Today, many household and other devices use laser diodes (semiconductors) to create a targeted beam. And the most important point in assembling a laser system yourself is connecting the diode.
Laser diode
From this article you will learn about everything you need for a high-quality connection of a laser diode.
The laser model differs from the LED diode in its very small crystal area. In this connection, a significant concentration of power is observed, which leads to a short-term excess of the current value in the junction. Because of this, such a diode can easily burn out. Therefore, in order for the laser diode to last as long as possible, a special circuit is needed - a driver.
Note! Any laser type diode must be powered with a stabilized current. Although some varieties that give red light behave quite stably, even if they have unstable nutrition.
Red laser diode
But, even if a driver is used, a diode cannot be connected to it. A “current sensor” is also needed here. Its role is often played by the common wire of a low-resistance resistor, which is connected to the gap between these parts. As a result, the circuit has one significant drawback - the power minus is “severed” from the minus present in the circuit’s power supply. In addition, this circuit has one more disadvantage - power loss occurs at the current-measuring resistor.
When planning to connect a laser diode, you need to understand which driver it should be connected to.
At the moment, there are two main types of drivers that can be connected to our semiconductor:
Simplified switching driver circuit
Note! When using linear integrated circuit stabilizer chips, the current will decrease as the input voltage across the diode drops.
Line Driver Circuit
Due to the fact that any laser diode can be powered through two different types of drivers, the connection diagram will be different.
The circuit that will be used to power the laser diode may contain not only a driver and a “current sensor”, but also a power source - a battery or battery.
Connection diagram option
Typically, the battery/battery in this case must have a voltage of 9 V. In addition to them, the circuit must include a laser module and a current-limiting resistor.
Note! In order not to spend money on a diode, you can remove it from the DVD drive. Moreover, it must be a computer device, and not a standard player.
Computer DVD drive
The laser semiconductor has three terminals (legs), two of which are located on the sides and one in the middle. The middle output should be connected to the negative terminal of the selected power source. The positive terminal must be connected to the left or right “leg”. The choice of left or right side depends on the semiconductor manufacturer. Therefore, you need to determine which output will be: “+” and “-”. To do this, power must be applied to the semiconductor. Two batteries, each 1.5 volts, as well as a 5 ohm resistor will do the job perfectly here.
The negative terminal at the power supply should be connected to the central negative terminal defined at the diode. In this case, the positive side must be connected to each of the two remaining terminals of the semiconductor in turn. Thus, it can also be connected to a microcontroller.
Power for the laser diode can be provided using 2-3 AA batteries. But if you wish, you can also include a battery from a mobile phone in the circuit. In this case, you must remember that you will need an additional 20 Ohm limiting resistor.
The semiconductor can be powered from 220 V. But here it is necessary to create additional protection against high-frequency voltage surges.
Option for powering a diode from a 220 V network
Such a scheme should include the following elements:
The resistance and stabilizer will form a block that can prevent current surges. To prevent voltage surges, a zener diode is needed. The capacitor will prevent the appearance of high-frequency bursts. If such a circuit was assembled correctly, then stable operation of the semiconductor will be guaranteed.
The most convenient way to create a laser installation with your own hands will be a red semiconductor, which has an output power of approximately 200 milliwatts.
Note! This is the semiconductor that any computer DVD player is equipped with. This greatly simplifies the search for a light source.
The connection looks like this:
DO NOT aim at the eyes, otherwise you may completely lose your vision;
Diode check
Red beam from a homemade device
It can then be focused using a biconvex lens. Focus it for a few seconds on one point on the paper that absorbs the red spectrum. The laser will leave a red light on it.
As you can see, we have a working device that is connected to a 220 V network. Using various circuits and connection options, you can create different devices, even a pocket laser pointer.
When connecting a laser diode, you need to remember about safe handling and also know the nuances that are present in its operation. After this, all that remains is to choose the circuit you like and connect the semiconductor. The main thing to remember is that all contacts must be well sealed, otherwise the part may burn out during operation.
Calculation of lumens per square meter for different rooms
Self-assembled laser engraver/cutter based on a 2.5 Watt laser module.
