Introduction: PCB Heater (Diy Joule Heating)

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.

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...

Comments

author
eefmf (author)2012-08-24

Very Interesting.
What is the resistance of the board?
What voltage and current did you use?

author
stephenniall (author)eefmf2012-08-24

It says above, the boards resistance is 8ohms. But increases with heat, I've been using 12vdc at 16amps

author
eefmf (author)stephenniall2012-08-25

Do you know the width, thickness and length of the track?
There is a website that gives current capacity= htp://pcbinfo.blogspot.co.uk/2005/04/current-carrying-capacity-of-tracks.html

12vDC at 16 amps gives 0.75ohms and 192watts.
Dont run that out of liquid or it will melt the copper.
If it is 8ohms 16volts would give 2amps and 32watts.

Another problem is that copper corrodes in liquid.

author
stephenniall (author)eefmf2012-08-25

No, Will measure them with a set of calipers tomorrow. It has been fine so far.

I was thinking of trying a simple electroplating & Electroplating it with tin to see what happens. Its all still in the 'thinking' stage yet.

author
warhawk8080 (author)stephenniall2017-02-06

Electroplating would add metal to the traces, which would lower resistance and increase current flow, you want a smooth dielectric, like clear coat high temp paint or something, nail polish, polyerethane

author
warhawk8080 (author)eefmf2017-02-06

Conformal coat with nail polish or polyerethane ;)

author
warhawk8080 (author)stephenniall2017-02-06

Math is wrong

12vdc at 8 ohms would only pull approx 1.5A at around 18watts...and only drop as he says when the heat of the board increases

author
nadav (author)2012-08-22

I would change the design to be a large spiral (like on an electric stove top). Because, right now, the heat will cause stress on the 90 degree bends on the PCB.

Also, the corners (90 degree turns) would heat more then the straight sections, so having a spiral layout, would give you a much more evenly heated surface.

Still though, its an interesting project, it definitely gets me thinking what it could be used for.

Cheers,
Nadav

author
stephenniall (author)nadav2012-08-23

That will be in my second version, I will use bended corners in my straight sections aswell in future revisions.

author

There's nothing wrong with your design as is!!

author
Lectric Wizard (author)nadav2012-08-23

Why would DC cause the bends to heat more than the straight runs ?? I can see high freq doing that but DC ?

author

Imagine the tiny electrons driving in their electron cars, metaphorically speaking, along the straight runs, then they hit a turn. Not one of those spiraling turn you see on the freeway, but like those indy car race track 90° turns. Well since electrons don't really slow down for turns, the 90° turn takes a beating. DC is more harsh than AC or PWM, because the tiny electrons are going balls to the walls all the time, unlike AC or PWM which crosses the X-axis giving the copper time to rest every cycle time.

author
AustinC42 (author)Janusmarine2016-05-03

Please, don't comment unless you actually know what you're talking about. What you've said here is complete garbage.

In reality, the corners aren't much of a problem. They will get slightly warmer, but not by much. This is mostly because there's more copper being heated at the corners than along the straight tracks.

author
Lectric Wizard (author)AustinC422016-12-15

Thanks Austin42. After 50 years in power electronics and broadcasting I knew what it was ...

author
Xellers (author)Janusmarine2016-07-23

I love this comment.

author
MostafaA4 (author)2016-09-14

i want reduce the area of the heat bed to 5 cm x 5 cm can you help me

author
Roshy10 (author)2013-03-30

you could use it to heat a pcb etching tank/tray, but you would need plenty of lacquer to stop it etching its self

author
AlexS123 (author)Roshy102015-10-23

I guess you could use a solder mask, it should provide pretty good protection.

author
redwolf007666 (author)2014-01-30

concerning the power supply. can this be done by a simple AA battery or batteries?thanks

author
AlexS123 (author)redwolf0076662015-10-23

Unfortunately regular batteries have way too low power to heat such thing, you need a high power power supply.

author
ams (author)2015-10-20

You could achieve this with a Sharpie permanent marker for etchent resist you can leave the etch resist on except at the electrical power connect points.

author
yaly (author)2014-11-04

I need to make a 50 cm x 50 cm version of this, any suggestions how to do it ?

author
Feint Nightmare (author)2014-03-17

Hi guys , can some one tell me if I can use this to make a 40 x 40 heatbed ?

if so what should be the thickness of the copper? if I buy copper sheets and place them on a mica sheet or some other material that is suitable will that work?

that way I can directly make my glass a heatbed

looking forward to ur reply :)

Jim Jose (jimjose99@gmail.com)

author
nodoubtman (author)2014-02-27

After the iron,under the copper it's all black, is it possible that my
iron is too hot, the iron settings is before steam. What do you suggest?
thank you!|

author
waldosan (author)2012-08-22

you need to put a potentiometer in series with this, it'll allow you to limit the amount of current going through it, i think you'll find also that dc power supplies will work better than ac, just on principle and what not.

