How to connect a laser diode. Laser diodes: operating principle, types and application. Step-by-step connection instructions
The dream of a small pocket laser became a reality with the advent and development of semiconductor laser diodes. There are a lot of articles on the Internet about how you can make a burning laser from a CD drive. But you shouldn’t limit yourself to just this information.
Laser diode selection:
If you have a serious goal of making a laser, then look through the reference book and choose a laser diode that suits the parameters. If not, you have a faulty DVD RW drive, then you will have to fork out the cash and buy a laser LED. Moreover, in this case, you can, to the best of your financial capabilities, select a laser of the power you need. What should we do with him next? I recommend reading and listening to our article so as not to waste time assembling dubious laser diode connection circuits.
Classification of laser systems:
High energy is concentrated in the laser beam and therefore there is a danger of damaging vision if lasers are handled carelessly. There is a hazard classification for laser installations in accordance with EN60825-1, Figure No. 1.
Figure No. 1 – Classification of hazards of laser installations When working with laser diodes, you must STRICTLY FOLLOW SAFETY RULES. Do not direct the laser beam directly into the eyes, as this may lead to complete or partial loss of vision. Do not give your laser unit to children, do not leave it in easily accessible places! Eliminate the possibility of unauthorized (accidental) activation of the laser, use your creation only for peaceful purposes!!! Wear safety glasses when setting up and operating it.
About laser diode:
As a rule, a laser diode is a miniature device with three (Figure 2) or four legs, depending on the type.
Figure No. 2 – Appearance of a laser LED with three legs Why three legs? The fact is that inside the case, in addition to the laser emitting diode, there is also a photodiode, Figure No. 3.
Figure No. 3 – Laser LED circuit The photodiode is designed to control (regulate or limit) the laser current. Structurally, it looks like this: Figure No. 4.
Figure No. 4 – Cross-section of a laser diode. Low-power laser diodes operate at voltages of a few volts and currents in the range of approximately 50 to 80 mA. Indicated in the corresponding passports on them (Datasheet). For example, the operating current (50-60 mA) should never be exceeded! Pulse overloads are also dangerous. Therefore, when powering a laser LED, care must be taken to ensure that such peaks are absent. It is most reliable to use batteries rather than a power supply as a power source for the diode. But this is not always suitable - especially if you want to do a permanent installation.
So, if you want to connect your laser diode (LD) to an unstabilized (simple) power supply, I recommend using diagram No. 5:
Figure No. 5 – Diagram for connecting the LD to an unstabilized power source C1– 10 µF
C2 – 47 pF
C3, C4 – 10 nF
R1 – 10 K
R2 – 1.5 K
R3 – 33 Ohm
VT1 – BC548
VT2-BD675
VD1 – Laser diode
VD2 – 3.3 V/ 1.3 W
Thanks to this connection of the laser diode, it is possible to prevent its failure. The voltage drop across resistor R2 opens transistor VT 1, it controls the base current of transistor VT 2. In the control loop, the photodiode current fluctuates around 400 μA. Capacitor C4 eliminates impulse noise, and a capacitive voltage divider, consisting of capacitors C2 and S3, ensures that the regulation process starts immediately when the supply voltage is applied.
My laser option:
I also tried to make a laser from a DVD RW drive and I want to warn you right away that the idea is good, but it is quite difficult to implement. Disassembling a working DVD RW drive is stupid, and in broken drives, as a rule, the laser diode is already scorched and cannot be restored. Even if you managed to remove the working laser diode, be prepared for the fact that it requires a special collecting lens, since the laser diode itself does not shine focused. And to form the required beam divergence you will need good optics. Lenses from a DVD RW drive do not give the desired effect. I simply bought a ready-made laser module like HLDPM12-655-5 (in a housing with optics and polarity reversal protection), and connected it to a regular power supply.
Laser diodes are used in a wide variety of amateur radio designs. The laser diode can be powered either from a battery or rechargeable power supply, or from a stationary network with an industrial voltage of 220 volts. In the latter case, more careful protection against surges of current or voltage is necessary, since the laser diode is a rather sensitive element to such phenomena and can fail even with a very short-term excess of current or voltage.