In short - XY-kinematics, Marlin firmware and D8-L2500 laser module. The engraver turned out just right - he knows how to burn, both with dots and lines, and most importantly - to cut!
Let me immediately remind you about TB: when working with a laser, use glasses (special ones, taking into account the wavelength of the laser), do not point it at your eyes. The laser is very powerful - even a small reflected radiation can seriously damage the retina.
So, recently I have been struggling to improve the Neje DK-5 laser engraver in order to increase (primarily) the working area and power for processing various materials. In the end, I came to the conclusion that it would be easier to make another one, in the image of simple Chinese engravers on the profile.
As a basis, I took a Chinese kit on an aluminum structural profile 2020 and 2040. Looking ahead, I will say that practice has shown that it is easier to do everything on the same profile 2040, since the ease of installation and rigidity of the frame significantly increases (it is easier to attach elements of body panels to a double profile , legs, cable channels).
The basis of any laser engraver is the laser module. I had experience working with diodes torn from all kinds of equipment, as well as with a module from Neje, but I wanted something more. The Chinese sell all-in-one solid-state laser assemblies: a module in the form of an aluminum radiator of a cylindrical (less often) or rectangular shape (most often). Inside the radiator there is a cylinder with a laser diode, from which two contacts protrude for connecting the supply current. Also installed inside the laser module (and filled with a certain substance) is a current driver for the diode, most often CC (continuous current), less often a driver with support for TTL signals to control the laser power. Often there is a cooling fan on the side or at the end of the radiator. At the other end of the laser output there is a focusing or collimating lens (depending on the purpose of the module). Power supply is usually 5V or 12V.
Here's an example of what's inside (photo not mine, from the open air).
Solid-state laser modules (diode) range from hundreds of milliwatts (for example, 0.3 W) to several units (for example, 5.5 Chinese watts). The more power, the higher the price, and for powerful modules the price is so high that it is easier to consider installing a CO2 tube, but that is a completely different story. Keep in mind that Chinese watts do not always correspond to reality (it is very difficult to estimate the real radiation power). And you can easily buy the same laser diode, labeled 5.5W, 8W or 10W. Perhaps they will differ in the increased current to the diode itself, which greatly (by several times) reduces the life time of the diode.
Since I wanted to not only burn wood, but also cut anything (plastic, plywood, cardboard, etc. - but not metals!), the Neje module was no longer enough for me, especially since the ones torn from CDs don’t roll, and they burn out quickly. It was decided to look for and purchase a several-watt laser module from China; I mainly chose from 450 nanometer laser modules (one of the most affordable).
There are the following types of laser heads on the girbest:
1. 2.5W 12v;
2. 0.5 W 12V;
3. 0.5 W 5 V.
All lasers are 445nm (violet laser), with cooling fan and power supply included.
In addition to the difference in power, it is obvious that the supply voltage is also different. Modules for 5V are very convenient for power supply with power banks/batteries, as well as for ready-made cases with 5V drives. Don't forget that the fan should also be 5V.
When powering stepper motors from 12V, it makes sense to purchase a 12V laser module in order to unify the power supply for the engraver (that is, you only need 1 12V power supply). This is exactly my option. Included with the D8-2500 is a 12V and 5A power supply, which is clearly enough for the laser diode, and in addition remains to power the Ramps electronics and servos.
In the end, I ordered 2.5W/12V. This is what they sent:
Here are some photos of the laser module itself.
Turned on the laser to check the power circuits and correct connections. Somehow I didn’t realize to install an absorbing substrate, and ended up burning my photophone.
So, I’ll tell you about my engraver project, which resulted in an upgrade of my Neje. A kind of mess from an axe. I twisted the laser and removed the electronics. I realized that you can’t make porridge from this. Replaced electronics and laser. As a result, I decided to leave Neje alone and put it away.
I would like to say that there are ready-made frames for installing lasers - XY plotters. But I decided to assemble the frame myself, especially since it is not so difficult.
The idea was very simple - the use of a 2020/2040 structural profile as a frame and guides for a simple A3 engraver, like in Chinese engravers. Rigidity is ensured by special (standard) connections for the structural profile. (internal connectors, corners). Profile dimensions – dimensions of the printed area (minus the carriage). The format was chosen to be slightly larger than an A4 sheet with the expectation of small-sized materials. After Neje with its 3.5x3.5, the difference is simply huge.