hooking it up to a car battery though will set fire to something, prototype boards aren't supposed to be able to catch on fire but then hydrogen peroxide and chlorine isn't supposed to glow.

it seems though like a solid concept, i'm sure you've heard of peltier devices (hot on one side, cold on the other) but this seems more like it'd function better as a space heater!

author
stephenniall (author)waldosan2012-08-22

I intend on building a LM317 Adjustable current regulator to regulate the current that flows through, I've been using DC Power supplies, All the devices i've used are DC, They transfer the power from the Mains sockets (240V AC) to the voltages in DC, Via transformers.

Thanks for your comment !

author
PocketBrain (author)stephenniall2014-01-14

Also, you might not want to control current through the thing with a linear regulator; it also will express a lot of heat and fail quickly if it's not rated. Pulse Width Modulation or duty cycle modulation (sometimes used to describe a slower frequency of PWM) will be an effective method of controlling the heat output of the thing. Basically, it should be ON or OFF at any point in time; the ratio of ON to OFF is what controls the heat output. If you do choose to use the LM317, select one that can take 1.5 amps and shed 5W of power; my calculations say max. current with a mimimum of 1.25V output would be about 1.34A, and max. power would be about 4.75W. I think PWM control would be sexier; just a PWM-controlled fixed-frequency oscillator switching a power MOSFET and that part of the system would run cool.

author
waldosan (author)stephenniall2012-08-24

unless your getting your mains from a dryer plug your voltage should be 120ish though i could be wrong about that if your living in Europe or something like that, the lm317 is a variable voltage regulator rated for one amp so if you try to use it as an amperage regulator you'll just fry it, actually you won't even do that, it has built in safety features so it just wouldn't work. dc power supplies, like car batteries and wall warts, are rated for certain amp levels usually this is below the amount of amps you'd be pulling if you'd shorted out the leads, in batteries this means they get very hot and might burst if your not careful, in wall warts this means that they make a funny buzzing noise and depending on how much your trying to pull they can catch on fire!

it's a great idea you got here, i'm thinking more and more about using it as a heating pad for a 3-d printer or something like that.

author
stephenniall (author)waldosan2012-08-24

We're using an ACCOUNT to DC wall adaptor, which changes our UK 240Vac plugs and converts it to the voltage the lm317 takes, the lm317 will be on its on circuit board with a big heat sink for best heat distri ution.

author

AC* sorry, autocorrect. Seems to change everything I type.

author
stephenniall (author)waldosan2012-08-24

We're using an ACCOUNT to DC wall adaptor, which changes our UK 240Vac plugs and converts it to the voltage the lm317 takes, the lm317 will be on its on circuit board with a big heat sink for best heat distri ution.

author
PocketBrain (author)waldosan2014-01-14

Bad idea, as the potentiometer potentially will overheat quickly, heat unevenly, and fail quickly. It would be best to use PWM to control its power. Keep in mind, there do exist pots that are rated for high-power use, but they are expensive and bulky, and still produce waste heat.

author
PocketBrain (author)2014-01-14

Your etching looks really clean, good work. I am thinking about using this kind of element to heat my 3D printer's build plate. Of course, it will require a good PWM controller. ;-) I have also thought of using this type of heater to warm the etchant solution when doing my own board etches; warm, agitated etchant works quickly and more efficiently. Thanks for the Instructable!

author
DIY-Guy (author)2013-01-13

Stephenniall: Nice work.
This could be a nice little small batch yogurt incubator, or a seedling germinator with moisture protection. Perhaps one of the high temp plastic films could be bonded to the surface, mabe Kapton?

author
Lectric Wizard (author)2012-08-23

Nice Instructable. There is a company that makes a similar device on flexible circuit boards for use in video & film cameras. They are used to keep the batteries warm & the lenses from fogging up. It would be interesting to see if double sided boards would work better or if the heat would be too much for the substrate...just a thought.

author

Haven't thought about using it with double sided boards, It might be something i'll look into.

author
ironsmiter (author)stephenniall2012-08-23

if that is standard fiberglass board, it should handle the heat just fine. Probably work better for heating two different things, rather than trying to soak the heat from the secondary through the board to the primary surface.
Well, I should amend that a bit. as long as your heat levels are below 220F(104C) you should be OK. over that temperature, you run the risk of melting the epoxy that binds the fiberglass together.

author
rimar2000 (author)2012-08-22

Very interesting.

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Bio: Hey, I'm Ste. I live in Manchester, In England. I'm still in full time education, I've been lurking on Instructables for five ... More »
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