Connecting a diode from a DC source.
The circuit includes a nine-volt battery or accumulator, a current-limiting resistor and the laser module itself. If you do not have a separate laser diode, you can take it from a DVD drive. It should be remembered that in this case we are talking about a computer player, and not a regular player. The laser is removed from it with great care, after which it is necessary to determine the power connection. As a rule, the manufacturer supplies laser diodes with three leads, two at the edges and one in the middle. In most cases, it is the middle electrode that is connected to the negative terminal of the power source. You need to connect either the right or the left to the positive pole, it all depends on the manufacturer and brand of laser equipment. In order to determine which pin is positive, power should be applied to the diode. For this purpose, two 1.5 volt batteries and a five ohm resistor are used. The negative terminals of the batteries are directly connected to the central negative terminal of the diode. The positive side of the batteries, through a resistor, is alternately connected to each of the two remaining terminals of the diode. As soon as the laser lights up slightly, it means that the positive pole has been found. In this way, polarity can be determined very quickly and easily, since the operating principle of a laser diode is identical to the operation of a conventional valve. The future laser is powered by two or three AA batteries, but if desired, you can also use a mobile phone battery for this purpose. In the latter case, it is necessary to use an additional twenty-five ohm limiting resistor, and in the case of batteries, use a five ohm resistor.
Connecting a diode from a 220 V network
This type of connection may cause unwanted voltage surges and high-frequency surges. In this case, additional protection should be provided to the sensitive element in order to avoid its damage. The circuit consists of a voltage stabilizer, a capacitor, current-limiting resistors and a laser diode itself. The voltage stabilizer and resistance form a block that prevents current surges. To protect against voltage surges, a zener diode is installed, and a capacitor will help prevent high-frequency surges. As a result of using such a circuit, stable operation of the laser diode is completely guaranteed.
A short review of a 1.5 Chinese watt laser module, but at the same time cheap.
Suitable for installation on any type of 3D printer, as well as for homemade designs
Installation is simple: the laser module is installed on the print head with ties and connected instead of a blower.
There is no need to update the firmware. You can print from a flash drive.
More detailed information under the cut
Greetings! And straight to the point))))
I have long wanted to get a laser engraver with a large working area. Well, how big - more than 3.5 by 3.5 mm (Neje, KKmoon and similar Decker). These Chinese crafts of ultra-cheap design use mechanics from old computer drives, and accordingly there is no possibility of modernization.
The simplest thing that can come to mind is installing a laser module on the head of a 3D printer. There are options for installation together with an existing hotend (), you can install a new X-carriage (effector holder for kossel) instead of the standard one. 
There are different power options for the laser module driver - it can be powered from the hotend heater wires, while the TTL signal is taken from the model's blower fan. If with minimal modification, you can simply install it together with the hotend, power it from the fan (setting it to 100%). Next, we focus the lens to a point, manually lower the effector to the table (raise the table to the laser, etc.), determining the height at which the laser beam is focused to the point. This height will be constant for subsequent “printing”, adjusted for the height of the material. In this option, flashing will not be required - everything remains as is and you can use the printer as a printer, only prepare G-code files for the engraver through the plugin.
By the way, as an option, you can collect . The easiest way is to use several sections of structural profile, rollers, and belts. Here there is, and here - about for assembling carriages.
You can use an Arduino Uno/Nano + CNC Shield as a simple control board, it is possible to buy an original EleksMaker board for compatibility with software like Benbox (and essentially get an inexpensive copy of a Chinese engraver for an inexpensive price), and nothing prevents you from installing an Arduino Mega+ Ramps, and use work from an SD card and control (display + encoder).
All of these components are inexpensive and available.
In any case, the most important thing is to find and connect the laser module correctly. 