About electronics: there are options for RAMPS/LCD/SD/Marlin or CNCshield/GRBL. I removed the stepper motors from the old device (nema17 - can be purchased, they are standard. Great efforts are not needed, since the laser head is lightweight / I think that with small axes you can use inexpensive nema17 type 17H2408. I ordered a profile cut to size and fittings (corners and hardware), plus rollers for carriages.
In any case, if you are interested in assembling a printer yourself, then there is practically no problem finding drawings for printing on a printer (stl) or drawings for cutting acrylic.
A definite plus of the D8-L2500 laser module kit is the presence of a 12V 5A power supply, which is very convenient. I will power the steppers from the same power supply.
What is required for assembly
1 Laser head Engraver/burner - 1 pc.
2 Power supply 12V For powering the laser and drives (1 piece, included in the kit
laser)
3 5V power supply To power the electronics board (optional)
4 2040 profile longitudinal parts of the frame, X-axis - 2 pieces x 420mm
5 2040 profile transverse parts of the frame - 2 pcs x350mm
6 2040 profile Crossbar Y axis - 1 piece x380mm
7 Nema17 Two in X, one in Y - 3 pcs.
with drive ones not necessarily powerful
gears
8 Belt GT2-6mm Two sections in X, one in Y -1.5 meters approximately
9 Limit switches Extreme positions of X-Y axes - 2 pcs.
10 RAMPS 1.4 Control set - 1 piece (*took everything as a set)
11 Ardu Mega R3 electronics* - 1 piece
12 Display+SD shield+cables - 1 pc.
13 A4988 driver, with radiators - 2 pcs.
14 Set of hardware (screws M3, M4, M5, nuts M3 - Set
M4, M5, T-nuts, washers, etc.) For fastening the frame, straps,
engines, for assembling carriages,
etc.
15 Internal corners For fastening frame corners - 4 pcs.
16 Legs or stands In the corners - 4 pcs.
17 Set of wires -Kit
18 Cable channels** - 1.5 meters approximately
19 Rollers For carriages *** 12 (three carriages of 4 pcs each)
* Electronics can be replaced with Arduino Uno/Nano and CNC shield with drivers (A4988/DRVxxxx)
**There is also a spiral cable channel.
*** You can use 3 rollers, or different rollers (by diameter), depending on the selected carriages.
In terms of hardware, I can only give you an approximate estimate; I took a stock of different denominations, then actually looked at what would fit. I recommend buying in wholesale or ordering from Ali (I ended up spending several times more buying at retail than I would have taken a couple of lots on Ali for 50-100 nuts and screws).
If the carriages are made of acrylic, you don’t have to make a double one - I played it safe, because of this the thickness of the carriage has increased and the working area has decreased by almost 6 cm. You can also take the rollers more conveniently, with a pressed-in M5 bushing.
The original OpenBuilds version assumed the use of only 3 rollers - two running ones and one smaller one for pressing.
To make the carriages lighter, instead of several washers, I used printed bushings. Everything is selected and done in three minutes, and printed in about the same time. You can use washers or make other spacers. When designing, it is better to take into account a small margin in the size of the holes, plus, due to plastic shrinkage.
This is what happened.
Second pass on corrugated cardboard. I made two passes due to the thickness. So cardboard cuts well. Unfortunately, the second order with wire extensions for servos and a cable duct did not arrive in time - I now have a limited work area - the wires are stretched, so there will be no test on a large canvas (well, or I’ll post it later).
A small minus - the work of such an engraver in an apartment is evil))) There is a lot of smoke from cardboard and wood. For this reason, I did not cut plastic and acrylic. Need a good hood.
The plans are to make legs, something like a body, and put the wires into the channels (it is possible to run the wires inside the profile or along grooves, with them secured with clips). Ventilation, exhaust hood and housing are very necessary.
So far the plans are to adapt the laser module to work with PWM by replacing the driver with an external one.
And I'm looking for software to convert images to LCD. What I tried did not help me.
