How To Make A PCB Using A Laser Printer

When working with electronic circuits, sooner or later we feel the need to make our own PCBs to get a more functional and better looking circuit board.

I already made a video in the past to show how that could be done, for simple circuits, by drawing the circuit manually on the copper clad with a special kind of pen that uses an ink impervious to the chemicals needed to etch the PCB.

This time, I am presenting you a different technique, that allows you to draw the traces, and also the silk layer, with any of the design tools of your choice available on the Internet and the market in general. All you need to have is a laser printer. You can refer to this newer video for a demonstration of the process.

The whole process works on the concept that the printouts of the laser printers are made with a toner that has the characteristic of being able to protect the copper from the etching chemicals, like the ink from the pen in the original video. This is because the toner is made with a sort of plastic material.

Unfortunately, we cannot use a laser printer to print the masks directly on the copper clad, because the PCB boards are too thick for the printer. Therefore, we need to find a way to print on paper and then tranfer the printed ink to the copper afterwords.

This is made possible by a certain quality of glossy paper that do not allow the toner to stick permanently on its surface when exposed to heat. Even paper from magazines that are printed on glossy paper works relatively well for this to happen. However, there are specialized papers, that are designed specifically for this, which are called Thermal Transfer Paper For PCBs. A quick search on-line will give you plenty of places where you can buy it at a relatively modest price.

Once you have your PCB design ready and printed on such paper, the process to create PCBs becomes really straightforward.

First step is the transfer of the traces drawing to the copper. The copper needs to be perfectly clean, so it is always better to use a piece of steel wool to scrape away copper oxide and other dirt from the copper surface. Just move the wool in a circular fashion to remove all the particles of oxide from the copper clad and make sure to use gloves, otherwise the contact with the skin of your hands will soon oxidize again the copper.

Once all the oxide is removed, you need to deep clean the copper to remove any particle of dust from it. To do so, you can use some alcohol. Once done, let the board stand for a a while to make sure it is completely dry.

Then lay the board on the printout, making sure the copper is in contact with the drawing. Wrap the paper all around the board to make sure it will not move during the transfer process.

Once the PCB is wrapped with the paper, put it on the table copper-side up and use an iron at the max temperature, with no steam, to heat uniformly the whole surface of the paper and the pcb wrapped in it. Be careful not to burn yourself in the process, of course. You do not need to press hardly, the weight of the iron is just enough. Just make sure you keep moving the iron so that the whole surface is heated uniformly. Do that for a while, until the copper clad becomes almost as hot as the iron. Don’t worry about burning the paper. it is not going to happen. Paper burns at 451 F while the iron, even at the hottest temperature, doesn’t normally go over 400F.

Once the paper and the clad are well heated, put aside the iron and unwrap the board, making sure that when you remove the paper from the copper side you do that slowly and uniformly. The ink from the printout will now have moved from the paper to the copper.

Second step is the actual etching. Use a plastic container, fill it with some ferric chloride solution, enough to cover the whole pcb, then dump the board in the solution. Once the board is in the solution, you’ll notice that the ferric chloride starts changing color. From the initial brown color, it starts becoming darker and darker. This happens because of the copper on the board that starts dissolving in the solution.

While the etching process continues, try to agitate the solution periodically, which will speed up the reaction. A warmer room will also help. Every now and then, check the status of the board and remove it from the solution as soon as you don’t see any more copper on the surface of it.

Once the etching is completed, remove the PCB from the solution and start rinsing it immediately, to stop the reaction that would continue to attack the remaining copper on the surface.

You now need to remove the toner film from the copper traces, otherwise you will not be able to solder the components on it. To do so, use a Lacquer thinner on a piece f paper or cotton and work slowly a little bit at a time. Do this in a well ventilated area. Solvent vapors are both unpleasant to breath and harmful.

Third step is to drill the holes. It is only necessary if you use pass through components, of course. If you use surface mounted components, this step is not necessary, unless you need holes to hold in place the board.

Finally, the fourth and last step is to do another transfer, on the components side of the board, to transfer the drawing for the silk layer. The procedure is exactly the same, but this time the toner will be lay down directly on the board support, not on the copper.

