12V regulated power supplies is regularly needed for various electronics circuit testing. I have been trying to drive a Nema17 stepper motor using A4988 stepper motor driver and series of lithium ion batteries. I don't know why but the stepper motor is not moving and there is 15V across the motor battery connectors on the A4988 motor driver module. So I thought could this be problem due to not using a voltage regulator. I don't think that the problem is due to regulated supply but anyway I wanted to work on PCB design since it's been months I haven't made a PCB at home. And I wanted to improve my PCB design skills. So here I will be making a 12V voltage regulator using LM317 IC along with schematic and pcb layout to actually fabrication the PCB layout at home.
I started with the schematic design of the 12V voltage regulator using LM317.
We have already shown different FM transmitter circuit that you can build at home. Here it is explained the building blocks of a typical simple FM transmitter so that one can also modify, improve an FM transmitter circuit or any wireless communication circuits.
The following shows a simple FM transmitter circuit diagram.
The above FM circuit consist of following blocks.
a. Power Supply
b. Audio Input Circuit
c. Audio Pre-Amplifier
d. Oscillator and Modulator circuit
e. Antenna
a. The power supply circuit consist of 9V battery, a power supply smoothing capacitor to reduce power supply noise and a switch.
b. The audio input circuit consist of and electret microphone, pull up resistor R1 and coupling capacitor C2. See Wireless FM Microphone Circuit for more.
c. The audio microphone pre-amplifier circuit is made up of BJT transistor 2N3565 which is biased with the resistors R2, R3 and R4.
d. The oscillator and modulator circuit is made up of the transistor 2N5179 BJT transistor, air coil inductor L1, capacitors C1 and C6, biasing resistors R5, R6 and R7. The BJT transistor along with the inductors L1, capacitors C1 and C6 makes up the Colpitts oscillator. The coil size can be calculated using the online air core inductor calculator at the FM frequency band. The inductance required for the oscillator can be calculated using the online oscillator calculator.
C3 is a coupling capacitor that couples the amplified audio signal from the pre-amplifier into the oscillator and modulator circuit. The capacitor C5 is used to couple the high frequency oscillatory signal to the ground and thus preventing the high frequency component going into the amplifier circuit.
The FM modulator is a reactance modulator. The audio signal changes the transistor junction capacitances which in turns are added and subtracted from to the oscillator tank capacitances(C1,C6) that then changes the frequency of oscillation of the FM wave.
The resulting FM signal is then ac coupled to the antenna via the coupling capacitor C7.
Once you know what blocks are essential to build an FM transmitter circuit, you have choices to use another different type of oscillators, modulator, audio input circuit, battery and antenna.
For example you can use crystal oscillator, Colpitts oscillator, Hartley oscillator, FET Pierce oscillator etc. You can use different type of FM modulator like varactor FM modulator circuit.
So, grab your soldering
iron, gather your components, and let's embark on this electrifying
journey of building your very own FM transmitter!
I used the LM317 voltage regulator online calculator to come up with resistors values for desired output voltage and current. Below is screenshot, using 390Ohm resistor for R1 and output voltage of 12V we get approximately 3.3KOhm resistor.
So these values were used in the above LM317 12V voltage regulator schematic.
I added two capacitors C1 and C2 along with a power indicator LED and associated LED at the output. I place the components and routed the copper traces. I am designing a single layer PCB. The PCB trace routing is easy. Then I also put ground plane which will connected to our ground in the schematic. Following shows the PCB layout of the LM317 based voltage regulator.
And the 3D view of the prototype view of the LM317 voltage regulator.
You can download this LM317 voltage regulator model from ee-diary 3d models.
Now I have captured video while doing the schematic, circuit simulation and then PCB design. Note that in the video the two Terminal headers of 5mm 3D model is missing while in the above animation it is shown. This is because I searched and downloaded the 3D model of the Terminal headers after I made the video.
Following is the full video of making a 12V voltage regulator with LM317 IC in Proteus and ARES.
So the next thing to do is to actually make the PCB at home. So writing about the PCB on this blog post would make the blog post a bit long. So I will write about the PCB fabrication at home in my next blog post.
There is also another PCB that I have ordered from China. These are PCB for minimal Arduino Board which uses ATmega328P microcontroller which is placed onto the 28 IC holder on the PCB. There is also GSM module PCB design but this is more complex and expensive for me for now. As said earlier I just want to improve my PCB design and fabrication skills and knowledge.
My another project with LM317 voltage regulator includes the LASER transmitter and receiver circuit. The LASER in that project need a constant regulated power supply of 2.78V with input voltage of 5V. Again calculating the resistors values to get output of 2.78V we can manually calculate or use the online LM317 calculator to calculate these values.