Another thought is that you can add a third axis with a gentle stroke. This will allow for more flexible adjustment to materials with greater thickness.
conclusions
In general, the purchase of this module freed up my time, which was spent on altering diodes without housings. There is no need to select a lens and power supply for each one, or shove everything into the body. The cost of the module is quite high, but if you compare the cost of the finished design of a laser engraver of this type, then in the end the benefits are obvious. The fact is that the cost of a laser is more than half the cost of the entire engraver. The rest is the cost of the profile, engines and electronics (little things).
It's no secret that each of us as a child wanted to have a device like a laser machine that could cut metal seals and burn through walls. In the modern world, this dream can easily come true, since it is now possible to build a laser with the ability to cut various materials.
Of course, at home it is impossible to make a laser machine so powerful that it will cut through iron or wood. But with a homemade device you can cut paper, polyethylene sealing or thin plastic.
Using a laser device, you can burn various patterns on sheets of plywood or wood. It can be used to illuminate objects located in remote areas. The scope of its application can be both entertaining and useful in construction and installation work, not to mention the realization of creative potential in the field of engraving on wood or plexiglass.
Tools and accessories you will need to make your own laser:
Figure 1. Laser LED circuit diagram.
These materials will be quite sufficient for the upcoming work.
So, for a laser device, first of all, you need to select a DVD-RW drive with a mechanical breakdown, since the optical diodes must be in good condition. If you do not have a worn-out drive, you will have to purchase it from people who sell it for spare parts.
When purchasing, keep in mind that most drives from the manufacturer Samsung are unsuitable for the manufacture of cutting lasers. The fact is that this company produces DVD drives with diodes that are not protected from external influences. The lack of a special housing means that the laser diode is subject to thermal stress and contamination. It can be damaged with a light touch of your hand.
Figure 2. Laser from a DVD-RW drive.
The best option for a laser would be a drive from the manufacturer LG. Each model is equipped with a crystal with varying degrees of power. This indicator is determined by the writing speed of dual-layer DVDs. It is extremely important that the drive is a recording drive, since it contains an infrared emitter, which is needed to make a laser. A regular one will not work, since it is intended only for reading information.
DVD-RW with a 16X recording speed is equipped with a red crystal with a power of 180-200 mW. The 20X speed drive contains a 250-270 mW diode. High-speed recording devices of the 22X type are equipped with laser optics, the power of which reaches 300 mW.
Return to contents
This process must be done with great care, since the internal parts are fragile and can be easily damaged. Having dismantled the case, you will immediately notice the necessary part; it looks like a small piece of glass located inside the mobile carriage. Its base needs to be removed; it is shown in Fig. 1. This element contains an optical lens and two diodes.
At this stage, you should immediately warn that the laser beam is extremely dangerous to human vision.
If it hits the lens directly, it damages the nerve endings and the person may remain blind.
The laser beam is blinding even at a distance of 100 m, so it is important to watch where you point it. Remember that you are responsible for the health of others while such a device is in your hands!
Figure 3. LM-317 chip.
Before you begin, you need to know that the laser diode can be damaged not only by careless handling, but also by voltage surges. This can happen in a matter of seconds, which is why diodes operate based on a constant source of electricity. When the voltage increases, the LED in the device exceeds its brightness standard, as a result of which the resonator is destroyed. Thus, the diode loses its ability to heat, it becomes an ordinary flashlight.
The crystal is also affected by the temperature around it; as it drops, the laser performance increases at a constant voltage. If it exceeds the standard norm, the resonator is destroyed according to a similar principle. Less commonly, the diode is damaged by sudden changes, which are caused by frequent switching on and off of the device over a short period.
After removing the crystal, you must immediately tie up its ends with exposed wires. This is necessary to create a connection between its voltage outputs. To these outputs you need to solder a small capacitor of 0.1 µF with negative polarity and 100 µF with positive polarity. After this procedure, you can remove the wound wires. This will help protect the laser diode from transients and static electricity.
Return to contents
Before creating a battery for the diode, it is necessary to take into account that it must be powered from 3V and consumes up to 200-400 mA, depending on the speed of the recording device. You should avoid connecting the crystal directly to batteries as this is not a simple lamp. It can deteriorate even under the influence of ordinary batteries. The laser diode is a self-contained element that is supplied with electricity through a regulating resistor.