You can see how this process allows you to quickly repeat the whole procedure on as many boards as you like. You just need to print multiple copies of the layouts on the thermal paper and go through the previous four steps.

Hope yo liked this procedure, and don’t forget to go watch the corresponding video, so you will see exactly how this procedure works.

Making A Small And Fast Computer Using a Raspberry Pi 4B

Converting the Raspberry Pi to use a SSD or a Hard disk via the USB V.3 connector, instead of the microSD card, allows for a big increase in the speed of the device. The conversion can be done very easily with an RPi 4B, since it already has the capability of booting from a USB-attached storage device, but can be easily done also to older RPi versions with a simple modification to their firmware, following the procedure on the RPi official web site.

The conversion consists in removing the microSD card from the RPi and use instead a hard disk. And for that, I bought on Amazon a nice Samsung 500GB external solid state disk for a very reasonable price. Since it connects through a USB v3 cable, it seems perfect for the job.

If you need a SSD like this, or a different one, you could use my affiliate link to buy one, so you will indirectly support this site and the eleneasy YouTube channel at no extra cost to you. You can also watch the video where I show you how to make the conversion.

And since I now have two devices, the RPi and the SSD, that need to stay connected and work together, I decided to 3D-print a nice box to save some desk space.

There are two parts: one for the actual box and one for its cover. They are both made out of a simple cube, but I made a few slits on the bottom of the box and on the cover to help with the air flow, so the components inside will not overheat, especially the RPi.

Here is the OpenSCAD code I used to design the object:

$fa=0.5;
$fs=0.5;


// BODY

difference()
{
	cube([100, 100, 65]);
	translate([2, 2, 2]) cube([96, 96, 64]);
	translate([1, 1, 63]) cube([98, 98, 3]);
	
	translate([5, 20, -1]) cube([88, 2, 4]);
	translate([5, 34.5, -1]) cube([88, 2, 4]);
	translate([5, 49, -1]) cube([88, 2, 4]);
	translate([5, 63.5, -1]) cube([88, 2, 4]);
	translate([5, 78, -1]) cube([88, 2, 4]);
	
	translate([2, 97, 20]) cube([15, 4, 20]);

	translate([35, 97, 10]) cube([56, 4, 20]);
	
	translate([97, 8 , 10]) cube([4, 70, 15]);
}




// COVER

translate([110, 0, 0]) difference()
{
	cube([98, 98, 2]);
	translate([10, 20, -1]) cube([78, 2, 4]);
	translate([10, 34.5, -1]) cube([78, 2, 4]);
	translate([10, 49, -1]) cube([78, 2, 4]);
	translate([10, 63.5, -1]) cube([78, 2, 4]);
	translate([10, 78, -1]) cube([78, 2, 4]);
}

Pleass refer to my YouTube video for the details of the project.

A Short Guide To Multimeters

Short guide to choose the right multimeter for your needs.

Picture showing a number of multimeters, both digital and analog.

The very first instrument that an hobbyist buys for the electronics lab is the Multimeter. There are several choices in the market and it is very difficult to make the right decision.

Sometimes it is the amount of available money that forces our hand when choosing the instrument, and sometimes the inexperience drive us to make the wrong judgement.

In this article I will try to provide a set of useful information that will help you make an informed decision. But, always remember that the cheapest solution is not always really the cheapest one. When you are uncertain between a couple of models, always choose the one with the best features. That will avoid future regrets, the moment you realize that the missing features where those that you needed the most. Making the wrong choice may force you, later on, to buy a second instrument because you realize the one you got does not satisfy your needs.

Let’s start with the first categorization: analog versus digital.

In this era of digital devices permeating the market in all electronics categories, the choice of buying a digital multimeter seems obvious. But is it? We need to explore a number of properties and features of both kind o devices. Only after you know pros and cons of each, you will be able to make a decision based on what you envision being the usage that you’ll make with the instrument. And, sometimes, you’ll find that having both kind of instruments is better that having only one.

Picture of a digital multimeter measuring volts.