There was already a talk about powerful laser modules on Muska (and there was even an article about a laser engraver), when purchasing, pay attention to the possibility of TTL power control (or buy a separate driver with TTL for the laser diode/module)
And keep in mind that the name of the laser module usually indicates the power desired by the Chinese, which is only achievable at 100% power. Average/recommended power usually hovers around 50-60% of maximum. That is, if you paid about $300 for a module with 5500mW, then you will most likely have about 3...3.5W to work with. When operating for a long time at maximum power, Chinese diodes quickly lose their service life (and die).
Let's leave powerful diode modules for other publications, but there have been no publications on Muska about their cheap analogues yet. In general, the goal was to get an inexpensive module under $25, but at the same time capable of engraving on wood/cardboard and perhaps even cutting thin materials.
I’ll immediately point out the options that caught my eye.
Firstly, There is always the opportunity to break down/ask for spare parts an old DVD-RW drive and remove the laser. Usually they say to search at speeds >16x, since they use slightly more powerful lasers.
This is a practically free option, suitable for trying your hand at it and seeing what happens. By the way, if you break a couple of drives, you will also get mechanics for two axes))))
Here is information on a similar method, disassemble it carefully, do not damage the module, which is afraid of static.
The laser from the drive is typically capable of engraving cardboard and wood. For fans, you can pop balloons and light matches. Powered by 1*3.7V battery or 5V (power bank)
Secondly, You can buy very inexpensive laser diodes, usually sold in several pieces. Here is an example of laser diodes with a wavelength of 808nm radiation.
There are three pins on the body, but two are used (minus on the body, plus on the left).
For both the first case (laser or DVD-RW drive) and the second, you will need to purchase an additional housing, lens, and also for powering the diode.
There is a good third way: This is the purchase of an inexpensive laser diode module, in a sleeve, with a lens.
Here are the options for , for , for .
They are sold as replacement versions (for upgrade or repair) of Neje/Kkmoon type lasers 
They look like a sleeve with a diameter of 12mm, a height of 45mm, with two contacts for powering the diode. The module is supplied without a driver and, accordingly, you will need to solder or buy a driver. . B provided a photo of a disassembled laser module 
So, the module comes with a driver inside, the driver is powered by a voltage of 4.5V....5V, the maximum power consumption is 1.5W (the emitted power is correspondingly less). This driver does not have TTL. There are two control options - either M106 S255 (MAX) then M106 S0 (MIN), or power on/off, which is essentially the same thing. The second option is to replace the “native” driver.
A few words about drivers. It is necessary to power a laser diode not with voltage, but with current; depending on the current, it will emit stronger or weaker radiation.
Here is the simplest power supply circuit for laser diodes from drives. 
The resistor that is selected in series with the diode is very important - it limits the current on the diode.
So, I decided to try it here
Below is a photo of the package and the laser. It arrived quite quickly after payment, about 20 days. There is not a word in the declaration about lasers (accessories) 
Inside the parcel there is a package with a laser, small and light 
The module weight is only 17-18 grams 
Dimensions: diameter 12mm... 
... length 45 mm 
The ring with the lens can be completely unscrewed. Here in the photo you can clearly see the lens and spring. 
If you look into the laser module with the lens removed, then... you can see little. Only the chip in the housing. 
Closer photo 
On the reverse side the wires are fixed with hot glue 
Now photos of additional components for assembly.
For initial testing, a 300mA driver was purchased 
And 
Photo of a laser with a heatsink 
And they are assembled 
The total assembly weight is 65 grams - this is important for the moving parts of the future system 
Comparison of a 1500 mW laser with a 300 mW laser module 
For comparison - 300mW 808nm diodes and a radiator for them
At the same time, I conducted experiments with the lot
diodes 
body with lens 
This is what the diode looks like installed in the case 
and the diode itself 
assembled radiator with lens 
So, I purchased the simplest driver just to monitor the performance of the laser. It can power the laser up to 300mA (read milliwatt 600....700), but does not fully reveal the capabilities of the laser module.
Suitable for powering homemade laser modules made from DVD-RW. If you will power diodes from a laser or purchased 300mW diodes, then you must first set the minimum supply current. 