The power supply system can be configured in three ways with varying degrees of complexity. Each of them requires recharge from a constant voltage source (batteries).
The first method involves electrical regulation using a resistor. The internal resistance of a device is measured by detecting the voltage as it passes through the diode. For drives with a 16X write speed, 200 mA will be sufficient. If this indicator increases, there is a possibility of damaging the crystal, so you should stick to the maximum value of 300 mA. It is recommended to use a telephone battery or AAA batteries as a power source.
The advantages of this power supply are simplicity and reliability. Among the disadvantages are the discomfort when regularly recharging the battery from the phone and the difficulty of placing batteries in the device. In addition, it is difficult to determine the right moment to recharge the power source.
Figure 4. LM-2621 chip.
If you use three AA batteries, this circuit can be easily installed in a Chinese-made laser pointer. The finished design is shown in Fig. 2, two 1 Ohm resistors in sequence and two capacitors.
For the second method, the LM-317 chip is used. This method of arranging a power system is much more complicated than the previous one; it is more suitable for stationary type laser installations. The scheme is based on the manufacture of a special driver, which is a small board. It is designed to limit the electric current and create the necessary power.
The connection circuit of the LM-317 microcircuit is shown in Fig. 3. It will require elements such as a 100 ohm variable resistor, 2 10 ohm resistors, a 1H4001 series diode and a 100 μF capacitor.
A driver based on this circuit maintains electrical power (7V) regardless of the power source and ambient temperature. Despite the complexity of the device, this circuit is considered the simplest for assembly at home.
The third method is the most portable, making it the most preferred of all. It provides power from two AAA batteries, maintaining a constant voltage level supplied to the laser diode. The system maintains power even when the battery level is low.
When the battery is completely discharged, the circuit will stop functioning, and a small voltage will pass through the diode, which will be characterized by a weak glow of the laser beam. This type of power supply is the most economical, its efficiency factor is 90%.
To implement such a power system, you will need an LM-2621 microcircuit, which is housed in a 3x3 mm package. Therefore, you may encounter certain difficulties during the period of soldering parts. The final size of the board depends on your skills and dexterity, since the parts can be placed even on a 2x2 cm board. The finished board is shown in Fig. 4.
The choke can be taken from a regular power supply for a desktop computer. A wire with a cross-section of 0.5 mm is wound onto it with a number of turns of up to 15 turns, as shown in the figure. The throttle diameter from the inside will be 2.5 mm.
Any Schottky diode with a value of 3 A is suitable for the board. For example, 1N5821, SB360, SR360 and MBRS340T3. The power supplied to the diode is adjusted by a resistor. During the setup process, it is recommended to connect it to a 100 Ohm variable resistor. When testing functionality, it is best to use a worn or unwanted laser diode. The current power indicator remains the same as in the previous diagram.
Once you find the most suitable method, you can upgrade it if you have the necessary skills to do so. The laser diode must be placed on a miniature heatsink so that it does not overheat when the voltage increases. After completing the assembly of the power system, you need to take care of installing the optical glass.
Laser diodes - Previously, manufacturing lasers was associated with great difficulties, since it requires a small crystal and the development of a circuit for its operation. For a simple radio amateur, such a task was impossible.
With the development of new technologies, the possibility of obtaining a laser beam in everyday conditions has become a reality. The electronics industry today produces miniature semiconductors that can generate a laser beam. Laser diodes became these semiconductors.
The increased optical power and excellent functional parameters of the semiconductor make it possible to use it in high-precision measuring devices both in production, in medicine, and in everyday life. They are the basis for writing and reading computer disks, school laser pointers, level gauges, distance meters and many other useful devices for humans.
The emergence of such a new electronic component is a revolution in the creation of electronic devices of varying complexity. High-power diodes form a beam, which is used in medicine to perform various surgical operations, in particular to restore vision. The laser beam is able to quickly correct the lens of the eye.
Laser diodes are used in measuring instruments in everyday life and industry. The devices are manufactured with different power levels. A power of 8 W is enough to assemble a portable level gauge at home. This device is reliable in operation and is capable of creating a laser beam of very long length. Getting a laser beam into the eyes is very dangerous, since at a short distance the beam is capable of damaging soft tissues.