A digital instrument is definitively easy to read, especially if it has a large display, and it is even better if it tells you the measurement unit along with the value, like in the one depicted on the left. On the other end, to be able to show you a number, the digital instrument needs to make an analog to digital conversion, which takes time to complete. After all the quantity under measurement is always an analog one.

The problem with the analog to digital conversion is that it takes time; it is not instantaneous. As a result, if you are measuring a quantity that slowly changes over time, you could end up with a situation where the quantity changes before the instrument has completed the conversion. In such a case, you would not be able to see any useful reading on the display. The numbers would keep change continuously and inconsistently.

Picture of an analog multimeter measuring volts.

An analog instrument, on the other end, is not that easy to read. Depending on the type of measurement you have to make, and how big is the value under measurement, you will have to find on the display the right scale to use, and that can be confusing, sometimes. The good thing about this instrument, however, is the fact that the needle always responds instantaneously to the quantity being measured.

It might take some time for the needle to reach the right position on the scale, because of its inertia. But that same inertia allows the needle to find itself an average of the value if the quantity is slowly changing over time. Not that the measurement will be precise. It will not, but it will give you an idea of what is going on, while with the digital instrument, you would just see a bunch of numbers continuously changing in a pseudo random way.

Is then the analog instrument better than the digital? Well, wait a minute here. There are still several parameters to evaluate.

Let’s talk about precision. Both digital and analog instruments can have a pretty good precision, but with the analog instrument sometimes you have to guess the best reading, because the needle is not exactly on a mark on the scale, but is instead in between two marks. And things get even worst when accounting for the parallax error. When you look at the mark underneath the needle, depending on the position of your eyes compared to the needle itself and the scale, you may find that moving your head a little bit on one side or the other, the measurement changes. And that’s why the best analog instruments have a mirror on the display. If you look at the needle with one eye only and you position yourself in such a way that you don’t see the reflection of the needle on the mirror, then you are perfectly vertical on top of the needle and you can make a better measurement. And of course this takes time, usually more time than taking a measurement with a digital instrument. Digital instruments, on the other way, may have the precision of just a couple of digits or more. The more the better of course. For a decent lab instrument, you may want to go with instruments, either digital or analog, where you can make a read of at least 3 digits, better 4.

And after all the effort to make a good measurement, you could find yourself with a perfectly useless measure. Why? Because of the impedance that the multimeter puts in parallel to the points under test. And this bring us to yet another difference between analog and digital multimeters.

The majority of analog multimeters present a low input impedance, which means that they draw a certain amount of current from the test points. And this extra current could cause an extra drop of voltage across another resistor that is part of the device under test. The result would be that the reading looses accuracy.

A digital instrument, on the other end, usually has a very high input impedance, in the order of several mega-ohms, compared to the tens of kilo-ohms of the analog instruments. Just because of that, measurements taken with a digital multimeter are usually more accurate.

But then, that is not always true. There are analog multimeters that are equipped with an amplification stage with FET or MOSFET. Those analog multimeters have an input impedance comparable to the one of the digital instruments. Always read the specs of the device you are buying and try to figure out if the input impedance is in the order of the kilo- or mega-ohms. The higher the better.

To conclude, to make the right choice when buying an instrument, normally go with a digital one, unless you already know that the majority of readings you will ever make will be done on slowly changing values. Buy always an instrument that gives you the best precision you can afford, with the highest input impedance. And keep in mind that for a multimeter to be useful in an electronic lab, you want to be able to measure magnitudes very small but not necessarily that high. Shoot for an instrument that will make you read micro-amps and milli-volts, for example.

Last, if you can afford it, you could buy both a digital and an analog instrument. Analog instruments are cheap nowadays, and can be easily found also in the second hand market, like on eBay. And once you have a decent analog instrument, you don’t have necessarily shell a lot of money on a digital instrument. There are decent digital multimeters below the one hundred dollars value. Take a look at the Merchandise section of this web site for such an instrument.

If you would like to know more on this topic, and see both the analog and digital multimeters in action, I suggest you to watch this Youtube video.

Happy experiments!