To begin with, we twist the variable resistor to the minimum position (counterclockwise), connect a 50...80 Ohm resistor instead of the laser and set the current to about 50 mA.
Be sure to leave the multimeter in current measurement mode in the circuit. Then we will also turn on the laser with a multimeter and monitor it.
As for the 1500mW laser module from the review, it already comes with an installed driver; it can be powered up to 5V. At first I played it safe and applied a little less voltage. The photo shows that the laser module begins to light up and you can try to focus it on a point 
So, the test has passed.
I used the DPS5005 module to power the laser module and control the current/voltage 
You can already engrave wood, the only thing is you need to hold it for a while
Here is a photo of a hand sample 
Next, you can set the voltage to the recommended 4.5....5V 
Well, traditionally - lights matches, pops balloons, I won’t dwell on that
For further experiments I used a Geeetech Me Creator printer with the extruder removed. A new holder was drawn for the carriage, and the laser power was turned on separately.
3D model of a carriage holder 
Screenshot from a 3D printer slicer 
Appearance of the laser installed on the X-carriage 
View from above. 
Photos in progress. It is difficult to catch the dot with a camera - in special glasses the dot is very small, about 0.1 mm. It is better not to look at it without protective glasses. 
Printed normally from an SD card, without firmware modification 
The simplest G-code for coordinates was launched from an SD card to check the functionality of the idea. 
Find out in more detail what a 1.5 Watt Chinese laser can do
To prepare images for engraving, I recommend using
Here is the plugin menu. In Z-offset, write the height at which your laser focuses. Control is carried out by commands M106/M107 through adjusting the fan speed. 
So, this laser module is one of the cheapest, and allows you to keep it under $20.
In order to reveal all the capabilities of the laser module, I ordered a current driver up to 1500 mW and with TTL. When it arrives, I’ll disassemble the module housing and want to connect it bypassing the native driver.
Well, I want to draw a new carriage so that the extruder and laser can be installed at the same time.
Otherwise it’s not very convenient to throw them around.
In general, everything. The idea is interesting, good, I hope it will suit many people, at least try their hand at it.
I liked the review
+51
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This circuit, which is quite accurate and does not require many components, is designed to drive a laser diode and is designed to meet the requirements of medical equipment. The device is currently undergoing clinical trials. The performance of laser diodes is subject to short- and long-term drift due to temperature and aging. They are usually driven by direct current, so their optical output power is monitored and the current is adjusted according to changes in power.
The body of the design is grounded, so the DC source configuration is designed to include a power transistor in the upper arm of the laser, rather than the simpler opposite option. In addition, to avoid “tattooing” the patient, the current must be initially limited.
In a single-supply +5V circuit, current-sensing and current-limiting resistor R1 and p-channel MOSFET Q1 form the source follower (Figure 1). The MOSFET's gate voltage is slightly higher than the source voltage, so the transistor is partially on and the laser diode current creates a voltage drop across resistor R1. In the worst case, when Q1 is fully open, the maximum laser current is given by
R DS(SAT) = 25 mOhm - open channel resistance of the MOS transistor,
V LASER = 2.0 V - voltage on the laser diode.
The R DS(SAT) and V LASER values were taken from the transistor and laser diode data sheets, respectively. The choice of resistor R1 is determined by the requirements for the laser current (in this case, 250 mA) taking into account the correction introduced by the forward voltage of the laser diode, a typical value of which is 2.0 V. Solving the equation for R1, we obtain:
where I LASER = 250 mA.
The resistance R DS(SAT) is so small that it can be ignored. With known values of R1 and the maximum current of the laser diode, the power dissipated by R1 can be calculated using the formula
which means that a resistor with a permissible power dissipation of 800 mW will provide a small additional margin.
The laser current is set using a DAC, the output voltage of which is set ratiometrically. The +5 V source voltage is used as a reference here, so the DAC output tracks all power fluctuations. During operation, the required value of the control voltage is set at the ADC output. Divider R2, R3 scales this setting relative to the nominal +5 V supply.