In a simple diode, a positive voltage is applied to the anode, then we are talking about biasing the diode in the forward direction. Holes from the “p” region are injected into the “n” region of the p-n junction, and from the “n” region into the “p” region of the semiconductor. When a hole and an electron are located next to each other, they recombine and release photon energy with a certain wavelength and phonon. This process is called spontaneous emission. In LEDs it is the main source.
But under certain conditions, a hole and an electron are capable of remaining in one place for a long time (several microseconds) before recombination. If a photon with a resonance frequency passes through this area at this time, it will cause forced recombination, and a second photon will be released. Its direction, phase and polarization vector will absolutely coincide with the first photon.
The semiconductor crystal is made in the form of a thin rectangular plate. In fact, this plate plays the role of an optical waveguide in which radiation acts in a limited volume. The surface layer of the crystal is modified to form the “n” region. The bottom layer serves to create the “p” area.
The end result is a flat p-n junction of significant area. The two side ends of the crystal are polished to create parallel smooth planes that form an optical resonator. A random photon perpendicular to the planes of spontaneous emission will travel along the entire optical waveguide. In this case, before leaving outside, the photon will be reflected several times from the ends and, passing along the resonators, will create forced recombination, forming new photons with the same parameters, which will cause an increase in radiation. When the gain exceeds the loss, the creation of a laser beam will begin.
The use of such lasers is justified to create increased radiation power without high-quality beam convergence. Some dispersion is allowed. This effect is used to pump other lasers, in chemical production, and laser printers. However, if a certain focusing of the beam is necessary, the waveguide must be made with a width comparable to the wavelength.
In this case, the beam width depends on the boundaries that are imposed by diffraction. Such devices are used in optical storage devices, fiber optic technology, and laser pointers. It should be noted that these lasers are not capable of supporting multiple longitudinal modes and emitting a laser beam at different wavelengths at the same time. The band gap between the energy levels of the “p” and “n” regions of the diode affects the wavelength of the beam.
The laser beam immediately diverges at the output, since the emitting component is very thin. To compensate for this phenomenon and create a thin beam, converging lenses are used. For wide multi-house lasers, cylindrical lenses are used. In the case of single-house lasers, when symmetrical lenses are used, the laser beam will have an elliptical cross-section, since the vertical divergence exceeds the beam size in the horizontal plane. A good example of this is the laser pointer.
In the considered elementary device, it is impossible to distinguish a specific wavelength, except for the wave of the optical resonator. In devices that have a material capable of amplifying the beam over a wide range of frequencies, and with several modes, action at different waves is possible.
Typically, laser diodes operate at a single wavelength, which, however, has significant instability and depends on various factors.
The design of the diodes discussed above has an n-p structure. Such diodes have low efficiency, require significant input power, and operate only in pulse mode. They cannot work any other way, as they will quickly overheat, so they are not widely used in practice.
Double heterostructure lasers have a layer of substance with a narrow band gap. This layer is located between layers of material that has a wide bandgap. Typically, aluminum gallium arsenide and gallium arsenide are used to make a double heterostructure laser. Each of these connections with two different semiconductors is called a heterostructure.
The advantage of lasers with this special structure is that the region of holes and electrons, called the active region, is located in the middle thin layer. Consequently, many more pairs of holes and electrons will create amplification. In the region with low gain there will be few such pairs left. In addition, light will be reflected from the heterojunctions. In other words, the radiation will be completely located in the region of greatest effective gain.
By making the middle layer of the diode thinner, it begins to function as a quantum well. Therefore, electronic energy will be quantized vertically. The difference between the energy levels of quantum wells is used to produce radiation instead of a future barrier.
This is effective in controlling the beam waveform depending on the thickness of the middle layer. This type of laser is much more efficient, unlike a single-layer laser, since the density of holes and electrons is distributed more evenly.
The main feature of thin-layer lasers is that they are not able to effectively contain a beam of light. To solve this problem, two additional layers are applied on both sides of the crystal, which have a lower refractive index, unlike the central layers. This structure is similar to a light guide. It holds the beam much better. These are heterostructures with separate confinement. Most lasers were produced using this technology in the 90s.
