated at 12 Volts DC, 1.2 Amps - It heated up quickly & got to a moderate temperature, Too hot to touch.

A Xbox 360 Power Supply - 12 Volts 16.5 Amps (Or so the label says), I would rate this the overall best out of the other two.

I have also tested it using a 12 Volt Car battery, But it didn't run very well.

Step 5: Future Uses & Updates

I intend on building another one of these with a similar pattern, but larger. I will also be building a high current power supply for it.

The design of this is incredibly flexible & quite powerful for its size, My one was only 10cm by 6cm, But would make water incredibly hot. I intend on using a better power supply & I believe this could be used to boil water.

Thanks for reading...