For example, if the DAC output voltage is set to half scale, that is, +2.5 V, the voltage between R2 and R3, (or at the non-inverting input of op-amp IC1), will be +3.5 V. Included in the feedback loop, IC1 regulates the voltage at the gate of Q1 and , respectively, the current flowing through R1, Q1 and the laser diode. The circuit mode is stabilized when the feedback voltage becomes equal to +3.5 V. In this steady state, 5 V - 3.5 V = 1.5 V drops across resistor R1, and the current is 125 mA, that is, in the middle of the scale. Similarly, if the DAC output is set to a minimum value of 0 V, the voltage at the non-inverting input of IC1 will be +2 V. IC1 will increase the voltage at the gate of Q1 until the voltage drop across R1 increases to 3 V, and the current accordingly increases. up to 250 mA. This is the saturation point where Q1 is fully on and the forward voltage across the laser diode is +5V minus the voltage drop across R1.
The complete circuit must include elements R4 and C1, ensuring the stability of the control loop and having a cutoff frequency f equal to
Special attention should be paid to the process that occurs in the circuit during an abrupt change in the control voltage, during which the op-amp, which previously worked as an adder of the setpoint and feedback voltages, becomes a voltage follower, and a step tends to appear at its output. In this regard, in our example, capacitor C2 is added, forming a low-frequency filter for the setpoint voltage with a cutoff frequency
where R2||R3 = 12 kOhm.
If the cutoff frequency of this filter is much less than the feedback loop bandwidth, the op amp will be able to track setpoint step changes with minimal overshoot during DAC switching.
R5 provides some bias to the op amp by ensuring that a small amount of current is always guaranteed to flow through resistor R1. When the DAC output is set to +5V full scale, the laser current driven by the op amp will always be slightly higher than the setting. Therefore, the op-amp output, trying to turn off Q1, will go into saturation. Without R5, the op amp's input offset voltage could be perceived as a false setpoint and cause Q1 to be turned on to restore balance.
This is one of the main reasons why ratiometric DAC switching is used. If the DAC's reference voltage were fixed, programming low currents would be virtually impossible. If the voltage at the DAC output is set slightly below the exact value of +5 V, then even with small fluctuations in the +5 V supply voltage, the control voltage will change quite significantly. However, in a ratiometric circuit, the DAC tracks changes in the +5 V supply voltage, and the relative control voltage at its output remains stable.
The price for the ability to accurately set low currents is a poor power supply ripple suppression ratio. However, in the medical application for which the laser was intended, the current regulation loop is itself part of the power regulation loop, and the power supply ripple in it is minimal. If necessary, you can add a small voltage stabilizer to the board, and at the cost of slightly increasing the number of components you will get stable, low-noise laser power.
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 that 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.
Design and principle of operation
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 pass 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.
There are different types of laser diodes. The main ones are made on particularly thin layers. Their structure is capable of creating radiation only in parallel. But if the waveguide is made wide in comparison with the wavelength, then it will function in various transverse modes. Such laser diodes are called multi-house laser diodes.
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.
Varieties
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.
Quantum well diode
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.
Heterostructure laser diodes
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.
Connection features
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 consequently 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.
Types of drivers
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.
Connecting to a home network
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.
Connection procedure
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.
- Before connecting using a battery, check the operation of the laser diode.
- You need to choose the brightest semiconductor. If the diode is taken from a computer disk drive, then it emits infrared light. The laser beam must not be pointed at the eyes, as this will cause eye damage.
- The diode is mounted on a radiator for cooling, in the form of an aluminum plate. To do this, pre-drill a hole.
- Apply thermal paste between the diode and the radiator.
- Connect a 20 Ohm and 5 watt resistor according to the circuit with batteries and a laser.
- Bypass the diode with a ceramic capacitor of any capacity.
- Turn the diode away from you and check its operation by connecting the power. A red beam should appear.
When connecting, be aware of safety. All connections must be of high quality.