Lasers with feedback Mainly used for fiber optic communications. To stabilize the wave at the pn junction, a transverse notch is made to create a diffraction grating. Because of this, only one wavelength is returned to the resonator and amplified. Such lasers have a constant wavelength. It is determined by the grating notch pitch. The notch changes under the influence of temperature. This laser model is the basis of telecommunication optical systems.
There are also laser diodes VСSEL and VECSEL, which are surface-emitting models with a vertical resonator. Their difference is that the model VESSEL The resonator is external, and its design is available with optical and current pumping.
Laser diodes are used in many applications where a directed light beam is needed. The main process in assembling a device using a laser with your own hands is the correct connection.
Laser diodes differ from LED diodes in that they have a miniature crystal. Therefore, a large amount of power is concentrated in it, and therefore the amount of current, which can lead to its failure. To facilitate the operation of the laser, there are special device circuits called drivers.
Lasers require a stable power supply. However, there are models of them that have a red glow of the beam and operate normally even with an unstable network. If there is a driver, then the diode still cannot be connected directly. To do this, you additionally need a current sensor, the role of which is often played by a resistor connected between these elements.
This connection has the disadvantage that the negative pole of the power supply is not connected to the minus of the circuit. Another disadvantage is the power drop across the resistor. Therefore, before connecting the laser, you must carefully select the driver.
There are two main types of drivers that can ensure normal operation of laser diodes.
Pulse driver made by analogy with a pulse voltage converter capable of increasing and decreasing this parameter. The output and input powers of such a driver are approximately equal. However, there is some heat generation, which consumes a small amount of energy.
Line driver operates according to a circuit that most often supplies more voltage to the diode than required. To reduce it, a transistor is needed to convert excess energy into heat. The driver has low efficiency, so it is not widely used.
When using linear microcircuits as stabilizers, as the input voltage decreases, the diode current will decrease.
Since lasers are powered by two types of drivers, the connection diagrams are different.
The circuit may also include a power source in the form of a battery or accumulator.
The batteries must produce 9 volts. The circuit must also have a current-limiting resistor and a laser module. Laser diodes can be found in a faulty computer disk drive.
The laser diode has 3 outputs. The middle pin is connected to the minus (plus) of the power supply. The plus connects to the right or left leg, depending on the manufacturer. To determine the correct pin to connect to, power must be applied. To do this, you can take two 1.5 V batteries and a resistance of 5 Ohms. The minus of the source is connected to the middle leg of the diode, and the plus first to the left, then to the right leg. Through such an experiment, you can see which of these legs is the “working” one. Using the same method, the diode is connected to the microcontroller.
Laser diodes can be powered by AA batteries or a cell phone battery. However, we must not forget that an additional limiting resistor of 20 ohms is required.
To do this, it is necessary to provide auxiliary protection against high frequency surges.
The stabilizer and resistor create a block that prevents current surges. A zener diode is used to equalize the voltage. The capacitance prevents high frequency voltage surges. Proper assembly ensures stable operation of the laser.
The most convenient for operation will be a red diode with a power of about 200 mW. Such laser diodes are installed on computer disk drives.
When connecting, be aware of safety. All connections must be of high quality.
In this post I will describe how I assembled a purple laser pointer from junk I had on hand. For this I needed: a violet laser diode, a collimator to converge the light beam, driver parts, a housing for the laser, a power supply, a good soldering iron, straight hands, and the desire to create.
If you are interested and want to dig deeper into electronics, please refer to cat.
I came across a dead Blu-ray cutter. It was a shame to throw it away, but I didn’t know what could be made of it. Six months later I came across a video that showed such a homemade “toy”. This is where Blu-ray comes in handy!
The drive's read-write system uses a laser diode. In most cases it looks like this:
Or like this.
To power the “red” diode, 3-3.05 volts are needed, and from 10-15 to 1500-2500 milliamps, depending on its power.
But the “purple” diode requires as much as 4.5-4.9 volts, so powering it through a resistor from a lithium battery will not work. We'll have to make a driver.
Since I had a positive experience with the ZXSC400 chip, I chose it without hesitation. This chip is a driver for high-power LEDs. Datasheet. I didn’t bother with the wiring in the form of a transistor, diode and inductance - everything is from the datasheet.
I made a printed circuit board for the laser driver, known to many radio amateurs as LUT (Laser Ironing Technology). For this you need a laser printer. The diagram was drawn in the SprintLayout5 program and printed on film for further transfer of the drawing to textolite. You can use almost any film, as long as it doesn’t get stuck in the printer and it prints well. Film from plastic envelope folders is quite suitable.
If there is no film, no need to be upset! We borrow a women's glossy magazine from a friend or wife, cut out the most uninteresting page from it and adjust it to A4 size. Then we print.
In the photo below you can see a film with applied toner in the form of a circuit layout, and a piece of PCB prepared for transferring the toner. The next step will be preparing the PCB. It is best to take a piece twice as large as our diagram, so that it is more convenient to press it to the surface during the next step. The copper surface must be sanded and degreased.
Now you need to transfer the “drawing”. We find an iron in the closet and turn it on. While it is warming up, we place a piece of paper with the circuit on the PCB.
As soon as the iron heats up, you need to carefully iron the film through the paper.
This video shows the process very clearly.
When it “sticks” to the PCB, you can turn off the iron and move on to the next step.
After transferring the toner using a regular iron, it looks like this:
If some tracks were not transferred, or were not transferred very well, they can be corrected with a CD marker and a sharp needle. It is advisable to use a magnifying glass, the tracks are quite small, only 0.4 mm. The board is ready for etching.
We will poison with ferric chloride. 150 rubles per jar, lasts a long time.
We dilute the solution, throw our workpiece there, “stir” the board and wait for the result.
Don't forget to control the process. Carefully pull out the board with tweezers (it’s also better to buy one, this way we will save ourselves from excess mat and “snot” of solder on the future board when soldering).
Well, the board is etched!
Carefully clean it with fine sandpaper, apply flux, and tin it. This is what happens after servicing.
You can apply a little more solder to the contact pads than everywhere else, to make soldering the parts more convenient, and without applying additional solder.
We will assemble the driver according to this scheme. Please note: R1 - 18 milliOhm, but not megaohm!
When soldering, it is best to use a soldering iron with a thin tip; for convenience, you can use a magnifying glass, because the parts are quite small. For this soldering, flux LTI-120 is used.
So, the board is practically soldered.
The wire is soldered in place of the 0.028 Ohm resistor, since we are unlikely to find such a resistor. You can solder 3-4 SMD jumpers in parallel (they look like resistors, but labeled 0), they have about 0.1 ohm of real resistance.
But there weren’t any, so I used regular copper wire of similar resistance. I didn’t measure it exactly - just some calculations from some online calculator.
We are testing.
The voltage is set to only 4.5 volts, so the light is not very bright.
Of course, the board looks a bit dirty before the flux is washed off. You can wash it off with simple alcohol.
Now it’s worth writing about the collimator. The fact is that the laser diode itself does not shine with a thin beam. If you turn it on without optics, it will shine like a regular LED with a divergence of 50-70 degrees. In order to create a beam, you need optics and a collimator itself.
The collimator was ordered from China. It also contains a weak red diode, but I didn’t need it. The old diode can be knocked out with a regular M6 bolt.
We unscrew the collimator, unscrew the lens and the back part, and unsolder the driver from the diode. We clamp the remaining fastener in a vice. You can knock out the diode by hitting it.
The diode is knocked out.
Now you need to press in the new purple diode.
But you can’t press the legs of the diode, and it’s inconvenient to press them in any other way.
What to do?
The back of the collimator is great for this.
We insert the new diode with its legs into the hole in the back of the cylinder, and clamp it in a vice.
Smoothly tighten the vice until the diode is completely pressed into the collimator.
So, the driver and collimator are assembled.
Now we attach the collimator to the “head” of our laser, and solder the diode to the driver outputs using wires, or directly to the driver board.
As a body, I decided to use a simple flashlight from a hardware store for a hundred rubles.
It looks like this:
All hardware for the laser and collimator.
A magnet is attached to the clothespin for easy attachment.
All that remains is to insert the laser device into the housing and tighten it.
Sprint layout 5, PCB layout files in
